Thymus gland

Thymus gland is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells or T lymphocytes mature. T cells are critical to the adaptive immune system, where the body adapts specifically to foreign invaders. The thymus is located in the upper anterior (front) part of the chest, directly behind the sternum and in front of the heart. It is made up of two lobes, each consisting of a central medulla and an outer cortex, surrounded by a capsule.

Structure

The thymus is of a pinkish-gray color, soft, and lobulated on its surfaces. At birth, it is about 5 cm in length, 4 cm in breadth, and about 6 mm in thickness. The organ enlarges during childhood, and atrophies at puberty. Although it is large in infancy, by the age of 25 it is atrophied and replaced by adipose tissue.

Function

The primary function of the thymus is the production and "education" of T-lymphocytes (T cells), which are critical cells of the adaptive immune system. The thymus also produces a hormone, thymosin, which stimulates the development of disease-fighting T cells.

Clinical significance

The thymus can become abnormal if underactive, which can result in severe immune deficiency and increased susceptibility to infection. If overactive, it can lead to the development of autoimmune diseases.

See also

• Immune system
• Lymphatic system
• Endocrine system

References

Thymus gland Resources
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