How the Thymus Gland Works
The thymus gland is located near the thyroid gland in the region between the neck and chest. It has a temporary function in the human body. Its temporary status results in size change. It grows during childhood and is largest during puberty, then it begins to atrophy and shrink.
Purpose of the Thymus
The thymus gland functions to strengthen the immune system and produce the hormones and cells that fight abnormalities and invading organisms. In fact, its main purpose is to produce the immune cells that protect against disease for a lifetime.
How the Thymus Functions
- The thymus produces a particular variety of hormone; thymosin, thymulin, thymopoietin, thymocyte humoral factor.
- White blood cells known as lymphocytes pass into the thymus gland.
- The hormones produced in the thymus help mature the lymphocytes.
- Mature lymphocytes are called T-lymphocytes or T-cells.
- T-cells identify and attack abnormal cells within the body and cells that have invaded the body.
Life Cycle of the Thymus
Hormone and T-cell production are proportional to the size of the thymus gland. When the gland is large it produces higher levels of hormones and cells, and the immune system is stronger.
- Children are born with relatively large thymus glands. A newborn will have a thymus gland weighing approximately 15 grams. A two-year-old child will have a thymus gland weighing between 30 and 40 grams. At this time the thymus gland functions at full capacity.
- Once puberty passes the thymus gland progressively begins to function less. It also decreases in size. The gland's tissue is replaced by fat and other connective tissues.
- By age 25 the thymus gland will weigh approximately 25 grams.
- By age 70 the thymus will only weigh approximately 6 grams.
Immunity decreases with age as the thymus gland produces fewer and fewer T-cells. As a result, the elderly become more susceptible to diseases such as pneumonia.