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thymus |
Also found in: Dictionary/thesaurus, Medical, Acronyms, Wikipedia, Hutchinson | 0.03 sec. |
thymusPyramid-shaped lymphoid organ (see lymphoid tissue) between the breastbone and the heart. Starting at puberty, it shrinks slowly. It has no lymphatic vessels draining into it and does not filter lymph; instead, stem cells in its outer cortex develop into different kinds of T cells (see lymphocytes). Some migrate to the inner medulla and enter the bloodstream; those that do not may be destroyed to prevent autoimmune reactions. This process is most active during infancy. If a newborn's thymus is removed, not enough T cells are produced, the spleen and lymph nodes have little tissue, and the immune system fails, causing a gradual, fatal wasting disease. Thymus removal in adults has little effect. thymus a glandular organ of vertebrates, consisting in man of two lobes situated below the thyroid. In early life it produces lymphocytes and is thought to influence certain immunological responses. It atrophies with age and is almost nonexistent in the adult How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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The third branchial pouch gives rise to the thymus and the inferior parathyroid glands, and these structures follow a common route during embryogenesis through part of the neck to their final location. However, the mice could still produce T cells, a job that only the thymus performs. Brains and spleens were removed from all mice, and neoplastic tissues involving lymph nodes were removed from 4 infected and 1 uninfected mouse, and the thymus was removed from 2 infected mice (Table). |
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