Final answer:
The thymus tissue in humans is often replaced by adipose tissue as a person ages, and this affects the thymus's ability to contribute to the immune response.
Step-by-step explanation:
As a person ages, the thymus tissue is often replaced by adipose tissue. The thymus gland is a vital part of the immune system, particularly during early life, where it serves as the site for T cell maturation. The gland is most prominent in infants and gradually becomes smaller throughout adulthood. Located behind the sternum, the thymus is surrounded by a connective tissue capsule and is divided into lobules by extensions called trabeculae. With age, the glandular functioning tissue tends to diminish and is often replaced by fatty tissue, which impacts the gland's ability to contribute to the immune response and production of thymosins.