After the age of 20 years, RBCs are mainly produced in the marrow of Vertebrae, Sternum, Ribs, and Pelvis.
The red bone marrow is the prime site for the production of RBC’s from birth till age 20.
It is the process of formation, development, and maturation of Red blood cells in the bone marrow.
In adults – Hematopoiesis occurs in the Central skeleton (Vertebrae, Sternum, Ribs, Skull, Sacrum, and pelvis), proximal ends of the long bones like Femur, Tibia, and Humerus.
From birth till maturity – occurs in bone marrow, spleen, and liver.
By the 7 th month till birth – it starts in the bone marrow.
By the 3 rd to 7 th month of Intra-uterine life – Hematopoiesis occurs in liver and spleen.
In human embryo – Yolk sac is the main site of Hematopoiesis.
The site of Hematopoiesis depends on the age of the person as follows –.
Lymphopoiesis – formation of lymphocytes.
Granulopoiesis – formation of granulocytes.
Leucopoiesis is further subdivided into – The production of erythrocytes is called as Erythropoiesis the leukocytes are called as Leucopoiesis and that of platelets is Thrombopoiesis.
Lymphoid stem cells/Lineage – differentiates in the Redbone marrow and then migrates to the lymphoid tissue.
Myeloid stem cells/Lineage – Differentiate in the Redbone marrow and form Erythrocytes, Granulocytes (Neutrophils, Eosinophils, and Basophils), Monocytes and Thrombocytes.
The Pluripotent stem cells give rise to two types of Stem cells or lineages – The cellular components of blood are developed from the Hematopoietic stem cells also known as Pluripotent Stem cells or totipotent stem cells which further differentiate and mature into typical blood cells. Hematopoiesis is the production, Development and the maturation of various cellular components of the blood HEMATOPOIESIS – THE FORMATION OF BLOOD CELLS
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