588 GlossaryVisceral(VISS-er-uhl) Pertaining to organs within a body
cavity, especially thoracic and abdominal organs (Chap-
ter 8).
Visceral effectors(VISS-er-uhl e-FEK-turs) Smooth mus-
cle, cardiac muscle, and glands; receive motor nerve
fibers of the autonomic nervous system; responses are
involuntary (Chapter 8).
Visceral muscle(VIS-ser-uhl MUSS-uhl) Another name
for smooth muscle tissue (Chapter 4).
Vital capacity(VY-tuhl kuh-PASS-i-tee) The volume of air
involved in the deepest inhalation followed by the most
forceful exhalation; average: 3500–5000 mL (Chap-
ter 15).
Vitamin(VY-tah-min) An organic molecule needed in small
amounts by the body for normal metabolism or growth
(Chapter 17).
Vitreous humor (VIT-ree-us HYOO-mer) The semi-
solid, gelatinous substance in the posterior cavity of the
eyeball; helps keep the retina in place (Chapter 9).
Vocal cords(VOH-kul KORDS) The pair of folds with-
in the larynx that are vibrated by the passage of air,
producing sounds that may be turned into speech
(Chapter 15).
Voluntary muscle(VAHL-un-tary MUSS-uhl) Another
name for striated or skeletal muscle tissue (Chapter 4).
Vomer(VOH-mer) The flat bone that forms the lower,
posterior portion of the nasal septum (from the Latin
“plowshare”) (Chapter 6).
Vomiting(VAH-mi-ting) Ejection through the mouth of
stomach and intestinal contents (Chapter 16).
Vulva(VUHL-vah) The female external genital organs
(Chapter 20).—W–X–Y–Z—
Wart(WART) An elevated, benign skin lesion caused by a
virus (Chapter 5).
White blood cells(WIGHT BLUHD SELLS) The cells
that destroy pathogens that enter the body and provide
immunity to some diseases; the five kinds are neutrophils,
eosinophils, basophils, lymphocytes, and monocytes
(Syn.—leukocytes) (Chapter 4).
White matter(WIGHT) Nerve tissue within the central
nervous system that consists of myelinated axons and
dendrites of interneurons (Chapter 8).
Worm (WURM) An elongated invertebrate; parasitic
worms include tapeworms and hookworms (Chapter 22).
Xiphoid process(ZYE-foyd) The most inferior part of the
sternum (from the Greek “sword-like”) (Chapter 6).
Yellow bone marrow (YELL-oh BOWN MAR-roh)
Primarily adipose tissue, found in the marrow cavities of
the diaphyses of long bones and in the spongy bone of
the epiphyses of adult bones (Chapter 6).
Yolk sac(YOHK SAK) An embryonic membrane that forms
the first blood cells for the developing embryo (Chap-
ter 21).
Z line(ZEE LYEN) The lateral boundary of a sarcomere in
muscle tissue; anchors myosin and actin filaments
(Chapter 7).
Zoonoses (ZOH-oh-NOH-seez) (Sing.—zoonosis) Dis-
eases of animals that may be transmitted to people under
certain conditions (Chapter 22).
Zygote(ZYE-goht) A fertilized egg, formed by the union of
the nuclei of egg and sperm; the diploid number of chro-
mosomes (46 for people) is restored (Chapter 20).30Scanlon(p3) Glossary 8/17/06 11:08 AM Page 588