Thymus


Thymus
: An organ in which lymphocytes mature and multiply. It lies behind the breastbone.
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[NA] A primary lymphoid organ, located in the superior mediastinum and lower part of the neck, that is necessary in early life for the normal development of immunologic function. It reaches its greatest relative weight shortly after birth and its greatest absolute weight at puberty; it then begins to involute, and much of the lymphoid tissue is replaced by fat. The t. consists of two irregularly shaped parts united by a connective tissue capsule. Each part is partially subdivided by connective tissue septa into lobules, 0.5 to 2 mm in diameter, which consist of an inner medullary portion, continuous with the medullae of adjacent lobules, and an outer cortical portion. It is supplied by the inferior thyroid and internal thoracic arteries, and its nerves are derived from the vagus and sympathetic nerves. SYN: t. gland. [G. thymos, excrescence, sweetbread]

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thy·mus 'thī-məs n, pl thy·mus·es also thy·mi -.mī a glandular structure of largely lymphoid tissue that functions in cell-mediated immunity by being the site where T cells develop, that is present in the young of most vertebrates typically in the upper anterior chest or at the base of the neck, that arises from the epithelium of one or more embryonic branchial clefts, and that tends to disappear or become rudimentary in the adult called also thymus gland

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n.
a bilobed organ in the root of the neck, above and in front of the heart. The thymus is enclosed in a capsule and divided internally by cross walls into many lobules, each full of T-lymphocytes (white blood cells associated with antibody production). In relation to body size the thymus is largest at birth. It doubles in size by puberty, after which it gradually shrinks, its functional tissue being replaced by fatty tissue. In infancy the thymus controls the development of lymphoid tissue and the immune response to microbes and foreign proteins (accounting for allergic response, autoimmunity, and the rejection of organ transplants). T-lymphocytes migrate from the bone marrow to the thymus, where they mature and differentiate until activated by antigen.
thymic adj.

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Thy·mus (thiґməs) thyme; a genus of herbs of the family Labiatae, native to south central Europe and grown extensively elsewhere. T. vulgaґris L. is garden thyme, a source of thyme oil and thymol.

Medical dictionary. 2011.

Look at other dictionaries:

  • thymus — [ timys ] n. m. • 1541; mot lat., du gr. thumos, méd. « excroissance charnue » ♦ Anat. Organe glandulaire situé à la partie inférieure du cou, composé de deux lobes, très développé pendant l enfance et régressant après la puberté. Rôle du thymus… …   Encyclopédie Universelle

  • thymus — hy mus (th[imac] m[u^]s), a. [NL., fr. Gr. qy mos.] (Anat.) Of, pertaining to, or designating, the thymus gland. n. The thymus gland. [1913 Webster] {Thymus gland}, or {Thymus body}, a ductless gland in the throat, or in the neighboring region,… …   The Collaborative International Dictionary of English

  • Thymus — Thymus, aus dem Entoderm entstehendes, hinter dem Brustbein liegendes lymphatisches Organ sowie Hormondrüse der Wirbeltiere; Differenzierungsort der T Lymphocyten und damit wichtiger Teil des Immunsystems. Verschiedene Peptide mit Hormonwirkung,… …   Deutsch wörterbuch der biologie

  • thymus — ► NOUN (pl. thymi) ▪ a gland situated in the neck which produces white blood cells for the immune system. DERIVATIVES thymic adjective. ORIGIN Greek thumos excrescence like a thyme bud, thymus gland …   English terms dictionary

  • thymus — [thī′məs] n. [ModL < Gr thymos, orig., a warty excrescence] a gland in the upper thorax or neck of all vertebrates, involved in the production of lymphocytes: in humans, it is most prominent at puberty, after which it disappears or becomes… …   English World dictionary

  • thymus — thymus. См. вилочковая железа. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Thymus [1] — Thymus (gr.), s. Thymion …   Pierer's Universal-Lexikon

  • Thymus [2] — Thymus (Th. L.), Pflanzengattung aus der Familie der Labiatae Satureineae Origneae, 14. Kl. 1. Ordn. L., Staubgefäße von einander entfernt, oben noch mehr auseinandertretend, die getrennten Staubbeutel an das verbreiterte fast dreieckige… …   Pierer's Universal-Lexikon

  • Thymus — Tourn. (Thymian, Quendel), Gattung der Labiaten, Halbsträucher oder kleine Sträucher mit kleinen, ganzrandigen, gegenständigen Blättern, meist wenigblütigen Scheinwirteln, die bald entfernt voneinander und achselständig, bald zu endständigen,… …   Meyers Großes Konversations-Lexikon

  • Thymus — L., Thymian, Pflanzengattg. der Labiaten, Kräuter oder Halbsträucher, meist der Mediterranflora. Sowohl die getrockneten, beblätterten und blühenden Zweige von T. serpyllum L. (Feldthymian, Quendel, Feldkümmel), als auch die von T. vulgāris L.… …   Kleines Konversations-Lexikon

  • thymus — (n.) gland near the base of the neck, 1690s, Modern Latin, from Gk. thymos a warty excrescence, used of the gland by Galen, lit. thyme, probably so called because of a fancied resemblance to a bunch of thyme (see THYME (Cf. thyme)) …   Etymology dictionary


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