**The Thymus: The Training School of T Lymphocytes**

The endocrine gland responsible for training T lymphocytes is called the thymus. The thymus plays a crucial role in the development and maturation of T cells, which are a type of white blood cell involved in immune responses. It is often referred to as the "training school" for T lymphocytes due to its unique function in the immune system.

**Structure and Location of the Thymus:**
The thymus is a bi-lobed gland located in the upper chest region behind the sternum (breastbone) and between the lungs. It is relatively large in infants and children, but gradually decreases in size as a person reaches adulthood. The thymus is composed of two main regions: the cortex and the medulla.

**Cortex of the Thymus:**
The cortex of the thymus contains numerous immature T cells, also known as thymocytes. These thymocytes originate from hematopoietic stem cells in the bone marrow and migrate to the thymus for further development. The cortex provides an environment rich in specialized cells called thymic epithelial cells (TECs) and dendritic cells, which play a crucial role in T cell education.

**T Cell Education in the Cortex:**
Within the cortex, thymocytes undergo a process called positive and negative selection. Positive selection involves the recognition and selection of T cells with receptors that can recognize the body's own major histocompatibility complex (MHC) molecules. This ensures that T cells can recognize and respond to antigens presented by the body's own cells.

Negative selection, on the other hand, eliminates T cells that have receptors capable of recognizing self-antigens too strongly. This process prevents the development of autoreactive T cells that could potentially attack the body's own tissues. T cells that pass both positive and negative selection move on to the medulla for further maturation.

**Medulla of the Thymus:**
The medulla of the thymus is the final stage of T cell maturation. T cells that have successfully passed positive and negative selection in the cortex migrate to the medulla. Here, they undergo further maturation and differentiation to become fully functional T cells.

**Role of the Thymus in Immune Response:**
The mature T cells produced in the thymus are instrumental in immune responses. They are responsible for recognizing and eliminating infected or abnormal cells, as well as coordinating immune responses against pathogens. The thymus is therefore considered a vital organ for maintaining a healthy immune system.

In conclusion, the endocrine gland known as the thymus serves as the training school for T lymphocytes. Through a complex process of positive and negative selection, the thymus ensures that T cells are properly educated and capable of recognizing foreign antigens while avoiding self-reactivity. The mature T cells that emerge from the thymus play a crucial role in the immune response, protecting the body against infections and diseases.

Thymus Gland is known as training school of T- lymphocytes or Throne of immunity....

Situated beneath sternum ventral aorta .....

Immature lymphocytes from bone marrow migrate into Thymus gland where it mature into lymphocyte and provide immunity...and also regulates synthesis of antibodies....

I hope it's helps u....