Medical Terminology
Glossary
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dartos - contractile tissue under the skin of the scrotum
debility - weakness of tonicity in functions or organs of the body
decibel (db) - a LETTER of measurement for relative sound intensity (loudness)
decidua - that portion of the endometrium of the uterus (all but the deepest layer) that is modified for pregnancy and shed after childbirth
deciduous - falling off or being shed seasonally or at a particular stage of development; in the body, referring to the first set of teeth
decubitus ulcer - tissue destruction due to a constant deficiency of blood to tissues overlying a bony projection subjected to prolonged pressure against an object like a bed, cast, or splint; also bedsore, pressure sore, trophic ulcer
decussation - a crossing-over; usually refers to the crossing of most of the fibers in the large motor tracts to opposite sides in the medullary pyramids
deep fascia - a sheet of connective tissue wrapped around a muscle to hold it in place
defecation - discharge of feces from the rectum
defibrillation - delivery of a very strong electrical current to the heart in an attempt to stop ventricular fibrillation
degeneration - a change from a higher to a lower state; a breakdown in structure
deglutition - the act of swallowing
dehydration - excessive water loss from the body or its parts
delirium - a transient disorder of abnormal cognition (perception, thinking or memory) and disordered attention, accompanied by disturbance of sleep-wake cycles and psychomotor behavior; also called acute confusional state (ACS)
dementia - an organic mental disorder resulting in permanent or progressive general loss of intellectual abilities (e.g., memory, judgement, and abstract thinking) and changes in personality; most common cause is Alzheimer's disease
demineralization - loss of calcium and phosphorus from bones
denaturation - disruption of the tertiary structures of a protein by agents, such as heat, pH changes, or other physical or chemical methods; as a result, the protein loses its physical and biological properties
dendrite - a nerve cell process that carries a nerve impulse toward the cell body
dendritic cell - one type of antigen-presenting cell with long branchlike projections, for example, Langerhans cells in the epidermis
dens - tooth
dental caries - gradual demineralization of the enamel and dentin of a tooth; it may invade the pulp and alveolar bone; also called tooth decay
denticulate - finely toothed or serrated; characterized by a series of small, pointed projections
dentin - osseus tissues of a tooth, enclosing the pulp cavity
dentition - the eruption of teeth; the number, shape and arrangement of teeth
deoxyribonucleic acid/DNA - nucleic acid in the shape of a double helix; constructed of nucleotides consisting of 1 of 4 nitrogenous bases (adenine, cytosine, guanine, or thymine), deoxyribose, and a phosphate group; the genetic information is encoded in the nucleotides
depolarization - in neurophysiology, the reduction of voltage across a cell membrane; expressed as a movement toward less negative (more positive) voltages on the interior side of the cell membrane
depression - movement in which a part of the body moves downward
dermatology - medical specialty dealing with diseases of the skin
dermatome - an instrument for incising the skin or cutting thin transplants of skin; the cutaneous area developed from one embryonic spinal cord segment and receiving most of its innervation from one spinal nerve
dermis - a layer of dense connective tissue lying deep to the epidermis; the true skin or corium
detritus - particulate matter produced by or remaining after the wearing away or disintegration of a substance or tissue; scales, crusts, or loosened skin
detrusor muscle - muscle in the wall of the urinary bladder
diabetes insipidus - condition caused by hyposecretion of antidiuretic hormone (ADH) and characterized by thirst and by excretion of large amounts of urine
diabetes mellitus - hereditary condition caused by hyposecretion of insulin; characterized by hyperglycemia, increased urine production, excessive thirst and excessive eating
diagnosis - distinguishing one disease from another or determining the nature of a disease from signs and symptoms by inspection, palpation, laboratory tests, and other means
dialysis - the process of separating small molecules from large by the difference in their rates of diffusion through a selectively permeable membrane
diapedesis - the passage of white blood cells through intact blood vessel walls
diaphragm - partition separating one area from another, e.g., the dome-shaped skeletal muscle between the thoracic and abdominal cavities; or a dome-shaped structure that fits over the uterine cervix, usually with a spermicide, to prevent conception
diaphysis - the shaft of a long bone
diarrhea - frequent defecation of liquid feces caused by increased intestinal motility
diarthrosis - articulation in which opposing bones move freely, as in a hinge joint
diastole - in the cardiac cycle, the phase of relaxation or dilation of the heart muscle, especially, the ventricles
diastolic blood pressure - the force exerted by blood on arterial walls during ventricular relaxation; the lowest blood pressure measured in the large arteries, about 80 mm Hg under normal conditions for a young, adult male
diencephalon - part of the brain consisting primarily of the thalamus and the hypothalamus
differential - a white blood cell count that reports the number of each kind of white blood cell in a sample of 100 cells
differentiation - the acquisition of specific functions different from those of the original general type
diffusion - a passive process in which there is a net or greater movement of molecules or ions from a region of high concentration to a region of low concentration until equilibrium is reached
digestion - mechanical and chemical breakdown of food to simple molecules that can be absorbed and used by body cells
dilate - to expand or swell
dilation and curettage - following dilation of the uterine cervix, the uterine endometrium is scraped with a curette (spoon-shaped instrument); also called a D and C
diploid - having the number of chromosomes characteristically found in somatic cells of an organism; symbolized 2n
diplopia - double vision
dislocation - the displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsules; also called luxation
dissect - to separate tissues & parts of a cadaver (corpse) or an organ for anatomical study
dissociation - the separation of inorganic acids, bases, and salts into ions when dissolved in water; also called ionization
distal - farther from the attachment of an extremity to the trunk or to a structure; farther from the point of origin
diuretic - chemical that inhibits sodium reabsorption, reduces antidiuretic hormone (ADH) concentration, & increases urine volume by inhibiting facultative reabsorption of water
diurnal - repeating daily; pertaining to daylight hours (opposite: nocturnal)
divergence - an anatomical arrangement in which the synaptic end bulbs of one presynaptic neuron terminate on several postsynaptic neurons
diverticulitis - inflammation of diverticula, saclike outpouchings of the colonic wall, when the muscularis becomes weak
diverticulum - sac or pouch in the wall of a canal or organ, especially in the colon
donor insemination - deposition of seminal fluid within the vagina or cervix at a time during the menstrual cycle when pregnancy is likely; may be homologous (husband's semen) or heterologous (donor's semen); also called artificial insemination
dorsal ramus - a branch of a spinal nerve containing motor and sensory fibers supplying the muscles, skin, and bones of the posterior part of the head, neck, and trunk
dorsiflexion - bending the foot in the direction of the dorsum (upper surface)
dropsy - a condition in which there is abnormal accumulation of water in the tissues and cavities
ductus arteriosus - a small vessel connecting the pulmonary trunk with the aorta; found only in the fetus
ductus epididymis - tightly coiled tube inside the epididymis, distinguished into a head, body, and tail; it is the site where spermatozoa under-go maturation
ductus (vas) deferens - duct that conveys spermatozoa from the epididymis to the ejaculatory duct; also called the seminal duct
ductus venosus - a small vessel in the fetus that helps the circulation bypass the liver
duodenal gland - gland in the submucosa of the duodenum that secretes an alkaline mucus to protect the lining of the small intestine from the action of enzymes & to help neutralize the acid in chyme; also called Brunner's gland
duodenum - the first 25 cm (10 in.) of the small intestine
dura mater - outer membrane (meninx) covering the brain and spinal cord
dynamic equilibrium - the maintenance of body position, mainly the head, in response to sudden movements such as rotation
dysfunction - absence of complete normal function
dyslexia - impairment of the brain's ability to translate images received from the eyes or ears into understandable language
dysmenorrhea - painful menstruation
dysphagia - difficulty in swallowing
dysplasia - change in the size, shape, and organization of cells due to chronic irritation or inflammation; may revert to normal if stress is removed or may progress to neoplasia
dyspnea - shortness of breath
dystocia - difficult labor due to such factors as pelvic deformities, malpositioned fetus, and premature rupture of fetal membranes
dystrophia - progressive weakening of a muscle
dysuria - painful urination