PATHOLOGY

Detailed explanation-1: -Primary lymphoid organs: These organs include the bone marrow and the thymus. They create special immune system cells called lymphocytes. Secondary lymphoid organs: These organs include the lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body (for instance in the bowel).

Detailed explanation-2: -Types and functions of lymphocytes Both originate from stem cells in the bone marrow and are initially similar in appearance. Some lymphocytes migrate to the thymus, where they mature into T cells; others remain in the bone marrow, where-in humans-they develop into B cells.

Detailed explanation-3: -The thymus is inside the ribcage, just behind the breastbone. It filters and monitors our blood content. It produces cells called T-lymphocytes which circulate around the body. These cells are important for cell mediated response to an immune challenge, such as may occur when we have an infection.

Detailed explanation-4: -Some examples of Secondary Lymphoid Organs are spleen, lymph nodes, peyer’s patches (in the intestine), etc. They store and activate mature Lymphocytes and thus initiates adaptive Immune response. They are thus known as “Lymphocyte activation sites” in the body.