Hematopoiesis hemablood poieto make Blood cell formation Occurs
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 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Hematopoiesis (General) Figure 10. 4 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Hematopoeisis (More Complex) 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 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 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 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Control of Erythrocyte Production Normal blood oxygen levels Figure 10. 5, step 1 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Imb ala nce Normal blood oxygen levels Imb ala nce Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Figure 10. 5, step 2 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Imb ala nce Normal blood oxygen levels Imb ala nce Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Reduced O 2 levels in blood Figure 10. 5, step 3 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Imb ala nce Normal blood oxygen levels Imb ala nce Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Reduced O 2 levels in blood Kidney releases erythropoietin Figure 10. 5, step 4 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Imb ala nce Normal blood oxygen levels Imb ala nce Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Reduced O 2 levels in blood Kidney releases erythropoietin Erythropoietin stimulates Red bone marrow Figure 10. 5, step 5 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Imb ala nce Normal blood oxygen levels Imb ala nce Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Reduced O 2 levels in blood More RBCs Kidney releases erythropoietin Enhanced erythropoiesis Erythropoietin stimulates Red bone marrow Figure 10. 5, step 6 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Normal blood oxygen levels 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 Reduced O 2 levels in blood More RBCs Kidney releases erythropoietin Enhanced erythropoiesis Erythropoietin stimulates Red bone marrow Figure 10. 5, step 7 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
Imb ala nce Normal blood oxygen levels Imb ala Increased O 2 - carrying ability of blood nce Stimulus: Decreased RBC count, decreased availability of O 2 to blood, or increased tissue demands for O 2 Reduced O 2 levels in blood More RBCs Kidney releases erythropoietin Enhanced erythropoiesis Erythropoietin stimulates Red bone marrow Figure 10. 5 Copyright © 2009 Pearson Education, Inc. , publishing as Benjamin Cummings
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