THYMUS GLAND -
Noun: A small, ductless gland near the base of the neck and above the heart, the thymus is the center for the lymphocyte immune system. During the first few years of life, the thymus programs billions of lymphocytes that have made their way to it from the bone marrow. When programed, they have become T cells , the "T" standing for "Thymus". As the T cells mature in the thymus, they adopt one of four different functions . Each T- cell is programed to recognise one of over a million antigens which exist in the human environment. While in the thymus, T-cells also learn to recognise a set of proteins displayed on the walls of our own body cells which identifies them as self and friendly and not to be attacked. Any T-cell which fails to recognise the self as friendly is killed in the thymus. Yet an occasional one is believed to survive and become capable of triggering an autoimmune disease later on.The thymus gland aids in the development of lymphocytes necessary to protect the young from disease. It reaches is maximum development at puberty and as we age it slowly shrinks, causing a subsequent decline in immunity. Until recently this shrinkage was thought to be a normal aspect of ageing. It is now known that shrinkage of the thymus is not inevitable and can be reversable. See Immune Recovery Programs . The other lymphocytes mature in the bone marrow and become B-lymphocytes and then spend their life in the Lymphatic system . See picture of Lymph Nodes for location of where Thymus would be.

Greek - thymos = a warty unnatural growth (referring to the fact that it can have no function in adults).

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