GENERAL HISTOLOGY

Detailed explanation-1: -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: -This system includes the bone marrow, spleen, thymus, lymph nodes, and lymphatic vessels (a network of thin tubes that carry lymph and white blood cells).

Detailed explanation-3: -The lymphatic system, spleen, tonsils, thymus, and bone marrow are the major parts and organs that make up the immune system. The bone marrow and the thymus gland are known as the primary lymphoid organs and the lymphatic system, spleen, and tonsils are known as secondary lymphoid organs.