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Understanding Blood: The Body's Lifeline and Guardian

Learn about the fascinating world of blood in the cardiovascular system. Discover its volume, composition, and crucial functions like oxygen transport and immune defense. Dive into hematocrit, erythrocytes, hemoglobin, leukocytes, platelets, and the intricate process of hemostasis.

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Understanding Blood: The Body's Lifeline and Guardian

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  1. Cardiovascular System: Blood

  2. General Properties of Blood • Volume in adult body • Female = 4 -5 liters • Male = 5 – 6 liters • pH = 7.35 to 7.45 • Temp = 38 oC • 100.4 oF

  3. Hematocrit • Hematocrit • = percent volume • of whole blood • occupied by RBC p 682

  4. p 681

  5. Erythrocytes or Red Blood Cells • No nucleus • Life span = about 120 days • Average Count • Male = 5.4 million / mm3 (μL) • Female = 4.8 million / mm3 (μL) • Production called erythropoiesis • Takes about 4 days • Rate = 2 to 3 million per second ! p 687

  6. Erythrocytes on the tip of a hypodermic needle p 685

  7. Hemoglobin • Globin = one of four protein chains • Heme = one of four nonprotein parts with an Fe++ at their center that binds with O2 for transport • About 280 million hemoglobin molecules per RBC p 686

  8. What kind of feedback system? p 688

  9. Recycling Iron • On average about 26 mg of Fe+2 is used to make new hemoglobin per day • Body only requires about 1-2 mg per day from diet to replace Fe+2 lost in kidney & GI tract p 689

  10. Hemoglobin Recycling • Iron • Amino Acids from globin proteins p 689

  11. Leukocytes or White Blood Cells • 5,000 to 10,000 / mm3 (μL) • Compared to about 5 million for RBC • Granulocytes • Eosinophils • Basophils • Neutrophils • Agranulocytes • Monocytes • Lymphocytes

  12. Protection against foreign invaders in body • Neutrophils – phagocytosis • Eosinophils – phagocytosis • Basophils – release histamine & heparin • Lymphocytes – produce immune response to remove foreign antigens • Monocytes – differentiate into macrophages • (large phagocytes) p 698-9

  13. Platelets (Thrombocytes) • Not really cells, but fragments of a larger cell called a megakaryocyte • Average 250,000 / mm3 (μL) • Play a major role in hemostasis or stopping bleeding p 703

  14. Hemostasis p 704

  15. Vascular Spasm • Vascular spasm is vasoconstriction of a damaged vessel to stop or slow flow of blood for 20 to 30 minutes to • “buy time” for other mechanisms to start working p 704

  16. Platelet Plug Formation • Platelet Adhesion = platelets stick to exposed collagen • Platelet Aggregation = platelets stick to each other & build up a mass called a platelet plug • Platelet Activation = platelets develop cytoplasmic processes (pseudopods) & degranulate (exocytosis of granule contents) p 704

  17. Platelet Activation: Degranulation • Granules contain: • ADP = primary stimulus for platelet aggregation & activation • Thromboxane A2 = stimulates aggregation, degranulation, & vasoconstriction • Serotonin = stimulates vasoconstriction • Platelet derived growth factors (PDGF) = promote division of endothelia, smooth muscle & fibroblasts • Ca++ = increases local supply • = POSITIVE FEEDBACK LOOP

  18. Coagulation • Three Basic Stages: • 1) Form Prothrombin Activator • Extrinsic pathway • Intrinsic pathway • 2) Form Thrombin • 3) Form Fibrin p 704

  19. Clot Retraction • Platelets contract and pull on fibrin strands • Clot becomes denser & stronger • Pulls edges of damaged vessel together • Squeezes out serum

  20. Fibrinolysis • Plasmin activated by; • Factor XII • Plasmin • Thrombin • Tissue Plasminogen Activator (t-PA) p 708

  21. To Clot or Not to Clot • Thrombin diluted by blood • Fibrin inactivates most of thrombin at wound • Liver removes active clotting factors from blood (leaves inactive factors) • Anticoagulants; • Antithrombin from liver inactivates thrombin • Heparin from mast cells & basophils helps prevent coagulation

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