Medical Glossary

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A

 

Abdominal cavity- the part of the body between the bottom of the ribs and the top of the thighs, containing most of the digestive and urinary systems along with some reproductive organs

 

ABO blood groups-The system by which human blood is classified, based on proteins occurring on red blood cells; the four classification groups are A, AB, B, and O 

Abortion- termination of a pregnancy; can occur because of natural causes (called a miscarriage) or be a medical intervention 

Abscess- an accumulation of pus in a body tissue, usually caused by a bacterial infection 

ACE inhibitor- a drug typically used to treat high blood pressure (Angiotensin-Converting Enzyme inhibitor) 

Achilles tendon- the tendon at the back of the lower leg that connects the calf muscle to the heel bone 

Acid-base balance- the mechanisms that the body uses to keep its fluids close to neutral (neither basic nor acidic) so that the body can function properly 

Acidosis- a condition marked by abnormally high acid levels in the blood, associated with some forms of diabetes, lung disease, and severe kidney disease 

Acid reflux- a disorder in which acid in the stomach comes up into the esophagus, because the valve separating the stomach and esophagus does not function properly

Acne- a skin condition characterized by inflamed, pus-filled areas that occur on the skin's surface, most commonly occurring during adolescence 

Acquired- a word describing any condition that is not present at birth, but develops some time during life 

AIDS- Acronym for Acquired immuno deficiency syndrome. An infection by the human immunodeficiency virus (HIV), which causes a weakening of the immune system 

Acute- describes a condition or illness that begins suddenly and is usually short-lasting 

Acute respiratory disease- an urgent condition in which oxygen levels in the blood are lower than normal and breathing is difficult 

Addiction- dependence on a substance (such as alcohol or other drugs) or an activity, to the point that stopping is very difficult and causes severe physical and mental reactions

Adenitis- infection and inflammation of a gland, especially a lymph node 

Adipose tissue- another term for fatty tissue; it stores energy, insulates, and cushions the body 

Adjuvant therapy- the use of drugs or radiation therapy in the treatment of cancer along with surgery 

Adrenal failure- a condition in which the adrenal glands do not produce enough of the hormones that control important functions such as blood pressure 

Adrenal glands- two small glands located on top of the kidneys that secrete several important hormones into the blood 

Adverse reaction- an unintended and unwanted side effect of some sort of treatment, usually drug therapy 

Aerobic exercise- physical activity during which the heart and lungs must work harder to meet the body's increased oxygen demand 

Affective disorder- a mental disorder involving abnormal moods and emotions; affective disorders include manic-depressive disorder 

Afterbirth- the placenta and membranes that are eliminated from the woman's uterus following the birth of a child 

Afterpains- normal contractions of the uterus after childbirth that usually occur for the first few days after delivery 

AIDS- see Acquired immunodeficiency syndrome 

AIDS-related complex- symptoms including weight loss, fever, and enlarged lymph nodes experienced by people who are infected with HIV but do not yet have AIDS 

Air embolism- the blockage of an artery by air bubbles, which may have entered during surgery or after an injury 

Airway obstruction- blockage of the passage of air through the windpipe to the lungs 

Airways- the passageways that air moves through while traveling in and out of the lungs during breathing 

Albinism- a condition in which people are born with insufficient amounts of the pigment melanin, which is responsible for hair, skin, and eye color 

Alcoholic cardiomyopathy- heart damage and failure caused by intake of too much alcohol 

Alimentary canal- another term for the digestive tract 

Alkalosis- dangerously decreased acidity of the blood, which can be caused by high altitudes, hyperventilation, and excessive vomiting 

Alkylating agents- substances used in cancer treatment that interfere with the division of cells 

Allergen- a substance that causes an allergic reaction 

Allergic rhinitis- irritation of the nasal passages and the whites of the eyes, causing sneezing, runny nose, and sore eyes 

Allergy- a negative reaction to a substance that in most people causes no reaction 

Alopecia- baldness or loss of hair, mainly on the head, either in defined patches or completely; the cause is unknown 

ALS- see Amyotrophic lateral sclerosis 

Altitude sickness- headaches, dizziness, and nausea usually experienced at heights above 8,000 ft because of reduced oxygen in the air 

Alzheimer disease- a condition that occurs late in life and worsens with time in which brain cells degenerate; it is accompanied by memory loss, physical decline, and confusion 

Amenorrhea- absence of menstrual periods, occurring either after or before menstruation has begun 

Amniocentesis- a procedure in which a small amount of amniotic fluid is removed from the mother's womb in order to detect abnormalities of the fetus 

Amniotic fluid- clear fluid that surrounds a fetus during pregnancy and cushions and protects it 

Amyotrophic lateral sclerosis- the most common of a group of disorders known as motor neuron diseases, in which the nerves in the brain that control the movement of muscles degenerate and muscle function is gradually lost; commonly called Lou Gehrig's disease 

Anabolic steroid- a drug similar to the male hormone testosterone that builds muscles and strengthens bones, but has adverse side effects 

Anal fissure- a long, open sore on the skin of the anus 

Anal fistula- an abnormal tubelike passage connecting the anus to the surface of the surrounding skin 

Analgesic- a drug that relieves pain, such as aspirin or acetaminophen 

Anal sphincter- a ring of muscle fibers at the opening of the rectum, controlling the opening and closing of the anus 

Anaphylactic shock- a life-threatening allergic reaction resulting in difficulty breathing and low blood pressure 

Anatomy- the structure of bodies; commonly refers to the study of body structure 

Androgen- a hormone (such as testosterone) that causes development of male characteristics and sex organs 

Anemia- a condition in which the blood does not contain enough hemoglobin, the compound that carries oxygen from the lungs to other parts of the body 

Anencephaly- a fatal birth defect in which the brain and spinal cord have failed to develop, resulting in the absence of a portion of the skull and brain 

Anesthesia- a loss of sensation in a certain part of the body or throughout the body 

Anesthetic- a substance that temporarily causes a person to be unable to feel pain, either in a certain area or over the entire body 

Aneurysm- an abnormal swelling of the wall of an artery, caused by a weakening in the vessel wall 

Angina pectoris- pain experienced in the chest, arms, or jaw because of a lack of oxygen to the heart muscle 

Angioma- a tumor made of blood vessels or lymph vessels that is not cancerous 

Angioplasty- the use of surgery to make a damaged blood vessel function properly again; may involve widening or reconstructing the blood vessel 

Anorexia nervosa- a dangerous eating disorder mainly affecting young girls in which the sufferer has an intense fear of looking fat, avoids food, and loses weight excessively

Antacid- a drug that neutralizes stomach acids; used to treat indigestion, heartburn, and acid reflux 

Antibiotic resistance- the development by bacteria of the ability to live in the presence of a certain antibiotic, making treatment difficult 

Antibiotics- bacteria-killing substances that are used to fight infection 

Antibody- a protein made by white blood cells that reacts with a specific foreign protein as part of the immune response 

Anticoagulants- drugs used to stop abnormal blood clotting, such as to prevent stroke 

Antiemetics- drugs used to treat nausea and vomiting 

Antihistamine- a drug that relieves an allergic reaction by stopping the effects of histamine, the substance responsible for the negative symptoms associated with the reaction

Antihypertensives- drugs used to relieve the symptoms and prevent the damage that can occur from high blood pressure 

Antioxidants- substances that protect against cell damage by guarding the cell from oxygen free radicals 

Antipsychotics- drugs used to treat severe mental disorders 

Antiseptics- chemicals applied to the skin that prevent infection by killing bacteria and other harmful organisms 

Anus- the opening through which feces are passed from the body 

Aorta- the main artery in the body, carrying oxygenated blood from the heart to other arteries in the body 

Aortic stenosis- narrowing of the opening of the aortic valve in the heart, which increases resistance to blood flow from the left ventricle to the aorta; commonly a birth defect or caused by scarring and calcium accumulation in the valve from rheumatic fever 

Apgar score- a system for evaluating the health of a newborn baby; rated on a scale of 0-10 

Aplasia- the complete or partial failure of any organ or tissue to grow 

Aplastic anemia- a severely reduced number of red blood cells, white blood cells, and platelets 

Apnea- a possibly life-threatening condition in which breathing stops, for either a short or long period of time 

Appendectomy- surgical removal of the appendix to treat appendicitis 

Appendicitis- inflammation of the appendix 

Appendix- a short, tubelike structure that branches off the large intestine; does not have any known function 

ARC- see AIDS-related complex 

Arteriosclerosis- a disorder causing thickening and hardening of artery walls 

Arteritis- inflammation of the walls of an artery that causes the passageway to become narrower; can lead to tissue damage because oxygen is not properly supplied 

Artery- a large blood vessel that carries blood from the heart to tissues and organs in the body 

Arthritis- a disease of the joints characterized by inflammation, pain, stiffness, and redness 

Arthroscopy- a procedure used to examine the inside of a joint using a viewing tube (an endoscope) 

Artificial insemination- injection of semen into the cervix 

Artificial respiration/ventilation- the forcing of air (either by mouth-to-mouth or mouth-to-nose means) into the lungs of a person who has stopped breathing 

Ascites- excess fluid in the abdominal cavity, which leads to swelling 

Ascorbic acid- the chemical term for vitamin C 

Aspermia- the failure either to produce or to ejaculate sperm 

Asphyxia- the medical term for suffocation; can be caused by choking on an object, by lack of oxygen in the air, or by chemicals such as carbon monoxide, which reduce the amount of oxygen in the blood 

Asthma- a disorder characterized by inflamed airways and difficulty breathing 

Astigmatism- a disorder in which the front surface of the eye (the cornea) is not correctly spherical, resulting in blurry vision 

Atherectomy- a procedure performed to remove plaque that is blocking an artery 

Atheroma- fatty deposits on the inner walls of blood vessels, which can cause narrowing and decrease blood flow 

Atherosclerosis- narrowing of the lining of the arteries due to the accumulation of fat and other materials; leads to coronary heart disease, stroke, and other disorders 

Athlete's foot- an infection between the toes caused by a fungus, which leads to sore, cracked, and peeling skin 

Atresia- a birth defect in which a normal body opening or canal is absent; usually requires surgical repair soon after birth 

Atria- the two upper chambers of the heart; the singular form is atrium 

Atrial fibrillation- an irregular heartbeat in which the upper chambers of the heart (the atria) beat inconsistently and rapidly 

Atrial flutter- an irregular heartbeat in which the upper chambers of the heart (the atria) beat rapidly but consistently 

Atrial septal defect- a hole located in the wall between the two upper chambers of the heart 

Atrophy- the shrinkage or near disappearance of a tissue or organ 

Attention-deficit disorder- a disorder mainly present in children and adolescents, characterized by learning and behavior problems, inability to pay attention, and sometimes hyperactivity 

Audiogram- a graph showing a person's hearing ability, determined from a set of tests examining hearing acuity of different sound frequencies 

Aura- a "warning" signal that comes before a migraine headache or an epileptic seizure, which might include emotions or sensations of movement or discomfort 

Auscultation- the act of listening to sounds within the body, such as the heartbeat, with a stethoscope 

Autism- a mental disorder characterized by an inability to relate to other people and extreme withdrawal 

Autoimmune disease- a disorder in which the body's immune system attacks itself 

Autonomic nervous system- the part of the nervous system that controls automatic body functions, such as heart rate, sweating, pupil dilation, and digestion; divided into the sympathetic nervous system and the parasympathetic nervous system 

Autopsy- the examination of a body following death, possibly to determine the cause of death or for research 

Autosomal dominant- a term describing a gene on any chromosome other than the sex chromosomes that produces its effect whenever it is present; can also describe the effect of the gene itself 

Autosomal recessive- a term used to describe a gene on any chromosome other than the sex chromosomes that produces its effect only when two copies of it are present; can also describe the effect of the gene itself 

Axilla- medical term for the armpit

B

Bacillus- any bacteria that is rod-shaped; responsible for diphtheria, dysentery, tetanus, and tuberculosis, as well as other diseases

Bacteremia- a condition in which bacteria are present in the bloodstream; may occur after minor surgery or infection and may be dangerous for people with a weakened immune system or abnormal heart valves

Bacteriostatic- term used to describe a substance that stops the growth of bacteria (such as an antibiotic)

Bacterium- a tiny, single-celled microorganism, commonly known as a germ; some bacteria, called pathogens, cause disease

Bacteriuria- bacteria in the urine; large amounts can indicate bladder, urethra, or kidney infection

Ball-and-socket joint- a joint consisting of a ball-shaped bone that fits into a cup-shaped bone, making the joint free to rotate; examples include the hip and shoulder

Balloon angioplasty- a technique that uses a balloon catheter to open arteries clogged with fatty deposits

Balloon catheter- a hollow tube with a small, inflatable balloon at the tip; used to open a narrowed artery or organ that has become blocked

Barbiturates- a group of sedatives that reduce activity in the brain; are habit-forming and are possibly fatal when taken with alcohol

Barium enema- a technique in which barium is placed into the large intestine and rectum and then X-rays are taken to check for possible disorders of these organs

Barrier method of contraception- a birth-control technique using a condom, diaphragm, or another similar device to block the path of sperm to an egg

Bartholin's glands- two pea-sized glands that, when sexually aroused, release a fluid that lubricates the vagina

Basal cell carcinoma- a type of skin cancer that is caused by exposure to large amounts of sunlight; commonly found on the neck, face, and arms

Basal metabolic rate- the lowest rate at which a person can possibly use energy and remain alive; at this rate, only absolutely necessary functions such as breathing are maintained

B cell- a white blood cell that makes antibodies to fight infections caused by foreign proteins

BCG vaccine- a vaccine used to protect against tuberculosis

Becker's muscular dystrophy- a hereditary disease in which the muscles weaken and waste away; similar to Duchenne muscular dystrophy but starts later in life and advances more slowly

Bell's palsy- another name for facial palsy, the usually one-sided, temporary numbing of the facial muscles, caused by an inflamed nerve

Bends- see Decompression sickness

Benign tumor- a tumor that is not cancerous, which means it does not spread through the body, but may grow and become dangerous

Beta blocker- a type of drug used to treat high blood pressure and heart disorders by reducing the strength and rate of the pumping by the heart

Beta carotene- a pigment found in orange vegetables and fruits, which the body converts to vitamin A; possibly protects against cancer

Bifocal- a lens that corrects both near and distant vision by having two parts with different focusing strengths

Bilateral- a term describing a condition that affects both sides of the body or two paired organs, such as bilateral deafness (deafness in both ears)

Bile- a yellow-green liquid produced in the liver whose function is to remove waste from the liver and break down fats as food is digested

Bile duct- a tube that carries bile from the liver to the gallbladder and then to the small intestine

Biliary Atresia- a birth defect in which the bile ducts are not completely developed; often a liver transplant is necessary

Biliary colic- a severe pain in the upper right section of the abdomen, usually caused by a gallstone passing out of the bladder or through the bile ducts

Biliary tract- the system of organs and ducts through which bile is made and transported from the liver to the small intestine

Bilirubin- the orange-yellow pigment in bile, causing jaundice if it builds up in the blood and skin; the levels of bilirubin in the blood are used to diagnose liver disease

Binging and purging- behavior characteristic of the disorder bulimia in which a person overeats then rids themselves of the food before it can be absorbed by the body, either by forced vomiting or through the use of laxatives

Biochemistry- the science that studies the chemistry of living organisms, including humans

Bioequivalent- a drug that has the same effect on the body as another drug

Biofeedback- a technique used to gain control over a function that is normally automatic (such as blood pressure or pulse rate); the function is monitored and relaxation techniques are used to change it to a desired level

Bipolar disorder- an illness in which the patient goes back and forth between opposite extremes; the most notable bipolar disorder is manic-depressive disorder, which is characterized by extreme highs and lows in mood 

Birth canal- the passage that includes the uterus and vagina through which the baby passes at birth

Birth control- the regulation of the number of children born, referring either to the prevention of pregnancy (by birth control pill, sterilization, etc) or the prevention of birth (by abortion, etc)

Birth defect- an abnormality that is present when a baby is born Birthmark- any area of discolored skin that is present when a baby is born

Bisexuality- sexual interest in members of both sexes

Bladder- an organ located in the pelvis whose function is to collect and store urine until it is expelled

Blepharitis- inflammation of the eyelids

Blind spot- a spot in the field of vision that is not sensitive to light; it is a product of the entrance of the optic nerve into the eyeball, where no light receptors are present on the retina

Blood-brain barrier- a layer of tightly bound cells that prevents certain substances carried in the bloodstream from entering the brain

Blood clot- a semisolid mass of blood that forms to help seal and prevent bleeding from a damaged vessel

Blood poisoning- see Septicemia

Blood pressure- the tension in the main arteries that is created by the beating of the heart and the resistance to flow and elasticity of the blood vessels

Blood transfusion- the transfer of blood or any of its parts to a person who has lost blood due to an injury, disease, or operation

Blood type- a category used to describe a person's blood according to the kinds of proteins present on the surface of the red blood cells

Blymphocyte- a type of white blood cell that makes antibodies and is an important part of the immune response

Boil- an inflamed, raised area of skin that is pus-filled; usually an infected hair follicle

Bone marrow- the fatty yellow or red tissue inside bones that is responsible for producing blood cells

Bone marrow transplant- a surgical procedure in which defective or cancerous bone marrow is replaced with healthy marrow, either from the patient or a donor

Bone spur- an abnormal growth of bone out of another bone, often located on the heel and usually painful

Booster- an additional dose of a vaccine taken after the first dose to maintain or renew the first one

Botulism- poisoning from poorly preserved food contaminated with a dangerous bacterial toxin that results in paralysis

Bowel- see Intestine

Bradycardia- a slow heart rate, usually below 60 beats per minute in adults

Brain damage- permanent death or damage of brain cells resulting in decreased mental ability

Brain death- the condition in which the brain stops functioning while the heart continues to beat

Breech birth- childbirth in which the baby is turned around in the uterus and emerges head-last instead of head-first

Bronchiolitis- an infection caused by a virus in the bronchioles (the smallest airways in the lungs), mainly affecting young children

Bronchitis- inflammation of the bronchial tubes, which connect the trachea to the lungs

Bronchoconstrictor- a substance that causes the lung airways to tighten up and become more narrow

Bronchodilator- a drug that widens the airways in the lungs to improve breathing; works by relieving muscle contraction or buildup of mucus

Bronchospasm- the temporary narrowing of the airways in the lungs, either as a result of muscle contraction or inflammation; may be caused by asthma, infection, lung disease, or an allergic reaction

Bruise- see Contusion

Bruxism- an unaware clenching or grinding of the teeth, usually during sleep

Bubonic plague- a form of plague in which lymph nodes in the groin and armpit swell

Bulimia- a disorder in which a person eats large amounts of food then forces vomiting or uses laxatives to prevent weight gain (called binging and purging)

Bunion- a hard, fluid-filled pad along the inside joint of the big toe; may be caused by wearing high-heeled shoes or a genetically weak joint

Burkitt's lymphoma- a cancer of lymph tissue that most frequently occurs in the abdomen, the ovaries, and the bones of the face; it is associated with malaria

Bursa- a fluid-filled sac that cushions and reduces friction in certain parts of the body

Bursitis- inflammation of a bursa due to excessive pressure or friction, or from injury

Butterfly bandage- a butterfly-shaped bandage that can help close a minor cut for proper healing

Bypass- a surgical technique in which the flow of blood or another body fluid is redirected around a blockage

C

 

Calcification- the depositing of calcium salts in the body, which occurs normally in teeth and bones but abnormally in injured muscles and narrowed arteries

Calcitonin- a hormone made in the thyroid gland that controls calcium levels in the blood by slowing the loss of calcium from bones; used to treat hypercalcemia (excess calcium in the blood)

Calcium- a plentiful mineral in the body and the basic component of teeth and bones; essential for cell function, muscle contraction, transmission of nerve impulses, and blood clotting

Calcium channel blocker- a drug used to treat chest pain, high blood pressure, and irregular heartbeat by preventing the movement of calcium into the muscle

Callus- a thickened area of skin due to consistent pressure or friction, or the area around a bone break where new bone is formed

Calorie- a unit that is used to measure the energy content in food

Canal- a tunnel-like passage

Cancer- a group of diseases in which cells grow unrestrained in an organ or tissue in the body; can spread to tissues around it and destroy them or be transported through blood or lymph pathways to other parts of the body

Cancer staging- a method to determine how much a cancer has developed

Candidiasis- a yeast infection caused by the fungus Candida albicans; occurs most often in the vagina, but also in the mouth, on moist skin, or on the penis

Canker sore- small, painful sore that usually occurs on the inside of the lip or cheek, or sometimes under the tongue; caused by bacteria, irritation of the area, stress, or allergies

Capillary- a tiny blood vessel that connects the smallest arteries to the smallest veins and allows exchange of oxygen and other materials between blood cells and body tissue cells

Carbohydrate- a substance, mainly sugar and starch, that is a main source of energy for the body and is found in sources such as cereals, breads, pastas, grains, and vegetables

Carbon dioxide- a colorless, odorless gas present in small amounts in the atmosphere and formed during respiration

Carcinogen- anything that can cause cancer

Carcinoma- a cancer that occurs on the surface or lining of an organ

Cardiac arrest- the sudden cessation of the heart's pumping action, possibly due to a heart attack, respiratory arrest, electrical shock, extreme cold, blood loss, drug overdose, or a severe allergic reaction

Cardiogenic shock- a severely dangerous condition involving decreased blood output from the heart, usually as a result of a heart attack

Cardiomegaly- a condition marked by enlargement of the heart, either because of a thickened heart muscle or an enlarged heart chamber; usually a result of the heart having to work harder than normal, as occurs with high blood pressure

Cardiomyopathy- a disease of the heart muscle that results in decreased output and reduced blood flow

Cardiopulmonary resuscitation- the administration of heart compression and artificial respiration to restore circulation and breathing

Cardiovascular system- the heart and blood vessels that are responsible for circulating blood throughout the body

Carditis- inflammation of the heart

Carotene- an orange pigment present in colored plants such as carrots that is converted by the body to the essential nutrient vitamin A

Carotid arteries- four main arteries that carry blood to the head and neckCarpal bones- eight bones that together make the wrist

Carpal tunnel syndrome- a condition in which pressure on the median nerve in the wrist causes soreness, tingling, and numbness in the thumb and index and middle fingers

Cartilage- a connective tissue (softer than bone) that is part of the skeletal system, including the joints

Cast- a hard plaster or fiberglass shell that molds to a body part such as an arm and holds it in place for proper healing

Cataract- a disorder in which the lens of the eye becomes less transparent and in some cases a milky white, making vision less clear

Catheter- a hollow, flexible tube inserted into the body to put in or take out fluid, or to open up or close blood vessels

Catheterization- a technique in which a hollow, flexible tube is used to drain body fluids (such as urine), to introduce fluids into the body, or to examine or widen a narrowed vein or artery

CAT scanning- see Computed tomography scanning

Cat-scratch fever- an illness transmitted to humans through a cat's bite or scratch, which is thought to be caused by an unidentified bacteria; characterized by a swollen lymph node or blister near the bite or scratch, fever, rash, and headache; most commonly occurring in children

Cauliflower ear- a deformed ear caused by repeated injury

Cauterization- the use of heat, an electric current, or a chemical to destroy tissue or stop bleeding

Cecum- the beginning of the large intestine, which is connected to the appendix at its lower end

Cell- the tiny structures that make up all the tissues of the body and carry out all of its functions

Cellulitis- a skin infection caused by bacteria (usually streptococci); can lead to tissue damage and blood poisoning if untreated; characterized by fever, chills, heat, tenderness, and redness

Central nervous system- the brain and spinal cord Cerebellum- a region of the brain located at the back; responsible for coordination of movement and maintaining balance

Cerebral palsy- a group of disorders of movement and posture resulting from damage to the brain early in a child's development; causes muscle weakness, difficulty coordinating voluntary movements, and sometimes complete loss of motion

Cerebrospinal fluid- a clear, watery fluid circulating in and around the brain and spinal column, which contains glucose, proteins, and salts for nutrition

Cerebrovascular disease- a disease affecting any artery supplying blood to the brain; may cause blockage or rupture of a blood vessel, leading to a stroke

Cerebrum- the largest part of the brain and the site of most of its activity, including sensory and motor functions

Cervical cap- a small rubber cup that is placed tightly over the cervix to prevent pregnancy

Cervical dysplasia- changes that occur in the cells on the surface of the cervix that usually precede the stages of cancer

Cervical incompetence- a weakness of the neck of the uterus, which can lead to spontaneous abortion due to an inability to support the weight of the fetus

Cervical smear- a procedure in which cells are scraped off of the cervix and examined to detect changes that might precede the stages of cancer; also called a Pap smear

Cervicitis- inflammation of the cervix Cervix- a small, round organ making up the neck of the uterus and separating it from the vaginaCesarean section- an operation performed to remove a fetus by cutting into the uterus, usually through the abdominal wall

Chancre- a painless sore that has a thick, rubbery base and a defined edge; usually occurs on the genitals after the contraction of the sexually transmitted disease syphilis

Chemotherapy- the treatment of infections or cancer with drugs that act on disease-producing organisms or cancerous tissue; may also affect normal cells

Chickenpox- a contagious disease that causes a rash and a fever; most commonly occurs during childhood

Chlamydia- microorganisms that cause several human infections and can be transmitted sexually

Cholecystectomy- the surgical removal of the gallbladder

Cholera- a bacterial infection of the small intestine that causes severe watery diarrhea, dehydration, and possibly death

Cholesterol- a substance in body cells that plays a role in the production of hormones and bile salts and in the transport of fats in the bloodstream

Chondritis- inflammation of cartilage

Chondroma- a noncancerous tumor that occurs in cartilage

Chondromalacia patellae- painful damage to the cartilage behind the kneecap

Chondrosarcoma- a cancerous cartilage tumor that develops inside of bone or on its surface

Chorionic villus sampling- a method of diagnosing fetal defects in which a small amount of tissue is taken from the placenta and analyzed for abnormalities

Choroiditis- inflammation of the blood vessels behind the retina that line the back of the eye

Chromosome analysis- examination of a person's chromosomes either to determine if that person has an abnormality or to investigate one

Chronic- describes a disorder that continues for a long period of time

Chronic obstructive lung disease- a combination of the lung diseases emphysema and bronchitis, characterized by blockage of airflow in and out of the lungs

Cilia- tiny, hairlike structures on the outside of some cells, providing mobility

Circumcision- the surgical removal of the foreskin of the penis

Cirrhosis of the liver- gradual loss of liver function due to cell damage and internal scarring

Claudication- a cramping pain in one or both legs while walking, which can cause limping

Claustrophobia- fear of being confined in an enclosed or crowded space

Clavicle- the medical term for the collarbone

Cleft lip- a birth defect in which the upper lip is split vertically, extending into one or both nostrils

Cleft palate- a birth defect in which the roof of the mouth is split, extending from behind the teeth to the nasal cavity; often occurs with other birth defects such as cleft lip and partial deafness

Clinical trial- carefully monitored and planned testing of a new drug or treatment

Clitoris- a small female organ located near the opening of the vagina that swells when sexually aroused

Clone- an exact copy of a gene, cell, or organism Closed fracture- a bone break that does not break the skin

Clotting factor- a substance in the blood that is needed for blood to harden and stop a wound from bleeding

Clubfoot- a genetic disorder in which the foot is twisted and misshapen

Cluster headache- severe pain that occurs suddenly and affects one side of the head, including the face and neck

CNS- see Central nervous system

Coagulation- a process that plays a large role in the hardening and thickening of blood to form a clot

Cocarcinogen- a substance that does not cause cancer by itself, but increases the effect of a substance that does cause cancer

Coccyx- four fused bones that form a triangular shape at the base of the spine (also known as the tailbone)

Cochlea- a coiled organ in the inner ear that plays a large role in hearing by picking up sound vibrations and transmitting them as electrical signals

Coitus- sexual intercourse

Cold sore- a small blister anywhere around the mouth that is caused by the herpes simplex virus

Colectomy- the complete or partial surgical removal of the large intestine (the colon), usually as treatment of a cancerous tumor or a narrowing and blockage of the intestine

Colic- waves of pain in the abdomen that increase in strength, disappear, and return; usually caused by a stone blocking a bile or urine passageway or an intestinal infection

Colitis- inflammation of the large intestine (the colon), which usually leads to abdominal pain, fever, and diarrhea with blood and mucus

Collapsed lung- a condition in which all or part of a lung cannot expand and fill with air

Colon- the main part of the large intestine, between the cecum and the rectum

Colonoscopy- investigation of the inside of the colon using a long, flexible fiberoptic tube

Color blindness- any vision disorder in which the person sees colors abnormally, has trouble distinguishing between them, or cannot see them at all

Colostomy- a surgical procedure in which some part of the colon is cut and moved to the surface of the abdomen so that feces can be passed into a bag worn outside of the body

Coma- a condition in which the area of the brain involved in maintaining consciousness is somehow affected, resulting in a state of unconsciousness in which the patient does not respond to stimulation 

Comminuted fracture- a crushed or shattered bone

Common cold- an infection caused by a virus, which results in an inflamed lining of the nose and throat; characterized by a stuffy and runny nose and, sometimes, a sore throat

Communicable disease- a disease that can be passed from one individual to another

Compound fracture- a bone break that breaks the skin

Compression fracture- a break in a short bone in which its soft tissue is crushed

Computed tomography scanning- a technique for producing cross-sectional images of the body in which X-rays are passed through the body at different angles and analyzed by a computer; also called CT scanning or CAT scanning

Concussion- disturbance of electrical activity in the brain due to a blow to the head or neck, causing temporary loss of consciousness 

Congenital- present or existing at the time of birth

Congestive heart failure- inability of the heart to efficiently pump blood through the body, causing buildup of blood in the veins and of other body fluids in tissue

Conjunctiva- the clear membrane covering the white of the eye and the inside of the eyelid that produces a fluid that lubricates the cornea and eyelid

Conjunctivitis- inflammation of the conjunctiva; commonly called pinkeye

Connective tissue- strong tissue that connects and supports body structures

Constipation- difficult or infrequent bowel movements of hard, dry feces Contraindication- an aspect of a patient's condition that makes the use of a certain drug or therapy an unwise or dangerous decision

Contusion- damage to the skin and underlying tissue as a result of a blunt injury; a bruise

Corn- a thickened callus on the foot that is caused by an improperly fitting shoe

Cornea- the clear, dome-shaped front portion of the eye's outer covering

Coronary- describes structures that encircle another structure (such as the coronary arteries, which circle the heart); commonly used to refer to a coronary thrombosis or a heart attack 

Coronary arteries- the arteries that branch off from the aorta and supply oxygen-rich blood to the heart muscle 

Coronary artery bypass surgery- an operation in which a piece of vein or artery is used to bypass a blockage in a coronary artery; performed to prevent myocardial infarction and relieve angina pectoris

Coronary heart disease- disorders that restrict the blood supply to the heart, including atherosclerosis

Coronary thrombosis- the blockage of a coronary artery by a blood clotCorpuscle- a tiny, rounded structure in the body, such as a red or white blood cellCorticosteroids- synthetic drugs that are used to replace natural hormones or to suppress the immune system and help prevent inflammation

CPR- see Cardiopulmonary resuscitation 

Creatinine- a waste product that is filtered from the blood by the kidneys and expelled in urine

Croup- a usually mild and temporary condition common in children under the age of 4 in which the walls of the airways become inflamed and narrow, resulting in wheezing and coughing

Cruciate ligaments- two ligaments in the knee that cross each other and help stabilize the knee joint

CT scanning- a procedure that uses X-rays and computers to create cross-sectional images of the body to diagnose and monitor disease

Culture- the artificial growth of cells, tissue, or microorganisms such as bacteria in a laboratory

Curettage- the use of a sharp, spoonlike instrument (a curet) to scrape away tissue that is abnormal or to obtain a sample that can be analyzed

CVS- see Chorionic villus sampling

Cyanosis- a bluish discoloration of the skin, caused by low levels of oxygen in the blood

Cyst- a lump filled with either fluid or soft material, occurring in any organ or tissue; may occur for a number of reasons but is usually harmless unless its presence disrupts organ or tissue function

Cystectomy- surgical removal of the bladder; the bladder is often replaced with a short length of small intestine

Cystic fibrosis- an inherited disorder in which the lungs are prone to infection, and fats and other nutrients cannot be absorbed into the body

Cystoscopy- examination of the urethra and bladder using a long, thin, fiberoptic tube 

Cystostomy- the surgical placement of a drainage opening in the bladder

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