See also: thyme - plant -
Thyme is a gland belonging to the lymphatic system and, more generally, to the immune system. It is an unequal organ, located in the upper part of the anterior mediastinum between the sternum and the large vessels that come out of the heart.
Once "trained", the T lymphocytes do not remain in the thymus, but migrate to other peripheral lymphatic organs (lymph nodes, spleen, tonsils, etc.) where they multiply to fully perform their defensive role.
The thymus is a highly vascularized organ and consists of two lobes. Each lobe is wrapped in a fibrous capsule that penetrates dividing it into numerous lobules. Inside they recognize a dark peripheral part, called cortex, and a lighter inner part, called medulla. The cortical portion is densely populated by immature lymphocytes, while the developed ones cluster in the inner part, where the cell population is much lower.
The activity and size of the thymus reaches their maximum expression at the beginning of the adolescent period, when the gland weighs about 30-40 grams. After this period, the thymus regresses slowly due to the action of the sex hormones and, a bit like the bone marrow present in the diaphyseal canal, is progressively replaced by adipose tissue (physiological atrophy). Once the development is over, the body has sufficient immune defenses to make up for the progressive involution of the thymus; if on the other hand the atrophy affects it prematurely the sensitivity to infections increases considerably.
The involution of the thymus is favored by excessive stress, while its immune function is supported by an adequate intake of vitamin A.
The thymus gland also produces peptide factors, sometimes classified as hormones, which influence the maturation of lymphocytes (thymosin, thymopoietin, timulin, interleukins). Thanks to these substances, the thymus would have an endocrine action, aimed at the development of lymphocytes in intra and extra-thymic sites.