Thymus

The Thymus is an obscure organ located deep within the chest. It may not function throughout human life but it is a very important organ when it is active. Read on to explore more about the thymus.

What is the Thymus?

The thymus gland is a very unique organ that is at its largest in children and shrinks away as the body grows older. It is about 2.5 to 5 cms wide, 4 to 6 cms long and 1 cm thick at birth. At its largest instance, (Viz. during puberty) the thymus weighs just under 30 grams. After puberty, the thymus slowly starts to shrink and by the age of 75, it is nothing more than fatty tissue.

Thymus Location

The thymus gland is located in the anterior part of the chest, right behind the breastbone (or the sternum) and between the lungs. It has a pinkish-grey complexion and is lobed, with primary two lobes and smaller lobes radiating from within. The two lobes may be separated or united and generally vary in size.

Histology of Thymus

There are two general cell lines of interest in the thymus. These are thymic epithelial cells and lymphoid cells. The lymphoid cells migrate into the thymus during the intrauterine angiogenesis. The thymic epithelium is important for the maturation and development of these lymphoid cells.

The lymphoid progenitor cells can access the thymus in the 10th week of gestation. A well-differentiated thymus is observed in the 12th week of gestation.

Thymus Function

One of the most important functions of the thymus is to stimulate the production of very specialized cells called T-cells (also called T-lymphocytes). These cells are responsible for directly fending off foreign pathogens such as viruses and bacteria. They also regulate the immune system, helping to prevent autoimmunity, wherein, the body’s immune system elicits immune responses on its own healthy cells.

Thymus also secretes thymosin to stimulate the development of T-cells.

Thymus Gland Disorders

The most common disorders caused by the dysfunctioning of thymus gland are- Myasthenia gravis, pure red cell aplasia, and hypogammaglobulinemia.

Myasthenia gravis is caused due to abnormal enlargement of the thymus. The enlarged thymus produces antibodies that destroy the muscle receptor sites. Thus the muscles become very weak.

Pure red aplasia is caused when the patient’s own immune cells attack the blood-forming stem cells. This happens when there is a tumour in the thymus.

Hypogammaglobulinemia occurs when the body does not produce enough antibodies.

Thymosin- The Thymus Hormone

To stimulate the production of T-Cells, the thymus secretes a hormone called Thymosin. Then, a type of white blood cell called lymphocytes pass through the thymus and gets transformed into T-Cells. Once these T-cells have matured, they migrate to the lymph nodes in the body and consequently aid the immune system. The thymus gland is only active until puberty, however, they produce all the T-cells required by the body well before this period.

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Further Reading

Important Questions

  1. Where is the thymus gland located?

  2. Name the hormone produced by the thymus.

  3. What is the function of the thymus?

  4. What are T-Cells?

  5. Write a short note on the Thymus.

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