PATHOLOGY

Detailed explanation-1: -The thymus reaches maximum weight (20 to 37 grams) by the time of puberty. As one ages, the thymus slowly shrinks, eventually degenerating into tiny islands of fatty tissue. By the age of 75 years, the thymus weighs only 6 grams.

Detailed explanation-2: -The pituitary gland is located just below (anterior pituitary) or in (posterior pituitary) the brain. This gland reaches its maximum size in middle age and then gradually becomes smaller.

Detailed explanation-3: -The thymus is a primary lymphoid organ responsible for the production of immunocompetent T cells and, with aging, it atrophies and declines in functions. Universality of thymic involution in all species possessing thymus, including human, indicates it as a long-standing evolutionary event.

Detailed explanation-4: -The thymus is the primary organ responsible for de novo generation of immunocompetent T cells with a diverse repertoire of antigen-recognition. However, it is the organ being most ostensibly seen to decrease in size along with age.

Detailed explanation-5: -The size of thymus reduces with age. Therefore there is reduced production of thymosins in older individuals and their immune responses become weak.