1. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.4 Hematopoiesis (General)

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hematopoeisis (More Complex)

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Leukocyte Formation  Comes from the differentiation of two different cells produced by the hemocytoblast  Regulated by chemical signals called interleukins that increase a certain type of wbc division

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings  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

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Control of Erythrocyte Production Figure 10.5, step 1 Normal blood oxygen levels

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5, step 2 Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Normal blood oxygen levels Imbalance

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5, step 3 Reduced O 2 levels in blood Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Normal blood oxygen levels Imbalance

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5, step 4 Reduced O 2 levels in blood Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Kidney releases erythropoietin Normal blood oxygen levels Imbalance

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5, step 5 Reduced O 2 levels in blood Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Erythropoietin stimulates Kidney releases erythropoietin Red bone marrow Normal blood oxygen levels Imbalance

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5, step 6 Reduced O 2 levels in blood Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Erythropoietin stimulates Kidney releases erythropoietin Enhanced erythropoiesis Red bone marrow More RBCs Normal blood oxygen levels Imbalance

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5, step 7 Reduced O 2 levels in blood Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Increased O 2 - carrying ability of blood Erythropoietin stimulates Kidney releases erythropoietin Enhanced erythropoiesis Red bone marrow More RBCs Normal blood oxygen levels

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10.5 Reduced O 2 levels in blood Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Increased O 2 - carrying ability of blood Erythropoietin stimulates Kidney releases erythropoietin Enhanced erythropoiesis Red bone marrow More RBCs Normal blood oxygen levels Imbalance