Chapter 45 Hematopoiesis and Hematopoietic Failure

Chapter 45 Hematopoiesis and Hematopoietic Failure
 Hematopoiesis : is the process of formation and development of blood cells from pluripotent
hematopoietic stem cell
 Hematopoietic Tissues:
ï‚· Hematopoiesis commences in the embryonic yolk sac, in which early erythroblasts in blood islands
form the first hemoglobinized cells.
ï‚· After 6 weeks’ gestation, the fetal liver begins producing primitive lymphocytoid cells,
megakaryocytes, and erythroblasts, and the spleen becomes a secondary site of erythropoiesis.
ï‚· Hematopoiesis then shifts to its definitive long-term site in the bone marrow, the principal site for
lifelong hematopoiesis in the normal host.
ï‚· Early in life, all fetal bones contain regenerative bone marrow, but the marrow becomes progressively
replaced by fat with age.
ï‚· In adults, active marrow resides only in the axial skeleton (i.e., sternum, vertebrae, pelvis, and ribs)
and in the proximal ends of the femur and humerus.
 Note :Bone marrow samples are taken from iliac crest or sternum.