GENERAL HISTOLOGY

Detailed explanation-1: -Lymphocytes develop in the thymus and bone marrow (yellow), which are therefore called central (or primary) lymphoid organs.

Detailed explanation-2: -Antibody-producing lymphocytes are called B lymphocytes or simply B cells because they develop in the bone marrow. Cellular immunity is accomplished by two types of lymphocytes: T cells, so named because they develop in the thymus, and NK cells, which develop in both the bone marrow and the thymus.

Detailed explanation-3: -T lymphocytes develop from a common lymphoid progenitor in the bone marrow that also gives rise to B lymphocytes, but those progeny destined to give rise to T cells leave the bone marrow and migrate to the thymus (see Fig. 7.2). This is the reason they are called thymus-dependent (T) lymphocytes or T cells.

Detailed explanation-4: -Red bone marrow produces all red blood cells and platelets and around 60–70% of lymphocytes in human adults. Other lymphocytes begin life in red bone marrow and become fully formed in the lymphatic tissues, including the thymus, spleen, and lymph nodes.