Thymus gland

The thymus gland is unusual in being part endocrine gland and part lymphoid organ. It is a bilobed structure situated just above the heart and aorta, behind the sternum, and is enclosed within a fibrous capsule. Each lobe is anatomically divided into an outer cortex and an inner medulla.

As an endocrine organ, the thymus secretes four hormones: thymulin, thymosin, thymopoietin, and thymic humoral factor (THF). Its primary and most important function, however, is to serve as the site where developing lymphocytes mature into fully immunocompetent T lymphocytes, which are essential for cell-mediated immunity. The thymus is largest and most active in childhood and gradually degenerates with age; this is directly linked to why elderly people fall sick more often …