Cardiovascular System: Blood
General Properties of Blood Volume in adult body • Female = 4 -5 liters • Male = 5 – 6 liters p. H = 7. 35 to 7. 45 Temp = 38 o. C 100. 4 o. F
Hematocrit = percent volume of whole blood occupied by RBC p 682
p 681
Erythrocytes or Red Blood Cells • No nucleus • Life span = about 120 days • Average Count • Male = 5. 4 million / mm 3 (μL) • Female = 4. 8 million / mm 3 (μL) • Production called erythropoiesis • Takes about 4 days • Rate = 2 to 3 million per second ! p 687
Erythrocytes on the tip of a hypodermic needle p 685
Hemoglobin Globin = one of four protein chains Heme = one of four nonprotein parts with an Fe++ at their center that binds with O 2 for transport About 280 million hemoglobin molecules per RBC p 686
What kind of feedback system? p 688
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 p 689 to replace Fe+2 lost in kidney & GI tract
Hemoglobin Recycling • Iron • Amino Acids from globin proteins p 689
Leukocytes or White Blood Cells • 5, 000 to 10, 000 / mm 3 (μL) Compared to about 5 million for RBC Granulocytes • Eosinophils • Basophils • Neutrophils Agranulocytes • Monocytes • Lymphocytes
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
Platelets (Thrombocytes) • Not really cells, but fragments of a larger cell called a megakaryocyte • Average 250, 000 / mm 3 (μL) • Play a major role in hemostasis or stopping bleeding p 703
Hemostasis p 704
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
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
Platelet Activation: Degranulation Granules contain: • ADP = primary stimulus for platelet aggregation & activation • Thromboxane A 2 = 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
Coagulation Three Basic Stages: 1) Form Prothrombin Activator • Extrinsic pathway • Intrinsic pathway 2) Form Thrombin 3) Form Fibrin p 704
Clot Retraction • Platelets contract and pull on fibrin strands • Clot becomes denser & stronger • Pulls edges of damaged vessel together • Squeezes out serum
Fibrinolysis Plasmin activated by; • Factor XII • Plasmin • Thrombin • Tissue Plasminogen Activator (t-PA) p 708
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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