Glossary 587
endoplasmic reticulum a network of membranes in the
cytoplasm of a cell
endosteum (ehn-DAHS-tee-um) tissue lining the
medullary cavity
endothelial cells (EHN-doh-THEE-lee-al) cells that
form the walls of lymphatic capillaries; their overlapping
structure helps fl uid enter the lymphatic capillaries and
makes it hard for the fl uid to leave
energy the capacity of a physical system to do work
enzymes proteins that speed up specifi c biological
reactions
ependymal cells (eh-PEHN-di-mal) units that form a
protective covering around the spinal cord and central
cavities within the brain
epicardium (EHP-i-KAHR-dee-um) the outermost layer
of the heart and the innermost layer of the pericardial sac
epidermal dendritic cells skin cells that initiate an
immune system response to the presence of foreign
bacteria or viruses
epidermis (EHP-i-DERM-is) the outer layer of skin
epididymis (EHP-i-DID-i-mis) a system of small ducts in
the testis, in which sperm mature
epiglottis (EHP-i-GLAHT-is) a fl ap of cartilaginous tissue
that covers the opening to the trachea; diverts food and
liquids to the esophagus during swallowing
epilepsy (EHP-i-LEHP-see) a group of brain disorders
characterized by repeated seizures over time
epimysium (EHP-i-MIZ-ee-um) the outermost sheath of
connective tissue that surrounds a skeletal muscle
epinephrine (ehp-i-NEHF-rin) the chief neurohormone of
the adrenal medulla that is used as a heart stimulant, a
vasoconstrictor (which narrows the blood vessels), and a
bronchodilator (which relaxes the bronchial tubes in the
lungs); adrenaline
epineurium (EHP-i-NOO-ree-um) the tough outer
covering of a nerve
epiphyseal plate (EHP-i-FIZ-ee-al) growth plate near the
ends of long bones where osteoblast activity increases
bone length
epiphysis (eh-PIF-i-seez) the bulbous end of a long bone
epithalamus (EHP-i-THAL-a-mus) the uppermost portion
of the diencephalon, which includes the pineal gland and
regulates sleep-cycle hormones
epithelia (EHP-i-THEE-lee-a) tissues that cover the body
and line cavities within the body
epithelial membranes (EHP-i-THEE-lee-al) thin sheets
of tissue lining the internal and external surfaces of the
body
epithelial tissue (EHP-i-THEE-lee-al) a class of tissue
that includes epithelia and glands
erectile dysfunction the inability to maintain an erection;
impotence
erectile tissue tissues that contain spaces in which blood
can pool and which, during sexual arousal, become
enlarged and rigid from engorgement with blood
erection the condition of erectile tissue when fi lled
with blood, which permits the penis to gain entry to the
female reproductive tract
equilibrium the condition of being evenly balanced
erythroblastosis fetalis (eh-RITH-roh-blas-TOH-sis
fee-TAL-is) a severe hemolytic disease of a fetus
or newborn caused by the production of maternal
antibodies against the fetal red blood cell antigens,
usually involving Rh incompatibility between the mother
and fetus
erythrocytes (e-RITH-roh-sights) red blood cells
erythropoiesis (eh-RITH-roh-poy-EE-sis) the process by
which red blood cells are produced
erythropoietin (EPO) (eh-RITH-roh-POY-eh-tin) a
hormone secreted by the kidneys that stimulates the
production of red blood cells
esophagus (eh-SAHF-a-gus) the muscular tube that
connects the pharynx and stomach
estrogen the female sex hormone that controls the
development and maintenance of female characteristics
ethmoidal sinuses (eth-MOY-dal) cavities in the lateral
masses of the ethmoid bone that are partly completed by
adjoining bones and communicate with the nasal cavity
ethmoid bone (EHTH-moyd) bone of the skull that forms
part of the nasal septum
Eustachian tube (yoo-STAY-shuhn) a channel that
connects the middle ear to the nasopharynx (back of the
throat) and serves to equalize pressure on either side of
the tympanic membrane
eversion movement in which the sole of the foot is rolled
outward
exchange vessels see capillaries
excretory ducts the channels through which tears are
released
exocrine gland a gland that secretes its product to the
outside world
exocytosis (EHK-soh-sigh-TOH-sis) the process in which
cell membranes fuse together and then push debris from
the cell vesicles to the outside of the cell
exophthalmos (EK-sahf-THAL-muhs) a condition in
which the eyes bulge outward due to an overactive
thyroid gland
expiration the process by which air is expelled from the
lungs; exhalation
expiratory reserve volume (ERV) the additional amount
of air that can be exhaled, or forced from the lungs,
immediately after a normal exhalation
expulsion the stage of labor that starts at full dilation and
ends when the baby is delivered
extensibility the ability to be stretched
extension movement that returns a body segment to
anatomical position in the sagittal plane
external acoustic meatus see auditory canal
external genitalia the reproductive structures on the
outside of the body
external otitis (oh-TIGH-tis) see swimmer’s ear
external respiration the process by which gas exchange
occurs between the alveoli in the lungs and the
pulmonary blood
external urethral orifi ce the opening at the end of the
urethra
external urethral sphincter a ring of skeletal muscle that
surrounds the intermediate part of the urethra where it
passes through the urogenital diaphragm; this muscle
is voluntarily controlled during release of urine from the
body
extracellular fl uid the fl uid—consisting of mostly water—
that surrounds a typical cell; interstitial fl uid
extracellular matrix the solid or gel-like substance that
surrounds a typical cell
extrinsic muscles (ek-STRIN-zik) muscles attached
to the outer surface of the eye that are responsible for
changing the direction of viewing
F
facet joints (FAS-eht) joints that connect the spinous
processes of the vertebrae