Final answer:
The thymus is the lymphatic organ where T lymphocytes mature during childhood, playing a key role in the immune system.
Step-by-step explanation:
The lymphatic organ responsible for the maturation of T lymphocytes during childhood is the thymus. This organ, situated in the chest, consists of an outer cortex and inner medulla, all encapsulated within a fibrous covering. It plays a crucial role as a primary lymphatic organ where immature T cells, also known as thymocytes, migrate from the bone marrow to mature. Once mature, T cells leave the thymus and enter into the rest of the lymphatic system to seek out and respond to pathogens. The thymus is especially active during childhood, shrinking in size and function with age.