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Medical Dictionary


decholesterolization (de′ko-les′ter-ol-i-za′shun)
Therapeutic reduction of the cholesterol concentration of the blood.

deci- (d)
Prefix used in the SI and metric system to signify one-tenth (10−1). [L. decimus, tenth]

decibel (dB, db) (des′i-bel)
One-tenth of a bel; unit for expressing the relative intensity of sound on a logarithmic scale. [L. decimus, tenth, + bel]

decidua (de-sid′u-a)
SYN: deciduous membrane. [L. deciduus, falling off (qualifying membrana, membrane, understood)] d. basalis the area of endometrium between the implanted chorionic vesicle and the myometrium, which develops into the maternal part of the placenta. SYN: d. serotina. d. capsularis the layer of endometrium overlying the implanted chorionic vesicle; it becomes progressively attenuated as the chorionic vesicle enlarges and, by the fourth month, is squeezed against the d. parietalis and thereafter undergoes rapid regression. SYN: d. reflexa, membrana adventitia (2) . ectopic d. decidual cells which may be found in the cervix, appendix, or areas other than the endometrium. d. menstrualis the succulent mucous membrane of the nonpregnant uterus at the menstrual period. d. parietalis the altered mucous membrane lining the main cavity of the pregnant uterus other than at the site of attachment of the chorionic vesicle. SYN: d. vera. d. polyposa d. parietalis showing polypoid projections of the endometrial surface. d. reflexa SYN: d. capsularis. d. serotina SYN: d. basalis. d. spongiosa the portion of the d. basalis attached to the myometrium. d. vera SYN: d. parietalis.

decidual (de-sid′u-al)
Relating to the decidua.

deciduate (de-sid′u-at)
Relating to those mammals ( e.g., humans, dogs, rodents) that shed maternal uterine tissue when expelling the placenta at birth, in contrast to indeciduate mammals (horse, pig). [see deciduation]

deciduation (de-sid-u-a′shun)
Shedding of endometrial tissue during menstruation. [L. deciduus, falling off]

deciduitis (de-sid-u-i′tis)
Inflammation of the decidua.

deciduoma (de-sid-u-o′ma)
An intrauterine mass of decidual tissue, probably the result of hyperplasia of decidual cells retained in the uterus. SYN: placentoma. Loeb d. mass of decidual tissue produced in the uterus, in the absence of a fertilized ovum, by means of mechanical or hormonal stimulation.

deciduous (de-sid′u-us)
1. Not permanent; denoting that which eventually falls off. 2. (D) (in dental formulas)In dentistry, often used to designate the first or primary dentition. See d. tooth. [L. deciduus, falling off]

decigram (des′i-gram)
One-tenth of a gram.

deciliter (des′i-le-ter)
One-tenth of a liter.

decimeter (des′i-me-ter)
One-tenth of a meter.

decimorgan (des′i-mor-gan)
See morgan.

decinormal (des-i-nor′mal)
One-tenth of normal, denoting the concentration of a solution.


decision tree
Alternative choices available at each stage of deciding how to manage a clinical problem, displayed graphically; at each branch or decision node, the probabilities of each outcome that can be predicted are shown; the relative worth of each outcome is described in terms of its utility or quality of life, e.g., as measured by probability of death, life expectancy, or freedom from disability.

de Clerambault
G., French psychiatrist, 1872–1934. See de Clerambault syndrome.

declinator (dek′lin-a-ter, -tor)
A retractor that holds certain structures out of the way during an operation.

declive (de-kliv′) [TA]
The posterior sloping portion of the monticulus of the vermis of the cerebellum; vermal lobule immediately caudal to the primary fissure; lobule VI. SYN: declivis, lobulus clivi. [L. declivis, sloping downward, fr. clivus, a slope]

declivis (de-kli′vis)
SYN: declive.

decoction (de-kok′shun)
1. The process of boiling. 2. The pharmacopeial name for preparations made by boiling crude vegetable drugs, and then straining, in the proportion of 50 g of the drug to 1000 mL of water. SYN: apozem, apozema. [L. decoctio, fr. de-coquo, pp. -coctus, to boil down]

décollement (da-kul-mon′)
Rarely used term for surgical separation of tissues or organs which are adherent, either normally or pathologically. [Fr. ungluing]

decompensation (de′kom-pen-sa′shun)
1. A failure of compensation in heart disease. 2. The appearance or exacerbation of a mental disorder due to failure of defense mechanisms. corneal d. corneal edema resulting from failure of the corneal endothelium to maintain deturgescence.

decompose (de′kom-poz)
1. To resolve a compound into its component parts; to disintegrate. 2. To decay; to putrefy. [L. de, from, down, + com-pono, pp. -positus, to put together]

decomposition (de′kom-po-zish′un)
SYN: putrefaction.

decompression (de′kom-presh-un)
Removal of pressure. [L. de-, from, down, + com-primo, pp. -pressus, to press together] cardiac d. incision into the pericardium or aspiration of fluid from the pericardium to relieve pressure due to blood or other fluid in the pericardial sac. SYN: pericardial d.. cerebral d. removal of a piece of the cranium, with incision of the dura, to relieve intracranial pressure. explosive d. SYN: rapid d.. internal d. removal of intracranial tissue, usually tumor, hematoma, or brain tissue; to relieve pressure. nerve d. release of pressure on a nerve trunk by the surgical excision of constricting bands or widening of a bony canal. optic nerve sheath d. a venting of the optic nerve sheath into the retrobulbar space, by slitting or by fenestrating the sheath. See optic nerve sheath fenestration. orbital d. removal of a portion of the bony orbit, usually superior (Naffziger operation), lateral (Krönlein operation), or inferior (Ogura operation). pericardial d. SYN: cardiac d.. rapid d. sudden severe expansion of gases due to a reduction in ambient pressure. SYN: explosive d.. spinal d. the removal of pressure upon the spinal cord as created by a tumor, cyst, hematoma, herniated nucleus pulposus, abscess, or bone. suboccipital d. d. of the posterior fossa by occipital craniectomy and opening of the dura. subtemporal d. d. of the brain by temporal craniectomy and opening of the dura over the inferolateral surface of the temporal lobe. trigeminal d. d. of the trigeminal nerve root.

decongestant (de-kon-jes′tant)
1. SYN: decongestive. 2. An agent that possesses this action.

decongestive (de-kon-jes′tiv)
Having the property of reducing tissue swelling. SYN: decongestant (1) .

decontamination (de′kon-tam-i-na′shun)
Removal or neutralization of poisonous gas or other injurious agents from the environment.

deconvolution (de-con-vo-loo′shun)
A mathematic technique for solution of functions whose input includes their output; used to solve for the image elements in computed tomography or magnetic resonance imaging. [de- + L. convulutio, a rolling up, fr. convolvo, to roll up]

decortication (de-kor-ti-ka′shun)
1. Removal of the cortex, or external layer, beneath the capsule from any organ or structure. 2. An operation for removal of the residual clot and/or newly organized scar tissue that form after a hemothorax or neglected empyema. [L. decortico, pp. -atus, to deprive of bark, fr. de, from, + cortex, rind, bark] cerebral d. destruction of the cerebral cortex, usually due to anoxia. reversible d. a temporary loss of function of the cerebral cortex.

decrement (dek′re-ment)
1. Decrease. 2. Decrease in conduction velocity at a particular point; a result of altered properties at that point. SEE ALSO: decremental conduction. [L. decrementum, fr. decresco, to decrease]

decrepitation (de-krep-i-ta′shun)
Crackling; the snapping of certain salts when heated. [L. de, from, + crepo, pp. crepitus, to crackle]

decrudescence (de-kroo-des′ens)
Abatement of the symptoms of disease. [L. de, from, + crudesco, to become worse, fr. crudus, crude]

decubital (de-ku′bi-tal)
Relating to a decubitus ulcer.

decubitus (de-ku′bi-tus)
1. The position of the patient in bed; e.g., dorsal d., lateral d.. See d. film. 2. Sometimes used in referring to a d. ulcer. [L. decumbo, to lie down] Andral d. position assumed by the patient who lies on the sound side in cases of beginning pleurisy. ventral d. pressure sores (d. ulceration) occurring in ventral locations, such as the abdominal wall or the anterior surface of an extremity.

decurrent (de-kur′ent)
Extending downward. [L. de-curro, pp. -cursus, to run down]

decussate (de′ku-sat, de-kus′at)
1. To cross. 2. Crossed like the arms of an X. [L. decusso, pp. -atus, to make in the form of an X, fr. decussis, a large, bronze Roman (2nd c. BC), 10-unit coin marked with an X to indicate its denomination]

decussatio, pl .decussationes (de-ku-sa′she-o, -o′nez) [TA]
1. In general, any crossing over or intersection of parts. 2. The intercrossing of two homonymous fiber bundles as each crosses over to the opposite side of the brain in the course of its ascent or descent through the brainstem or spinal cord. SYN: decussation. [L. (see decussate)] d. brachii conjunctivi SYN: decussation of superior cerebellar peduncles. d. fibrarum nervorum trochlearium [TA] SYN: decussation of trochlear nerve fibers. d. fontinalis decussationes tegmentales. d. lemnisci mediales [TA] SYN: decussation of medial lemniscus. d. motoria SYN: decussation of pyramids. d. pedunculorum cerebellarium superiorum [TA] SYN: decussation of superior cerebellar peduncles. d. pyramidum [TA] SYN: decussation of pyramids. d. sensoria SYN: decussation of medial lemniscus. decussationes tegmentales [TA] SYN: tegmental decussations, under decussation. d. tegmentalis anterior [TA] See tegmental decussations, under decussation. d. tegmentalis posterior [TA] See tegmental decussations, under decussation.

decussation (de-ku-sa′shun)
SYN: decussatio. [L. decussatio] anterior tegmental d. [TA] See tegmental decussations (2) . d. of brachia conjunctiva SYN: d. of superior cerebellar peduncles. dorsal tegmental d. [TA] See tegmental decussations. d. of the fillet SYN: d. of medial lemniscus. Forel d. tegmental decussations (2) . fountain d. tegmental decussations (1) . Held d. the crossing of some of the fibers arising from the cochlear nuclei to form the lateral lemniscus. d. of medial lemniscus the intercrossing of the fibers of the left and right medial lemniscus ascending from the gracile and cuneate nuclei, immediately rostral to the level of the d. of the pyramidal tracts in the medulla oblongata. SYN: decussatio lemnisci mediales [TA] , decussatio sensoria, d. of the fillet, sensory d. of medulla oblongata. Meynert d. tegmental decussations (1) . motor d. SYN: d. of pyramids. optic d. SYN: optic chiasm. posterior tegmental d. [TA] tegmental decussations (1) . d. of pyramids [TA] the intercrossing of the bundles of corticospinal fibers at the lower border region of the medulla oblongata. SYN: decussatio pyramidum [TA] , decussatio motoria, motor d.. rubrospinal d. tegmental decussations (2) . sensory d. of medulla oblongata SYN: d. of medial lemniscus. d. of superior cerebellar peduncles [TA] the d. of the left and right superior cerebellar peduncles in the tegmentum of the caudal mesencephalon. SYN: decussatio pedunculorum cerebellarium superiorum [TA] , decussatio brachii conjunctivi, d. of brachia conjunctiva, Wernekinck d.. tectospinal d. tegmental decussations (1) . tegmental decussations 1. the posterior tegmental d. [TA] (dorsal tegmental d. [TA], fountain d., Meynert's d.) is formed by the crossing of the left and right tectospinal and tectobulbar tracts; 2. the anterior tegmental d. [TA] (ventral tegmental d. [TA], Forel's d.) is formed by the crossing of the left and right rubrospinal and rubrobulbar tracts; both decussations are located in the mesencephalon. SYN: decussationes tegmentales [TA] . d. of trochlear nerve fibers [TA] the crossing of the two trochlear nerves at their exit through the velum medullare anterius. SYN: decussatio fibrarum nervorum trochlearium [TA] . ventral tegmental d. See tegmental decussations (2) . Wernekinck d. SYN: d. of superior cerebellar peduncles.

decussationes (de-kus-a-she-o′nez)
Plural of decussatio.

dedentition (de-den-tish′un)
Obsolete term denoting loss of teeth.

dedifferentiation (de-dif′er-en-she-a′shun)
1. The return of parts to a more homogeneous state. 2. SYN: anaplasia.

dedolation (de-do-la′shun)
A slicing wound made by a sharp instrument grazing the surface. [L. de-dolo, pp. -atus, to hew away]

deduction (de-duk′shun)
The logical derivation of a conclusion from certain premises. The conclusion will be true if the premises are true and the deductive argument is valid. Cf.:induction (9) .

de-efferentation (de-ef-er-en-ta′shun)
A loss of the motor nerve fibers to an area of the body. [L. de, from, + efferent]

deep (dep) [TA]
Situated at a deeper level in relation to a specific reference point. Cf.:superficialis. SYN: profundus [TA] .

de-epicardialization (de-ep-i-kar′de-al-i-za′shun)
Obsolete surgical destruction of the epicardium, usually by the application of phenol, designed (unsuccessfully) to promote collateral circulation to the myocardium.

Hermann, German physician, 1867–1915. See D. bodies, under body.

def, DEF
Abbreviation for decayed, extracted, and filled tooth. See d. caries index.

defatigation (de-fat-i-ga′shun)
Weariness, exhaustion, or extreme fatigue. [L. de-fatigo, pp. -atus, to tire out]

defecate (def′e-kat)
To perform defecation.

defecation (def-e-ka′shun)
The discharge of feces from the rectum. SYN: motion (2) , movement (3) . [L. defaeco, pp. -atus, to remove the dregs, purify]

defecography (de-fe-kog′ra-fe)
Radiographic examination of the act of defecation of a radiopaque stool. [defecation + G. grapho, to write]

defect (de′fekt)
An imperfection, malformation, dysfunction, or absence; an attribute of quality, in contrast with deficiency, which is an attribute of quantity. [L. deficio, pp. -fectus, to fail, to lack] aortic septal d., aorticopulmonary septal d. a small congenital opening between the aorta and pulmonary artery about 1 cm above the semilunar valves, e.g., aorticopulmonary window. SYN: aorticopulmonary window. atrial septal d. a congenital d. in the septum between the atria of the heart, due to failure of the foramen primum or secundum to close normally; may involve atrioventricular canal cushions; occasionally there is strong evidence of autosomal dominant inheritance [MIM*108800]. In varying degree, it is also a common feature of the autosomal recessive Ellis-van Creveld syndrome [MIM*225500] and the autosomal dominant Holt-Oram syndrome [MIM*142900]. atrial ventricular canal d. a d. caused by deficient or absent septal tissue immediately above and below the normal level of the atrioventricular valves, including the region normally occupied by the A-V septum in hearts with two ventricles. The A-V valves are abnormal to a varying degree. birth d. d. present at birth; sometimes referred to as congenital d.. congenital ectodermal d. SYN: congenital ectodermal dysplasia. coupling d. familial goiter. Eisenmenger d. SYN: Eisenmenger complex. endocardial cushion d. SYN: persistent atrioventricular canal. fibrous cortical d. a common 1 to 3 cm d. in the cortex of a bone, most commonly the lower femoral shaft of a child, filled with fibrous tissue. Nonosteogenic or nonossifying fibroma by convention refers to lesions greater than 3 cm in diameter. SEE ALSO: nonossifying fibroma. SYN: nonosteogenic fibroma. filling d. displacement of contrast medium by a space-occupying lesion in a radiographic study of a contrast-filled hollow viscus, such as a polyp on a barium enema; also applied to defects in the otherwise uniform distribution of radionuclide in an organ, such as a metastasis in the liver on a 99mTc-sulfur colloid scan. Gerbode d. a d. in the interventricular portion of the membranous septum, associated with a communication between the right ventricle and the right atrium through an abnormality in the tricuspid valve. iodide transport d. familial goiter. iodotyrosine deiodinase d. familial goiter. luteal phase d. a condition characterized by inadequate secretion of progesterone during the luteal phase of the menstrual cycle, with resultant infertility; subnormal luteal function commonly attributed to abnormal pituitary gonadotropin secretion. SYN: luteal phase deficiency. metaphyseal fibrous cortical d. a small fibrous cortical d. located in the metaphysis of a long bone. organification d. familial goiter. osteoporotic marrow d. (os′te-o-po-ro′tik) focal osteoporotic bone marrow d. of the jaw; a focal radiolucent d. composed of normal marrow. postinfarction ventricular septal d. a d. developed in the ventricular septum resulting from rupture of an acute myocardial infarction. relative afferent pupillary d. relative afferent pupillary d.. salt-losing d. renal tubular abnormality causing loss of sodium in the urine. ventricular septal d. a congenital d. in the septum (membranous or muscular) between the cardiac ventricles, usually resulting from failure of the spiral septum to close the interventricular foramen.

defective (de-fek′tiv)
Denoting or exhibiting a defect; imperfect; a failure of quality.

defemination (de-fem-i-na′shun)
A weakening or loss of feminine characteristics. [L. de-, away, + femina, woman]

defense (de-fens′)
The psychological mechanisms used to control anxiety, e.g., rationalization, projection. [L. defendo, to ward off] screen d. the use of falsified or incomplete memories or affects to cover repressed but associated memories and affects. ur-defenses ur-defenses.

defensins (de-fen′sinz)
A class of basic antibiotic polypeptides, found in neutrophils, that kill bacteria by causing membrane damage. These cytotoxic peptides contain 29–38 amino acid residues. [L. de-fendo, pp. de-fensum, to repel, avert, + -in]


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