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Medical Dictionary


threadworm (thred′werm)
Common name for species of the genus Strongyloides; sometimes applied to any of the smaller parasitic nematodes.

threonic acid (thre-on′ik)
The acid derived by oxidation of the CHO group of threose to COOH; a product of the oxidation of ascorbic acid by hypoiodite.

threonine (T, Thr) (thre′o-nen)
2-Amino-3-hydroxybutyric acid;the l-isomer is one of the naturally occurring amino acids, included in the structure of most proteins, and nutritionally essential in the diet of humans and other mammals. t. deaminase SYN: t. dehydratase. t. dehydratase an enzyme catalyzing the anaerobic deamination of l-t. to 2-ketobutyric acid and ammonia; a central step in t. catabolism. SYN: serine deaminase, t. deaminase.

threose (thre′os)
An aldotetrose; one of the two aldoses (the other is erythrose) containing four carbon atoms.

threshold (thresh′old)
1. The point at which a stimulus first produces a sensation. 2. The lower limit of perception of a stimulus. 3. The minimal stimulus that produces excitation of any structure; e.g., the minimal stimulus eliciting a motor response. SYN: limen (2) [TA] . [A.S. therxold] absolute t. the lowest limit of any perception whatever. Cf.:differential t.. SYN: stimulus t.. achromatic t. SYN: visual t.. auditory t. the intensity of any barely perceptible sound. brightness difference t. the smallest difference that can be perceived as a difference in brightness. SYN: light difference (2) . t. of consciousness the lowest point at which a stimulus sensation can be perceived. convulsant t. the smallest amount of stimulation, electric current, or drug required to induce a convulsion. differential t. the lowest limit at which two stimuli can be differentiated. SYN: t. differential. displacement t. the least distinguishable break in the contour of a line. double-point t. the least degree of separation of two points applied to the body surface that permits their being felt as two. erythema t. the dose at which erythema of the skin is produced by irradiation with ultraviolet, gamma, or x-rays. fibrillation t. least intensity of an electrical stimulus that will initiate fibrillation. galvanic t. SYN: rheobase. t. of island of Reil SYN: limen insulae. light differential t. the smallest difference in light intensity that can be appreciated. minimum light t. SYN: visual t.. t. of nose SYN: limen nasi. pain t. the smallest intensity of a painful stimulus at which the subject perceives pain. phenotypic t. a quantitative genetic trait with a continuous distribution termed its liability; may generate two kinds of phenotype, according to whether the liability lies above or below some critical t. at about which a radical change in behavior occurs. For instance, blood uric acid level is a liability with an approximately gaussian distribution. At a critical point of chemical saturation (the t.), crystallization occurs and the resulting gout or nongout is a t. trait. relational t. the smallest degree of difference between two stimuli that permits them to be perceived as different. renal t. concentration of plasma substance above which the substance appears in the urine. speech awareness t. the lowest sound intensity at which speech can be detected. SYN: speech detection t.. speech detection t. SYN: speech awareness t.. speech reception t. the intensity at which speech is recognized as meaningful symbols; in speech audiometry, it is the decibel level at which 50% of spondee words can be repeated correctly by the subject. stimulus t. SYN: absolute t.. swallowing t. 1. the moment that the act of swallowing begins after the mastication of food; 2. the critical moment of reflex action initiated by minimum stimulation, prior to the act of deglutition. visual t., t. of visual sensation the minimal light intensity evoking a visual sensation. SYN: achromatic t., minimum light t..

A vibration accompanying a cardiac or vascular murmur that can be palpated. SEE ALSO: fremitus. diastolic t. a t. felt over the precordium or over a blood vessel during ventricular diastole. hydatid t. the peculiar trembling or vibratory sensation felt on palpation of a hydatid cyst. SYN: Blatin syndrome, hydatid fremitus. presystolic t. a t. immediately preceding the ventricular contraction that is sometimes felt on palpation over the apex of the heart, as in mitral stenosis. systolic t. a t. felt over the precordium or over a blood vessel during ventricular systole.

thrix (thriks) [TA]
SYN: hair. [G.]

throat (throt)
1. The fauces and pharynx. SYN: gullet. 2. The anterior aspect of the neck. SYN: jugulum. 3. Any narrowed entrance into a hollow part. [A.S. throtu] sore t. a condition characterized by pain or discomfort on swallowing; it may be due to any of a variety of inflammations of the tonsils, pharynx, or larynx.

1. To pulsate. 2. A beating or pulsation.

See thrombo-.

thrombase (throm′bas)
SYN: thrombin.

thrombasthenia (throm-bas-the′ne-a)
An abnormality of platelets characteristic of Glanzmann t.. SEE ALSO: Bernard-Soulier syndrome. SYN: thromboasthenia. [thromb- + G. astheneia, weakness] Glanzmann t. [MIM*273800] a hemorrhagic diathesis characterized by normal or prolonged bleeding time, normal coagulation time, defective clot retraction, normal platelet count but morphologic or functional abnormality of platelets; several different kinds of platelet abnormalities have been described; caused by defect in platelet membrane glycoprotein IIb-IIIa complex; autosomal recessive inheritance, caused by mutation in the platelet-membrane glycoprotein IIb-IIIa complex gene (ITGA2B) on chromosome 17. SYN: constitutional thrombopathy, Glanzmann disease, hereditary hemorrhagic t.. hereditary hemorrhagic t. SYN: Glanzmann t..

thrombectomy (throm-bek′to-me)
The excision of a thrombus. [thromb- + G. ektome, excision]

thrombi (throm′bi)
Plural of thrombus.

1. An enzyme (proteinase), formed in shed blood, that converts fibrinogen into fibrin by hydrolyzing peptides (and amides and esters) of l-arginine; formed from prothrombin by the action of prothrombinase (factor Xa, another proteinase). 2. A sterile protein substance prepared from prothrombin of bovine origin through interaction with thromboplastin in the presence of calcium; causes clotting of whole blood, plasma, or a fibrinogen solution; used as a topical hemostatic for capillary bleeding with or without fibrin foam in general and plastic surgical procedures. SYN: factor IIa, fibrinogenase, thrombase, thrombosin. human t. t. obtained from human plasma by precipitation with suitable salts and organic solvents; same uses as t..

thrombinogen (throm-bin′o-jen)
SYN: prothrombin.

thrombinogenesis (throm′bi-no-jen′e-sis)
Thrombin production.

thrombo-, thromb-
Blood clot; coagulation; thrombin. [G. thrombos, clot (thrombus)]

thromboangiitis (throm′bo-an-ji-i′tis)
Inflammation of the intima of a blood vessel, with thrombosis. [thrombo- + G. angeion, vessel, + -itis, inflammation] t. obliterans inflammation of the entire wall and connective tissue surrounding medium-sized arteries and veins, especially of the legs of young and middle-aged men; associated with thrombotic occlusion and commonly resulting in gangrene. SYN: Buerger disease, Winiwarter-Buerger disease.

thromboarteritis (throm′bo-ar-ter-i′tis)
Arterial inflammation with thrombus formation.

thromboasthenia (throm′bo-as-the′ne-a)
SYN: thrombasthenia.

thromboblast (throm′bo-blast)
SYN: megakaryocyte. [thrombo- + G. blastos, germ]

thromboclastic (throm-bo-klas′tik)
SYN: thrombolytic.

thrombocyst, thrombocystis (throm′bo-sist, -sis′tis)
A membranous sac enclosing a thrombus. [thrombo- + G. kystis, a bladder]

thrombocytasthenia (throm′bo-si-tas-the′ne-a)
A term for a group of hemorrhagic disorders in which the platelets may be only slightly reduced in number, or even within the normal range, but are morphologically abnormal, or are lacking in factors that are effective in the coagulation of blood. [thrombocyte + G. astheneia, weakness]

thrombocyte (throm′bo-sit)
SYN: platelet. [thrombo- + G. kytos, cell]

thrombocythemia (throm′bo-si-the′me-a)
SYN: thrombocytosis. [thrombocyte + G. haima, blood]

thrombocytin (throm-bo-si′tin)
SYN: serotonin.

thrombocytopathy (throm′bo-si-top′a-the)
General term for any disorder of the coagulating mechanism that results from dysfunction of the blood platelets. [thrombocyte + G. pathos, suffering]

thrombocytopenia (throm′bo-si-to-pe′ne-a)
A condition in which there is an abnormally small number of platelets in the circulating blood. SYN: thrombopenia. [thrombocyte + G. penia, poverty] autoimmune neonatal t. SYN: isoimmune neonatal t.. essential t. a primary form of t., in contrast to secondary forms that are associated with metastatic neoplasms, tuberculosis, and leukemia involving the bone marrow, or with direct suppression of bone marrow by the use of chemical agents, or with other conditions. immune t. t. associated with antiplatelet antibodies. See isoimmune neonatal t.. isoimmune neonatal t. immune t. resulting from maternal-fetal platelet incompatibility. SYN: autoimmune neonatal t..

thrombocytopoiesis (throm′bo-si-to-poy-e′sis)
The process of formation of thrombocytes or platelets. [thrombocyte + G. poiesis, a making]

thrombocytosis (throm′bo-si-to′sis)
An increase in the number of platelets in the circulating blood. SYN: thrombocythemia. [thrombocyte + G. -osis, condition]

thromboelastogram (throm′bo-e-las′to-gram)
Registration of the coagulation process by a thromboelastograph.

thromboelastograph (throm′bo-e-las′to-graf)
Apparatus for registering elastic variations of a thrombus during the process of coagulation. [thromb- + G. elastreo, to push, + grapho, to write]

thromboembolectomy (throm′bo-em-bo-lek′to-me)
Extraction of an embolic thrombus. [thrombo- + G. embolos, embolus, + ektome, excision]

thromboembolism (throm′bo-em′bo-lizm)
Embolism from a thrombus. [thrombo- + G. embolismos, embolism]

thromboendarterectomy (throm′bo-end-ar-ter-ek′to-me)
An operation that involves opening an artery, removing an occluding thrombus along with the intima and atheromatous material, and leaving a clean, fresh plane internal to the adventitia. [thrombo- + endarterectomy]

thromboendocarditis (throm′bo-en′do-kar-di′tis)
SYN: nonbacterial thrombotic endocarditis.

thrombogen (throm′bo-jen)
SYN: prothrombin. [thrombo- + G. -gen, producing]

thrombogene (throm′bo-jen)
SYN: factor V.

thrombogenic (throm-bo-jen′ik)
1. Relating to thrombogen. 2. Causing thrombosis or coagulation of the blood.

thromboid (throm′boyd)
Resembling a thrombus. [thrombo- + G. eidos, resemblance]

thrombokatilysin (throm′bo-kat-i-li′sin)
Obsolete term for factor VIII.

thrombokinase (throm-bo-ki′nas)
SYN: thromboplastin.

thrombolic (throm-bol′ik)
Relating to a thrombolus.

thrombolus (throm′bo-lus)
An embolus composed mainly of agglutinated platelets. [thrombo- + G. embolos, embolus]

thrombolymphangitis (throm′bo-lim-fan-ji′tis)
Inflammation of a lymphatic vessel with the formation of a lymph clot.

thrombolysis (throm-bol′i-sis)
Fluidifying or dissolving of a thrombus. [thrombo- + G. lysis, a dissolving]

thrombolytic (throm-bo-lit′ik)
Breaking up or dissolving a thrombus. SYN: thromboclastic.

thrombomodulin (throm′bo-mo-doo-lin)
A glycoprotein present in the plasma membrane of endothelial cells that binds thrombin; participates in an additional regulatory mechanism in coagulation. [thrombo- + odulate + -in]

An all-inclusive term for circulating thrombocytes (blood platelets) and the cellular forms from which they arise (thromboblasts or megakaryocytes). It is analogous to erythron and leukon of the red and white blood cells, respectively.

thrombonecrosis (throm′bo-ne-kro′sis)
Necrosis of the walls of a blood vessel, with thrombosis in the lumen.

thrombopathy (throm-bop′a-the)
A nonspecific term applied to disorders of blood platelets resulting in defective thromboplastin, without obvious change in the appearance or number of platelets. [thrombo- + G. pathos, disease] constitutional t. SYN: Glanzmann thrombasthenia.

thrombopenia (throm-bo-pe′ne-a)
SYN: thrombocytopenia.

thrombophilia (throm-bo-fil′e-a)
A disorder of the hemopoietic system in which there is a tendency to the occurrence of thrombosis. [thrombo- + G. philos, fond]

thrombophlebitis (throm′bo-fle-bi′tis)
Venous inflammation with thrombus formation. [thrombo- + G. phleps, vein, + -itis, inflammation] t. migrans creeping or slowly advancing t., appearing in first one vein and then another. t. saltans t. occurring in the same vein, but at a distance from the original lesion, or appearing suddenly in a distant vein.

thromboplastid (throm-bo-plas′tid)
1. SYN: platelet. 2. A nucleated spindle cell in submammalian blood. [thrombo- + G. plastos, formed]

thromboplastin (throm-bo-plas′tin)
A substance present in tissues, platelets, and leukocytes necessary for the coagulation of blood; in the presence of calcium ions t. is necessary for the conversion of prothrombin to thrombin, an important step in coagulation of blood. It is now generally believed that t. activity may be developed through blood (intrinsic) or tissue (extrinsic) systems. Tissue t. (factor III) interacts with factor VII and calcium to activate factor X; active factor X combines with factor V in the presence of calcium and phospholipid to produce t. activity (also commonly called t.). SYN: platelet tissue factor, thrombokinase, thrombozyme, tissue factor, zymoplastic substance.

thromboplastinogen (throm′bo-plas-tin′o-jen)
Obsolete term for factor VIII.

thrombopoiesis (throm′bo-poy-e′sis)
Precisely, the process of a clot forming in blood, but generally used with reference to the formation of blood platelets (thrombocytes). [thrombo- + G. poiesis, a making]

thrombopoietin (throm′bo-poy′e-tin)
A cytokine that serves as a humoral regulator for the production of blood platelets through action on the receptor c-mp1. SYN: megakaryocyte growth and development factor, megapoietin. [thrombo- + G. poietes, maker, + in]

thrombosed (throm′bosd)
1. Clotted. 2. Denoting a blood vessel that is the seat of thrombosis.

thromboses (throm-bo′sez)
Plural of thrombosis.

thrombosin (throm′bo-sin)
SYN: thrombin.

thrombosis, pl .thromboses (throm-bo′sis, -sez)
Formation or presence of a thrombus; clotting within a blood vessel which may cause infarction of tissues supplied by the vessel. [G. t., a clotting, fr. thrombos, clot] atrophic t. t. due to feebleness of the circulation, as in marasmus. SYN: marantic t., marasmic t.. cerebral t. clotting of blood in a cerebral vessel. compression t. t. due to arrest of the circulation in a vessel by compression, as from a tumor. coronary t. coronary occlusion by thrombus formation, usually the result of atheromatous changes in the arterial wall and usually leading to myocardial infarction. creeping t. a gradually increasing t. involving one section of a vein after another in continuity. dilation t. t. due to slowed circulation consequent upon dilation of a vein. effort-induced t. SYN: Paget-von Schrötter syndrome. marantic t., marasmic t. SYN: atrophic t.. mural t. the formation of a thrombus in contact with the endocardial lining of a cardiac chamber, or a large blood vessel, if not occlusive. placental t. t. of the veins of the uterus at the placental site. plate t., platelet t. t. due to an abnormal accumulation of platelets. posttraumatic arterial t., posttraumatic venous t. intravascular clotting due to injury to a vessel wall.

thrombostasis (throm-bos′ta-sis)
Local arrest of the circulation by thrombosis. [thrombo- + G. stasis, a standing]


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