Age involution of thymus (human, postpuberal)

Stain: Azan. The size of the thymus is age-dependent, and undergoes a continuous process of involution, starting at postpuberal age. Due to depletion and reduced production of cortical thymocytes, as well as a gradual atrophy of the epithelial cells, the clear distinction between medulla (1) and cortex (2) disappears, and the thymic tissue gradually becomes replaced by more and more adipose cells (5). The connective tissue capsule (3) and trabeculae are more interspersed with adipocytes. Hassall bodies still are discernible (4). At (6) a large interlobular blood vessel is seen.