What happens to the size of the thymus as a person grows?

Step-by-step solution

The primary lymphoid organs in the human body are the bone marrow and thymus, where immature lymphocytes differentiate into antigen-sensitive lymphocytes. The thymus is quite large at the time of birth but keeps reducing in size with age. By the time puberty is attained, it reduces to a very small size. The spleen mainly contains lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne microorganisms. It also has a large reservoir of erythrocytes.