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Blood

Blood. http://health.howstuffworks.com/medicine/medication/aspirin3.htm. Overview of Blood Circulation. Circulates continuously Gas exchange occurs across capillary walls O 2 rich blood leaves lungs and is pumped systemically via the heart

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Blood

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  1. Blood http://health.howstuffworks.com/medicine/medication/aspirin3.htm

  2. Overview of Blood Circulation • Circulates continuously • Gas exchange occurs across capillary walls • O2 rich blood leaves lungs and is pumped systemically via the heart • CO2 rich blook enters heart and is pumped into lungs to be oxygenated

  3. Composition of Blood • Fluid tissue • Liquid plasma and formed elements • Hematocrit – the percentage of RBCs out of the total blood volume

  4. Physical Characteristics and Volume • Blood is a sticky, opaque, metallic taste • Color varies from scarlet to dark red • The pH of blood is 7.35–7.45 • Temperature is 38C • Blood accounts for approximately 8% of body weight • Average volume: 5–6 L for males, and 4–5 L for females

  5. Functions and Distribution of Blood • Protects against fluid loss • Provides immunity • Regulates pH • Maintains osmotic pressure

  6. Blood Plasma • Blood plasma contains over 100 solutes, including: • Proteins: albumin, transferrin, globulins, complement and clotting proteins • Waste products: lactic acid, urea, creatinine • Nutrients – glucose, carbohydrates, amino acids • Electrolytes – sodium, potassium, calcium, chloride, bicarbonate • Respiratory gases – oxygen and carbon dioxide

  7. Formed Elements • Erythrocytes, leukocytes, and platelets Life span is variable • Stem cell renewal or division

  8. Erythrocytes (RBCs) • Biconcave discs • Anucleate • Essentially no organelles • Spectrin allows flexibility • Hemoglobin (97%) • Anerobic ATP generation

  9. Structure of Hemoglobin Figure 17.4

  10. Production of Erythrocytes • Hematopoiesis –born of blood • Stem cells in the red bone • Maintain constant level

  11. Erythropoiesis Regulation • Indirectly through thyroxine, androgens, GH • Vitamin B12 • Erythropoietin (EPO) • release by the kidneys • triggered by hypoxia • Increases division of erythroblasts and maturation rate • Oxygen carrying ability of the blood

  12. Erythropoietin Mechanism Imbalance Start Homeostasis: Normal blood oxygen levels Stimulus: Hypoxia due to decreased RBC count, decreased amount of hemoglobin, or decreased availability of O2 Imbalance Increases O2-carrying ability of blood Reduces O2 levels in blood Kidney (and liver to a smaller extent) releases erythropoietin Enhanced erythropoiesis increases RBC count Erythropoietin stimulates red bone marrow Figure 17.6

  13. Fate and Destruction of Erythrocytes • The life span =100–120 days • Dying RBCs are engulfed by macrophages • Iron returned to blood bound by transferrin • Heme is degraded into bilirubin, bile, feces • Globin metabolized or excreted

  14. Erythrocyte Recycling Low O2 levels in blood stimulate kidneys to produce erythropoietin. 1 Erythropoietin levels rise in blood. 2 Erythropoietin and necessary raw materials in blood promote erythropoiesis in red bone marrow. 3 New erythrocytes enter bloodstream; function about 120 days. 4 Aged and damaged red blood cells are engulfed by macrophages of liver, spleen, and bone marrow; the hemoglobin is broken down. 5 Hemoglobin Heme Globin Bilirubin Amino acids Iron stored as ferritin, hemosiderin Iron is bound to transferrin and released to blood from liver as needed for erythropoiesis Bilirubin is picked up from blood by liver, secreted into intestine in bile, metabolized to stercobilin by bacteria and excreted in feces Circulation Food nutrients, including amino acids, Fe, B12, and folic acid are absorbed from intestine and enter blood Raw materials are made available in blood for erythrocyte synthesis. 6 Figure 17.7

  15. Erythrocyte Disorders • Anemia – blood has abnormally low oxygen-carrying capacity • It is a symptom rather than a disease itself • Blood oxygen levels cannot support normal metabolism

  16. Erythrocyte Disorders • Hemorrahgic anemia • Hemolytic anemia • Aplastic anemia • Iron-deficiency anemia • Pernicious anemia • Thalassemias • Sickel-cell anemia • Polycythemia

  17. Leukocytes (WBCs) • Leukocytes, the only blood components that are complete cells: • Are less numerous than RBCs • Make up 1% of the total blood volume • Capable of diapedesis and margination

  18. Percentages of Leukocytes Figure 17.9

  19. Summary of Formed Elements Table 17.2.1

  20. Stem cells Hemocytoblast Myeloid stem cell Lymphoid stem cell Committed cells Myeloblast Myeloblast Myeloblast Lymphoblast Develop- mental pathway Promyelocyte Promyelocyte Promyelocyte Promonocyte Prolymphocyte Eosinophilic myelocyte Basophilic myelocyte Neutrophilic myelocyte Eosinophilic band cells Neutrophilic band cells Basophilic band cells Monocytes Lymphocytes Eosinophils Basophils Neutrophils (a) (b) (c) (e) (d) Some become Agranular leukocytes Granular leukocytes Some become Macrophages (tissues) Plasma cells Figure 17.11

  21. Leukocytes Disorders • Leukocytosis • Leukemia refers to cancerous conditions involving WBCs • Myelocytic leukemia • Lymphocytic leukemia • Acute leukemia • Chronic leukemia

  22. Platelets • Fragments of megakaryocytes • Platelets are part of the clotting

  23. Hemostasis • A series of reactions for stoppage of bleeding • Three phases occur in rapid sequence • Vascular spasms • Platelet plug formation • Coagulation (blood clotting)

  24. Detailed Events of Coagulation Figure 17.13b

  25. Clot Retraction and Repair • Clot retraction – stabilization of the clot by squeezing serum from the fibrin strands • Repair • Platelet-derived growth factor (PDGF) stimulates rebuilding of blood vessel wall • Fibroblasts form a connective tissue patch • Endothelial cells multiply , restoring the lining

  26. Factors Preventing Undesirable Clotting • Endothelial lining of blood vessels • Platelet adhesion is prevented by: • Heparin and PGI2 secreted by endothelial cells • Vitamin E quinone, a potent anticoagulant • Aspirin • Wafarin (coumadin)

  27. Hemostasis Disorders • Thrombus • Embolus • Thrombocytopenia • Hemophilias • Hemophilia A, B, C

  28. Human Blood Typing • Humans have 30 varieties of naturally occurring RBC antigens • The antigens of the ABO and Rh blood groups cause vigorous transfusion reactions when they are improperly transfused • Other blood groups (M, N, Dufy, Kell, and Lewis) are mainly used for legalities

  29. ABO Blood Groups Table 17.4

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