The following is an alphabetical compilation of the terms and definitions that appear in the main body entries. Although the list is comprehensive, it is by no means exhaustive and is intended to serve as a starting point for further research.
abdomen
(AB-do-men), commonly called the belly, is the portion of the body between the thorax (THOR-aks) and the pelvis.
abdominal
(ab-DAH-mih-nul) refers to the area of the body below the ribs and above the hips that contains the stomach, intestines, and other organs.
abnormalities
are things or events that are out of the ordinary; not normal.
abscess
(AB-ses) is a localized or walled-off accumulation of pus caused by infection that can occur anywhere in the body.
acetaminophen
(uh-see-teh-MIH-noh-fen) is a medication commonly used to reduce fever and relieve pain.
acetylcholine
(uh-SEET-l-koh-leen) is a neu-rotransmitter in the brain that functions to excite nerve cells.
acid reflux
is a condition in which stomach acid flows upward into the esophagus, often causing a burning sensation (so-called heartburn) in the upper abdomen or chest.
acne
(AK-nee) is a condition in which pimples, blackheads, whiteheads, and sometimes deeper lumps occur on the skin.
acquired immunodeficiency syndrome
(or AIDS) is an infection that severely weakens the immune system. It is caused by the human immunodeficiency virus.
acromegaly
(akro-MEG-al-ee) is a disease in which the pituitary gland secretes too much growth hormone with the effect of gradual and permanent enlargement of flat bones, the hands and feet, abdominal organs, and some facial features.
acute
describes an infection or other illness that comes on suddenly and usually does not last very long.
addiction
(uh-DIK-shun) is a strong physical or psychological dependence on a physical substance.
adenoids
(AH-din-oyds) are the fleshy lumps of tissue behind the nose that contain collections of infection-fighting cells of the immune system.
adenovirus
(ah-deh-no-VY-rus) is a type of virus that can produce a variety of symptoms, including upper respiratory disease, when it infects humans.
ADHD
(or Attention Deficit Hyperactivity Disorder) is a condition that makes it hard for a person to pay attention, sit still, or think before acting.
adrenal glands
(a-DREEN-al glans) are the pair of endocrine organs located near the kidneys.
aerobic exercise
(air-OH-bik) is designed to increase oxygen consumption by the body; it helps keep the heart and lungs in shape.
aerobic metabolism
(air-OH-bik) uses oxygen to extract energy from carbohydrate sources, fatty acids and amino acids by oxidizing the carbohydrates to carbon dioxide (CO2) and capturing the energy of electron transport across the cell.
aerosolize
(AIR-o-suh-lize) is to put something, such as a medication, in the form of small particles or droplets that can be sprayed or released into the air.
AIDS
(or Acquired Immunodeficiency [ih-my-oo-no-dih-FIH-shen-see] Syndrome) is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).
air pollution
is a mixture of solid particles and gases in the air; can be natural or human-made.
allergen
(AL-uhr-jen) is a substance that provokes a response by the body's immune system or causes a hypersensitive reaction. Also called an antigen.
allergy
(AL-uhr-jee) is an immune system-related sensitivity to certain substances, for example, cat dander or the pollen of certain plants, that causes various reactions, such as sneezing, runny nose, wheezing, or swollen, itchy patches on the skin, called hives.
alopecia areata
(al-o-PEA-shah a-ree-AH-ta) is a condition that leads to sudden hair loss, often in small, round patches on the scalp. The cause is not known.
alpha interferon
is an injectable drug that strengthens the immune system and inhibits virus replication. The drug is a human-made version of the natural alpha interferon the body's immune system produces.
alpha-fetoprotein
(AL-fah FEE-toe-PRO-teen) is a substance produced by a fetus and present in maternal blood and amniotic fluid that is measured to determine the likelihood of neural tube defects.
alveoli
(al-VE-ol-i) are air sacs in the lungs through which oxygen and carbon dioxide exchange. Oxygen enters the bloodstream; carbon dioxide leaves the bloodstream to be exhaled through the lungs.
Alzheimer's disease
(ALTS-hy-merz) is a condition that leads to gradually worsening loss of mental abilities, including memory, judgment, and abstract thinking, as well as changes in personality.
amino acids
(a-MEE-no acids) are the chief building blocks of proteins. In humans, certain amino acids are required to sustain life.
amnesia
(am-NEE-zha) is the loss of memory about one or more past experiences that is more than normal forgetfulness.
amniocentesis
(am-nee-o-sen-TEE-sis) is a test during which a long, thin needle is inserted into the mother's uterus to obtain a sample of the amniotic fluid from the sac that surrounds the fetus. The fetal cells in the fluid are then examined for genetic defects.
amniotic sac
(AM-nee-AH-tik SAK) is the sac formed by the amnion, the thin but tough membrane that lines the outside of the embryo in the uterus and is filled with fluid to cushion and protect the embryo as it grows.
amoebas
(uh-MEE-buz) are small, one-celled animals that live in fresh- and saltwater. Amoebas can only be seen with a microscope.
amputation
(am-pyoo-TAY-shun) is the removal of a limb, other appendage, or outgrowth of the body.
amygdala
(a-MIG-da-la) is a small almond-shaped structure in the brain that plays a part in processing emotions.
amyloidosis
is a condition in which excessive amounts of a protein known as amyloid are created by the body and deposited in tissues causing damage.
anabolic steroids
(a-nah-BAH-lik STIR-oyds) are drugs and hormones that cause muscle and bone growth and a shift from fat to muscle in the body.
anaerobic metabolism
(an-air-OH-bik) extracts energy from only carbohydrate sources without the presence of oxygen to facilitate the reaction.
anal
refers to the anus, the opening at the end of the digestive system through which waste leaves the body.
analgesics
(an-al-JEEZ-iks) are medications to reduce or relieve pain.
androgen deficiency
(AN-dro-gen de-fish-ens-see) is reduced male hormones in men, also called male menopause.
androgens
are male sex hormones, especially testosterone.
androgynous
(an-DRAW-gin-us) refers to having characteristics of both sexes.
anemia
(uh-NEE-me-uh) is a blood condition in which there is a decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.
anencephaly
(AN-en-SEF-uh-lee) is a condition present at birth in which most of the brain is missing.
anesthesia
(an-es-THEE-zha) is a state in which a person is temporarily unable to feel pain while under the influence of a medication.
anesthetic
(an-es-THET-ik) is a medicine that decreases the sensation of pain.
aneurysm
(AN-yoo-rizm) is a weak spot in the wall of an artery (arteries carry blood from the heart to other parts of the body). The weak spot can rupture or break, causing massive internal bleeding.
angiogram
(an-GEE-oh-gram) is a test in which x-rays are taken as dye is injected into the body, showing the flow of blood through the heart and blood vessels.
anorexia
(an-o-REK-see-a) is an emotional disorder characterized by dread of gaining weight, leading to self-starvation, dangerous loss of weight, and malnutrition.
anorexia nervosa
(an-o-REK-se-uh ner-VO-suh) is an emotional disorder characterized by dread of gaining weight, leading to self-starvation and dangerous loss of weight and malnutrition.
antagonist
(an-TAG-oh-nist) is a chemical that acts within the body to reduce or oppose the effects of another chemical.
anthrax
(AN-thraks) is a rare infectious disease caused by the bacterium Bacillus anthracis.
antibacterial
(an-tie-bak-TEER-ee-al) refers to any substance that kills or prevents the growth of bacteria, such as an ointment, drug, or other medication.
antibiotic
(an-tie-by-AH-tik) is a drug that kills or slows the growth of bacteria.
antibody
(AN-tih-bah-dee) is a protein molecule produced by the body's immune system to help fight a specific infection caused by a microorganism, such as a bacterium or virus.
anticoagulants
(ant-i-KO-ag-u-lant) are medications that interfere with blood clotting or coagulation.
anticonvulsants
(an-tie-kon-VUL-sents) are medications that affect the electrical activity in the brain and are given to prevent or stop seizures.
antidepressant medications
are used for the treatment and prevention of depression.
antifungal drugs
(an-ty-FUNG-al) are medications that kill fungi.
antigen
(AN-tih-jen) is a substance that is recognized as a threat by the body's immune system, which triggers the formation of specific antibodies against the substance.
antihistamine
(an-ti-hiss-tah-meen) is a drug that opposes the action of histamine and is often used to treat allergic reactions.
antihypertensives
are medications used for the treatment of high blood pressure or hypertension.
antimalarial drugs
(an-tie-ma-LAR-ee-ahl) are used to treat malaria, a disease caused by a parasite that is transmitted by mosquitoes.
antipsychotic drugs
(an-tie-sigh-KO-tik) are medications that counteract or reduce the symptoms of a severe mental disorder such as schizophrenia.
antireflux
is a treatment for acid reflux; can include diet modification or surgery.
antiseptic
(an-tie-SEP-tik) is a substance that inhibits the growth and development of microorganisms.
antisocial behavior
is behavior that differs significantly from the norms of society and is considered harmful to society.
antitoxin
(an-tih-TOK-sin) is an agent that counteracts the effects of toxins, or poisons, on the body. It is produced to act against specific toxins, such as those made by the bacteria that cause botulism or diphtheria.
antivenin
is an antibody (protein) capable of neutralizing a specific venom.
antiviral
is a substance or medication used to treat or prevent a viral infection.
anus
(A-nus) is the opening at the end of the digestive system, through which waste (stool or feces) leaves the body.
anxiety
(ang-ZY-e-tee) is a condition marked by a sense of dread, fear of the future, or distress over a possible threat to a person's physical or mental well-being.
anxiety disorders
(ang-ZY-e-tee dis-OR-derz) are a group of conditions that cause people to feel extreme fear or worry that sometimes is accompanied by symptoms such as dizziness, chest pain, or difficulty sleeping or concentrating.
aorta
(ay-OR-ta) is the major artery that carries blood from the heart to the rest of the body.
aortic aneurysm
(ay-OR-tik AN-yoo-rizm) is a weak spot in the aorta, the body's largest blood vessel. The weak spot can rupture or break, causing massive internal bleeding.
aplastic anemia
is a disease in which there is (A-plas-tik uh-NEE-me-uh) a lack of or deficiency of all types of blood cells caused by the failure of the bone marrow to produce enough new blood cells.
appendectomy
a surgical procedure in which the appendix is removed.
appendicitis
(ah-pen-dih-SY-tis) is an inflammation of the appendix, the narrow, finger-shaped organ that branches off the part of the large intestine in the lower right side of the abdomen.
appendix
(ah-PEN-diks) is the narrow, finger-shaped organ that branches off the part of the large intestine in the lower right side of the abdomen. Although the organ is not known to have any vital function, the tissue of the appendix is populated by cells of the immune system.
arterial blood gas
is a type of blood test that measures the percentage of gases—specifically, oxygen and carbon dioxide—in the blood.
arterioles
(ar-TEER-ee-oles) are small arteries.
arteriosclerosis
(ar-TEER-ee-o-skler-O-siss) is a condition in which arteries of the body become narrowed and hardened from the buildup of calcium, cholesterol, and other substances, causing decreased blood flow through these vessels.
artery
is a vessel that carries oxygenated blood from the heart to tissues in the body.
arthritis
(ar-THRY-tis) refers to any of several disorders characterized by inflammation of the joints.
arthropods
are members of a group of organisms that lack a spinal column and have a segmented body and jointed limbs. This group includes various insects, ticks, spiders, lice, and fleas.
arthroscopic
(AR-thro-SKOP-ik) surgery, also called arthroscopy, is the insertion of a specialized device called an endoscope to examine and treat the inside of a joint.
artificial tears
are eye drops used to lubricate or provide moisture for the eyes.
asbestos
is a group of minerals that occurs naturally in the environment as silicates. When asbestos fibers are breathed in (inhaled), they can cause scarring and inflammation in the lungs.
aseptic meningitis
(a-SEP-tik meh-nin-JY-tis) is a milder, nonbacterial form of meningitis that is usually caused by a virus.
aspiration
(as-puh-RAY-shun) is the sucking of fluid or other material out of the body, such as the removal of a sample of joint fluid through a needle inserted into the joint.
asthma
(AZ-mah) is a condition in which the airways of the lungs repeatedly become narrowed and inflamed, causing breathing difficulty.
ataxia
is a disorder involving an unsteady gait.
atherosclerosis
(aah-thuh-ro-skluh-RO-suhs) is a condition in which plaque builds up in arteries. This can lead to narrowing and hardening of these arteries, which can slow or block blood flow to the heart and other organs and increase the risk of heart disease.
atopy
(AT-uh-pee) is an allergic hypersensitivity that affects parts of the body not in direct contact with the allergen, such as hay fever, asthma, or eczema.
atrial fibrillation
(AY-tree-al fib-ri-LAY-shun) is the arrhythmic or irregular beating of the left upper chamber of the heart. This irregular heartbeat leads to an irregular flow of blood and to the formation of blood clots that can leave the heart and travel to the brain, causing a stroke.
aura
is a warning sensation that precedes a seizure or other neurological event.
autism
(AW-tih-zum) is a developmental disorder in which a person has difficulty interacting and communicating with others and usually has severely limited interest in social activities.
autism spectrum disorder
(AW-tih-zum) is a range or spectrum of developmental disorders in which people have difficulty interacting and communicating with others and usually have severely limited interest in social activities.
autoimmune disease
(aw-toh-ih-MYOON) is a disease in which the body's immune system attacks some of the body's own normal tissues and cells.
autonomic nervous system
is a branch of the peripheral nervous system that controls various involuntary body activities, such as body temperature, metabolism, heart rate, blood pressure, breathing, and digestion. The autonomic nervous system has two parts—the sympathetic branch and the parasympathetic branch.
autopsy
(AW-top-see) is an examination of a body after death to look for the cause of death or the effects of a disease.
autosomal dominant
refers to a mode of inheritance in which only one copy of an abnormal gene is necessary to cause disease.
bacteremia
(bak-tuh-REE-me-uh) is the presence of bacteria in the blood.
bacteria
(bak-TEER-ee-a) are single-celled microorganisms, which typically reproduce by cell division. Some, but not all, types of bacteria can cause disease in humans. Many types can live in the body without causing harm.
bacterial vaginosis
(back-TER-i-all VAG-in-OH-sis) is a condition of the vagina caused by an overgrowth of normal bacteria. Symptoms include an abnormal discharge and fishy odor. This condition is treated with oral antibiotics and vaginal gels.
barbiturates
(bar-BI-chur-ate) are drugs that depress the central nervous system, causing mild sedation to total anesthesia.
Bartholin's gland
(BAR-tha-lin) either of two very small glands inside the vagina that are important for vaginal lubrication during sexual intercourse.
battery
(in reference to testing) refers to a group of related tests that are given together.
bedsores
are skin sores caused by prolonged pressure on the bony prominences of the hips, sacrum, heels, elbows, and shoulders; typically seen in people who are confined by illness or paralysis to beds or wheelchairs. Also called pressure sores.
behavior therapy
is a type of counseling that works to help people change their actions.
behavioral
means related to the way a person acts.
Bell's palsy
(PAWL-zee) is a condition in which there is damage to the facial nerve, also called the seventh cranial nerve, causing weakness or loss of function of muscles on one side of the face.
benign
(beh-NINE) refers to a condition that is not cancerous or serious and will probably improve, go away, or not get worse.
beriberi
is a disease caused by a deficiency in the vitamin thiamine (B1).
bifocals
or multifocal (progressive) lenses are prescription eyeglasses that have lenses divided into two or more sections. The bottom section allows a person to see things clearly that are close, and the top section allows a person to see things clearly that are far away.
bile
is a greenish-brown fluid manufactured in the liver that is essential for digesting food. Bile is stored in the gallbladder, which contracts and discharges bile into the intestine to aid digestion of fats after a person eats.
bile duct
is a passageway that carries bile, a substance that aids the digestion of fat, from the liver to the gallbladder (a small pouch-like organ where the bile is temporarily stored) and from the gallbladder to the small intestine.
biliary tract
(BIH-lee-ah-ree) refers to the organs and ducts, including the liver and gallbladder, that produce, store, and transport bile, a substance that aids in digestion.
biofeedback
is a technique that helps people gain some voluntary control over normally involuntary body functions
biohazard
is a biological agent or condition that poses a threat to humans.
biopsy
(BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.
bipolar disorder
is a recurrent mood disorder (previously called manic-depressive disorder) in which patients have extreme mood swings from depression to mania or a mixture of both.
bisexual
(bi-SEK-shoo-al) means being sexually attracted to both sexes.
bladder
(BLAD-er) is the organ that stores urine produced by the kidneys prior to discharge from the body.
blood clot
is a thickening of the blood into a jelly-like substance that helps stop bleeding. Clotting of the blood within a blood vessel can lead to blockage of blood flow.
blood transfusion
(trans-FYOO-zhunz) is the process of giving blood (or certain cells or chemicals found in the blood) to a person who needs it due to illness or blood loss.
blood-brain barrier
is a biological shield in the body that helps prevent germs or other potentially harmful materials in the blood from entering the brain and spinal cord.
body image
is a person's impressions, thoughts, feelings, and opinions about his or her body.
boils
are skin abscesses, or collections of pus in the skin.
bone marrow
is the soft, spongy area in the interior of the bones in which blood cells are produced.
borderline personality disorder
is a serious mental illness characterized by unstable moods, poor self-image, and unhealthy interpersonal relationships along with an inability to regulate emotional responses.
brain stem
is the portion of the brain that connects the brain to the spinal cord. It also controls involuntary muscle movement, regulates essential bodily functions such as breathing and heart rate, and relays messages between the body and the brain.
bronchitis
(brong-KYE-tis) is a disease that involves inflammation of the larger airways in the respiratory tract, which can result from infection or other causes.
bronchodilators
(brong-ko-DY-lay-tors) are drugs used in the treatment of asthma to widen the bronchi, which are the major airways in the lungs.
bronchoscopy
(brong-KOS-ko-pee) is a procedure used to examine the bronchi, the major air passages in the lungs, with an instrument called a bronchoscope, which is a tool for looking inside the lungs that is made up of a lighted tube with viewing lenses. A broncho-scope has channels through which samples of material can be taken from the lungs for study in the laboratory.
bulimia
(bu-LEE-me-a) is an eating disorder in which a person has episodes of out-of-control overeating, or binges, and then tries to make up for them by making themselves vomit, by taking laxatives, or by exercising to excess to avoid gaining weight.
bursa
is a small fluid-filled sac found around most major joints in the body to cushion bones and tendons.
CADASIL
(Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leu-koencephalopathy) is an inherited form of cerebrovascular disease that occurs when the thickening of blood vessel walls blocks the flow of blood to the brain. The disease primarily affects small blood vessels in the white matter of the brain.
caisson
(KAY-son) is a watertight container that divers or construction workers use underwater.
calories
(KAL-or-eez) are units of energy that are used to describe both the amount of energy in food and the amount of energy the body uses.
cancer
is a condition characterized by the overgrowth of abnormal cells leading to a growth or tumor and the potential to spread to other parts of the body.
candidiasis
(kan-dih-DYE-uh-sis) is an overgrowth of Candida, a type of yeast, in or on the body.
capillaries
are the smallest blood vessels that connect the arterioles and venules and provide oxygen to tissues.
carbohydrates
are the nutrients in food that help provide energy to the body.
carbon dioxide
(CAR-bon dy-OK-side) is an odorless, colorless gas that is formed in the tissues and breathed out through the lungs.
carbon monoxide
(KCAR-bon mon-OK-side) is a colorless, odorless gas that is toxic to the body and can cause fire.
carcinogens
(kar-SIN-o-jenz) are substances or agents that can cause cancer.
carcinoma
(kar-sih-NO-muh) is a cancerous tumor that arises in the epithelium (eh-puh-THEE-lee-um), the sheets of cells that line body surfaces, such as the insides of hollow organs and cavities
cardiomyopathy
(KAR-dih-oh-my-OP-ah-thy) is a chronic disease of the heart muscle, in which the muscle is abnormally enlarged, thickened, and/or stiffened.
cardiopulmonary resuscitation
(CPR) is an emergency procedure during which one breathes for a person who is not breathing and provides chest compressions to initiate a heartbeat for someone whose heart is not beating.
cardiovascular
(car-dee-oh-VAS-cue-lar) system refers to the heart and blood vessels.
carrier
is a person who has in his or her body a bacterium or virus or gene for a disease that can be transmitted to other people without the carrier becoming sick or developing the disease.
cartilage
(CAR-te-lej) is the tough, flexible tissue that covers the ends of the bones.
cataract
(KAH-tuh-rakt) is a condition in which the lens of the eye (or both eyes) become progressively less transparent, or becomes cloudy, leading to blurring of the vision.
catecholamines
(kat-e-KO-la-meens) are hormones and neurotransmitters like epineph-rine, norepinephrine, and dopamine.
catheter
(KAH-thuh-ter) is a small plastic tube placed through a body opening into an organ (such as the bladder) or through the skin directly into a blood vessel. It is used to give fluids to or drain fluids from a person.
cecum
(SEE-kum) is the pouch-like start of the large intestine that connects it to the small intestine.
cell division
is the process by which a cell divides to form two daughter cells, each of which contains the same genetic material as the original cell.
centenarians
are people who are at least 100 years old.
central nervous system
(SEN-trul NER-vus SIS-tem) is the part of the nervous system that includes the brain and spinal cord.
cerebellum
(se-RUH-BEL-um) is the back portion of the brain that is responsible for muscle coordination and balance.
cerebral cortex
(suh-REE-brul KOR-teks) is the part of the brain that controls functions such as conscious thought, listening, and speaking.
cerebral palsy
(se-RE-bral PAL-zee) is a group of conditions, all of which affect a person's ability to move. They are usually caused by injury to the brain before or soon after birth.
cerebrospinal fluid
(seh-ree-bro-SPY-nuhl) is the fluid that surrounds the brain and spinal cord.
cerebrum
(suh-REE-brum) is the largest front and upper part of the brain that is responsible for mental processes.
cervical
refers to the cervix (SIR-viks), the lower, narrow end of the uterus that opens into the vagina.
cervix
(SIR-viks) is the lower, narrow end of the uterus that opens into the vagina.
cesarean section
(si-ZAR-ee-an SEK-shun) is the surgical incision of the walls of the abdomen and uterus to deliver offspring in cases where the mother cannot deliver through the vagina.
chancre
(SHANG-ker) is a usually painless sore or ulcer that forms where a disease-causing germ enters the body, such as with syphilis.
chelation therapy
(chee-LAY-shun) is a technique used to treat patients with lead or mercury poisoning by administering medications that combine with the metal to keep the body from absorbing it.
chemotherapy
(KEE-mo-THER-uh-pee) is the treatment of cancer with powerful drugs that kill cancer cells.
chlamydia
(kla-MIH-dee-uh) are microorganisms that can infect the urinary tract, genitals, eye, and respiratory tract, including the lungs.
cholesterol
(ko-LES-ter-ol) is a fatlike substance found in the blood and body tissues.
chorionic villus sampling
(KOR-ee-on-ik VIL-lus) is a test in which a small tube is inserted through the cervix and a small piece of the placenta supporting the fetus is removed for genetic testing.
chromosomes
(KRO-mo-sohmz) are threadlike structures inside cells on which the genes are located. There are 46 (23 pairs) of chromosomes in normal human cells. Genes on the X and Y chromosomes (known as the sex chromosomes) determine whether a person is male or female. Females have two X chromosomes; males have one X and one Y chromosome.
chronic
(KRAH-nik) means lasting a long time or recurring frequently.
chronic fatigue syndrome
(KRON-ik fat-TEEG) is a debilitating and complicated disorder in which individuals feel intense fatigue that lasts six months or longer. Symptoms may include insomnia, muscle pain, and impaired concentration. Because other illnesses have these symptoms, doctors must rule out a number of conditions in order to make a diagnosis.
chronic obstructive pulmonary disease
(COPD) is a progressive disease that makes it hard to breath.
chronic traumatic encephalopathy
(CTE) is an ultimately fatal neurodegenerative disease with cognitive impairment and dementia caused by repeated brain injuries such as concussion.
circulatory system
(SIR-kyoo-luh-tor-ee) is composed of the heart and blood vessels that moves blood throughout the body.
circumcision
is a surgical procedure in which the fold of skin covering the tip of the penis is removed.
cirrhosis
(sir-O-sis) is a condition that affects the liver involving long-term inflammation and scarring, which can lead to problems with liver function.
cleft lip
is a gap or split in the upper lip. It occurs when the lip of a fetus does not develop properly during the first months of pregnancy.
cleft palate
is a gap or split in the roof of the mouth (the palate). It is a type of birth defect resulting from the tissues of the face not joining together properly during pregnancy.
clinical psychologist
is a mental health professional who has earned a nonmedical doctoral degree. Clinical psychologists can perform psychological evaluations and provide mental health counseling and therapy.
clitoris
(kle-TOR-is) is the small, sensitive part of the female genitals at the front of the vulva.
cloning
(KLOH-ning) is a process in which a group of cells or even an entire organism is grown from a single stem cell and is genetically identical to it.
clot
is a thickened mass of blood cells and protein formed to stop bleeding.
clotting
is the process by which the body forms a thickened mass of blood cells and protein to stop bleeding.
cochlear implants
(KOKE-lee-er) are surgically implanted electronic devices that provide a sense of sound to a person who is profoundly deaf or severely hard of hearing; the implants may help provide hearing in patients who are deaf because of damage to sensory hair cells in the cochlea.
cognitive
is conscious intellectual activity, including thinking, imagining, reasoning, remembering, and learning.
cognitive behavioral therapy
(KOG-nih-tiv be-HAY-vyuh-rul THAIR-uh-pee) is treatment that helps people identify negative ways of thinking and behaving and change them to more positive approaches.
colitis, ulcerative
(ko-LIE-tis, UL-sir-ah-tiv) is a common form of inflammatory bowel disease that causes inflammation with sore spots or breaks in the inner lining of the large intestine (colon). Symptoms include cramping, bleeding from the rectum, and diarrhea.
colon
(KO-lin), also called the large intestine, is a muscular tube through which food passes as it is digested, just before it moves into the rectum and out of the body through the anus.
colonized
means that a group of organisms, particularly bacteria, are living on or inside the body without causing symptoms of infection.
colonoscopy
is a medical procedure in which an instrument is inserted into the colon in order to take pictures of it.
colostomy
(ko-LOS-to-mee) is a surgical procedure in which a part of the large intestine is removed, and the end of the intestine is attached to an opening made in the abdomen. The stool is passed through this opening into a special bag.
coma
(KO-ma) is an unconscious state like a very deep sleep. A person in a coma cannot be awakened, and cannot move, see, speak, and may not be able to hear.
comedones
(KOM-e-dones) are acne pimples. Blackheads are open comedones. Whitehe-ads are closed comedones. Cosmetics that are labeled noncomedogenic (non-kom-e-do-JEN-ik) are less likely to cause pimples.
communication disorders
affect a person's ability to use or understand speech and language.
complement proteins
are proteins that circulate in the blood and play a role in the immune system's response to infections. More than 30 complement proteins had been identified as of 2016.
compression stocking
is a specialized type of stocking that places controlled pressure on the legs to prevent pooling of blood in the legs and promote blood return through the veins to the heart.
computed tomography
(kom-PYOO-ted toe-MAH-gruh-fee), or CT, is a technique in which a machine takes many x-rays of the body to create a three-dimensional picture. Formerly called computerized axial tomography (CAT).
concussion
(kon-KUH-shun) is an injury to the brain produced by a blow to the head or violent shaking.
conduct disorder
is diagnosed in children and adolescents who have had serious problems with lying, stealing, and aggressive behavior for at least six months.
confabulation
refers to filling in gaps in memory by making up or fabricating facts. The gaps occur because the person's memory function is impaired.
congestive
(kon-JES-tiv) means characterized by accumulation of too much fluid.
congestive heart failure
(kon-JES-tiv) is a condition in which a damaged or overworked heart cannot pump enough blood to meet the oxygen and nutrient needs of the body.
conjunctivitis
(kon-jung-tih-VY-tis), often called pink eye, is an inflammation of the thin membrane that lines the inside of the eyelids and covers the surface of the eyeball.
connective tissue
is tissue that connects, supports, binds, or separates other tissues or organs.
consensual sex
is sexual activity in which both people freely agree to participate.
constipation
is the sluggish movement of the bowels, usually resulting in infrequent, hard stools.
constricted pupil
is when the pupil of the eye becomes smaller, usually in response to light, but sometimes because of certain medications or diseases.
contact urticaria
(ur-ti-KAIR-ee-uh), which can be caused by contact with a variety of compounds, such as foods, preservatives, fragrances, plant and animal products, metals, and rubber latex, produces an immediate reaction of localized redness and swelling.
contagious
(kon-TAY-jus) means transmissible from one person to another, usually referring to an infection.
contaminant
is any substance that makes unclean or impure the substance into which it is placed. For example, smoke is a contaminant in air.
contraception
(kon-tra-SEP-shun) is the deliberate prevention of conception or impregnation.
conversion disorder
is a mental disorder in which psychological symptoms are converted to physical symptoms, such as blindness, paralysis, or seizures. A person with conversion disorder does not intentionally produce symptoms.
convulsions
(kon-VUL-shuns), also called seizures, are involuntary muscle contractions caused by electrical discharges within the brain and are usually accompanied by changes in consciousness.
cornea
(KOR-nee-uh) is the transparent circular layer of cells over the central colored part of the eyeball (the iris) through which light enters the eye.
coronary aneurysm
(KOR-uh-nair-e AN-yuh-rih-zum) is an abnormal stretching and weakening of a blood vessel that supplies blood to the heart. If it breaks open, it may cause serious damage to the heart, sometimes leading to death.
coronary arteries
(KOR-uh-nair-e AR-tuh-reez) are the blood vessels that supply blood directly to the heart.
coronary artery disease
is disease of the arteries that supply blood to the heart muscle, usually arteriosclerosis (increased rigidity of the arterial wall) and atherosclerosis (development of fatty plaque on the interior linings of the vessel wall).
correlated
means linked in a way that can be measured and predicted.
cortex
(KOR-teks) is the outermost layer of the brain. It controls the brain's higher functions, such as thinking, learning, and personality.
Cortisol
(KOR-ti-sol) is a hormone that plays a part in regulating metabolism, blood pressure, and the immune system. As the body's primary stress hormone, it also plays a critical role in the stress response.
cortisone
(KOR-ti-zone) is a medication used to relieve inflammation.
cri du chat
(KREE-doo-SHA), French for cat's cry, is a genetic disorder that can cause intellectual disability, a small head, and a cat-like whine.
Crohn's disease
(KRONZ) is an often inherited, chronic inflammatory disease that typically affects the small and/or large intestine but can affect any part of the digestive system. The disease causes crater-like ulcers or sores in the inner surface of the bowel. Mild cases may be treated with medication; serious cases may be treated with surgery.
croup
(KROOP) is an infection involving the trachea (windpipe) and larynx (voice box) that typically occurs in childhood. It causes inflammation and narrowing of the upper airway, sometimes making it difficult to breathe. The characteristic symptom is a barking cough.
CT scans
is the shortened name for computed tomography (to-MOG-ra-fee), which uses computers to view structures inside the body. Formerly called computerized axial tomography (CAT).
culture
(KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days the organisms will grow and can be identified.
cutaneous
(kyoo-TAY-nee-us) means related to or affecting the skin.
cystic fibrosis
(SIS-tik fy-BRO-sis) is a disease that causes the body to produce thick mucus that clogs passages in many of the body's organs, including the lungs.
cysts
(SISTS) are shell-like enclosures that contain small organisms in a resting stage.
cytomegalovirus
(sy-tuh-MEH-guh-lo-vy-rus) is a common infection usually causing no symptoms. It poses little risk for healthy people, but it can lead to serious illness in people with weak immune systems.
debridement
(dee-BRIDE-mint) is the removing of skin tissue, such as skin damaged from burns.
decongestants
(dee-con-JES-tents) are medications used to relieve congestion in the nasal passages and sinuses.
DEET
(abbreviation for N, N-Diethyl-meta-tolu-amide) is the active ingredient in many insect repellents.
degenerative
(dee-JEN-er-uh-tiv) means progressively worsening or becoming more impaired.
dehydrated
is a term used when there is loss of large amounts of water or body fluids from the body.
dehydration
(dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unreplaced loss of body fluids, such as through sweating, vomiting, or diarrhea.
delirium
(dih-LEER-e-um) is a condition in which a person is confUsed, is unable to think clearly, and has a reduced level of consciousness.
delirium tremens
(DTs) is seen in severe forms of withdrawal from alcohol. DTs includes tremors, confusion, agitation, hallucinations, disorientation, fear, and quick mood changes, among many other serious symptoms.
delusions
(de-LOO-zhuns) are false beliefs or judgment that remain even in the face of proof that they are not true.
dementia
(dih-MEN-sha) is a loss of mental abilities, including memory, understanding, and judgment.
dementia pugilistica
(dih-MEN-sha pyu-jeh-LlS-the-kah) is a neurologic disorder characterized by impaired movement, speech, and cognition, which affects boxers who have experienced repeated concussion or other head injuries.
depersonalization
(dee-per-son-al-i-ZAY-shun) is a mental condition in which people feel they are living in a dream or are removed from their body and are watching themselves live.
depression
(dih-PRESH-un) is a mental state characterized by feelings of sadness, despair, and discouragement.
derealization
(dee-reel-i-ZAY-shun) is a mental condition in which people feel the external world is strange or unreal.
dermatitis
is a skin condition characterized by a red, itchy rash. It may occur when the skin comes in contact with something to which it is sensitive.
desensitization
(de-sens-ih-tih-ZAY-shun) is a method for reducing a person's reaction to an allergen.
developing countries
are countries that are poor but are seeking to become more advanced both economically and socially.
developmental delay
is a condition in which a child is less developed mentally, physically, socially, or psychologically than considered normal for the child's age.
deviated septum
is a condition in which the wall of tissue between the nasal passages, the septum, divides the passageways unevenly, sometimes causing breathing difficulties and blocking drainage from the sinuses.
dextrocardia
is mirror-image rotation that is confined to the heart.
diabetes
(dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood. This can lead to increased urination, dehydration, weight loss, weakness, and a number of other symptoms and complications related to chemical imbalances within the body.
dialectical behavior therapy
(DIE-ah-lek-ti-kal be-HAY-vyuh-rul THAIR-uh-pee) (DBT) is a more formalized type of cognitive-behavioral therapy originally designed to treat borderline personality disorder.
dialysis
(dye-AL-uh-sis) is a process that removes waste, toxins (poisons), and extra fluid from the blood. Usually dialysis is done when a person's kidneys are unable to perform these functions normally.
diaphragm
(DY-uh-fram) is the muscle that separates the chest and abdominal cavities. It is the chief muscle used in breathing.
dietitian
is a person who has specialized knowledge and experience in human nutrition and diet therapy. Also called a nutritionist.
differentiation
(DIF-feh-rent-see-AY-shun) is the process in which embryonic or adult stem cells give rise to more specialized cells.
digestive system
is the system that processes food. It includes the mouth, esophagus, stomach, intestines, colon, rectum, and other organs involved in digestion, including the liver and pancreas.
dilatation
(DIH-luh-tay-SHUN) is the act of dilating or opening a blood vessel.
dilate
(DY-late) means to become enlarged or stretched beyond the usual boundaries.
diphtheria
(dif-THEER-e-uh) is an infection of the lining of the upper respiratory tract (the nose and throat). It is a disease that can cause breathing difficulty and other complications, including death.
disinfect
means to destroy harmful organisms by physical or chemical means.
disseminated
describes a disease that has spread widely in the body.
diuretic
(dye-yoor-EH-tik) is medication that increases the body's output of urine.
dizygotic
(dye-zye-GOT-ik) means derived from two different fertilized eggs.
DNA
or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-klay-ik AH-sid) is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.
dopamine
(DOE-puh-meen) is a neurotrans-mitter in the brain that is involved in the brain structures that control motor activity (movement).
dopamine agonists
(DO-puh-meen ash-guh-nists) are medications that mimic the actions of the brain chemical dopamine in the body. One of dopamine's normal jobs is controlling prolactin production. But dopamine agonists are stronger and longer-lasting than natural dopamine, so they can effectively treat pro-lactinomas.
double vision
is a vision problem in which a person sees two images of a single object.
double-jointed
is having joints with exceptional range-of-motion.
douche
(DOOSH) is water or a medicated liquid that is squirted into a body cavity to clean it or to treat a localized condition.
Down syndrome
is a genetic disorder that can cause intellectual disability, shortness, and distinctive facial characteristics, as well as many other features.
DSM-5
is the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, published by the American Psychiatric Association. This book is used by physicians in the United States to classify and diagnose mental conditions.
duodenal
(do-uh-DEE-nul) refers to the upper part of the small intestine.
duodenum
(dew-eh-DEE-num) is the first part of the small intestine that connects to the stomach.
dura mater
(DUR-uh MAY-ter) is the outermost of the three membranes that cover the brain and spinal cord.
dust mites
are tiny insects that live in dust and in materials such as carpets, pillows, mattresses, and furniture.
dysarthria
(dis-ARTH-ree-yah) is a condition in which the muscles used for speech are weakened or the person has difficulty in controlling them, causing slowed or slurred speech.
dysplasia
(dis-PLAY-zha) means abnormal growth or development.
dyspnea
is difficult or labored breathing; shortness of breath.
earwax
is the waxlike substance in the ear that traps dust and other particles to prevent them from damaging the inner ear. Also known as cerumen (suh-ROO-men).
eating disorder
is a condition in which a person's eating behaviors and food habits are so unbalanced that they cause physical and emotional problems.
Ebola virus disease
(formerly referred to as Ebola hemorrhagic fever) is a communicable disease caused by a virus that causes severe bleeding, organ failure, and death.
echocardiogram
(eh-ko-KAR-dee-uh-gram) is a diagnostic test that uses sound waves to produce images of the heart's chambers and valves and blood flow through the heart.
echoviruses
are a group of viruses found in the intestinal tract. The word echo in the name is an acronym for “enteric cytopathic human orphan”. When these viruses were named, they were not associated with any disease (hence the use of the word orphan). However, these viruses were later associated with various diseases, including meningitis and encephalitis.
ectopic pregnancy
(ek-TAH-pik) is an abnormal pregnancy in which the fertilized egg lodges and grows outside the uterus, usually within one of the fallopian tubes.
eczema
(EG-ze-mah) is an inflammatory skin condition characterized by redness, itchiness, and oozing blisters that become crusty and hard.
edema
(e-DEE-ma) is swelling in the body's tissues caused by excess fluids.
Ehler-Danlos syndrome
(AY-ler DAN-lahs) is an inherited syndrome that affects the connective tissue of the skin, joints, and blood vessels.
ejaculate
(e-JAH-kyoo-late) means to discharge semen from the penis.
elastic bandage
is a stretchable material bandage used to create localized pressure.
electrocardiogram
(e-lek-tro-KAR-dee-o-gram), also known as an EKG, is a test that records and displays the electrical activity of the heart.
electroencephalogram
(EEG) is an instrument that records the electrical activity of the brain.
electrolysis
(ee-lek-TRAW-li-sis) is a method of destroying hair roots by passing an electric current through them.
electrolytes
(ee-LEK-troh-lites) are ions such as sodium, potassium, or calcium that are dissolved in bodily fluids including the blood and that regulate or affect most metabolic processes.
electromyogram
(ee-lek-tro-MY-eh-gram) (EMG) is a visual record made by an electromyograph, which measures the electrical activity associated with functioning muscle.
elephantiasis
(eh-luh-fan-TIE-uh-sis) is the significant enlargement and thickening of body tissues caused by an infestation of parasites known as filaria.
embryo
(EM-bree-o), in humans, is the developing organism from the end of the second week after fertilization to the end of the eighth week.
embryology
(EM-bree-AH-lo-gee) is the branch of biology that deals with the development of sperm and ova, fertilization, and the development of the fertilized ovum.
empathy
(EM-pah-thee) is the ability to identify with the emotions and feelings of others.
emphysema
(em-fuh-ZEE-mah) is a lung disease in which the tiny air sacs in the lungs become permanently damaged and are unable to maintain the normal exchange of oxygen and other respiratory gases with the blood, often causing breathing difficulty.
encephalitis
(en-seh-fuh-LYE-tis) is an inflammation of the brain, usually caused by a viral infection.
encephalopathy
is any disease of the brain; encephalo comes from the Greek word for brain and pathy comes from the Greek word for disease.
endemic
(en-DEH-mik) describes a disease or condition that is present in a population or geographic area at all times.
endocarditis
(en-doh-kar-DYE-tis) is an inflammation of the valves and internal lining of the heart, known as the endocardium (en-doh-KAR-dee-um), usually caused by an infection.
endocrine
(EN-do-krin) refers to a group of glands, such as the thyroid, adrenal, and pituitary glands, and the hormones they produce. The endocrine glands secrete their hormones into the bloodstream, and the hormones travel to the cells that have receptors for them. Certain hormones have effects on mood and sometimes cause emotional swings.
endocrine system
is a system of ductless glands, including the thyroid and pituitary among others, that secrete hormones and control many bodily functions.
endocrinologist
(en-do-krin-OL-o-jist) is a doctor who specializes in treating patients with hormone-related disorders.
endoscope
(EN-doh-skope) is a tool for looking inside parts of the body. It consists of a lighted tube and optical fibers and/or lenses.
endoscopy
(en-DOS-ko-pee) is a type of diagnostic test in which a lighted tube-like instrument is inserted into a part of the body.
enema
(EH-nuh-muh) consists of a procedure in which liquid is injected through the anus into the intestine, to force the intestines to empty.
enterocytes
(en-TARE-o-sites) are cells in the lining of the small intestine that absorb nutrients from food and send these nutrients into the bloodstream.
enterovirus
(en-tuh-ro-VY-rus) is a group of viruses that can infect the human gastrointestinal tract and spread through the body causing a number of symptoms.
enzyme
(EN-zime) is a protein that helps speed up a chemical reaction in cells or organisms.
epidemic
(eh-pih-DEH-mik) is an outbreak of disease, especially infectious disease, in which the number of cases suddenly becomes far greater than usual. Usually epidemics are outbreaks of diseases in specific regions, whereas widespread epidemics are called pandemics.
epididymis
(eh-pih-DIH-i-mis) is a long coiled tube that stores sperm and transports it from the testes.
epidural
(ep-I-DOO-ral) means the part of the spinal canal that lies outside the dura mater, the outermost of the three meninges that cover the brain and spinal cord.
epiglottis
(eh-pih-GLAH-tis) is the soft flap of tissue that covers the opening of the trachea (windpipe) when a person swallows to prevent food or fluid from entering the airway and lungs.
epilepsy
(EP-i-lep-see) is a condition of the nervous system characterized by recurrent seizures that temporarily affect a person's awareness, movements, or sensations. Seizures occur when powerful rapid bursts of electrical energy interrupt the normal electrical patterns of the brain.
epinephrine
(eh-pih-NEH-frin) is a chemical substance produced by the body that can also be given as a medication to constrict, or narrow, small blood vessels, stimulate the heart, and cause other effects, such as helping to open narrowed airways in conditions like asthma and croup.
epithelial
(ep-eh-THELE-ee-al) tissue is made up of cells closely packed and ranged in one or more layers and covers the whole surface of the body. This tissue is adapted to form the covering or lining of all internal and external body surfaces.
Epstein-Barr virus
(EP-stine-BAHR Vl-rus) is a common virus that causes infectious mononucleosis.
erectile dysfunction
(er-EK-tile dys-FUNC-shun) is difficulty in achieving or maintaining an erection of the penis, also called impotence.
ergonomics
(er-go-NOM-iks) is a science that helps people to know the best postures and movements to use while working, in order to avoid injury and discomfort.
erythrocytapheresis
(eh-RITH-row-sigh-tah-ferr-ee-sis) involves withdrawing blood from a patient's body, sending the blood to a machine that separates the red blood cells from whole blood, and returning the blood (minus its red blood cells) to the patient.
esophagus
(eh-SAH-fuh-gus) is the soft tube that carries food from the throat to the stomach.
estrogen
(ES-tro-jen) is a steroid hormone that stimulates the development of female sexual characteristics and maintenance of the female reproductive system.
ethical
means having to do with questions of what is right and wrong, or with moral values.
ethics
is a guiding set of principles for conduct, a system of moral values.
euphoria
(yoo-FOR-ee-uh) is an abnormally high mood with the tendency to be overactive and overly talkative, and to have racing thoughts and overinflated self-confidence.
eustachian tubes
(yoo-STAY-she-un) are the tiny channels that allow air to flow between the middle ears and the throat.
exacerbation
(EX-as-er-BAY-shun) refers to a worsening, aggravation, or increase in severity of a disease or its signs and symptoms.
exotoxin
(ek-so-TOK-sin) is a substance produced by bacteria that has harmful effects on the infected person.
extension
(eks-TEN-shun) is the movement of a joint that brings the parts of a limb (e.g., arms, legs, or spine) into a straight line, or increases the angle of a joint.
extrauterine
means outside the uterus or womb.
factitious
means false. In medical cases, it refers to an impression of illness produced falsely.
failure to thrive
is a condition in which an infant fails to gain weight and grow at the expected rate.
fallopian tubes
(fa-LO-pee-an toobz) are the two slender tubes that connect the ovaries and the uterus in females. They carry the ova, or eggs, from the ovaries to the uterus.
feces
(FEE-seez) are the wastes excreted from the gastrointestinal tract through the anus.
femur
(FEE-mur) is the long bone of the upper leg.
ferritin
(FERR-ih-tin) is a protein in cells that binds to, stores, and releases iron.
fetal
(FEE-tal) refers to an unborn human after it is an embryo, from nine weeks after fertilization until childbirth.
fetal alcohol syndrome
occurs when a fetus is exposed to alcohol. The condition is associated with mental, physical, and behavioral differences. Oppositional behavioral problems, learning difficulties, intellectual disability, and stunted growth can occur in the children of women who drink alcohol while they are pregnant.
fetus
(FEE-tus) is the term for an unborn human after it is an embryo, from nine weeks after fertilization until birth.
fibromyalgia
(fi-bro-my-AL-ja) is a group of disorders characterized by achy, tender, and stiff muscles.
fissures
are tears in tissue.
fistulas
(FIS-tu-las) are abnormal connections between two organs or leading from an internal organ to the surface of the body.
flashbacks
are intensely vivid recurring mental images of a past traumatic event. People having a flashback may feel or act as if they were reliving the experience.
Flavivirus family
(FLAY-vih-vy-rus) is a group of viruses that includes those that cause dengue fever and yellow fever.
flexion
(FLEK-shun) is the act of bending or the state of being in a bent position, as well as a decrease in the angle of the bones forming a joint.
follicles
are tiny pits in the skin from which hair grows.
food chain
refers to the eating relationships between different organisms in a specific environment.
foreign
means coming from outside a person's body.
formula
is a prepared, nutritious drink or a dry drink mix designed specifically for infants.
fragile X syndrome
is a mutation on the X chromosome that causes an inherited range of mental disability from mild to severe and also increases the risk of developing ASD.
fraternal twins
refers to twins are who born at the same time but develop from two separate fertilized eggs. Unlike identical twins, who develop from only one fertilized egg that splits into two and who look exactly alike, fraternal twins may not look the same at all or be the same gender. Identical twins have the same genes, but fraternal twins are no more likely to share genes than non-twin siblings.
frostbite
is damage to tissues resulting from exposure to low environmental temperatures. It is also called congelation (kon-jeh-LAY-shun).
fulminant
(FUL-muh-nant) means a sudden and severe worsening of symptoms. Fulminant hepatitis often leads to liver failure and death.
fungal infection
(FUN-gul in-FEK-shun) is a disease caused by fungus (FUN-gus), a microorganism that can grow in or on the body, causing infections of internal organs or of the skin, hair, and nails. The plural form of fungus is fungi (FUNG-eye).
fungus
(FUN-gus) is a microorganism that can grow in or on the body, causing infections of internal organs or of the skin, hair, and nails. The plural form is fungi (FUNG-eye).
gallbladder
is a small pear-shaped organ on the right side of the abdomen that stores bile, a liquid that helps the body digest fat.
gallstones
(GAWL-stonz) are hard masses that form in the gallbladder or bile duct.
gamma globulin
(GAH-muh GLAH-byoo-lin) is a type of protein in the blood that contains the antibodies produced by the cells of the body's immune system that help defend the body against infection-causing germs, such as bacteria and viruses.
gangrene
(GANG-green) is the decay or death of living tissue caused by a lack of oxygen supply to the tissue and/or bacterial infection of the tissue.
gastroesophageal reflux disease
is a disorder of the digestive tract. GERD causes symptoms such as heartburn, nausea, and chest pain.
gastrointestinal
(gas-tro-in-TES-tih-nuhl) means having to do with the organs of the digestive system, the system that processes food. It includes the mouth, esophagus, stomach, intestines, colon, and rectum and other organs involved in digestion, including the liver and pancreas.
gene mutations
are changes in genes, which are the parts of deoxyribonucleic acid (DNA) molecules that transmit hereditary information from parents to their offspring.
gene therapy
is a treatment that works by altering genes.
general anesthesia
(an-es-THE-zha) means using drugs or inhaled gases to create a state of unconsciousness and muscle relaxation throughout the body to block pain during surgery. Local anesthesia blocks or numbs pain in one part of the body while patients remain awake.
genes
(JEENS) are chemical structures composed of deoxyribonucleic acid (DNA) that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are contained in the chromosomes found in the body's cells.
genetic
(juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.
genetic engineering
is manually changing the makeup of an organism's genes.
genetic predisposition
is an inherited tendency to get a certain disease.
genetically
(je-NE-ti-klee) means stemming from genes, the material in the body that helps determine a person's characteristics, such as hair or eye color.
genetics
(juh-NEH-tiks) is the branch of science that deals with heredity and the ways in which genes control the development and maintenance of organisms.
genitals
(JEH-nih-tuls) are the external sexual organs.
German measles
is a viral infection that usually causes a rash and mild fever. Also called rubella (roo-BEH-luh).
gestational
(jes-TAY-shun-al) means related to pregnancy.
gland
is an organ that produces substances such as hormones and chemicals that regulate body functions.
glaucoma
(glau-KO-ma) is a group of disorders that cause pressure to build within the eye, which may result in loss of vision.
glial cells
are common support cells in the central nervous system that do not have electrical impulses.
glomerulus
(glom-ER-you-lus) is from a Greek word meaning filter. The glomerulus is a knot of blood vessels that have the job of filtering the blood.
glucagon
is a hormone produced by alpha cells in the islets of Langerhans of the pancreas. Glucagon stimulates the release of glycogen from the liver, which stores glucose in the form of glycogen for use in raising blood sugar when needed.
gonorrhea
(gah-nuh-REE-uh) is a sexually transmitted infection (STI) spread through all forms of sexual intercourse. The bacteria can also be passed from an infected mother to her baby during childbirth. Gonorrhea can affect the genitals, urethra, rectum, eyes, throat, joints, and other tissues of the body.
Goodpasture's syndrome
is an autoimmune disorder of unknown cause, characterized by circulating antibodies in the blood that attack the membrane of the kidney's glomeruli and the lung's alveoli.
gout
occurs when deposits of uric acid in the joints cause inflammation and pain.
grafts
are tissue or organ transplants.
gram-negative bacterial infections
are serious infections caused by bacteria such as staph-ylococci (“staph”), streptococci (“strep”), pneumococci, and the bacteria responsible for causing diptheria and anthrax.
granuloma
(gran-yoo-LO-muh) is chronically inflamed and swollen tissue that often develops as the result of an infection.
growth hormone
is a chemical substance produced by the pituitary gland that regulates growth and other body functions.
Guillain-Barre syndrome
(GHEE-yan ba-RAY) is a rare disorder characterized by progressive symmetrical paralysis and loss of reflexes, usually beginning in the legs. The paralysis characteristically involves more than one limb (most commonly the legs). Some people recover completely in several months, but it is fatal for 5 percent of those with the syndrome.
gum disease
is an infection caused by bacteria that affect the tissues surrounding and supporting the teeth.
gynecologist
(gy-ne-KOL-o-jist) is a doctor who specializes in the reproductive system of women.
hair follicle
(FAH-lih-kul) is the skin structure from which hair develops and grows.
hallucinogenic drugs
are substances that cause a person to have hallucinations.
hamstrings
are the three muscles at the back of the thigh that flex and rotate the leg and extend the thigh.
hay fever
is an acute allergic reaction to pollen that causes sneezing, runny nose, nasal congestion, and watery eyes. Also called allergic rhinitis.
heart attack
is a general term that refers to a sudden, intense episode of heart injury. It is usually caused by a blockage in a coronary artery, which stops blood flow to the heart, depriving it of oxygen.
heart disease
is a broad term that covers many conditions that prevent the heart from working properly to pump blood throughout the body.
heart failure
is a condition in which a damaged heart cannot pump enough blood to meet the oxygen and nutrient demands of the body. Also called congestive heart failure.
heart murmur
is an abnormal sound from the heart, heard with a stethoscope, that is usually related to abnormal flow of blood through the heart. Some murmurs indicate a problem with a heart valve or other part of the heart's structures, but many heart murmurs are benign (do not indicate any problem).
Heimlich maneuver
(HYM-lick) is a technique performed to remove an obstruction, such as a chunk of food, from the upper airway where it is preventing air from passing through to the lungs. Named for its founder, H.J. Heimlich.
Helicobacter pylori
(HEELih-ko-bak-ter pie-LOR-eye) is a bacterium that causes inflammation and ulcers, or sores, in the lining of the stomach and the upper part of the small intestine.
hemodialysis
(HEE-mo-dye-AL-is-is) is a method for removing waste products from the blood in patients with kidney failure.
hemoglobin
(HE-muh-glo-bin) is the oxygen-carrying pigment of the red blood cells.
hemolytic
(he-muh-LIH-tik) refers to the destruction of red blood cells and the subsequent release of hemoglobin into the bloodstream.
hemophilia
(hee-mo-FIL-e-a) is a hereditary disease that results in abnormal bleeding because the blood fails to clot. It occurs almost exclusively in males.
hemorrhage
(HEH-muh-rij) is uncontrolled or abnormal bleeding
hemorrhoids
(HEM-o-roidz) are a mass of dilated veins in swollen tissue at the margin of the anus or nearby within the rectum.
hepatitis
(heh-puh-TIE-tis) is an inflammation of the liver. Hepatitis can be caused by viruses, bacteria, and a number of other non-infectious medical conditions.
hepatitis C
(heh-puh-TIE-tis C) is an inflammation of the liver caused by an infection with the hepatitis C virus.
hepatocellular
(hep-a-to-SEL-ular) refers to the cells of the liver.
herbicide
(erb-IH-side) is a substance that is toxic or poisonous to plants. Herbicides are sold commercially to destroy unwanted plants and vegetation.
hernias
(HER-nee-ah) are protrusions of organs through connective tissue or cavity walls.
heroin
is a narcotic, an addictive painkiller that produces a high, or a euphoric effect. Euphoria (yoo-FOR-ee-a) is an abnormal, exaggerated feeling of well-being.
herpes
(HER-peez) is a viral infection that can produce painful recurring skin blisters around the mouth or the genitals, and sometimes symptoms of infection elsewhere in the body.
herpes simplex
(HER-peez SIMplex) is a virus that can cause infections of the skin, mouth, genitals, and other parts of the body.
herpesvirus family
(her-peez-VY-rus) is a group of viruses that can store themselves permanently in the body. The family includes varicella zoster virus, Epstein-Barr virus, and herpes simplex virus.
heterosexual
(he-te-ro-SEKshoo-al) refers to a tendency to be sexually attracted to the opposite sex.
high blood pressure
is a condition in which the pressure of the blood in the arteries is above normal. Also called hypertension.
histamine
(HIS-tuh-meen) is a substance released by the body during inflammation. It causes blood vessels to expand and makes it easier for fluid and other substances to pass through vessel walls.
HIV
(or human immunodeficiency virus [HY-OO-mun ih-myoo-no-dih-FIH-shen-see]) is the virus that causes AIDS (acquired immunodeficiency syndrome).
hives
are swollen, itchy patches on the skin.
homophobia
is prejudice against or dislike of homosexuals.
hormone
is a chemical substance that is produced by a gland and sent into the bloodstream carrying messages that have certain effects on other parts of the body.
host
is an organism that provides another organism (such as a parasite or virus) with a place to live and grow.
HTLV-1
short for human T-cell lymphotropic virus type 1, is a virus that is associated with certain kinds of adult leukemia and lymphoma.
human immunodeficiency virus
(HYOO-mun ih-myoo-no-dih-FIH-shen-see), or HIV, is the virus that causes AIDS (acquired immunodeficiency syndrome), an infection that severely weakens the immune system.
human papillomavirus
(HPV) is a sexually transmitted disease that affects both men and women. HPV often goes away without causing any damage, but it can lead to medical issues such as genital warts or cancer.
Huntington disease
is a genetic condition that leads to involuntary twitching or jerking of the muscles in the face, arms, and legs, along with a gradual loss of mental abilities.
hydrocephalus
(HY-droe-SEF-uh-lus) is a condition, sometimes present at birth, in which there is an abnormal buildup of fluid within the skull, leading to enlargement of the skull and pressure on the brain.
hydrocephaly
(hi-dro-SEH-fah-lee) means having an abnormally large amount of cerebrospinal fluid in the brain, resulting in an enlarged skull and brain atrophy.
hydroxyurea
is a drug that was originally used to treat certain cancers by interfering with cancer cell growth. It is used to treat some hemoglobinopathies and works by decreasing the amount of HbS and increasing the amount of fetal hemoglobin the body produces.
hypersensitivity
is being excessively sensitive or abnormally susceptible physically to a specific agent such as a drug.
hypertension
(HI-per-ten-chen) is abnormally high arterial blood pressure
hyperthyroidism
(HI-per-THY-royd-ih-zum) is excessive activity of the thyroid gland, characterized by an enlarged thyroid gland, increased metabolic rate, rapid heartbeat, and high blood pressure.
hypnosis
refers to a trancelike state, usually induced by another person. The person under hypnosis may recall forgotten or suppressed memories and may be unusually responsive to suggestions.
hypoglycemia
(hi-po-gly-SEE-mee-uh) is a condition that occurs when the amount of glucose, or sugar, in the blood becomes too low. Symptoms can include dizziness, trembling, sweating, and confusion.
hypogonadism
(HI-poh-go-NAD-ih-zum) is dysfunction of the male gonads with impaired production of hormones and germ cells.
hypomania
(hy-po-MAIN-e-uh) is a manic episode that is less severe than typical, and only lasts about four days.
hypothalamus
(hy-po-THAL-uh-mus) is a structure located deep within the brain that regulates automatic body functions such as heart rate, blood pressure, temperature, respiration, and the release of hormones.
hypothyroidism
(hi-po-THY-royd-ih-zum) is an impairment of the functioning of the thyroid gland that causes too little thyroid hormone to be produced by the body. Symptoms of hypothyroidism can include tiredness, paleness, dry skin, and in children, delayed growth and mental and sexual development.
hypoxia
(hip-AK-see-ah) is a condition that occurs when insufficient oxygen reaches the tissues of the body.
hysterectomy
(his-ter-RECK-toe-me) is a surgical way to remove the uterus and sometimes the cervix.
ibuprofen
(eye-bew-PRO-fin) is a nonsteroidal anti-inflammatory drug (NISAD) used to reduce fever and relieve pain or inflammation.
identical twins
are twins produced when a single egg from the mother is fertilized and divides to form two separate embryos of the same sex with nearly identical DNA.
idiopathic
(id-e-o-PA-thik) means arising from an unknown cause.
imaging
uses magnetic waves, instead of x-rays, to scan the body and produce detailed pictures of the body's structures.
immune
(ih-MYOON) means resistant to or not susceptible to a disease.
immune disorder
(ih-MYOON) is a disorder of the immune system, the system of the body composed of specialized cells and the substances they produce that help protect the body against disease-causing germs.
immune globulin
(ih-MYOON GLAH-byoo-lin), also called gamma globulin, is the protein material that contains antibodies.
immune system
(im-YOON SIS-tem) is the system in the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
immunization
(ih-MYOON-ih-za-shun), also called vaccination, is giving a preparation of killed or weakened germs, or a part of a germ or product it produces, to prevent or lessen the severity of the disease caused by that germ. It is usually given by an injection.
immunosuppressants
(im-yoo-no-suh-PRES-ants) are substances that weaken the body's immune system.
impetigo
(im-pih-TEE-go) is a bacterial skin infection that usually occurs around the nose and mouth. It causes itching and fluid-filled blisters that often burst and form yellowish crusts.
impotence
(IMM-po-tense) is a condition in which a male cannot achieve or sustain an erection.
impulsive
means acting quickly before thinking about the effect of a certain action or behavior.
impulsivity
is behavior in which people do not think through consequences before acting.
in vitro
(in-VEE-tro) means in the laboratory or other artificial environment rather than in the living body, which is referred to as in vivo.
inborn
means present from birth or inherited.
incidence
means rate of occurrence.
incontinence
(in-KON-ti-nens) is loss of control of urination or bowel movement.
incubation
(ing-kyoo-BAY-shun) is the period of time between infection by a germ and when symptoms first appear. Depending on the germ, this period can be from hours to months.
infarction
(in-FARK-shen) is the obstruction of the blood supply to an organ or area of tissue resulting in death of the tissue.
infection
(in-FEK-shun) is the invasion and proliferation of microorganisms in the body, including bacteria, viruses, or parasites.
infertility
(in-fer-TIH-lih-tee) is the inability of females to become pregnant or of males to cause pregnancy.
inflammation
(in-fla-MAY-shun) is the body's reaction to irritation, infection, or injury and often involves swelling, pain, redness, and warmth.
inflammatory bowel disease
describes conditions with chronic or recurring inflammation of the gastrointestinal tract.
influenza
(in-floo-EN-zuh), also known as the flu, is a contagious viral infection that attacks the respiratory tract, including the nose, throat, and lungs.
influenza A
(in-floo-EN-zuh A) is one member of a family of viruses that attacks the respiratory tract.
inhalants
(in-HAY-lunts) are substances that a person can sniff, or inhale, to get high.
insecticides
are chemicals used to kill insects and prevent infestation.
insomnia
is an abnormal inability to get adequate sleep.
insulin
is a hormone produced by beta cells in the pancreas. It is crucial in controlling the level of glucose (sugar) in the blood and in helping the body use glucose to produce energy.
intellectual disability
is a condition in which people have below average intelligence that limits their ability to function normally.
interdisciplinary approach
is when a coordinated group of experts from different specialties or fields work together in a team approach toward a common goal for patient care.
intestines
are the muscular tubes that food passes through during digestion after it exits the stomach.
intolerance
is lacking an ability to endure exposure to some environmental feature, such as sunlight, or an exceptional sensitivity, for example to milk, so that the food cannot be properly metabolized, as in glucose intolerance.
intraocular pressure
(in-tra-AWK-q-lar) is the fluid pressure inside the eye and is an important aspect in the evaluation of patients at risk from glaucoma.
intravenous
(in-tra-VEE-nus) or IV means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.
intravenous fluids
(in-tra-VEE-nus) are fluids injected directly into a vein.
intravenously
(in-tra-VEE-nus-lee) means given or injected directly through a vein.
intubation
(in-too-BAY-shun) is the insertion of a tube into the windpipe to allow air and gases to flow into and out of the lungs in a person who needs help breathing.
ions
are positively or negatively charged elements or compounds, such as hydrogen, sodium, potassium, and phosphate, which are necessary for cellular metabolism.
ischemia
(is-KEY-me-a) is the loss of oxygen and nutrients when there is inadequate blood flow to an organ or tissue.
ischemic
(is-KEE-mik) refers to an area or organ of the body that is lacking in adequate blood flow, often due to a tightening of or obstruction in blood vessels.
ischemic strokes
(is-KEE-mik) are events that occur when a blood vessel bringing oxygen and nutrients to the brain becomes clogged by a blood clot or other particle. As a result, nerve cells in the affected area of the brain cannot function properly.
isotope
(ICE-oh-tope) refers to a variety of a particular atom or chemical that contains an unstable combination of atomic particles.
jaundice
(JON-dis) is a yellowing of the skin, and sometimes the whites of the eyes, caused by a buildup in the body of bilirubin, a chemical produced in and released by the liver. An increase in bilirubin may indicate disease of the liver or certain blood disorders.
joint
is the structure where two or more bones come together, allowing flexibility and motion of the skeleton.
juvenile rheumatoid arthritis
is a joint disease in children with symptoms of high fever, rash, swollen lymph glands, enlarged spleen and liver, and inflammation around the heart and of the lungs. Arthritis in the joints appears later. This disease is also known as systemic-onset chronic arthritis or Still's disease.
Kawasaki disease
is an inflammatory illness in children that involves the body's blood vessels. The disease is characterized by high fever, swollen glands, and a rash, and it may lead to complications affecting the heart.
kidney
is one of the pair of organs that filter blood and remove waste products and excess water from the body in the form of urine.
kidney stone
is a hard structure that forms in the urinary tract. This structure is composed of crystallized chemicals that have separated from the urine. It can obstruct the flow of urine and cause tissue damage and pain as the body attempts to pass the stone through the urinary tract and out of the body.
kuru
(KUR-ew) is a progressive, fatal brain disease characterized by tremors and loss of muscle coordination. It is caused by eating contaminated brain tissue from other humans who had the disease.
Kwashiorkor
(kwash-ee-OR-kor) is a type of malnutrition caused by lack of protein in the diet.
lactic acid
is a compound primarily produced by muscle tissue and red blood cells as carbohydrates are metabolized when oxygen levels are low; it is a potential result of anaerobic metabolism.
laparoscope
(LAP-a-ro-skope) is a fiberoptic instrument inserted into an incision in the abdominal wall to perform a visual examination.
laparoscopy
(lap-uh-ROS-kuh-pee) is a type of surgery in which a small fiberoptic instrument is inserted through a very small incision to examine the inside of the abdomen or remove small amounts of tissue. Also called minimally invasive surgery.
larvae
(LAR-vee) are the immature forms of an insect or worm that hatch from eggs.
laryngitis
(lair-in-JY-tis) is an inflammation of the vocal cords that causes hoarseness or a temporary loss of voice.
larynx
(LAIR-inks) is the voice box (which contains the vocal cords) and is located between the base of the tongue and the top of the windpipe.
laser surgery
is a type of surgery that uses a very narrow and intense beam of light to cut or destroy body tissue.
latent
infections are dormant or hidden infections that do not show the signs and symptoms of active diseases.
lateral
(LAT-er-al) means the side of something.
latex
(LAY-tex) is a substance made from a rubber tree and is used in such items as medical equipment (especially gloves), toys, and other household products.
lesbian, gay, bisexual, and transgender
(LGBT) are women who are sexually attracted to other women, men who are attracted to other men, people who are attracted to both the same and opposite sexes, and people who do not identify with the gender assigned to them at birth or with strictly male-female gender assignments.
lesion
(LEE-zhun) is a general term referring to a sore or a damaged or irregular area of tissue
lethargy
(LETH-are-gee) is severe tiredness, sleepiness, drowsiness, or mental dullness.
leukemia
(loo-KEE-me-uh) is a form of cancer characterized by the body's uncontrolled production of abnormal white blood cells.
level of consciousness
is the state of wakefulness or alertness of an individual.
ligament
(LIG-a-ment) is a fibrous band oftissue that connects bones orcartilages(CAR-ti-lij-ez), serving to support or strengthen joints.
liposuction
is the removal of localized fat deposits by suction through a small tube, usually for cosmetic purposes.
listeriosis
(lis-teer-e-O-sis) is a bacterial infection that can cause a form of meningitis in infants, and produces other symptoms in children and adults.
liver
is a large organ located beneath the ribs on the right side of the body. The liver performs numerous digestive and chemical functions essential for health.
local anesthesia
(an-es-THEE-zha) means using medicine to block or numb pain in one part of the body while the patient remains awake. General anesthesia blocks pain over the entire body while the patient sleeps.
longitudinal research study
is a research method in which data are gathered for the same subjects repeatedly over a period of time.
low birth weight
means born weighing less than normal. In humans, it refers to a full-term (pregnancy lasting 37 weeks or longer) baby weighing less than 5 pounds.
LSD
short for lysergic acid diethylamide (ly-SER-jik A-sid dy-e-thel-AM-eyed), is a hallucinogen, a drug that distorts a person's view of reality and causes hallucinations.
lupus
(LOO-pus), or systemic lupus erythe-matosus, is a chronic, or long-lasting, disease that causes inflammation of connective t issue, the material that holds together the various structures of the body.
Lyme disease
(LIME) is a bacterial infection that is spread to humans by the bite of an infected tick. It begins with a distinctive rash and/or flu-like symptoms and, in some cases, can progress to a more serious disease with complications affecting other body organs.
lymph nodes
(LIMF nodz) are small bean-shaped masses of tissue containing i mmune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
lymphadenitis
(lim-fah-den-EYE-tis) is inflammation of the lymph nodes and channels of the lymphatic system.
lymphangitis
(lim-fan-JIE-tis) is inflammation of the lymphatic system, the system that carries lymph through the body. Lymph is a clear fluid that contains white blood cells.
lymphatic
(lim-FAH-tik) means relating to the system of vessels and other structures that carry lymph, a colorless fluid, throughout the body's tissues; the lymphatic system plays an important role in protecting the body from infections.
lymphatic system
(lim-FAH-tik) is a system that contains lymph nodes and a network of channels that carry fluid and cells of the immune system through the body.
lymphatic tissue
is tissue where white blood cells fight invading germs.
lymphocytes
(LIM-fo-sites) are white blood cells, which play a part in the body's immune system, particularly the production of antibodies and other substances to fight infection.
lymphoma
(lim-FO-muh) is a cancerous tumor of the lymphocytes, cells that normally help the body fight infection
macrocephaly
(ma-kro-SEH-fah-lee) means having an abnormally large head.
macula
(mack-u-k) is a small oval-shaped area on the retina that contains the fovea centralis, which is responsible for central vision.
magnetic resonance imaging
(MRI) uses magnetic waves, instead of x-rays, to scan the body and produce detailed pictures of the body's structures.
malaise
(muh-LAZE) is a general feeling of tiredness, discomfort, illness, or uneasiness that cannot be explained.
malaria
(mah-LAIR-e-uh) is a disease spread to humans by the bite of an infected mosquito.
malformation
(mal-for-MAY-shun) is an abnormal formation of a body part.
malignant
(ma-LIG-nant) refers to a condition that is severe and progressively worsening.
malingering
(ma-LING-er-ing) means intentionally pretending to be sick or injured to avoid work or responsibility.
mammals
are warm-blooded animals with backbones, who usually have fur or hair. Female mammals secrete milk from mammary glands to feed their young. Humans are mammals.
mammograms
are breast x-rays for detecting cancer.
Marfan syndrome
involves the body's connective tissue and is characterized by abnormalities in the skeleton, heart, and eyes. It is caused by an abnormal gene that usually is inherited. People with Marfan syndrome are generally taller than average, have little body fat, and have long, thin fingers.
marijuana
(mar-a-WA-na) is a mixture of dried, shredded flowers and leaves from the hemp plant that a person can smoke or eat to get high.
mastectomy
(ma-STEK-tah-mee) is the surgical removal of part or all of a breast and sometimes associated lymph nodes and muscles.
mastoiditis
(mas-toyd-EYE-tis) is an infection of the mastoid bone, located behind the ear.
measles
(ME-zuls) is a viral respiratory infection that is best known for the rash of large, flat, red blotches that appear on the arms, face, neck, and body.
mechanical ventilation
is the process by which a machine, called a ventilator, is connected to a patient who is unable to breathe naturally, in order to support normal functioning of the respiratory system.
medial
(MEE-dee-al) means located near the middle or midline.
meibomian gland
is a gland located on the inner rim of the eyelid. The meibomian glands secrete oil that prevents evaporation of tears on the eye. Also called tarsal glands.
meiosis
(my-OH-sis) is the process of reduction division in which the number of chromosomes per cell is cut in half.
membrane
(MEM-brain) is a thin layer of tissue that covers a surface, lines a cavity, or divides a space or organ.
meninges
(meh-NIN-jeez) are the membranes that cover and protect the brain and the spinal cord.
meningitis
(meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.
menisci
(men-IS-key) is the fibrocartilage-like tissue found in some joints. The singular form is meniscus (men-IS-kus).
menopause
(MEN-o-pawz) is the natural decline of reproductive hormones and the end of menstruation. It generally occurs in women during their 40s and 50s.
menstrual
(MEN-stroo-al) refers to menstruation (men-stroo-AY-shun), the discharging through the vagina of blood and tissue from the uterus that recurs each month in women of reproductive age.
menstrual cycle
(MEN-stroo-al SY-kul) culminates in menstruation (men-stroo-AY-shun), the discharging through the vagina of blood, secretions, and tissue debris from the uterus that recurs at approximately monthly intervals in females of reproductive age.
menstruation
(men-stroo-AY-shun) is the discharge of the blood-enriched lining of the uterus. Menstruation normally occurs in females who are physically mature enough to bear children. Menstruation ceases during pregnancy and with the onset of menopause.
mental disorder
is a range of conditions that affect a person's thinking, feeling, or mood, including depression, bipolar disorder, personality disorders, and anxiety disorders.
mental retardation
is a condition in which people have below average intelligence that limits their ability to function normally.
mesothelium
(me-zo-THEE-le-um) is epithelium derived from embryonic mesoderm that lines the body cavities.
metabolic
(meh-tuh-BALL-ik) pertains to the process in the body (metabolism) that converts food into energy and waste products.
metabolism
(meh-TAB-o-liz-um) is the process in the body that converts food into the energy necessary for body functions.
metabolize
refers to the processes within the body that are involved in converting food into energy and waste products.
metastases
(me-TAS-ta-seez) are new tumors formed when cancer cells from a tumor spread to other parts of the body.
metastatic
(MET-uh-STAT-ic) refers to a cancer that has spread from the part of the body where it first started to other organs or parts of the body.
microbes
(MY-krobes) are microscopic living organisms, such as bacteria, viruses, and fungi.
microcephaly
(my-kro-SEH-fah-lee) is the condition of having an abnormally small head, which typically results from having an underdeveloped or malformed brain.
micronutrients
(MY-kro-noo-tree-ents) are chemical elements or substances, such as vitamins or minerals, that are required in small amounts for normal growth and development.
migraine
(MY-grain) is a type of headache characterized by a throbbing or pulsating sensation, affecting one side of the head, and often accompanied by nausea and disturbed vision.
miscarriage
(MIS-kare-ij) is the end of a pregnancy through the death of the embryo or fetus before birth.
mitochondrial disease
(mi-toe-KON-dree-al) is a rare genetic disorder that is caused by abnormalities in the mitochondria, the tiny organelles inside body cells that provide energy for the cells.
mittelschmerz
(MITT-el-shmairts) is cramping pain that some women experience at the midpoint in their menstrual cycle when one of their ovaries releases an egg.
molecular
(mo-LECK-you-ler) testing is a way to study tumor cells in a laboratory to look for patterns in the cells' DNA. It can help diagnose tumors and help doctors better plan treatment.
mononucleosis
(mah-no-nu-klee-O-sis) is an infectious illness caused by a virus with symptoms that typically include fever, sore throat, swollen glands, and tiredness.
monozygotic
(mah-no-zye-GOT-ik) means derived from a single fertilized egg.
mood disorder
is a mental disorder that involves a disturbance in the person's internal emotional state. Depressive disorders, bipolar disorders, and mood disorders are associated with the use of drugs or medical illnesses.
morphine
(MOR-feen) is a narcotic, an addictive painkiller that produces a high.
motor
relates to body movement.
motor skills
are muscular movements or actions.
motor vehicle
is any vehicle that has a motor including cars, trucks, motorcycles, motorized bicycles, and scooters.
MRI
(short for magnetic resonance imaging) produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.
mucosa
(mu-KOH-sa) is the moist tissue that lines some organs and body cavities. It makes mucus, which is a thick, slippery fluid.
mucous membranes
are the thin layers of tissue found inside the nose, ears, cervix (SER-viks) and uterus, stomach, colon and rectum, on the vocal cords, and in other parts of the body.
mucus
(MYOO-kus) is a thick slippery substance that lines the interior of many body parts.
multiple sclerosis
(skluh-RO-sis), or MS, is an inflammatory disease of the nervous system that disrupts communication between the brain and other parts of the body. MS can result in paralysis, loss of vision, and other symptoms.
mumps
is a contagious viral infection that causes inflammation and swelling in the glands of the mouth that produce saliva.
Munchausen syndrome
(MUN-chow-zen SIN-drome) is a mental disorder in which a person pretends to have symptoms or causes symptoms of a disease in order to be hospitalized or receive tests, medication, or surgery.
muscle atrophy
is a decrease in muscle mass usually related to not using the muscle group or groups; also called muscle wasting.
muscular dystrophy
(DIS-tro-fee) is a group of inherited disorders that causes muscle weakening that worsens over time.
mycobacteria
(my-ko-bak-TEER-e-uh) belong to a family of bacteria called fungus bacteria because they are found in wet environments.
myocarditis
(my-oh-kar-DYE-tis) is an inflammation of the muscular walls of the heart.
myopathy
(MI-ah-path-ee) is any disorder that causes muscle weakening, often accompanied by muscle spasms or cramps.
myositis
(my-oh-SY-tis) is an inflammation of the muscles.
narcotic
(nar-KO-tik) is a drug that depresses the central nervous system, causing stupor or sleep.
nasal
(NA-zal) means of or related to the nose.
nasal polyps
(NA-zal POL-ips) are growths that occur inside the air passages of the nose. They are usually soft and painless.
nasal spray
(NA-zal) is a mist that is sprayed into the nose.
nasopharyngeal
(nay-zo-fair-in-JEE-ul) refers to the nose and pharynx (FAIR-inks), or throat.
nausea
(NAW-zha) refers to a feeling of being sick to one's stomach or needing to vomit.
Neglected Tropical Diseases (NTDs)
are a group of parasitic and bacterial diseases that cause substantial illness globally. They affect the world's poorest populations and impair physical and cognitive development, contribute to illness and death, make it difficult to farm or earn a living, and limit productivity in the workplace.
nematode
(NEE-muh-tode)is a parasitic roundworm that infects humans.
neonatal
(ne-o-NAY-tal) means pertaining to the first four weeks after birth.
nervous system
is a network of specialized tissue made of nerve cells, or neurons, that processes messages to and from different parts of the human body.
neuritis
(nuh-RYE-tis) is an inflammation of the nerves that disrupts their function.
neurologic
(new-ro-LOJ-ik) pertaining to the nervous system.
neurological
(nur-a-LAH-je-kal) refers to the nervous system, which includes the brain, spinal cord, and the nerves that control the senses, movement, and organ functions throughout the body.
neurological exam
(nur-a-LAH-je-kal) is a test of how well various parts of the nervous system are functioning.
neurologist
(new-RHAL-eh-jist) is a physician who specializes in diagnosing and treating diseases of the nervous system.
neuromuscular junction
(NUR-O-musk-u-lar JUNK-shun) is a synapse or meeting place between a motor neuron or nerve fiber and the skeletal muscle it controls.
neuromuscular system
(NUR-O-musk-u-lar SIS-tem) is the system made up of the muscles of the body and the nerves that supply and control them.
neurons
are nerve cells. Most neurons have extensions called axons and dendrites through which they send and receive signals from other neurons.
neuroscientists
are scientists who study the nerves and nervous system, especially their relationship to learning and behavior.
nodule
(nod-yule) is a small rounded lump or swelling.
nonsteroidal anti-inflammatory drugs
(NSAIDs) are over-the-counter and prescription medications, such as naproxen sodium and ibuprofen, for reducing pain and inflammation.
norepinephrine
(NOR-e-pi-ne-frin) is a body chemical that can increase the arousal response, heart rate, and blood pressure.
nucleus
is the part of the cell that contains its genetic information.
nurse midwife
is a nurse with specialized knowledge and experience in the care of pregnant women before, during, and after delivering a baby.
nutrients
are the components of food (protein, carbohydrate, fat, vitamins, and minerals) needed for growth and maintenance of the body.
nutritionist
is a person who has specialized knowledge and experience in nutrition. A nutritionist may also be called a dietitian.
nystagmus
(nis-TAG-mus) are rapid, involuntary movements of the eyes.
obese
(o-BEESE) refers to an excess of body fat. People are considered obese if they weigh more than 30 percent above what is healthy for their height.
obesity
(o-BEE-si-tee) is an excess of body fat. People are considered obese if they weigh more than 30 percent above what is healthy for their height.
obsessions
(ob-SESH-unz) are repeated disturbing thoughts or urges that a person cannot ignore and that will not go away.
obsessive-compulsive disorder
(OCD) is a condition that causes people to become trapped in a pattern of repeated, unwanted thoughts, called obsessions (ob-SESH-unz), and a pattern of repetitive behaviors, called compulsions (kom-PUL-shunz).
occupational therapist
is a health professional who has specialized knowledge and experience in assisting people to perform normal activities of daily living and working (occupation).
omnivorous
(om-NIH-vor-us) refers to an animal which eats animals and plants.
oncotic pressure
is the pressure difference of blood plasma and tissue fluid.
ophthalmologic
(off-thal-MOLL-o-jik) means related to the function, structure, and diseases of the eye.
ophthalmologist
(off-thal-MOLL-o-jist) is a medical doctor who specializes in treating diseases of the eye.
ophthalmoscope
(off-thal-ma-skope) is an instrument used to examine the inside of the eye visually.
opiates
(O-pea-aytz) are painkilling chemicals that can cause sleepiness and loss of sensation.
opioid
(O-pee-oyd) is a synthetic narcotic used to treat pain, such as morphine, codeine, or oxycodone.
opportunistic infections
are infections caused by infectious agents that usually do not produce disease in people with healthy immune systems but can cause widespread and severe illness in patients with weak or faulty immune systems.
optic nerve
is the nerve that sends messages, or conducts impulses, from the eyes to the brain, making it possible to see. The optic nerve is also referred to as the second cranial nerve.
oral
means by mouth or referring to the mouth.
orthotic
refers to a support or brace for weak or ineffective joints or muscles.
osteoarthritis
(os-tee-o-ar-THRY-tis) is a common disease that involves inflammation and pain in the joints (places where bones meet), especially those in the knees, hips, and lower back of older people.
osteomyelitis
(ah-stee-o-my-uh-LYE-tis) is a bone infection that is usually caused by bacteria. It can involve any bone in the body, but it most commonly affects the long bones in the arms and legs.
osteoporosis
(os-tee-o-por-O-sis) is the loss of bone mass that makes the bones weak and brittle.
otitis externa
is an infection in the outer ear.
otitis media
is an infection in the middle ear.
otolaryngologist
(OH-to-LAH-rin-GOL-o-jist) is a doctor who has specialized knowledge of and experience in treating people with diseases of the ears.
otoscope
is an instrument typically designed with a light and a set of lenses for visual examination of the eardrum and the passage of the outer ear.
outpatient
is a medical procedure that is conducted in a doctor's office or hospital but does not require an overnight stay in a hospital bed.
ovaries
(O-vuh-reez) are the sexual glands from which ova, or eggs, are released in women.
over-the-counter medications
are medications or treatments that can be purchased without a doctor's prescription or order.
ovulation
(ov-yoo-LAY-shun) is the release of a mature egg from the ovary.
oxygen
(OK-si-jen) is an odorless, colorless gas essential for the human body. It is taken in through the lungs and delivered to the body by the bloodstream.
oxygenated blood
is blood carrying oxygen for circulation throughout the body.
pacemaker
is a device whose function is to send electrical signals that control the heartbeat.
palate
(PAL-it) is the structure at the roof of the mouth. Damage or poor functioning of the palate can affect swallowing, the voice, and breathing.
palliative
(PAL-ee-at-iv) means to ease or relieve the symptoms of a disease without curing it.
palpation
(pal-PAY-shun) is the examination by touching and feeling the body for indicators of disease or injury.
palpitation
is the sensation of a rapid or irregular heartbeat.
pancreas
(PAN-kree-us) is a gland located behind the stomach that produces enzymes and hormones necessary for digestion and metabolism.
pandemic
(pan-DEH-mik) is a worldwide outbreak of disease, especially infectious disease, in which the number of cases suddenly becomes far greater than usual.
Pap smear
is a common diagnostic test used to look for cancerous cells in the tissue of the cervix.
parainfluenza
(pair-uh-in-floo-EN-zuh) is a family of viruses that cause respiratory infections.
paralysis
(pah-RAHL-uh-sis) is the loss or impairment of the ability to move some part of the body.
paranoia
(pair-a-NOY-a) refers to either an unreasonable fear of harm by others (delusions of persecution) or an unrealistic sense of self-importance (delusions of grandeur).
parasite
(PAIR-uh-site) is an organism such as a protozoan (one-celled animals), worm, or insect that must live on or inside a human or other organism to survive. An animal or plant harboring a parasite is called its host. A parasite lives at the expense of the host and may cause illness.
parasitic
(pair-uh-SIH-tik) refers to organisms such as protozoa (one-celled animals), worms, or insects that can invade and live on or inside human beings and may cause illness. An animal or plant harboring a parasite is called its host.
Parkinson's disease
is a disorder of the nervous system that causes shaking, rigid muscles, slow movements, and poor balance.
parotid gland
(puh-RAH-tid) is the salivary gland located in the jaw just beneath and in front of each ear.
pasteurize
(PAS-cha-rise) is to sterilize a substance, generally a liquid like milk, by bringing it to high temperature and keeping it at that temperature long enough to destroy disease organisms in it without changing its other characteristics
pathogenic
means capable of causing disease.
pathogens
(PAH-tho-jens) are microorganisms that can cause disease in another living organism.
PCP
short for phencyclidine (fen-SY-kle-deen), is a hallucinogen, a drug that distorts a person's view of reality.
peak flow meter
is a hand-held device that allows an individual to determine volume of air flow through the lungs.
pellagra
is a disease caused by the lack of the vitamin niacin (B3) or tryptophan (an amino acid).
pelvic exam
is an internal examination of a woman's reproductive organs.
pelvic inflammatory disease
is an infection of a woman's internal reproductive organs, including the fallopian tubes, uterus, cervix, and ovaries.
penile
(PEE-nile) refers to the penis, the external male sexual organ.
penis
(PEE-nis) refers to the male genital organ that carries the duct for the transfer of sperm during sexual intercourse and for eliminating urine. It consists largely of erectile tissue.
perianal disease
affects the regions around the anus.
pericarditis
(per-ih-kar-DYE-tis) is an inflammation of the sac surrounding the heart.
perinatal
(per-ee-NAY-tal) means existing or occurring around the time of birth, with reference to the fetus.
perishable
means able to spoil or decay, as in perishable foods.
peritonitis
(per-ih-to-NI-tis) is an inflammation of the peritoneum, the membrane that lines the abdominal cavity.
personality disorders
are a group of mental disorders characterized by long-term patterns of behavior that differ from those expected by society. People with personality disorders have patterns of emotional response, impulse control, and perception that differ from those of most people.
pertussis
(per-TUH-sis), or whooping cough, is a bacterial infection of the respiratory tract that causes severe coughing.
pesticide
(PEST-ih-side) is a substance used to kill insects or other organisms harmful to plants or animals.
pet dander
refers to microscopic parts of the pet's skin that flake off and get into the air people breathe.
pH
a logarithmic scale, from 1 to 14, used to describe the acidity or alkalinity of a solution or fluid. A pH level of less than 7 indicates an acidic solution while a pH greater than 7 indicates an alkaline solution.
phagocytes
(FAG-oh-sites) are cells that protect the body by ingesting and destroying bacteria and harmful foreign particles.
pharyngitis
(far-in-JI-tis) is inflammation of the pharynx, part of the throat.
phenylketonuria
(FEN-ul-ke-ton-U-ree-a), or PKU, is a genetic disorder of body chemistry that, if left untreated, causes intellectual disability.
phlebitis
(fle-BY-tis) refers to inflammation of a vein.
phobia
(FO-bee-a) is an intense, persistent, unreasonable fear of (and avoidance of) a particular thing or situation.
phonemes
(FO-neemz) are the smallest units of spoken language, such as the “puh201D; sound at the start of the word pat.
photosensitive
means responsive to light.
physical therapist
is a health professional who has specialized knowledge and experience in assisting people to reduce pain and improve or restore mobility.
physical therapy
is a healthcare profession responsible for assisting people with impairment or limitation of movement. Physical therapists design treatment and exercise programs to decrease pain, strengthen muscles, improve lexibility, and increase physical endurance.
physiologic
(fiz-ee-o-LOJ-ik) refers to an organism's healthy and normal functioning.
pigment
(PIG-ment) is a substance that imparts color to another substance.
pink eye
(also called conjunctivitis) is an inflammation of the thin membrane that lines the inside of the eyelids and covers the surface of the eyeball.
pituitary gland
(pih-TOO-ih-tare-e gland) is the small oval-shaped gland at the base of the skull that produces several hormones that affect various body functions.
placebo
(plah-SEE-bow) is an inactive medicine or procedure that provides relief despite having no physiological effect.
placenta
(pluh-SEN-ta) is an organ that provides nutrients and oxygen to a developing baby; it is located within the womb during pregnancy.
plastic surgery
is the surgical repair, restoration, or improvement in the shape and appearance of body parts.
platelets
(PLATE-lets) are tiny disk-shaped particles within the blood that play an important role in clotting.
pneumococcal bacteria
is a class of bacteria that can cause infection resulting in pneumonia, infection of the blood (bacteremia/sepsis), middle-ear infection (otitis media), or bacterial meningitis.
pneumonia
(nu-MO-nyah) is inflammation of the lungs.
poliomyelitis
(po-lee-o-my-uh-LYE-tis) is a condition caused by the polio virus that involves damage of nerve cells. It may lead to weakness and deterioration of the muscles and sometimes paralysis.
polyneuropathy
is degeneration (pathy) of-many (poly) peripheral nerves (neuro) throughout the body at the same time.
polyp
(POH-lip) is a bump or growth usually on the lining or surface of a body part (such as the nose or intestine). Size can range from tiny to large enough to cause pain or obstruction. They may be harmless or benign, but they also may be cancerous or malignant.
pornography
(por-NAH-gra-fee) refers to any material, such as magazines or videos, that shows sexual behavior and is meant to cause sexual excitement.
positron emission tomography
(POZ-i-tron i-MISH-en toe-MAH-gruh-fee) uses a radiotracer that accumulates in an area of the body and emits gamma rays that are detected as diagnostic images. Also called PET imaging or PET scanning.
post-concussion syndrome
(PCS) is a condition in which signs and symptoms of concussion persist for at least three months following the injury.
post herpetic neuralgia
(post HER-peh-tic nur-al-JAH) is nerve pain due to damage caused by the varicella zoster virus, generally confined to a specific area of the skin following an outbreak of shingles (herpes zoster) in that same area.
post-traumatic stress disorder
(post-traw-MAT-ik STRES dis-OR-der) is a mental disorder that interferes with everyday living and occurs in people who survive a terrifying event, such as school violence, military combat, or a natural disaster.
poverty
the state of being extremely poor, that is, having little or no money, material goods, or means of support. To participate in supplemental assistance programs, the U.S. federal and state governments define poverty based on total household income. This amount is adjusted yearly.
prepubescent
refers to the time in life before a child or adolescent reaches puberty, which is physical sexual maturity, such as development of breasts in girls, and more mature testicles in boys.
preeclampsia
(PREE-eh-CLAMP-see-ah) is a complication of pregnancy characterized by high blood pressure, sometimes with fluid retention; it also indicates signs of damage to another organ, usually the kidneys.
premature birth
(pre-ma-CHUR) means born too early. In humans, it means being born after a pregnancy term lasting less than 37 weeks.
prenatal
(pre-NAY-tal) means existing or occurring before birth, with reference to the fetus.
prevalence
of a disease or condition refers to how common it is in a given population.
prion diseases
(PREE-on) are rare diseases that cause degeneration of the neuromuscular system in humans and animals. Also called transmissible spongiform encephalopathies (TSEs).
progesterone
(pro-JES-teh-ron) is a female steroid sex hormone that prepares for and supports pregnancy.
prognosis
(prog-NOE-sis) a forecast of the probable outcome of an illness, usually including the patient's chances of recovery.
prophylactic
(pro-fih-LAK-tik) refers to something that is used to prevent an illness or other condition, such as an infection or pregnancy.
prophylaxis
(pro-fih-LAK-sis) means taking specific measures like using medication or a device to help prevent infection, illness, or pregnancy.
prostate
(PRAH-state) is a male reproductive gland located near where the bladder joins the urethra. The prostate produces the fluid part of semen.
prostate cancer
(PRAH-state) occurs in the small walnut-shaped gland that produces seminal fluid and transports sperm in men.
prostate disease
(PRAH-state) is any disease of the male reproductive gland located near where the bladder joins the urethra. The prostate produces the fluid part of semen.
prostatitis
(prah-sta-TIE-tis) is inflammation of the prostate gland.
prosthesis
(pros-THEE-sis) is an artificial substitute for a missing body part. It can be used for appearance only or to replace the function of the missing part (as with a prosthetic leg).
proto-oncogene
(pro-toe-AHNK-eh-gene) is a specialized gene that codes for regulating cell growth, stimulating cell division, and controlling cell death.
protozoa
(pro-tuh-ZOH-uh) are single-celled microorganisms (tiny organisms), some of which are capable of causing disease in humans.
psoriasis
(suh-RI-uh-sis) is an autoimmune skin condition marked by the buildup of dried, dead skin cells that form thick scales.
psychiatrist
(sy-KY-uh-trist) is a medical doctor who has completed specialized training in the diagnosis and treatment of mental illness. Psychiatrists can diagnose mental illnesses, provide mental health counseling, and prescribe medications.
psychoactive
(sy-ko-AK-tiv) means affecting a person's mood, behavior, perceptions, or consciousness.
psychoanalysis
(sy-ko-a-NAL-i-sis) is a method of treating a person with psychological problems, based on the theories of Sigmund Freud. It involves sessions in which a therapist encourages a person to talk freely about personal experiences, and the psychoanalyst interprets the patient's ideas and dreams.
psychological
(SI-ko-LOJ-i-kal) refers to mental processes, including thoughts, feelings, and emotions.
psychosis
(sy-KO-sis) refers to mental disorders in which the sense of reality is so impaired that a patient cannot function normally. People with psychotic disorders may experience delusions (exaggerated beliefs that are contrary to fact), hallucinations (something that a person perceives as real but that is not actually caused by an outside event), incoherent speech, and agitated behavior, but they usually are not aware of their altered mental state.
psychotherapies
(sy-ko-THER-a-peas) sometimes called talk therapies, are treatments of mental and behavioral disorders by support and insight to encourage healthy behavior patterns and personal understanding and growth in order to change destructive behaviors.
psychotherapist
(sy-ko-THER-uh-pist) is a mental health professional who works with people to help them change thoughts, actions, or relationships that play a part in their emotional or behavioral problems.
psychotherapy
(sy-ko-THER-a-pea) is the treatment of mental and behavioral disorders by support and insight to encourage healthy behavior patterns and personality growth.
psychotic disorders
(sy-KOT-IK) are mental disorders in which the sense of reality is so impaired that a person cannot function normally. People with psychotic disorders may experience delusions, hallucinations, incoherent speech, and agitated behavior, but they usually are not aware of their altered mental state.
puberty
(PU-ber-tee) is the period during which sexual maturity is attained.
pulmonary
refers to the lungs.
pulmonary diseases
are any abnormal condition of the respiratory system, characterized by cough, chest pain, mucus production, or harsh, vibrating, crackling, or wheezing sounds while breathing.
pulmonary embolism
is a blockage of the pulmonary artery or one of its branches that is frequently caused by thrombosis, or formation of a blood clot, in the lower extremities.
pus
is a thick creamy fluid, usually yellow or ivory in color, that forms at the site of an infection. Pus contains infection-fighting white cells and other substances.
pustule
is a blister-like bump on the skin containing pus, such as a pimple.
quadriceps
(KWAH-dri-seps) are the four-part large extensor muscles of the front of the thigh that join in a single tendon at the knee.
quarantine
is the enforced isolation (for a fixed period) of apparently healthy people or animals who may have been exposed to infectious disease.
rabies
(RAY-beez) is a viral infection of the central nervous system that is usually transmitted to humans by the bite of an infected animal.
radiation
is energy that is transmitted in the form of rays, waves, or particles. Only high-energy radiation, such as that found in x-rays and the sun's ultraviolet rays, has been proven to cause human cancer.
radiation therapy
is a treatment that uses high-energy radiation from x-rays and other sources to kill cancer cells and shrink cancerous growths.
radionuclide scans
(ray-dee-o-NU-klide) are tests that begin by giving a patient a small amount of a radioactive substance. The radioactive substance shows up on a scan, producing a view of the structure or function of the part of the body being studied.
rashes
are spotted, pink or red skin eruptions that may itch and are characteristic of dermatitis.
Raynaud's disease
(ray-NOZE) is a condition in which discoloration of the skin typically on the fingers and/or toes occurs when individuals experience changes in temperature or emotional events. An abnormal spasm of blood vessels causes the reduced supply of blood to the affected areas of the body.
reaction speed
is the time it takes to respond to a stimulus.
reaction time
is the time it takes a muscle or some other living tissue to respond to a stimulus.
receptors
are cell structures that form a chemical bond with specific substances, such as neurotransmitters.
recessive
describes a gene that is not dominant. A second identical recessive gene must be present for the associated trait to show in an individual. When a recessive gene is paired with a normal one, the individual is said to be a carrier of the trait.
rectum
is the final portion of the large intestine, connecting the colon to the outside opening of the anus
regurgitation
is the sensation of food or acid backing up into the throat or mouth. Another definition for regurgitation is vomiting.
rehabilitation
is a program that helps people return to more normal physical, mental, or emotional function following an illness or injury. Rehabilitation also helps people find ways to better cope with conditions that interfere with their lives.
rehabilitative therapy
helps people return to more normal physical, mental, or emotional function following an illness or injury.
remission
is an easing of a disease or its symptoms for a prolonged period.
renal
(REE-nal) refers to the kidneys.
replicate
(REP-luh-kate) means to create an identical copy.
respirator
is a machine that helps people breathe when they are unable to breathe adequately on their own.
respiratory
(RES-pi-ra-tor-ee) refers to the breathing passages and lungs.
respiratory failure
is a condition in which breathing and oxygen delivery to the body are dangerously altered. This failure may result from infection, nerve or muscle damage, poisoning, or other causes.
respiratory syncytial virus
(RES-puh-ruh-tor-e sin-SIH-she-ul), or RSV, is a virus that infects the respiratory tract and typically causes minor symptoms in adults but can lead to more serious respiratory illnesses in children.
respiratory tract
includes the nose, mouth, throat, and lungs. It is the pathway through which air and gases are transported down into the lungs and back out of the body. Also called the respiratory system.
restless legs syndrome
is a neurological disorder characterized by aching, burning, or creeping sensations in the legs and an urge to move the legs during sleep.
retina
(REH-tuh-na) is the tissue that forms the inner surface of the back of the eyeballs. It receives the light that enters the eye and transmits it through the optic nerve to the brain to produce visual images.
retinoic acid
(REH-tin-OH-ik acid) is a compound derived from retinol or vitamin A, often used in ointments to treat acne and other skin conditions.
retrovirus
is a virus in which the genetic information is found in ribonucleic acid (RNA), a nucleic acid that is found in all living cells.
Reye's syndrome
(RYES SIN-drome) is a rare condition that involves inflammation of the liver and brain, and sometimes appears after illnesses such as chickenpox or influenza. It has also been associated with taking aspirin during certain viral infections.
rheumatic fever
(roo-MAH-tik) is a condition associated with fever, joint pain, and inflammation affecting many parts of the body, including the heart. It occurs following infection with certain types of strep bacteria.
rheumatoid arthritis
(ROO-mah-toyd ar-THRY-tis) is a chronic disease characterized by painful swelling, stiffness, and deformity of the joints.
rheumatologist
(roo-ma-TOL-ojist) is a doctor who specializes in disorders involving the connective tissue structures of the body.
rhinitis
(rye-NYE-tis) is the medical term for inflammation of the tissues inside the nose.
rickets
(RICK-ets) is a condition of bones that causes them to soften and bend, creating deformity. In the early twentieth century, rickets was caused by lack of sunlight, and the lack of vitamin D, calcium, and phosphorus. As enriched foods and improved diets became more widespread, rickets practically disappeared in industrialized countries.
rickettsial
infections are caused by microorganisms that are similar to bacteria and viruses. Infectious agents include Rickettsia, Orientia, Ehrlichia, Neorickettsia, Neoehrli-chia, and Anaplasma.
ringworm
is a fungal infection of the skin or scalp that appears as a round, red rash.
risk factors
are any factors that increase the chance of developing a disease.
RNA
is the shortened name for ribonucleic acid (RY-bo-nyoo-KLAY-ik AH-sid), the chemical substance through which DNA sends genetic information to build new cells.
root canal
is a procedure in which a dentist cleans out the pulp of an infected tooth, removes the nerve, and then fills the cavity with a protective substance.
rubella
(roo-BEH-luh) is a viral infection that usually causes a rash and mild fever.
salicylic acid
is a pharmaceutical with antibacterial properties that is used to treat a variety of skin disorders.
salivary glands
(SAL-i-var-ee) are the three pairs of glands that produce the liquid called saliva, which aids in the digestion of food.
sarcoma
(sar-COHM-ah) is one of a group of tumors that occur in connective tissue and are mostly malignant.
scarlet fever
is an infection that causes a sore throat and a rash.
schizophrenia
(skit-so-FREE-nee-ah) is a s erious mental disorder that causes people to experience hallucinations, delusions, and other confusing thoughts and behaviors, which distort their view of reality.
sciatica
(sy-AT-i-ka) is pain along the course of either of the sciatic (sy-AT-ik) nerves, which run through the pelvis and down the backs of the thighs.
scleroderma
is a slowly progressive disease characterized by deposits of fibrous connective tissue in the skin and often the internal organs.
scrapie
(SKRAY-pee) is a fatal brain disorder of sheep characterized by itching of the skin and difficulty walking. It takes its name from the way in which affected animals rub or scrape themselves against a fence or tree.
scrotum
(SKRO-tum) is the pouch on a male body that contains the testicles.
scurvy
is a disease caused by a severe lack of vitamin C.
second-impact syndrome
is characterized by the more severe—potentially fatal—signs and symptoms from a second concussion sustained before the brain has recovered from an initial concussion.
sedatives
(SAID-uh-tivs) are drugs that produce a calming effect or sleepiness.
seizures
(SEE-zhurs), also called convulsions, are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.
selective serotonin reuptake inhibitors
(SSRIs) are a class of antidepressants that work by blocking the reabsorption of serotonin in brain cells, raising the level of the chemical in the brain. SSRIs include Prozac, Zoloft, Luvox, and Paxil.
self-esteem
is the value that people put on the mental image that they have of themselves.
semen
(SEE-men) is the sperm-containing whitish fluid produced by the male reproductive system.
separation anxiety
is a condition diagnosed when children show clinical signs of anxiety, such as unrealistic and repeated concerns about being harmed, when separated from their parent or primary caretaker.
sepsis
is a potentially serious spreading of infection, usually bacterial, through the bloodstream and body.
septic shock
is shock due to overwhelming infection and is characterized by decreased blood pressure, internal bleeding, heart failure, and, in some cases, death.
septicemia
(sep-tuh-SEE-me-uh) is a bacterial infection in the blood that spreads throughout the body, with potentially fatal results.
serotonin
(ser-o-TO-nin) is a neurotransmitter, a substance that helps transmit information from one nerve cell to another in the brain. It is associated with feelings of well-being.
serous
refers to thin watery fluid resembling serum.
sexual partner
is any person who has sexual relations with another, regardless of whether consent has been given, and by any sexual activity including vaginal, rectal, or oral sex. Also called sexual contact.
sexually transmitted infection
is an infection that can be passed from person to person by sexual contact.
shock
is a serious condition in which blood pressure is very low and not enough blood flows to the body's organs and tissues. Untreated shock may result in death.
shunt
is a small tube inserted to move fluid from one area to another
sickle cell anemia
is a hereditary condition in which the red blood cells, which are usually round, take on an abnormal crescent shape and have a decreased ability to carry oxygen throughout the body. Also called sickle cell disease.
side effects
are unwanted symptoms that may be caused by vaccines or medications.
sinuses
(SY-nuh-ses) are hollow, air-filled cavities in the facial bones.
sinusitis
(sy-nyoo-SY-tis) is an infection in the sinuses, which are hollow cavities in the facial bones surrounding the nose.
Sjogren's syndrome
is an autoimmune disorder that affects the glands in the body that make moisture, particularly in the mouth, throat, nose, eyes, and skin.
sleep apnea
is a disorder in which an individual stops breathing and then restarts breathing multiple times, sometimes 30 or more times an hour, during a sleep episode.
small intestine
is the part of the intestines—the system of muscular tubes that food passes through during digestion—that directly receives the food when it passes through the stomach.
social contagion
is a condition that is spread through social interactions or social media.
sociopathic
(sometimes called psychopathic) refers to mental instability or antisocial behavior.
somatic
(soh-MAT-ik) pertaining to or characteristic of the body
sonograms
(SON-o-gramz) are images or records made on a computer using sound waves passing through the body.
spasms
(SPAH-zumz) are involuntary muscular tightening or contractions.
speech therapist
is a health professional who assesses and treats voice, speech, swallowing, and language disorders.
sperm
are the tiny tadpole-like cells males produce in their testicles. Sperm can unite with a female's egg to result in conception.
spermicide
is a medication used to kill sperm used as a form of birth control.
spina bifida
(SPY-nuh BIF-ih-duh) is a condition present at birth in which the spinal column is imperfectly closed, leaving part of the spinal cord exposed and often leading to neurological and other problems.
spinal shock
is a condition that relates to the loss of neurological activity, including motor, sensory, reflex, and autonomic functions, below the level of injury.
spinal stenosis
(SPY-nal ste-NO-sis) is the narrowing of the spinal canal.
spleen
is an organ in the upper left part of the abdomen that stores and filters blood. As part of the immune system, the spleen also plays a role in fighting infection.
spondylolisthesis
(spon-di-lo-lis-THEE-sis) is a condition in which one vertebra slips over the other.
sporadic
(spoh-RAD-ik) means occurring at random or in scattered instances, with no apparent pattern.
spores
are a temporarily inactive form of a germ enclosed in a protective shell.
sputum
(SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.
Starling forces
are hydrostatic and oncotic pressures that control fluid movements in capillary membranes.
stem cell
is an unspecialized cell that gives rise to differentiated cells.
sterilize
(STAIR-uh-lyze) is to eliminate all live bacteria or microorganisms from something, usually through the use of heat, pressure, chemicals, or other antimicrobial agents.
steroid
(STIR-oyd) is any of a group of substances related to sterols, including cholesterol, bile acids, and certain hormones. Includes corticosteroids that are used to treat inflammation.
stethoscope
(STETH-o-skope) is a medical instrument used for listening to sounds produced in the chest, abdomen, and other areas of the body.
stigma
is a mark of shame.
stillbirth
is the birth of a dead fetus.
stimulant
(STIM-yoo-lunt) is a drug that produces a temporary feeling of alertness, energy, and euphoria.
stimulus
(STIM-yoo-lus) is an agent in the environment that excites a response or reaction. A stimulus might cause a person to function, become active, or respond. The plural form is stimuli.
stool transplant
is a procedure that involves transplanting stool, or feces, from a healthy donor to the colon, or large intestine, of someone who has experienced recurrent C. diff infections. Also called a fecal transplant.
strabismus
(struh-BIZ-mus) is a condition that causes the eyes to cross or not work together correctly, which may lead to permanent loss of vision in one eye.
strain
is a subtype of an organism, such as a virus or bacterium.
strep throat
is a contagious sore throat caused by a strain of bacteria known as Streptococcus.
stress test
measures the health of a person's heart while the heart is intentionally stressed by exercise or medication.
stretch marks
are stripes or lines on the skin (such as on the hips, abdomen, and breasts) from excessive stretching and rupture of elastic fibers, especially due to pregnancy or obesity.
stridor
(STRY-dor) is a high-pitched, squeaking noise that occurs while breathing in, usually present only if there is narrowing or blockage of the upper airway.
stupor
a state of sluggishness or impaired consciousness.
Sturge-Weber syndrome
is a neurological disease present at birth characterized by a port wine stain, seizures, and delay in development.
subacute sclerosing panencephalitis
(sub-uh-KYOOT skluh-RO-sing pan-en-seh-fuh-LYE-tis), or SSPE, is a chronic brain disease of children and adolescents that occurs months or years after having had measles; it causes convulsions, movement problems, and intellectual disability, and is usually fatal.
subdural
(sub-DOO-ral) means under the dura, the outermost of the three meninges that cover the brain.
submucosa
(sub-mu-KOH-sa) is the layer of tissue under the mucosa.
substance abuse
is the misuse of alcohol, tobacco, illegal drugs, prescription drugs, and other substances such as paint thinners or aerosol gases that change how the mind and body work.
sudden infant death syndrome
(SIDS) is the sudden, unexplained, unexpected death of a child in the first year of life.
suppository
(suh-POZ-uh-tor-ee) is a medicated delivery preparation that consists of a dissolvable cone or cylinder that is inserted into the vagina or rectum.
susceptibility
(su-sep-ti-BIL-i-tee) means having less resistance to and higher risk for infection or disease.
swimmer's ear
is an ear infection commonly seen in swimmers and people who do not dry their ears adequately after being in water.
swine flu
is a strain of flu virus that started in pigs that causes respiratory infection in humans.
sympathetic nervous system
is the system of nerves that prepares the body for stress or action by speeding up the heart and breathing rates and raising the blood pressure.
syndrome
is a group or pattern of symptoms or signs that occur together.
synovial fluid
(sih-NO-vee-ul) is the fluid produced in the synovium, the inner lining of the flexible capsule that encloses the joint space between two bones. This fluid lubricates and nourishes the joint.
synovitis
(sin-o-VY-tis) is inflammation of the membrane surrounding a joint.
syphilis
(SIH-fih-lis) is a sexually transmitted disease that, if left untreated, can lead to serious life-long problems throughout the body, including blindness and paralysis.
systemic
(sis-TEM-ik) is a problem affecting the whole system or whole body, as opposed to a localized problem that affects only one part of the body.
systemic lupus erythematosus
(sis-TEM-ik LOO-pus er-i-them-a-TO-sus), sometimes just called lupus, is a chronic inflammatory disease that can affect the skin, joints, kidneys, nervous system, membranes lining body cavities, and other organs.
tachycardia
is an elevated or very fast heartbeat.
tampon
is a plug of cotton or other material placed in the vagina during menstruation to absorb menstrual blood and other fluids.
temporal lobe epilepsy
(EP-uh-lep-see) is a form of epilepsy that affects the part of the brain located beneath the sides of the head, near the ears. Also called complex partial epilepsy.
tendon
(TEN-don) is a fibrous cord of connective tissue that attaches a muscle to a bone or other structure.
testes
(tes-TEEZ) are the organs that produce spermatozoa (male reproductive cells).
testicles
(TES-tih-kulz) are the paired male reproductive glands that produce sperm.
testicular cancer
is a cancer of the testicles. It is the most common form of cancer in men between the ages of 15 and 34 years.
testosterone
(test-TAHS-ter-own) is a hormone that stimulates development of male secondary sexual characteristics (such as facial hair), produced mainly in the testes, but also in the ovaries and adrenal cortex.
tetanus
(TET-nus) is a serious bacterial infection that affects the body's central nervous system.
tetany
(TE-tan-ee) is a nervous system disorder characterized by muscle cramps, spasms, and numbness in the arms and legs.
thalamus
(THAL-uh-mus) refers to a pair of large egg-shaped areas located in the middle of the brain just under the cerebral cortex. The plural form is thalami.
thorax
(thor-AKS) is the part of the body between the neck and the abdomen, including the cavity enclosed by the ribs, breastbone, and backbone.
thrombosis
is the formation or development of a blood clot or thrombus.
thymus gland
(THY-mus GLAND) is an organ located in the neck that produces cells for the immune system.
thyroid gland
(THYE-roid GLAND) is located in the lower part of the front of the neck. The thyroid produces hormones that regulate the body's metabolism (meh-TAB-o-liz-um), the processes the body uses to produce energy, grow, and maintain body tissues.
thyrotoxicosis
refers to an excessive amount of circulating thyroid hormone. It is not synonymous with hyperthyroidism, as increased levels of hormone can occur despite otherwise normal thyroid function.
tibia
(TIB-ee-ya) is the longer of two bones in the lower leg that connects with the knee above and the ankle below.
tick
is a small blood-sucking creature that may transmit disease-causing germs from animals to humans through its bite.
tolerance
(TALL-uh-runce) is a condition in which a person needs more of a drug to feel the original effects of the drug.
tonsils
are paired clusters of lymphatic tissue in the throat that help protect the body from bacteria and viruses that enter through a person's nose or mouth.
tourniquet
(tour-nih-KET) is a device, often a bandage twisted tight around an arm or a leg, used to stop blood flow or hemorrhage.
toxin
is a poisonous substance that is detrimental or lethal to the health of a person or the environment.
trachea
(TRAY-kee-uh) is the firm, tubular structure that carries air from the throat to the lungs. Also called the windpipe.
tracheostomy
(tray-kee-AHS-tuh-me) is a small opening through the neck into the trachea, or windpipe, which has been made to allow air to enter the lungs more directly. The surgical procedure to create a tracheostomy is usually performed when a person's upper airway is narrowed or blocked or when there are other problems causing breathing difficulty.
trachoma
(trahk-o-ma) is a speciic bacterial infection of the eye causing inflammation on the inner surface of the eyelids.
trans fat
is a fat derived from the partial hydro-genation of vegetable oils, also known as fatty acid.
transfusion
(trans-FYOO-zhun) is a procedure in which blood or certain parts of blood, such as speciic cells, are given to a person who needs them due to illness or blood loss.
transgender
is a person who identifies with and expresses a gender identity that differs from the one that corresponds to the person's sex at birth.
transient
(TRAN-shent) means brief, or producing effects for a short period of time.
transient ischemic attack
(TRANS-ee-ent iss-KEE-mik), or TIA, is an event similar to a stroke but goes away within a short period of time; it is sometimes called a mini-stroke.
transmissible
(trans-MIH-sih-bul) refers to any disease that can be transferred or spread.
transplant
(TRANS-plant) is a procedure in which an organ or tissue from a donor or made artiicially replaces a diseased organ or tissue.
trauma
refers to a wound or injury, either psychological or physical. Psychological trauma refers to an emotional shock that leads to lasting psychological damage.
traumatic brain injury
(TBI) is a common injury to the brain from a bump, blow, jolt, or shaking, most often from motor-vehicle accidents, sports injuries, or combat; concussions are the most common type of TBI.
tremors
is uncontrolled shaking, trembling, twitching, and/or quivering.
triglycerides
(try-GLISS-eh-rides) are a type of fatty substances found in the blood.
trimester
(tri-MES-ter) is any of three periods of approximately three months each into which a human pregnancy is divided.
truancy
is staying out of school without permission.
tuberculosis
(too-ber-kyoo-LO-sis) is a bacterial infection that primarily attacks the lungs but can spread to other parts of the body.
tumor
(TOO-mor) is an abnormal growth of body tissue that has no known cause or physiologic purpose. A tumor may or may not be cancerous.
Turner syndrome
is a genetic disorder that can cause several physical abnormalities, including shortness and lack of sexual development.
tympanogram
tests the condition of the middle ear and mobility of the eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal.
ulcerate
means to become eroded by infection, inflammation, or irritation.
ulcerative colitis
(UL-sir-ah-tiv ko-LYE-tis) is a common form of inflammatory bowel disease that causes inlammation with sore spots or breaks in the inner lining of the large intestine (colon). Symptoms include cramping, bleeding from the rectum, and diarrhea.
ultrasound
is a diagnostic test in which sound waves passing through the body create images on a computer screen. Also called a sonogram.
ultraviolet
is a wavelength of light beyond visible light; on the spectrum of light, it falls between the violet end of visible light and x-rays.
umbilical cord
(um-BIH-lih-kul) is the flexible cord that connects a baby to the placenta, the organ that unites the unborn child to the mother's uterus, the organ in which the baby develops.
uncircumcised
is the natural form of the penis at birth, with foreskin covering the head of the penis.
unpasteurized
(un-pas-CHUR-ized) refers to foods that have not undergone the process of pasteurization (pas-chu-rih-ZAY-shun), in which food is heated to a certain temperature over a period of time to kill organisms and help make the food safer to consume.
upper gastrointestinal system
consists of the mouth, esophagus, and stomach.
ureters
(YOOR-eh-ters) are tubelike structures that carry urine from the kidneys to the bladder.
urethra
(yoo-REE-thra) is the tube through which urine passes from the bladder to the outside of the body.
urethritis
(yoo-ree-THRY-tis) is inflammation of the urethra (yoo-REE-thra), the tube through which urine passes from the bladder to the outside of the body.
urinary tract
(YOOR-ih-nair-e TRAKT) is the system of organs and channels that makes urine and removes it from the body. It consists of the urethra, bladder, ureters, and kidneys.
urinary tract infection
(YOOR-ih-nair-e), or UTI, is an infection that occurs in any part of the urinary tract. The urinary tract is made up of the urethra, bladder, ureters, and kidneys.
urine
is the liquid waste material secreted by the kidneys and removed from the body through the urinary tract.
urologist
(yoor-OL-o-jist) is a physician with specialized knowledge of and experience in the treatment of diseases of the male genitalia and urinary system.
uterus
(YOO-teh-rus) is the muscular pear-shaped internal organ in a woman in which a baby develops until birth.
vaccination
(vak-sih-NAY-shun), also called immunization, is giving, usually by an injection, a preparation of killed or weakened germs, or a part of a germ or product it produces, to prevent or lessen the severity of the disease caused by that germ.
vaccine
(vak-SEEN) is a preparation of killed or weakened germs, or a part of a germ or product it produces, given to prevent or lessen the severity of the disease that can result if a person is exposed to the germ itself. Use of vaccines for this purpose is called immunization.
vagina
(vah-JY-nah) is the canal, or passageway, in a woman that leads from the uterus to the outside of the body.
vaginitis
(vah-jih-NYE-tis) is inflammation of the vagina (vah-JY-nah), the canal, or passageway, in a woman that leads from the uterus to the outside of the body.
vaporizer
is a device that converts water (or a liquid medication) into a vapor, a suspension of tiny droplets that remain in the air and can be inhaled.
varices
(VAR-uh-seez) (varix, singular) are veins, arteries, or lymph vessels that have become stretched or enlarged.
varicose vein
(VAR-i-kose VAYN) is an abnormally swollen or dilated vein.
vascular
refers to veins and arteries (the blood vessels).
vector
(VEK-tor) is an animal or insect that carries a disease-causing organism and transfers it from one host to another.
vegetative state
is a state of extreme mental impairment in which only involuntary bodily functions are sustained.
vein
is a vessel that carries unoxygenated blood to the heart. Veins have greater capacity and thinner walls than arteries and contain valves that prevent blood from lowing backward and away from the heart.
ventilator
(VEN-tuh-lay-ter) is a machine used to support or control a person's breathing.
ventricles
are open cavities within the brain that contain the luid which cushions and protects the central nervous system.
vertebrae
(VER-tuh-bray) are the bones that form a column surrounding the spinal cord; there are 39 vertebrae in the spine.
vertigo
(VER-ti-go) is the feeling that either the environment or one's own body is revolving or spinning, even though they are not.
viral infection
is an infection caused by a virus. Viral infections are treated by antiviral drugs and not antibiotics, which are used to treat bacterial infections.
virulent
comes from the Latin word for poisonous, and describes a microbe that is especially well suited to countering the immune system.
virus
(VY-rus) is a tiny infectious agent that can cause infectious diseases. A virus can reproduce only within the cells it infects.
visual cortex
is a portion of the brain's cerebrum that processes visual information transmitted from the eyes.
vocational
(vo-KAY-shun-al) means relating to training in a particular job skill.
voluntary muscle movements
are those physical actions, such as moving a hand or blinking an eyelid, over which an individual has conscious muscle control.
vulva
(VUL-vuh) refers to the organs of the female genitals that are located on the outside of the body.
vulvar
(VUL-var) means related to the organs of the female genitals that are located on the outside of the body.
warts
are small, hard growths on the skin or inner linings of the body that are caused by a type of virus.
water pollution
is contamination of the natural water supply including lakes, rivers, oceans, aquifers, and ground water by chemical, physical, radioactive, or pathogenic (disease-causing) microbial substances.
whiplash injuries
describe general injuries to the spine and spinal cord at the junction of the fourth and fifth vertebrae (VER-te-bray) in the neck occurring as a result of rapid acceleration or deceleration of the body.
yeast
(VEEST) is a general term describing single-celled fungi that reproduce by budding.
Zika virus
(ZEE-ka) is a microbe transmitted to humans by mosquitoes. Although most people have mild or no symptoms, Zika infection of a pregnant woman can cause serious birth defects in the fetus.
Disclaimer:
This information is not a tool for self-diagnosis or a substitute for professional care.