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ear canal: A tube leading from the eardrum to the outer ear.

eardrum: A thin membrane separating the ear canal and middle ear.

earwax: A substance that lubricates the inner ear and helps protect it from dirt, damage, and infections.

EBCT: Abbreviation for electron-beam computed tomography, a high-speed imaging technology use to evaluate the heart and measure calcium deposits in arteries.

eccentric action: When muscles move joints by lengthening. Also known as cerumen.

ECG: An abbreviation for electrocardiogram, a test that measures the electrical activity of the heart and detects heart problems.

echocardiography: A diagnostic tool that uses high-frequency sound waves (ultrasound) to make images of the heart's size, structure and motion.

eclampsia: A serious condition related to high blood pressure that can threaten the life of a pregnant woman and her fetus.

ectopic pregnancy: Pregnancy in which a fertilized egg implants in an abnormal location outside the uterus, usually in the fallopian tubes. Ending the pregnancy is necessary.

ectropion: When an eyelid, usually the lower one, flips outward so that the inner surface is exposed.

eczema: A condition in which areas of the skin are dry, itchy, red, and cracked. Also known as atopic dermatitis.

ED: Commonly used abbreviation for erectile dysfunction, the inability to get or maintain an erection sufficient for intercourse.

edema: Swelling caused by abnormal accumulation of fluid in tissues.

EEG: Abbreviation for electroencephalogram, a test that measures the electrical activity of the brain and detects problems.

effusion: An abnormal buildup of fluid in a joint or tissue.

eighth cranial nerve: A nerve responsible transmitting sound and information about balance to the brain. Also called the auditory nerve.

ejaculation: A sudden discharge of a fluid from a duct; often used to describe the expulsion of seminal fluid from the urethra of the penis during orgasm.

ejection fraction: The percent of blood pumped out of the left ventricle with each heartbeat. A normal ejection fraction is in the range of 55% to 70%.

EKG: An abbreviation for electrocardiogram, a test that measures the electrical activity of the heart and detects heart problems.

elastin: A flexible, stretchy protein found in skin and connective tissue.

electrocardiogram: A test that measures the electrical activity of the heart and detects heart problems.

electroencephalogram: A test that measures the electrical activity of the brain and detects problems.

electrolysis: A permanent hair removal technique that destroys follicles one at a time with a hair-thin needle inserted into the base of the follicle.

electrolyte: Minerals in the body that are electrically charged and play an important role in body processes, such as regulating fluid levels in the body. Examples include calcium and sodium.

electromyography: A test that checks the health of muscles and the nerves that control them.

electron-beam computed tomography: A high-speed imaging technology use to evaluate the heart and measure calcium deposits in arteries. Sometimes referred to as EBCT.

electrophysiologic testing: A procedure used to provoke known or suspected arrhythmias.

elimination diets: A way of diagnosing food allergies in which suspected foods are removed from the diet one at a time until the food causing a problem is found.

ellagic acid: A chemical found in certain plants, such as raspberries and strawberries, that might help protect against cancer.

embolic stroke: A type of stroke that occurs when a blood clot that has formed elsewhere in the body breaks off and travels through the bloodstream until it blocks an artery that normally supplies blood to the brain.

embolism: Blockage of a blood vessel by a clot (an embolus) that has traveled from another part of the body.

embolus: A blood clot or particle that forms in one part of the body then moves through the bloodstream and lodges in a blood vessel elsewhere, blocking blood flow.

emetic: Any drug or other substance used to cause vomiting.

EMG: Abbreviation for electromyography—a test that checks the health of muscles and the nerves that control them.

emission: The discharge or release of a substance, usually a fluid.

emmenagogue: Herbs that stimulate menstrual blood flow.

enamel: The hard outside layer of tooth material.

encephalitis: A severe and sometimes deadly inflammation of the brain that can be caused by a number of different viruses.

encoding: A multistage process by which sensation, perception, or thought is transformed into neural representations that can be stored in memory.

endarterectomy: Surgical removal of plaque or blood clots in an artery.

endemic: Continually present among people in a geographic region.

endocarditis: An inflammation of the heart lining or valves, usually caused by bacterial infection.

endocardium: The inner layer of the wall of the heart.

endogenous opioids: Painkilling substances made by the body.

endometrium: The lining of the uterus.

endorphins: Substances in the body that reduce pain and create a feeling of well-being.

endoscope: A thin, flexible tube equipped with a light and camera that is used to see inside an organ or body cavity.

endoscopy: Inserting a flexible tube equipped with a light and camera into the body to see inside a body cavity or organ.

endothelins: Proteins that cause blood vessels to narrow and blood pressure to rise.

endothelium-derived relaxing factor: Chemicals in the body that cause blood vessels to expand or relax, lowering blood pressure. Often referred to as EDRF.

end-stage renal disease: Complete, or nearly complete, kidney failure. Dialysis or a transplant is needed for survival.

enkephalin: A chemical produced in the brain that reduces pain.

enteric nervous system: Part of the nervous system that controls the gastrointestinal system.

enteropathic: Disease affecting the intestinal tract.

enthesis: A place where a ligament, tendon, or muscle attaches to bone.

entropion: An eyelid, usually the lower lid, which folds inward so that the eyelashes rub against and irritate the surface of the eye.

enzyme: A substance that speeds up another chemical reaction. For example, digestive enzymes help speed up the digestion of food.

eosinophils: White blood cells that play an important role in allergic reactions.

epicardium: The outer layer of the wall of the heart.

epicondylitis: Pain and swelling in the tendons in the elbow, usually because of overuse.

epidemic: The occurrence of more cases of disease than expected within a population in a geographic area over a set period of time.

epidemiological study: An investigation of the links between certain behaviors or risk factors and the occurrence of disease or good health in a population.

epidermis: The outermost layer of skin.

epidural space: The space between the spinal cord and the bones of the spinal column where painkillers are injected.

epinephrine: A chemical that narrows blood vessels, increases heart rate, and helps trigger the fight-or-flight response to danger. Also called adrenaline.

EpiPen: A device used to inject a dose of medication (epinephrine) when a severe allergic reaction occurs.

epithelial cells: Cells which line organs and structures in the body, protecting or enclosing them.

epithelium: A layer of cells which lines organs and structures in the body, protecting or enclosing them.

erectile dysfunction: The inability to get or maintain an erection sufficient for intercourse. Sometimes referred to as ED.

erector spinae: A group of muscles and tendons in the back.

ergonomics: Designing and arranging work objects so that the user is comfortable, efficient, and less likely to be injured.

ergots: Substances derived from or made from a fungus; often used to treat headache.

eructation: The act of bringing up air from the stomach through the mouth with a characteristic sound. Commonly known as belching.

erythema: Redness of the skin because of widening of capillaries just below the surface of the skin.

erythema nodosum: Painful, red lumps beneath the skin; associated with Crohn's disease.

erythrocyte sedimentation rate: A test involving red blood cells; used to check for different infections, inflammations, and cancers.

erythropoietin: A hormone that controls red blood cell production.

esophageal manometry: A test to measure the pressure inside the lower part of the esophagus.

esophagitis: Irritation and swelling of the esophagus.

esophagus: The tube that carries food and liquids from the mouth to the stomach.

essential fats: Two fatty acids, omega-3 and omega-6, that the body needs for good health but can't make so they must come from foods and supplements.

essential hypertension: High blood pressure with no known cause; also called primary hypertension.

esterified estrogens: Artificially made hormones used to manage menopausal symptoms.

esthetician: A person who specializes in non-medical skin care and beauty treatments.

estradiol: The primary form of the sex hormone estrogen produced by women.

estrogen: The main sex hormone in women.

estrogen receptor: A site on the surface of some cells to which estrogen molecules attach.

estrogen-replacement therapy: Use of medications containing the sex hormone estrogen by women to replace naturally-occurring estrogen lost during menopause.

etidronate: A medication used to treat bone loss due to Paget's disease.

eustachian tube: A tube connecting the middle ear and the back of the nose that lets air into the middle ear.

euthyroid: Having a thyroid gland that works properly.

excitatory neurotransmitter: A chemical that forwards a message from one neuron to another.

excitotoxin: A brain chemical that damages neurons.

executive functions: The component of thinking that organizes, plans, decides, and inhibits inappropriate impulses.

exercise: A structured program of physical activity that helps an individual become physically fit.

exercise stress test: The use of a treadmill, stationary bicycle, or other exercise machine while hooked up to heart-monitoring equipment. The test is used to determine if the heart's blood supply is sufficient and if the rhythm remains normal when the heart is stressed.

exophthalmos: A protrusion or bulging of the eye that occurs with Graves' eye disease. Tissues behind the eye swell, forcing the eyeball forward. Also called proptosis.

exostosis: Abnormal bony growths in the ear caused by swimming regularly in cold water. Sometimes called surfer's ear.

experience sampling: A research technique for learning about people's activity patterns and psychological processes that involves paging them at random times to obtain brief reports.

expression hopping: A common phenomenon whereby people jump to a different expression of addiction. For example, people with heroin addiction might transition to alcohol addiction. Hopping is especially common during the recovery process.

expression of addiction: The specific way in which a person manifests addiction, for example, through the use of cocaine, or compulsive gambling.

extend: To straighten out a joint (for example, extending the arms overhead).

external otitis: An infection or irritation of the outer ear, ear canal, or both. Also called swimmer's ear.

extracapsular cataract surgery: A surgical technique to remove a cataract from the eye.

extract: A product made from substances that are drawn out of a plant or herb.

extraocular muscles: Six paired muscles that direct the eyes' circular, side-to-side, and up-and-down movements.

extrinsic factor: An outside factor that has an effect on a person's environment or well-being.