MEDICAL BIOLOGY, ANATOMY, HUMAN PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

BIOLOGY

SECTION 1. BIOLOGICAL BASES OF HUMAN VITAL ACTIVITY

1.2. CELL. TISSUES. THE CONCEPT OF ORGAN, ORGAN SYSTEM, ORGANISM

HEMATOPOESIS (BLOOD FORMATION)

Hematopoesis refers to The Development of Blood. Postembryonic hematopoiesis represents The process of physiological blood regeneration (Fig. 1.21). The Organs where blood formation takes place are called Hematopoietic organs. These include: the Cytology/practical/86.html">Red Bone Marrow of flat bones and epiphyses of long tubular bones, the Spleen, Lymph Nodes, and the Thymus.

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Fig. 1.21. Postembryonic hematopoiesis, stained with Azure II-eosin: I-IV - morphologically undifferentiated Cells; V - morphologically differentiating cells.

The hematopoietic tissue of the red bone marrow is called myeloid tissue, and the process of formation of erythrocytes, granulocytes, monocytes, and platelets is termed myelopoiesis. The hematopoietic tissue located in the spleen, lymph nodes, and thymus (as well as The system of these organs) is called lymphoid tissue, and the process of formation of lymphocytes and plasmocytes within them is termed lymphopoiesis.

All mature blood elements originate from a single progenitor Cell known as the hematopoietic stem cell. The hematopoietic stem cell is a multipotent precursor of all Blood Cells and belongs to a self-maintaining cell population. In adult mammals, hematopoietic stem cells are concentrated mainly in the red bone marrow. Their total number in humans is approximately 5x10 . Blood stem cells originate during the Embryonic period in the yolk sac and subsequently migrate throughout the hematopoietic system.

The following types of hematopoiesis exist:

- erythropoiesis - the development of erythrocytes;

- granulocytopoiesis - the development of granulocytes (neutrophils, eosinophils, basophils);

- lymphopoiesis - the development of T- and B-lymphocytes;

- monocytopoiesis - the development of monocytes;

- thrombocytopoiesis - the development of Blood Platelets (thrombocytes).



Last update: 08/08/2026

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