Special Histology and Embryology: Practical Course - V. K. Napkhanyuk 2001

Organs of Hematopoiesis and Immune Defense

The Cytology/cytology/54.html">Organs of Hemopoiesis and immune defense (organa haemopoetica et immunitas) form an interconnected system responsible for the continuous renewal and Stability of the cellular composition of peripheral Blood, as well as the maintenance of immune Homeostasis throughout the body at various Levels of Organization.

The organs of hemopoiesis and immune defense include:

— Red Bone Marrow (medulla ossium rubra);

— Thymus (thymus);

— Lymph Nodes (nodi lymphatici);

— lymphatic nodules of the digestive tract and respiratory pathways (noduli lymphatici);

— Spleen (splen, lien).

Together with the blood, they form a unified system. Central and peripheral organs of hemopoiesis and immune defense are distinguished.

The central organs include:

— red bone marrow;

— thymus;

— the bursa of Fabricius equivalent, which is yet to be discovered in mammals.

In the red bone marrow, stem Cells differentiate into erythrocytes, granulocytes, platelets, B lymphocytes, and T lymphocyte precursors.

In the thymus, T lymphocyte precursors develop into mature T lymphocytes. Additionally, the central organs are sites of antigen-independent lymphocyte proliferation.

The peripheral organs include:

— lymph nodes;

— spleen;

— lymphatic nodules of the digestive tract and respiratory pathways.

The peripheral hemopoietic organs are where T AND B lymphocytes arriving from the central organs proliferate and undergo antigen-driven differentiation into effector cells responsible for immune defense. Furthermore, these organs serve as sites where Blood Cells that have completed their life cycle are destroyed.

The hemopoietic organs function harmoniously to maintain the morphological COMPOSITION OF THE blood and overall immune homeostasis. The coordination and regulation of all hemopoietic organs are mediated by humoral and nervous factors, as well as local microenvironmental influences within the organs themselves.