1. Lecture 1 Hematopoiesis, Abdulkarim Aldosari

2. Objectives Define hematopoiesis Describe the origin of hematopoieisis
Define erythropoiesis
List proper cell maturation of the erythrocytic series
Identify three areas of RBC metabolism crucial for normal erythrocyte survival and function
Describe RBC membrane biochemical structure and the consequences of structural membrane defects
Describe Hemoglobin structure, function and synthesis
RBC metabolic pathways

3. Hematopoiesis Blood cell formation – production and development
Occurs bone marrow, liver, spleen, lymph nodes, thymus
Bone marrow – sole site of effective hematopoiesis in normal adults
6 billion cells/kg of body weight per day
2.5 billion red cells
2.5 billion platelets
1.0 billion white cells
Rate adjusted to need, vary from nearly zero to many times the normal
Constant turnover of cells

4. Origin of Hematopoiesis
Yolk sac > fetal liver/spleen > BM
Primitive erythroblast > migrate to liver (6wks) – includes other myeloid and lymphoid cells.
At birth the bone cavities are the only site of hematopoietic activity - Starts at 7 months
Fig 1-16, pg. 10

5. Origin of Hematopoiesis

6. Origin of Hematopoiesis
Shaft of long bones – until 4 yrs.
Sternum, ribs, pelvis, vertebrae, skull – at yrs.
Other bones have mostly yellow marrow (fat)
At 40 yrs – equal amount of yellow and red marrow

7. Origin of Hematopoiesis
Takes place in the entire medullary space during infancy and early childhood
Later – occurs in the extravascular part of red marrow
Squeeze through the endothelial lining cells that separates the extravascular marrow from the intravascular compartment- venous sinus
Migrating cells enter the peripheral blood

8. Hematopoiesis Steady state of hematopoiesis i.e. production = removal
During increased demand for blood cells
strenuous exercise, high altitudes, smokers
To compensate - Spleen, liver and other tissues can start active hematopoiesis = Extramedullary hematopoiesis
Two pools of cells participate in hematopoietic activity:
Stem cell pool
Bone marrow pool

9. Hematopoiesis Hematopoietic stem cell pool
Pluripotential - multipotential stem cells (MSCs)
morphologically identical
Continuous self-renewal
Unipotential - committed progenitor cells
Restricted to single cell line
No self-renewal
Lymphoid or myeloid
Fig 1-15, pg. 9

10. Figure 1-15

11. Hematopoiesis Bone marrow pool Cells released to peripheral blood
proliferating and maturing cells - through the action of cytokines (growth factors) – CSF and IL progenitor cells divide and differentiate
Stored cells for later release to peripheral blood
Cells released to peripheral blood
Storage – WBCS , platelets
Functional – WBCs, platelets, RBCs
Fig 1-17, pg. 10