THYMUS GLAND

THYMUS:

Introduction:

·         The thymus gland is a lymphoid gland that plays an important role in the development of immune system. This is a prominent gland that gets degenerated with age.

·         Thymus gland secretes the peptide hormone called thymosin.

·         Thymus gland is the main organ of the lymphatic system.

·         Thymus gland promotes the development of specific cell of the immune system called as T-lymphocytes. T- Cells are white blood cells that protect against foreign organisms (bacteria and virus) that have managed to infect body cells.    

·         Thymus is largest in children. Once it reaches puberty, the thymus starts to shrink slowly and become replaced by fat. By age 75, the thymus is little more than fatty tissue.

·         From infancy to aldoscence, the thymus is relatively large in size. After puberty the thymus begins to decrease in size and continue to shrink with age. Thymus gland gets degenerated with age due to which production of thymosin also gets decreased. This is the reason of a weaker immune response found in old people.

                                    

Origin:

It arises from the endoderm of the embryo.

Location:

It is present on the dorsal side of the heart and the aorta (in the upper part of the thorax near the heart). Thymus gland is located in the mediastinum of the thoracic cavity, anterior and superior to the heart and lies posterior to the thoracic cavity and right about the pericardium of the heart.

Structure:

·         It is a soft, pinkish, roughly triangular organ.

·         Thymus gland is bilobed mass of lymphoid tissue.

·         The thymus gland has a two lobed structure that extends partially into the neck region.

·         The thymus has two lobes, each of which has small divisions which are called lobules.

·         The medulla is the inner area of the lobule and outer area is known as cortex. Immature T- lymphocytes stay in the cortex region whereas the medulla regions contain the mature T- lymphocytes. Only the mature cells can identify the foreign cells.

·         The thymus gland has an outer covering and it consists of three different types of cells- lymphocytes, epithelial cells and neuro-endocrine cells. Epithelial cells provide structure to the thymus, neuro- endocrine cells release hormones and lymphocytes protect us against infections.

                                       

                                                         

                                  

Hormone:

Thymosin:

·         When thymosin is released in the blood it has a stimulatory effect on the entire immune system. Apart from this, thymosin also promotes the production of antibody to provide humoral immunity.

·         Thymosins play a major role in the differentiation of T- lymphocytes, which provide CMI (Cell Mediated Immunity).

·         Thymosins also promote production of antibodies to provide humoral immunity.

                                     

Function of Thymus Gland:

         i.            It produces and process T- cells to strengthen the immune system. T-Cells are White blood cells that travel to the lymph node and the spleen after they become mature. These lymphocytes play an important role in the production of antibody that help fight against bacteria, virus and other pathogens.

       ii.            Thymus gland acts to regulate the immune system through the development of immune cells which is responsible for the development of CMI (Cell Mediated Immunity).

      iii.            Thymus also produce hormone that promote growth and maturation.

     iv.            Thymus gland secretes a hormone thymopoietin. It is actually a protein found in m- RNA and encoded by the TMPO gene. At the same time, gland produces thymosin hormone that plays a big role in stimulating lymphocytes as well as other lymphatic organ.

       v.            Thymic hormone influences structure of the endocrine system including pituitary gland and adrenal gland, to assist in growth and sexual development.

     vi.            The thymus and its hormones also influence other organs and organ systems including the kidneys, spleen, reproductive system and Central Nervous System (CNS).

    vii.            Thymus gland produces T- Cells which protect the body from itself by controlling cancerous cells. Thus, it protects the body from autoimmunity, which occur when the immune system turns against itself.

  viii.            Thymus gland plays an important role in the prevention of anomalous cell growth that often leads to tumours, malignancy and cancer. The T- cells first move from bone marrow to the gland and stay in the thymus gland until they become active. They enter the bloodstream after maturation and then move to the lymphatic organs to boost the defence mechanism.

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