Hematopoiesis Hematopoiesis Blood Cell Formation Hematopoiesis is the
Hematopoiesis
Hematopoiesis (Blood Cell Formation) • Hematopoiesis is the process of blood cell formation • Occurs in red bone marrow (myeloid tissue) • All blood cells are derived from a common stem cell (hemocytoblast) • Hemocytoblasts (Hema – Blood, Cyto – cell, Blast – immature stage of development) form two types of descendants • Lymphoid stem cell, which produces lymphocytes (WBCs) • Myeloid stem cell, which can produce all other formed elements (platelets and RBcs) © 2018 Pearson Education, Inc.
Figure 10. 3 The development of blood cells. Hemocytoblast stem cells Lymphoid stem cells Myeloid stem cells Secondary stem cells Erythrocytes Platelets Lymphocytes © 2018 Pearson Education, Inc. Basophils Eosinophils Monocytes Neutrophils
Formation of Red Blood Cells • Since RBCs are anucleate, they are unable to divide, grow, or synthesize proteins • RBCs 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 © 2018 Pearson Education, Inc.
Formation of Red Blood Cells • Rate of RBC production is controlled by a hormone called erythropoietin • Kidneys produce most erythropoietin as a response to reduced oxygen levels in the blood • Homeostasis is maintained by negative feedback from blood oxygen levels © 2018 Pearson Education, Inc.
Slide 1 Figure 10. 4 Mechanism for regulating the rate of RBC production. IMB AL AN CE Homeostasis: Normal blood oxygen levels 5 O 2–carrying ability of blood increases. 4 Enhanced erythropoiesis increases RBC count. IMB AL AN CE 1 Stimulus Low blood O 2–carrying ability due to • Decreased RBC count • Decreased amount of hemoglobin • Decreased availability of O 2 2 Kidneys (and liver, to a smaller extent) release erythropoietin. 3 Erythropoietin stimulates red bone marrow.
Slide 2 Figure 10. 4 Mechanism for regulating the rate of RBC production. IMB AL AN CE Homeostasis: Normal blood oxygen levels IMB AL AN CE 1 Stimulus Low blood O 2–carrying ability due to • Decreased RBC count • Decreased amount of hemoglobin • Decreased availability of O 2
Slide 3 Figure 10. 4 Mechanism for regulating the rate of RBC production. IMB AL AN CE Homeostasis: Normal blood oxygen levels IMB AL AN CE 1 Stimulus Low blood O 2–carrying ability due to • Decreased RBC count • Decreased amount of hemoglobin • Decreased availability of O 2 2 Kidneys (and liver, to a smaller extent) release erythropoietin.
Slide 4 Figure 10. 4 Mechanism for regulating the rate of RBC production. IMB AL AN CE Homeostasis: Normal blood oxygen levels IMB AL AN CE 1 Stimulus Low blood O 2–carrying ability due to • Decreased RBC count • Decreased amount of hemoglobin • Decreased availability of O 2 2 Kidneys (and liver, to a smaller extent) release erythropoietin. 3 Erythropoietin stimulates red bone marrow.
Slide 5 Figure 10. 4 Mechanism for regulating the rate of RBC production. IMB AL AN CE Homeostasis: Normal blood oxygen levels IMB AL 4 Enhanced erythropoiesis increases RBC count. AN CE 1 Stimulus Low blood O 2–carrying ability due to • Decreased RBC count • Decreased amount of hemoglobin • Decreased availability of O 2 2 Kidneys (and liver, to a smaller extent) release erythropoietin. 3 Erythropoietin stimulates red bone marrow.
Slide 6 Figure 10. 4 Mechanism for regulating the rate of RBC production. IMB AL AN CE Homeostasis: Normal blood oxygen levels 5 O 2–carrying ability of blood increases. 4 Enhanced erythropoiesis increases RBC count. IMB AL AN CE 1 Stimulus Low blood O 2–carrying ability due to • Decreased RBC count • Decreased amount of hemoglobin • Decreased availability of O 2 2 Kidneys (and liver, to a smaller extent) release erythropoietin. 3 Erythropoietin stimulates red bone marrow.
Platelet Plug Formation (Clotting) 12
Blood Coagulation • hemostatic (hemo- blood, stat – cease/stop) mechanism • causes the formation of a blot clot via a series of reactions which activates the next in a cascade 13
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