Glossary 559Dorsal(DOR-suhl) Toward the back (Syn.—posterior)
(Chapter 1).
Dorsal cavity(DOR-suhl KAV-i-tee) Cavity that consists
of the cranial and spinal cavities (Chapter 1).
Dorsal root(DOR-suhl ROOT) The sensory root of a
spinal nerve (Chapter 8).
Dorsal root ganglion(DOR-suhl ROOT GANG-lee-on)
An enlarged area of the dorsal root of a spinal nerve
that contains the cell bodies of sensory neurons (Chap-
ter 8).
Down syndrome (DOWN SIN-drohm) A trisomy in
which three chromosomes of number 21 are present;
characterized by moderate to severe mental retardation
and certain physical malformations (Chapter 20).
Duct(DUKT) A tube or channel, especially one that carries
the secretion of a gland (Chapter 4).
Ductus arteriosus(DUK-tus ar-TIR-ee-OH-sis) A short
fetal blood vessel that takes most blood in the pulmonary
artery to the aorta, bypassing the fetal lungs (Chapter 13).
Ductus deferens(DUK-tus DEF-eer-enz) The tubular
organ that carries sperm from the epididymis to the ejac-
ulatory duct (Syn.—vas deferens) (Chapter 20).
Ductus venosus(DUK-tus ve-NOH-sus) A short fetal
blood vessel that takes blood from the umbilical vein to
the inferior vena cava (Chapter 13).
Duodenum(dew-AH-den-um) The first 10 inches of the
small intestine; the common bile duct enters it. (Chap-
ter 16).
Dura mater(DEW-rah MAH-ter) The outermost layer of
the meninges, made of fibrous connective tissue (Chap-
ter 8).
Dwarfism(DWORF-izm) The condition of being abnor-
mally small, especially small of stature due to a hereditary
or endocrine disorder; pituitary dwarfism is caused by a
deficiency of growth hormone (Chapter 10).
Dyspnea(DISP-nee-ah) Difficult breathing (Chapter 15).
Dysuria(dis-YOO-ree-ah) Painful or difficult urination
(Chapter 18).—E—
Ear(EER) The organ that contains the sensory receptors
for hearing and equilibrium; consists of the outer ear,
middle ear, and inner ear (Chapter 9).
Eccrine gland(EK-rin) The type of sweat gland (exocrine)
that produces watery sweat; important in maintenance of
normal body temperature (Chapter 5).
Ectoderm(EK-toh-derm) The outer primary germ layer of
cells of an embryo; gives rise to the epidermis and nerv-
ous system (Chapter 21).
Ectoparasite(EK-toh-PAR-uh-sight) A parasite that lives
on the surface of the body (Chapter 22).
Ectopic focus(ek-TOP-ik FOH-kus) The initiation of a
heartbeat by part of the myocardium other than the
sinoatrial node (Chapter 12).Ectopic pregnancy(ek-TOP-ik PREG-nun-see) Implan-
tation of a fertilized ovum outside the uterus; usually
occurs in the fallopian tube but may be in the ovary or
abdominal cavity; often results in death of the embryo
because a functional placenta cannot be formed in these
abnormal sites (Chapter 20).
Eczema(EK-zuh-mah) An inflammatory condition of the
skin that may include the formation of vesicles or pus-
tules (Chapter 5).
Edema(uh-DEE-muh) An abnormal accumulation of tissue
fluid; may be localized or systemic (Chapter 19).
Effector(e-FEK-tur) An organ such as a muscle or gland
that produces a characteristic response after receiving a
stimulus (Chapter 8).
Efferent(EFF-er-rent) To carry away from a center or main
part (Chapter 8).
Efferent arteriole(EFF-er-ent ar-TIR-ee-ohl) The arteri-
ole that takes blood from a glomerulus to the peritubular
capillaries that surround the renal tubule (Chapter 18).
Ejaculation (ee-JAK-yoo-LAY-shun) The ejection of
semen from the male urethra (Chapter 20).
Ejaculatory duct(ee-JAK-yoo-la-TOR-ee DUKT) The
duct formed by the union of the ductus deferens and the
duct of the seminal vesicle; carries sperm to the urethra
(Chapter 20).
Ejection fraction(ee-JEK-shun FRAK-shun) The percent
of blood in a ventricle that is pumped during systole; a
measure of the strength of the heart (Chapter 12).
Elastin(eh-LAS-tin) A protein that is found in the form of
elastic fibers in several types of connective tissue
(Chapter 4).
Electrocardiogram(ECG or EKG) (ee-LEK-troh-KAR-
dee-oh-GRAM) A recording of the electrical changes
that accompany the cardiac cycle (Chapter 12).
Electrolytes(ee-LEK-troh-lites) Substances that, in solu-
tion, dissociate into their component ions; include acids,
bases, and salts (Chapter 19).
Electron(e-LEK-trahn) A subatomic particle that has a
negative electrical charge; found orbiting the nucleus of
an atom (Chapter 2).
Element(EL-uh-ment) A substance that consists of only
one type of atom; 92 elements occur in nature (Chap-
ter 2).
Embolism(EM-boh-lizm) Obstruction of a blood vessel by
a blood clot or foreign substance that has traveled to and
lodged in that vessel (Chapter 11).
Embryo(EM-bree-oh) The developing human individual
from the time of implantation until the eighth week of
gestation (Chapter 21).
Embryonic disc(EM-bree-ON-ik DISK) The portion of
the inner cell mass of the early embryo that will develop
into the individual (Chapter 21).
Emphysema(EM-fi-SEE-mah) The deterioration of alve-
oli and loss of elasticity of the lungs; normal exhalation
and gas exchange are impaired (Chapter 15).30Scanlon(p3) Glossary 8/17/06 11:08 AM Page 559