Medical Dictionary: E

ear canal: An inch-long passage leading from the outer ear to the eardrum.

eardrum: A drum-tight membrane between the ear canal and the middle ear. As it vibrates, it transfers sound waves to the bones in the middle ear.

earwax: A substance secreted by the sebaceous glands in the ear that helps clean the ear canal, keeps dirt out of the ear, and lubricates the skin in the ear.

echocardiography: An imaging test that uses ultrasound to obtain a structural picture of the heart.

eczema: See atopic dermatitis.

elastin: The protein that gives skin its elasticity.

electrocardiogram (EKG): A graph recording the electrical activity responsible for the contraction and relaxation of the heart.

electroencephalogram (EEG): A recording of brain waves obtained by attaching flat metal discs (electrodes) to the scalp; it shows changes in brain wave voltage and frequency (in cycles per second).

electromyography (EMG): A series of diagnostic procedures that involve measuring electrical activity in muscles to help diagnose neuromuscular disorders.

elimination diets: A way of diagnosing food allergies in which suspected foods are eliminated from the diet one at a time to see if the allergic condition improves. Also called avoidance diets.

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.

embolus: A fragment of a blood clot that travels from the site where it was formed and lodges in a vessel in another part of the body, blocking blood flow.

emmenagogue: An agent that stimulates menstrual blood flow.

endometrium: The lining of the uterus.

endorphins: Natural substances that inhibit pain signals.

endoscope: A thin, flexible tube with a camera at its tip that is inserted into the body in order to examine some internal portion of the body.

endoscopy: A diagnostic test that allows a physician to view the upper gastrointestinal tract via a flexible tube inserted down the patient’s throat.

enthesis: A site where ligaments or tendons attach to bone; plural is entheses.

enzyme: A protein that regulates chemical changes in other substances.

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

epicondylitis: degeneration of tendons in the elbow, often the result of overuse.

epidermis: The outermost layer of skin.

epinephrine (adrenaline): A stress hormone instrumental in causing physiological responses when the body is experiencing acute stress.

epinephrine: A chemical released by the sympathetic nervous system that constricts blood vessels and increases heart rate; also called adrenaline.

EpiPen: A device to administer epinephrine very quickly to stave off anaphylaxis in the event of a severe allergic reaction.

ergonomics: the science of designing and arranging things people use to enable the safest, most efficient interaction between people and things.

ergots: Substances derived from a fungus that grows on rye and other grains; often used to treat headache.

erythropoietin (EPO): A hormone that stimulates production of red blood cells; may be deficient in people with chronic kidney disease.

essential fats: Beneficial fats, such as omega-3 and omega-6, that come exclusively from foods and supplements; they are not manufactured by the body.

essential hypertension: High blood pressure for which there is no known underlying cause; also called primary hypertension.

estradiol: Produced by the ovaries, the dominant form of estrogen in premenopausal women.

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

estrogen: A catch-all term for primarily female steroid hormones that are produced in the ovaries, adrenal glands, placenta, and testes. In women, estrogen is responsible for the development of secondary sexual characteristics (including breast growth), the maturation and function of sexual organs, and the growth of the long bones.

euthyroid: A term used to describe normal thyroid status.

executive functions: A group of cognitive activities that involves the overall regulation of thinking and behavior; the higher-order processes that enable us to plan, sequence, initiate, and sustain our behavior toward some goal, incorporating feedback and making adjustments along the way.

extract: A product created by using a solvent such as alcohol to separate out (“extract”) certain chemicals from an herb. A fluid extract is an herbal product produced by repeatedly passing a mixture of alcohol and water over a plant mixture.

extrinsic factor: An influence in a person’s environment; extrinsic factors in home accidents might include the quality of lighting or the ways in which chemicals are stored.