− 2 alpha and 2 beta chains − fetal Hb - gamma replace beta chains; binds O 2 beter • Heme Group − ring with iron atom inside Alpha Beta Heme groups Blood - 12
Hemoglobin (Hb) Structure • Heme group − conjugated with each protein chain − hemoglobin molecule can carry four O 2 − binds oxygen to ferrous ion (Fe 2+ ) CH 3 CH CH 2 C C HC C C CH N CH C C C C CH 3 3 N Fe 2+ N CH 2 C C CH CH 2 C N C CH 2 HC C C CH COOH C C CH 2 Fe 2+ O=O Blood - 13
Clinical Correlates Carbon Monoxide Poisoning • Carbon monoxide binds to hemoglobin much more strongly than oxygen • It creates low oxygen conditions in tissue (hypoxia) • It is hard to detect because carboxyhemoglobin is very red Blood - 14
Erythrocytes and Hemoglobin • RBC count and hemoglobin concentration indicate amount of O 2 blood can carry − Hematocrit (packed cell volume) - % of blood composed of cells • men 42- 52% cells; women 37- 48% cells − RBC count • men 4.6-6.2, women 4-2-5.4 million/ L • Values are lower in women − androgens stimulate RBC production − women have periodic menstrual losses Blood - 15
Clinical Correlates Anemia Blood - 16 Anemia is insufficient RBS’s or hemoglobin in the blood • Inadequate erythropoiesis or hemoglobin synthesis causes pe r niciou s anemia − inadequate vitamin B 12 − iron-deficiency anemia − kidney failure and insufficient erythropoietin − Thalassemia – recessive genetic disease of globin − aplastic anemia - complete cessation • Hemorrhagic anemias • Hemolytic anemias
Physiology Objective: The creation of large numbers of blood cells is crucial to maintaining homeostasis, and pathologies of blood cell generation have important physiological consequences Blood - 17
Hemopoiesis • Adult produces 400 billion platelets, 200 billion RBCs and 10 billion WBCs every day • Hemopoietic tissues produce blood cells − Liver stops producing blood cells at birth − Spleen remains involved with WBC production • lymphoid hemopoiesis occurs in widely distributed lymphoid tissues, makes lymphocytes − Red bone marrow • pluripotent stem cells create all blood cells Blood - 18
Erythrocyte Homeostasis Blood - 19 • Stimulus for erythropoiesis − Hypoxemia - nadequate oxygen transport − Sensed by liver and kidneys − Erythropoietin secreted (85% kidneys) − Cell division is stimulated Hypoxemia liver and kidneys Secretion of EPO Increased RBC count Increased O 2 transport Stimulation of red marrow 3-4 days
Nutritional Needs for Erythropoiesis • Iron - key nutritional requirement − lost daily through urine, feces, and bleeding • men 0.9 mg/day and women 1.7 mg/day − low absorption requires consumption of 5-20 mg/day • dietary iron: ferric (Fe 3+ ) and ferrous (Fe 2+ ) • stomach acid converts Fe 3+ to absorbable Fe 2+ • some foods interfere with this Blood - 20
Gastroferritin Mixture of Fe 2+ and Fe 3+ is ingested 1 Stomach acid converts Fe 3+ to Fe 2+ 2 3 4 Fe 2+ Gastroferritin Fe 2+ binds to gastroferritin Gastroferritin transports Fe 2+ to small intestine and releases it for absorption Fe 3+ Blood - 21
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