Human Physiology Lecture 13: Cardiovascular System - Blood PDF

Human Physiology Lecture 13 Cardiovascular System - Blood Objectives: Blood Composition - Required Reading (Section 13.2 pp. 405-408 excluding Hematopoeisis) Plasma, Erythrocytes, Leukocytes and Platelets Hemostasis Textbook Ref...

Human Physiology Lecture 13 Cardiovascular System - Blood Objectives: Blood Composition - Required Reading (Section 13.2 pp. 405-408 excluding Hematopoeisis) Plasma, Erythrocytes, Leukocytes and Platelets Hemostasis Textbook Reference Chapter 13 Section 13.2 Blood Composition (pp. 405-417; selected sections) BIOL2010 Human Physiology 1  Socrative activity on readings 1. Using your laptop, tablet or cell phone log onto: https://b.socrative.com/ 2. Click “Student Login” at top 3. Room name: PHYSIO2010 4. Click join 5. The questions will appear when we begin BIOL2010 Human Physiology 2  Erythrocytes 5 million/mm3 No nuclei, mitochondria or organelles Biconcave disc – Shape due to spectrin which forms spectrin net BIOL2010 Human Physiology 3  Oxygen and Carbon Dioxide Transport Hemoglobin molecule – Greatly increases O2 transport 98.5% of transported O2 is bound to hemoglobin 1.5% of transported O2 is dissolved in plasma – Also binds to CO2, H+, and CO (carbonic anhydrase and carbon dioxide reactions) Figure 15.3 Hemoglobin. BIOL2010 Human Physiology 4  Life Cycle of Erythrocytes No cell division of mature RBCs Short life span = 120 days Replace 2–3 million RBCs/sec – = 200 billion/day Synthesized in red bone marrow – Erythropoiesis Old RBCs, filtered by spleen BIOL2010 Human Physiology 5  Life Cycle of Erythrocytes Erythrocyte production (erythropoieis) – Bone marrow – Hematopoietic growth factors (HGFs) (cytokine) – HGF for erythrocyte production Erythropoietin – HGF for leukocyte production Colony-stimulating factors and interleukins Figure 15.5 Production of blood cells and platelets. BIOL2010 Human Physiology 6  Life Cycle of Erythrocytes Dietary requirements for erythrocyte production – Iron Component of hemoglobin (heme portion) Normal hemoglobin content of blood – Men: 13–18 g/dL – Women: 12–16 g/dL Iron-deficiency anemia – Folic acid Necessary for DNA replication and thus cell proliferation – Vitamin B12 Necessary for DNA replication and thus cell proliferation Pernicious anemia BIOL2010 Human Physiology 7  Life Cycle of Erythrocytes Production Filtering and Destruction Star t EPO = erythropoetin T-iron = transferrin F-iron = ferritin Figure 15.4 Life cycle of erythrocytes. BIOL2010 Human Physiology 8 Granulocytes Agranulocytes Leukocytes Name % Leukocytes Function in Blood Neutrophils 50 -80% Phagocytosis of foreign material; numbers increase during infections Defend against parasitic invaders (e.g., parasitic Eosinophils 1–4% worms); granules contain toxic molecules that attack parasites May defend against large parasites by releasing toxic Basophils less than 1% substances Contribute to allergic reactions (histamine, heparin) Phagocytosis New monocytes circulate in blood then migrate to Monocytes 5% tissues  macrophages - Wandering macrophages - Fixed macrophages B lymphocytes (B cells) – secrete antibodies T lymphocytes (T cells) – secrete cytokines – directly Lymphocytes 30% damage foreign cells Null cells – most are natural killer cells Figure 15.6 Leukocytes and their roles in immunity. BIOL2010 Human Physiology 9  Leukocytes Synthesis of leukocytes – Derived from same hematopoietic stem cells as erythrocytes – Most develop to full maturity in bone marrow – T lymphocytes migrate to the thymus gland to develop into full maturity – Development is controlled by colony- stimulating factors and interleukins BIOL2010 Human Physiology 10  Platelets Platelets – colourless cell fragments formed when bits of megakaryocytes break off – Smaller than erythrocytes, contain mitochondria, smooth ER and cytoplasmic granules but no nucleus – Important in blood clot formation BIOL2010 Human Physiology 11  Hemostasis Hemostasis = mechanisms to stop bleeding Three steps: 1. Vascular spasm 2. Formation of platelet plug 3. Formation of blood clot (thrombus) BIOL2010 Human Physiology 12  Hemostasis Vascular Spasm – Resistance to blood flow increases (vasoconstriction) – Sympathetic nervous system activated  further vasoconstriction – Blood loss minimized Platelet Plug – Platelets = thrombocytes Granules containing secretory products for clotting Sticky for adherence – Plug forms around the site of vessel damage – Decreases blood loss – Necessary for production of a blood clot BIOL2010 Human Physiology 13  Hemostasis Platelet Plug – Many plasma proteins involved in formation of plug – Key protein = von Wellebrand factor (vWf) Secreted by megakaryocytes, platelets and endothelial cells – Note – vWf is always present in plasma, but accumulates at site of vessel damage BIOL2010 Human Physiology 14  Hemostasis Platelet Plug: Platelet Adhesion Blood vessel damage Exposure of subendothelium Von Willebrand factor binds to collagen fibers Platelets bind to vWf Anchors platelets Sticky Secretions BIOL2010 Human Physiology 15  Hemostasis Platelet Plug: Aggregation – Secretory products that are released from activated platelets: Serotonin: vasoconstriction Epinephrine: vasoconstriction ADP – Increases stickiness by morphological changes (positive feedback) – Stimulates production of thromboxane A2 (TXA2) from arachidonic acid – more aggregation Figure 15.7 Formation of a platelet plug. BIOL2010 Human Physiology 16  Hemostasis Preventing the spread of a platelet plug – Healthy cells release: – Prostacyclin (PGI2) From conversion of arachidonic acid in healthy cells – Nitric oxide NOTE – platelet plugs can’t stop blood loss, only slow it down, so next step in hemostasis is blood clot formation Figure 15.7 Formation of a platelet plug. BIOL2010 Human Physiology 17  Hemostasis Formation of a Blood Clot – Clotting = coagulation Blood is converted into a solid gel called a clot or thrombus – Occurs around platelet plug – Dominant hemostatic defense mechanism – Requires sequence of reactions – coagulation cascade Plasma proteins undergo series of proteolytic activations from hydrolysis of peptide bonds Figure 15.8 A fibrin clot. BIOL2010 Human Physiology 18  Activated Hemostasis simultaneously Uses coagulation factors and other chemicals present in Involves some plasma coagulation factors in damaged tissue next to the site of vessel damage Figure 15.9 Role of thrombin in forming fibrin clot. BIOL2010 Human Physiology 19  Hemostasis Factors limiting clot formation – Anticoagulants: proteins in plasma and on the surface of endothelial cells – Tissue factor pathway inhibitor Secreted by healthy endothelial cells Inhibits extrinsic pathway – Thrombomodulin Secreted by healthy endothelial cells Binds to thrombin, forming a complex that activates protein C (an anticoagulant that inhibits the intrinsic and extrinsic pathways) BIOL2010 Human Physiology 20  Hemostasis Factors limiting clot formation – Once formed, clots are dissolved by plasmin Plasminogen  plasmin via plasminogen activators – E.g. of plasminogen activator = tissue plasminogen activator (TPA) Dissolves clots enzymatically to break down fibrin BIOL2010 Human Physiology 21 Role of Coagulation Factors in Clot Formation Disorders – Hemophilia Genetic disorder caused by deficiency of gene for a specific coagulation factor (Factor VIII) – Von Willebrand's disease Reduced levels of vWf Decreased platelet plug formation – Vitamin K deficiencies Decreased synthesis of clotting factors BIOL2010 Human Physiology 22  Role of Coagulation Factors in Clot Formation Disorders Aspirin as an anticoagulant – Low doses - anticoagulant Inhibits formation of thromboxane A2 (TXA2) – Decreases platelet aggregation and platelet plug formation – High doses – increases likelihood of clot Inhibits formation of prostacyclin (PGI2) – Recall prostacyclin is important in preventing spread of platelet plug BIOL2010 Human Physiology 23