Question

Name the primary and secondary lymphoid organs.

Answer 1

The lymphoid or the lymphatic system is an extra circulatory system present in vertebrate organisms. It is also part of the immune system. The system is a combination of lymphoid organs, lymphatic vessels, and lymphoid tissues.

Complete step by step answer:
There are three types of lymphoid organs; they are primary, secondary and tertiary. The primary organs function as a site for the primitive or the stem cells to get differentiated into the B and T cells. The primary lymphoid organs are the bone marrow and thymus. Bone marrow synthesizes both B and T cells, and also the maturation of B cells takes place here, hence the name. The thymus is the organ present in the thoracic region. It is largest at the time of birth and gradually reduces in size with growth. The T lymphocytes mature and develop in this organ.
Secondary lymphoid organs are those in which the cells in the immune responses are matured and proliferated. The secondary organs are lymph nodes, spleen, and Mucosal Associated Lymphoid Tissue (MALT). The collection of lymph tissues and their organization constitutes the lymph nodes. These are located in the chest, pelvis, neck, and axilla. The spleen is the organ that produces the antibodies against the antigens, site for the destruction of RBCs and they produce the blood cells in the fetus. Other secondary lymphoid organs are the tonsils, and the Peyer’s patches in the intestines.

Note:
Tertiary lymphoid organs are those which are found only at the sites of chronic infections. They are the sites in diseases like cancers, graft rejections during organ transplantation, and autoimmune diseases. They function as an immune response to diseases like cancers.