1. Hematopoiesis (hema-blood / poie-to make)
Blood cell formation
Occurs in red bone marrow of skull, pelvis, ribs, sternum and epiphysis of long bones
All blood cells are derived from a common stem cell (hemocytoblast)
Hemocytoblast differentiation leads to the formation of all other formed elements in a series of steps

2. Hematopoiesis (General)
Figure 10.4

3. Hematopoeisis (More Complex)

4. Formation of Erythrocytes
Unable to divide, grow, or synthesize proteins as adult cells
Wear out in 100 to 120 days
When worn out, RBCs are eliminated by phagocytes in the spleen or liver
Lost cells are replaced by division of hemocytoblasts in the red bone marrow

5. Rate is controlled by a hormone (erythropoietin)
Kidneys produce erythropoietin as a response to reduced oxygen levels in the blood
Homeostasis is maintained by negative feedback from blood oxygen levels
Reminder: negative feedback means that a stimulus is reversed by the action of an effector

6. Control of Erythrocyte Production
Normal blood oxygen levels
Figure 10.5, step 1

7. Reduced O2 levels in blood
Stimulus: Decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2
Normal blood oxygen levels
Imbalance
Figure 10.5, step 3

8. Reduced O2 levels in blood
Stimulus: Decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2
Kidney releases erythropoietin
Normal blood oxygen levels
Imbalance
Figure 10.5, step 4

9. Reduced O2 levels in blood
Stimulus: Decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2
Erythropoietin stimulates
Kidney releases erythropoietin
Red bone marrow
Normal blood oxygen levels
Imbalance
Figure 10.5, step 5

10. Reduced O2 levels in blood
Stimulus: Decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2
Erythropoietin stimulates
Kidney releases erythropoietin
Enhanced erythropoiesis
Red bone marrow
More RBCs
Normal blood oxygen levels
Imbalance
Figure 10.5, step 6

11. Reduced O2 levels in blood
Stimulus: Decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2
Increased O2- carrying ability of blood
Erythropoietin stimulates
Kidney releases erythropoietin
Enhanced erythropoiesis
Red bone marrow
More RBCs
Normal blood oxygen levels
Figure 10.5, step 7

12. Figure 10.5 Imbalance Normal blood oxygen levels
Reduced O2 levels in blood
Stimulus: Decreased RBC count, decreased availability of O2 to blood, or increased tissue demands for O2
Increased O2- carrying ability of blood
Erythropoietin stimulates
Kidney releases erythropoietin
Enhanced erythropoiesis
Red bone marrow
More RBCs
Normal blood oxygen levels
Imbalance
Figure 10.5