Molecular, Cellular and Structural Immunology 2

Bone marrow is the site of generation of most blood cells, the generation is known as hematopoiesis.

It occurs initially during fetal development in the para-aortic mesenchyme then in the liver after 3/4 months gestation and then in the bone marrow.

It occurs mostly in the sternum, vertebrae, iliac bones and ribs. The red marrow has a sponge like reticular framework between long trabecule. The spaces contain a network of blood filled sinusoids lined by endothelial cells attached to discontinuous basal membranes. The blood cell precursors mature and migrate through the sinusidual basement membrane and between endothelial cells, entering the vascular circulation. The liver and spleen can become sites of extramedullary hematopoiesis.

Hematopoietic stem cell (HSCs) are pluripotent and self-renewing as at least one daughter cell maintains the properties of a stem cell whilst the other will differentiate. They are identified by the presence of CD34 and cKit surface markers and by…