Glossary 565Hemolysis(he-MAHL-e-sis) Lysis or rupture of red blood
cells; may be the result of an antigen–antibody reaction
or of increased fragility of red blood cells in some types
of anemia (Chapter 11).
Hemophilia(HEE-moh-FILL-ee-ah) A hereditary blood
disorder characterized by the inability of the blood to
clot normally; hemophilia A is caused by a lack of clotting
factor 8 (Chapter 11).
Hemopoietic tissue (HEE-moh-poy-ET-ik) A blood-
forming tissue, primarily the red bone marrow; lym-
phatic tissue produces some lymphocytes (Chapter 4).
Hemorrhoids(HEM-uh-royds) Varicose veins of the anal
canal (Chapter 13).
Hemostasis(HEE-moh-STAY-sis) Prevention of blood
loss; the mechanisms are chemical clotting, vascular
spasm, and platelet plug formation (Chapter 11).
Heparin(HEP-ar-in) A chemical that inhibits blood clot-
ting, an anticoagulant; produced by basophils. Also used
clinically to prevent abnormal clotting, such as following
some types of surgery (Chapter 11).
Hepatic duct(hep-PAT-ik DUKT) The duct that takes
bile out of the liver; joins the cystic duct of the gallblad-
der to form the common bile duct (Chapter 16).
Hepatic portal circulation(hep-PAT-ik POOR-tuhl) The
pathway of systemic circulation in which venous blood
from the digestive organs and the spleen circulates
through the liver before returning to the heart (Chapter
13).
Hepatitis(HEP-uh-TIGH-tis) Inflammation of the liver,
most often caused by the hepatitis viruses A, B, or C
(Chapter 16).
Herniated disc(HER-nee-ay-ted DISK) Rupture of an
intervertebral disc (Chapter 6).
Herpes simplex(HER-peez SIM-pleks) A virus that causes
lesions in the skin or mucous membranes of the mouth
(usually type 1) or genital area (usually type 2); either
type may cause death or mental retardation of infants of
infected women (Chapter 20).
Heterozygous(HET-er-oh-ZYE-gus) Having two differ-
ent alleles for a trait (Chapter 21).
Hexose sugar(HEKS-ohs) A six-carbon sugar, such as glu-
cose, that is an energy source (in the process of cell res-
piration) (Chapter 2).
Hilus(HIGH-lus) An indentation or depression on the
surface of an organ such as a lung or kidney (Chap-
ter 15).
Hinge joint(HINJ) A diarthrosis that permits movement in
one plane (Chapter 6).
Hip bone(HIP BOWNE) The flat bone that forms half of
the pelvic bone; consists of the upper ilium, the lower
posterior ischium, and the lower anterior pubis (Chap-
ter 6).
Hippocampus(hih-poh-KAM-pus) Part of the brain in
the temporal lobe on the floor of the lateral ventricle;it is essential for the formation of new memories (Chap-
ter 8).
Histamine(HISS-tah-meen) An inflammatory chemical
released by damaged tissues as part of innate immunity;
stimulates increased capillary permeability and vasodila-
tion (Chapter 5).
Hives(HIGHVZ) A very itchy eruption of the skin, usually
the result of an allergy (Chapter 5).
Hodgkin’s disease(HODJ-kinz) A malignancy of the lym-
phatic tissue; a lymphoma (Chapter 14).
Homeostasis (HOH-mee-oh-STAY-sis) The state in
which the internal environment of the body remains rel-
atively stable by responding appropriately to changes
(Chapter 1).
Homologous pair(hoh-MAHL-ah-gus) A pair of chromo-
somes, one maternal and one paternal, that contain genes
for the same characteristics (Chapter 21).
Homozygous(HOH-moh-ZYE-gus) Having two similar
alleles for a trait (Chapter 21).
Hormone(HOR-mohn) The secretion of an endocrine
gland that has specific effects on particular target organs
(Chapter 4).
Human leukocyte antigens (HLA)(HYOO-man LOO-
koh-sight AN-ti-jens) The antigens on white blood cells
that are representative of the antigens present on all the
cells of the individual; the “self ” antigens that are con-
trolled by several genes on chromosome number 6; the
basis for tissue typing before an organ transplant is
attempted (Chapter 11).
Humerus(HYOO-mer-us) The long bone of the upper
arm (Chapter 6).
Humoral immunity(HYOO-mohr-uhl im-YOO-ni-tee)
The mechanism of adaptive immunity that involves anti-
body production and the destruction of foreign antigens
by the activities of B cells, T cells, and macrophages
(Syn.—antibody-mediated immunity) (Chapter 14).
Hyaline membrane disease(HIGH-e-lin MEM-brayn) A
pulmonary disorder of premature infants whose lungs
have not yet produced sufficient pulmonary surfactant to
permit inflation of the alveoli (Chapter 15).
Hydrochloric acid (HIGH-droh-KLOR-ik ASS-id) An
acid secreted by the parietal cells of the gastric pits of the
stomach; activates pepsin and maintains a pH of 1–2 in
the stomach (Chapter 16).
Hydrogen bond(HIGH-droh-jen BAHND) A weak bond
that helps maintain the three-dimensional shape of pro-
teins and nucleic acids (Chapter 2).
Hymen(HIGH-men) A thin fold of mucous membrane
that partially covers the vaginal orifice (Chapter 20).
Hypercalcemia (HIGH-per-kal-SEE-mee-ah) A high
blood calcium level (Chapter 10).
Hypercapnia(HIGH-per-KAP-nee-ah) A higher than nor-
mal blood level of carbon dioxide (usually 45–50
mmHg) (Chapter 15).30Scanlon(p3) Glossary 8/17/06 11:08 AM Page 565