Organ in vertebrates, situated in the upper chest cavity in humans. The thymus processes lymphocyte
cells to produce T-lymphocytes (T denotes thymus-derived), which are responsible for binding to specific invading organisms and killing them or rendering them harmless.
The thymus reaches full size at puberty, and shrinks thereafter; the stock of T-lymphocytes is built up early in life, so this function diminishes in adults, but the thymus continues to function as an endocrine gland
, producing the hormone thymosin, which stimulates the activity of the T-lymphocytes.
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