eccrine glands: Sweat glands of the skin that produce a watery secretion.
echocardiography: The examination of the heart by using modified ultrasound techniques.
ectoderm: One of the three primary germ layers; covers the surface of the embryo and gives rise to the nervous system, the epidermis and associated glands, and a variety of other structures.
ectopic: Outside the normal location.
effector: A peripheral gland or muscle cell innervated by a motor neuron.
efferent: Away from.
efferent arteriole: An arteriole carrying blood away from a glomerulus of the kidney.
efferent fiber: An axon that carries impulses away from the central nervous system.
egestion: See defecation.
ejaculation: The ejection of semen from the penis as the result of muscular contractions of the bulbospongiosus and ischiocavernosus muscles.
ejaculatory ducts: Short ducts that pass within the walls of the prostate gland and connect the ductus deferens with the prostatic urethra.
elastase: A pancreatic enzyme that breaks down elastin fibers.
elastin: Connective tissue fibers that stretch and recoil, providing elasticity to connective tissues.
electrical coupling: A connection between adjacent cells that permits the movement of ions and the transfer of graded or conducted changes in the transmembrane potential from cell to cell.
electrocardiogram (ECG, EKG): A graphic record of the electrical activities of the heart, as monitored at specific locations on the body surface.
electroencephalogram (EEG): A graphic record of the electrical activities of the brain.
electrolytes: Soluble inorganic compounds whose ions will conduct an electrical current in solution.
electron: One of the three fundamental subatomic particles; bears a negative charge and normally orbits the protons of the nucleus.
electron transport system (ETS): The cytochrome system responsible for most of the energy production in cells; a complex bound to the inner mitochondrial membrane.
element: All the atoms with the same atomic number.
elephantiasis: A lymphedema caused by the infection and blockage of lymphatic vessels by mosquito-borne parasites.
elevation: Movement in a superior, or upward, direction.
elimination: The ejection of wastes from the body through urination or defecation.
embolism: The obstruction or closure of a vessel by an embolus.
embolus: An air bubble, fat globule, or blood clot drifting in the bloodstream.
embryo: The developmental stage beginning at fertilization and ending at the start of the third developmental month.
embryology: The study of embryonic development, focusing on the first 2 months after fertilization.
emesis: Vomiting.
emmetropia: Normal vision.
emulsification: The physical breakup of fats in the digestive tract, forming smaller droplets accessible to digestive enzymes; normally the result of mixing with bile salts.
enamel: Crystalline material similar in mineral composition to bone, but harder and without osteocytes, that covers the exposed surfaces of the teeth.
encephalitis: An inflammation of the brain.
endocarditis: An inflammation of the endocardium of the heart.
endocardium: The simple squamous epithelium that lines the heart and is continuous with the endothelium of the great vessels.
endochondral ossification: The conversion of a cartilaginous model to bone; the characteristic mode of formation for skeletal elements other than the bones of the cranium, the clavicles, and sesamoid bones.
endocrine gland: A gland that secretes hormones into the blood.
endocrine system: The endocrine glands of the body.
endocytosis: The movement of relatively large volumes of extracellular material into the cytoplasm via the formation of a membranous vesicle at the cell surface; includes pinocytosis and phagocytosis.
endoderm: One of the three primary germ layers; the layer on the undersurface of the embryonic disc; gives rise to the epithelia and glands of the digestive system, the respiratory system, and portions of the urinary system.
endogenous: Produced within the body.
endolymph: The fluid contents of the membranous labyrinth (the saccule, utricle, semicircular canals, and cochlear duct) of the inner ear.
endometrial glands: The secretory glands of the endometrium.
endometrium: The mucous membrane lining the uterus.
endomysium: A delicate network of connective tissue fibers that surrounds individual muscle cells.
endoneurium: A delicate network of connective tissue fibers that surrounds individual nerve fibers.
endoplasmic reticulum: A network of membranous channels in the cytoplasm of a cell that function in intracellular transport, synthesis, storage, packaging, and secretion.
endorphins: Neuromodulators, produced in the central nervous system, that inhibit activity along pain pathways.
endosteum: An incomplete cellular lining on the inner (medullary) surfaces of bones.
endothelium: The simple squamous epithelium that lines blood and lymphatic vessels.
enkephalins: Neuromodulators, produced in the central nervous system, that inhibit activity along pain pathways.
enteritis: An inflammation of the intestinal tract.
enterocrinin: A hormone secreted by the lining of the duodenum after exposure to chyme; stimulates the secretion of the submucosal glands.
enteroendocrine cells: Endocrine cells scattered among the epithelial cells that line the digestive tract.
enterogastric reflex: The reflexive inhibition of gastric secretion; initiated by the arrival of chyme in the small intestine.
enterohepatic circulation: The excretion of bile salts by the liver, followed by the absorption of bile salts by intestinal cells for return to the liver by the hepatic portal vein.
enterokinase: An enzyme in the lumen of the small intestine that activates the proenzymes secreted by the pancreas.
enzyme: A protein that catalyzes a specific biochemical reaction.
eosinophil: A microphage (white blood cell) with a lobed nucleus and red-staining granules; participates in the immune response and is especially important during allergic reactions.
ependyma: The layer of cells lining the ventricles and central canal of the central nervous system.
epicardium: A serous membrane covering the outer surface of the heart; also called visceral pericardium.
epidermis: The epithelium covering the surface of the skin.
epididymis: A coiled duct that connects the rete testis to the ductus deferens; site of functional maturation of spermatozoa.
epidural block: Anesthesia caused by the elimination of sensory inputs from dorsal nerve roots after drugs are introduced into appropriate regions of the epidural space.
epidural space: The space between the spinal dura mater and the walls of the vertebral foramen; contains blood vessels and adipose tissue; a common site of injection for regional anesthesia.
epiglottis: A blade-shaped flap of tissue, reinforced by cartilage, that is attached to the dorsal and superior surface of the thyroid cartilage; folds over the entrance to the larynx during swallowing.
epimysium: A dense layer of collagen fibers that surrounds a skeletal muscle and is continous with the tendons/aponeuroses of the muscle and with the perimysium.
epineurium: A dense layer of collagen fibers that surrounds a peripheral nerve.
epiphyseal cartilage: The cartilaginous region between the epiphysis and diaphysis of a growing bone.
epiphysis: The head of a long bone.
epistaxis: A nosebleed.
epithelium: One of the four primary tissue types; a layer of cells that forms a superficial covering or an internal lining of a body cavity or vessel.
eponychium: A narrow zone of stratum corneum that extends across the surface of a nail at its exposed base; also called cuticle.
equational division: The second division of meiosis.
equilibrium: A dynamic state in which two opposing forces or processes are in balance.
erection: The stiffening of the penis due to the engorgement of the erectile tissues of the corpora cavernosa and corpus spongiosum.
erythema: Redness and inflammation at the surface of the skin.
erythrocyte: A red blood cell; has no nucleus and contains large quantities of hemoglobin.
erythrocytosis: An abnormally large number of erythrocytes in the circulating blood.
erythropoietin: A hormone released by tissues, especially the kidneys, exposed to low oxygen concentrations; stimulates erythropoiesis (red blood cell formation) in bone marrow.
Escherichia coli: A normal bacterial resident of the large intestine.
esophagus: A muscular tube that connects the pharynx to the stomach.
essential amino acids: Amino acids that cannot be synthesized in the body in adequate amounts and must be obtained from the diet.
essential fatty acids: Fatty acids that cannot be synthesized in the body and must be obtained from the diet.
estrogens: A class of steroid sex hormones that includes estradiol.
eupnea: Normal quiet breathing.
evaporation: A movement of molecules from the liquid state to the gaseous state.
eversion: A turning outward.
excitable membranes: Membranes that conduct action potentials, a characteristic of muscle cells and nerve cells.
excitatory postsynaptic potential (EPSP): The depolarization of a postsynaptic membrane by a chemical neurotransmitter released by the presynaptic cell.
excretion: A removal from body fluids.
exocrine gland: A gland that secretes onto the body surface or into a passageway connected to the exterior.
exocytosis: The ejection of cytoplasmic materials by the fusion of a membranous vesicle with the cell membrane.
expiration: Exhalation; breathing out.
expiratory reserve: The amount of additional air that can be voluntarily moved out of the respiratory tract after one normal exhalation.
extension: An increase in the angle between two articulating bones; the opposite of flexion.
external auditory canal: A passageway in the temporal bone that leads to the tympanic membrane of the inner ear.
external ear: The auricle, external auditory meatus, external auditory canal, and tympanic membrane.
external nares: The nostrils; the external openings into the nasal cavity.
external respiration: The diffusion of gases between the alveolar air and the alveolar capillaries and between the systemic capillaries and peripheral tissues.
exteroceptors: General sensory receptors in the skin, mucous membranes, and special sense organs that provide information about the external environment and about our position within it.
extracellular fluid: All body fluids other than that contained within cells; includes plasma and interstitial fluid.
extraembryonic membranes: The yolk sac, amnion, chorion, and allantois.
extrafusal fibers: Contractile muscle fibers (as opposed to the sensory intrafusal fibers, or muscle spindles).
extrinsic pathway: A clotting pathway that begins with damage to blood vessels or surrounding tissues and ends with the formation of tissue thromboplastin.