MICROANATOMY

Detailed explanation-1: -Primary lymphoid organs: These organs include the bone marrow and the thymus. They create special immune system cells called lymphocytes.

Detailed explanation-2: -The red bone marrow and thymus are considered to be primary lymphoid organs, because the majority of immune cells originate in them.

Detailed explanation-3: -Recent data indicate that bone marrow plays an important role not only as a primary lymphoid organ responsible for haemopoiesis, but also as a secondary lymphoid organ with capability of antigen presentation exceeding that of lymph nodes.