558 Glossarythe liver when excess amino acids are used for energy
production; the amino groups are converted to urea
(Chapter 16).
Decomposition reaction (DE-com-poh-ZI-shun) A
chemical reaction in which bonds in a large molecule are
broken and the products are two or more smaller mole-
cules (Chapter 2).
Decubitus ulcer(dee-KEW-bi-tuss UL-ser) The break-
down and death of skin tissue because of prolonged pres-
sure that interrupts blood flow to the area (Syn.—pressure
ulcer) (Chapter 5).
Defecation reflex(DEF-e-KAY-shun) The spinal cord
reflex that eliminates feces from the colon (Chapter 16).
Dehydration(DEE-high-DRAY-shun) Excessive loss of
water from the body (Chapter 5).
Deltoid(DELL-toyd) 1. The shoulder region. 2. The large
muscle that covers the shoulder joint (Chapter 1).
Dendrite(DEN-dright) The cellular process of a neuron
that carries impulses toward the cell body (Chapter 4).
Dentin(DEN-tin) The bone-like substance that forms the
inner crown and the roots of a tooth (Chapter 16).
Depolarization (DE-poh-lahr-i-ZAY-shun) The reversal
of electrical charges on either side of a cell membrane in
response to a stimulus; negative charge outside and posi-
tive charge inside; brought about by a rapid inflow of
sodium ions (Chapter 7).
Dermatology(DER-muh-TAH-luh-jee) The study of the
skin and skin diseases (Chapter 5).
Dermis(DER-miss) The inner layer of the skin, made of
fibrous connective tissue (Chapter 5).
Detached retina(dee-TACHD RET-in-nah) The separa-
tion of the retina from the choroid layer of the eyeball
(Chapter 9).
Detrusor muscle (de-TROO-ser) The smooth muscle
layer of the wall of the urinary bladder; contracts as part
of the urination reflex to eliminate urine (Chapter 18).
Diabetes mellitus(DYE-ah-BEE-tis mel-LY E-tus) Hypo-
secretion of insulin by the pancreas or the inability of
insulin to exert its effects; characterized by hyper-
glycemia, increased urinary output with glycosuria, and
thirst (Chapter 10).
Diagnosis(DYE-ag-NOH-sis) The procedures used to
identify the cause and nature of a person’s illness
(Chapter 1).
Diaphragm (DYE-uh-fram) The dome-shaped skeletal
muscle that separates the thoracic and abdominal cavi-
ties; moves downward when it contracts to enlarge the
thoracic cavity to bring about inhalation (Chapter 1).
Diaphysis(dye-AFF-i-sis) The shaft of a long bone; con-
tains a marrow canal filled with yellow bone marrow
(Chapter 6).
Diarthrosis(DYE-ar-THROH-sis) A freely movable joint
such as hinge, pivot, and ball-and-socket joints; all are
considered synovial joints because synovial membrane is
present (Chapter 6).Diastole(dye-AS-tuh-lee) In the cardiac cycle, the relax-
ation of the myocardium (Chapter 12).
Differential WBC count(DIFF-er-EN-shul KOWNT) A
laboratory test that determines the percentage of each of
the five kinds of white blood cells present in the blood
(Chapter 11).
Diffusion(di-FEW-zhun) The process in which there is
movement of molecules from an area of greater concen-
tration to an area of lesser concentration; occurs because
of the free energy (natural movement) of molecules
(Chapter 3).
Digestive system(dye-JES-tiv SIS-tem) The organ system
that changes food into simpler organic and inorganic
molecules that can be absorbed by the blood and lymph
and used by cells; consists of the alimentary tube and
accessory organs (Chapter 16).
Diploid number(DIH-ployd) The characteristic or usual
number of chromosomes found in the somatic (body)
cells of a species (human 46) (Chapter 3).
Disaccharide(dye-SAK-ah-ride) A carbohydrate molecule
that consists of two monosaccharides bonded together;
includes sucrose, maltose, and lactose (Chapter 2).
Disease(di-ZEEZ) A disorder or disruption of normal
body functioning (Chapter 1).
Disinfectant(DIS-in-FEK-tent) A chemical that destroys
microorganisms or limits their growth on inanimate
objects (Chapter 22).
Dissociation(dih-SEW-see-AY-shun) The separation of an
inorganic salt, acid, or base into its ions when dissolved
in water (Syn.—ionization) (Chapter 2).
Distal (DIS-tuhl) Furthest from the origin or point of
attachment (Chapter 1).
Distal convoluted tubule(DIS-tuhl KON-voh-LOO-ted)
The part of a renal tubule that extends from a loop of
Henle to a collecting tubule (Chapter 18).
Disulfide bond(digh-SUL-fyed BAHND) A covalent bond
between the sulfur atoms of two amino acids in a protein;
helps maintain the three-dimensional shape of the pro-
tein (Syn.—disulfide bridge) (Chapter 2).
Diverticulitis(DYE-ver-tik-yoo-LY E-tis) Inflammation of
diverticula in the intestinal tract (Chapter 16).
DNA (Deoxyribonucleic acid) A nucleic acid in the
shape of a double helix. Makes up the chromosomes of
cells and is the genetic code for hereditary characteristics
(Chapter 2).
DNA replication (REP-li-KAY-shun) The process by
which a DNA molecule makes a duplicate of itself. Takes
place before mitosis or meiosis, to produce two sets of
chromatids (potential chromosomes) within a cell
(Chapter 3).
Dominant(DAH-ma-nent) In genetics, a characteristic that
will be expressed even if only one gene for it is present in
the homologous pair of chromosomes (Chapter 21).
Dormant(DOOR-ment) Temporarily inactive; a state of
little metabolic activity (Chapter 22).30Scanlon(p3) Glossary 8/17/06 11:08 AM Page 558