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Chapter 13

Chapter 13. Blood, Heart and Circulation. 13-1. Chapter 13 Outline Overview Blood Pulmonary and Systemic Circulations Heart Valves Cardiac Cycle Electrical Activity of the Heart Structure of Blood Vessels Heart Disease Lymphatic System. 13-2. Overview. 13-3.

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Chapter 13

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  1. Chapter 13 Blood, Heart and Circulation 13-1

  2. Chapter 13 Outline • Overview • Blood • Pulmonary and Systemic Circulations • Heart Valves • Cardiac Cycle • Electrical Activity of the Heart • Structure of Blood Vessels • Heart Disease • Lymphatic System 13-2

  3. Overview 13-3

  4. Functions of Circulatory System • Plays roles in transportation of respiratory gases, delivery of nutrients and hormones, and waste removal • And in temperature regulation, clotting, and immune function 13-4

  5. Components of Circulatory System • Include cardiovascular and lymphaticsystems • Heart pumps blood thru cardiovascular system • Blood vessels carry blood from heart to cells and back • Includes arteries, arterioles, capillaries, venules, veins • Lymphatic system picks up excess fluid filtered out in capillary beds and returns it to veins • Its lymph nodes are part of immune system 13-5

  6. Blood 13-6

  7. Composition of Blood • Consists of formed elements (cells) suspended and carried in plasma (fluid part) • When centrifuged, blood separates into heavier formed elements on bottom and plasma on top 13-7

  8. Composition of Blood • Total blood volume is about 5L • Plasma is straw-colored liquid consisting of H2O and dissolved solutes • Includes ions, metabolites, hormones, antibodies • Red blood cells (RBCs) comprise most of formed elements • % of RBCs in centrifuged blood sample = hematocrit • Hematocrit is 36-46% in women; 41-53% in men 13-8

  9. Plasma Proteins • Constitute 7-9% of plasma • 3 types of plasma proteins: albumins, globulins, and fibrinogen • Albumin accounts for 60-80% • Creates colloid osmotic pressure that draws H2O from interstitial fluid into capillaries to maintain blood volume and pressure • Globulins carry lipids • Gamma globulins are antibodies • Fibrinogen serves as clotting factor • Converted to fibrin • Serum is fluid left when blood clots 13-9

  10. Formed Elements • Are erythrocytes (RBCs) and leukocytes (WBCs) • RBCs are flattened biconcave discs • Shape provides increased surface area for diffusion • Lack nuclei and mitochondria • Each RBC contains 280 million hemoglobins • About 300 billion RBCs are produced each day 13-10

  11. Leukocytes • Have a nucleus, mitochondria, and amoeboid ability • Can squeeze through capillary walls (diapedesis) • Granular leukocytes help detoxify foreign substances and release heparin • Include eosinophils, basophils, and neutrophils 13-11

  12. Leukocytes continued • Agranular leukocytes are phagocytic and produce antibodies • Include lymphocytes and monocytes 13-12

  13. Platelets (thrombocytes) • Are smallest of formed elements, lack nucleus • Are amoeboid fragments of megakaryocytes from bone marrow • Constitute most of mass of blood clots • Release serotonin to vasoconstrict and reduce blood flow to clot area • Secrete growth factors to maintain integrity of blood vessel wall • Survive 5-9 days 13-13

  14. Hematopoiesis • Is formation of blood cells from stem cells in bone marrow (myeloid tissue) and lymphoid tissue • Marrow produces about 500 billion blood cells/day • In fetus occurs in liver 13-14

  15. Hematopoiesis continued • Erythropoiesis is formation of RBCs • Stimulated by erythropoietin (EPO) from kidney • Leukopoiesis is formation of WBCs • Stimulated by variety of cytokines • = autocrine regulators secreted by immune system 13-15

  16. Erythropoiesis • 2.5 million RBCs are produced/sec • Lifespan of 120 days • Old RBCs removed from blood by phagocytic cells in liver, spleen, and bone marrow • Iron recycled back into hemoglobin production 13-16

  17. RBC Antigens and Blood Typing • Antigens present on RBC surface specify blood type • Major antigen group is ABOsystem • Type A blood has only A antigens • Type B has only B antigens • Type AB has both A and B antigens • Type O has neither A or B antigens 13-17

  18. Transfusion Reactions • People with Type A blood make antibodies to Type B RBCs, but not to Type A • Type B blood has antibodies to Type A RBCs but not to Type B • Type AB blood doesn’t have antibodies to A or B • Type O has antibodies to both Type A and B • If different blood types are mixed, antibodies will cause mixture to agglutinate 13-18

  19. Transfusion Reactions continued • If blood types don't match, recipient’s antibodies agglutinate donor’s RBCs • Type O is “universal donor” because lacks A and B antigens • Recipient’s antibodies won’t agglutinate donor’s Type O RBCs • Type AB is “universal recipient” because doesn’t make anti-A or anti-B antibodies • Won’t agglutinate donor’s RBCs 13-19

  20. Rh Factor • Is another type of antigen found on RBCs • Rh+ has Rho(D) antigens; Rh- does not • Can cause problems when Rh- mother has Rh+ babies • At birth, mother may be exposed to Rh+ blood of fetus • In later pregnancies mom may produce Rh antibodies • In Erythroblastosis fetalis, this happens and antibodies cross placenta causing hemolysis of fetal RBCs 13-20

  21. Hemostasis • Is cessation of bleeding • Promoted by reactions initiated by vessel injury: • Vasoconstriction restricts blood flow to area • Platelet plug forms • Plug and surroundings are infiltrated by web of fibrin, forming clot 13-21

  22. Role of Platelets • Platelets don't stick to intact endothelium because of presence of prostacyclin (PGI2--a prostaglandin) and NO • Keep clots from forming and are vasodilators 13-22

  23. Role of Platelets • Damage to endothelium allows platelets to bind to exposed collagen • von Willebrand factor increases bond by binding to both collagen and platelets • Platelets stick to collagen and release ADP, serotonin, and thromboxane A2 • = platelet release reaction 13-23

  24. Role of Platelets continued • Serotonin and thromboxane A2 stimulate vasoconstriction, reducing blood flow to wound • ADP and thromboxane A2 cause other platelets to become sticky and attach and undergo platelet release reaction • This continues until platelet plug is formed 13-24

  25. Role of Fibrin • Platelet plug becomes infiltrated by meshwork of fibrin • Clot now contains platelets, fibrin and trapped RBCs • Platelet plug undergoes plug contraction to form more compact plug 13-25

  26. Conversion of Fibrinogen to Fibrin • Can occur via 2 pathways: • Intrinsic pathway clots damaged vessels and blood left in test tube • Initiated by exposure of blood to negatively charged surface of glass or blood vessel collagen • This activates factor XII (a protease) which initiates a series of clotting factors • Ca2+ and phospholipids convert prothrombin to thrombin • Thrombin converts fibrinogen to fibrin which polymerizes to form a mesh • Damage outside blood vessels releases tissuethromboplastin that triggers a clotting shortcut (= extrinsic pathway) 13-26

  27. 13-27

  28. 13-28

  29. Dissolution of Clots • When damage is repaired, activated factor XII causes activation of kallikrein • Kallikrein converts plasminogen to plasmin • Plasmin digests fibrin, dissolving clot 13-29

  30. Anticoagulants • Clotting can be prevented by Ca+2 chelators (e.g. sodium citrate or EDTA) • or heparin which activates antithrombin III (blocks thrombin) • Coumarin blocks clotting by inhibiting activation of Vit K • Vit K works indirectly by reducing Ca+2 availability 13-30

  31. Pulmonary and Systemic Circulations 13-31

  32. Structure of Heart • Heart has 4 chambers • 2 atria receive blood from venous system • 2 ventricles pump blood to arteries • 2 sides of heart are 2 pumps separated by muscular septum 13-32

  33. Structure of Heart continued • Between atria and ventricles is layer of dense connective tissue called fibrous skeleton • Which structurally and functionally separates the two • Myocardial cells of atria attach to top of fibrous skeleton and form 1 unit (or myocardium) • Cells from ventricles attach to bottom and form another unit • Fibrous skeleton also forms rings, the annuli fibrosi, to hold heart valves 13-33

  34. Pulmonary and Systemic Circulations • Blood coming from tissues enters superior and inferior vena cavae which empties into right atrium, then goes to right ventricle which pumps it through pulmonary arteries to lungs 13-34

  35. Pulmonary and Systemic Circulations continued • Oxygenated blood from lungs passes thru pulmonary veins to left atrium, then to left ventricle which pumps it through aorta to body 13-35

  36. Pulmonary and Systemic Circulations continued • Pulmonary circulation is path of blood from right ventricle through lungs and back to heart • Systemic circulation is path of blood from left ventricle to body and back to heart • Rate of flow through systemic circulation = flow rate thru pulmonary circuit 13-36

  37. Pulmonary and Systemic Circulations continued • Resistance in systemic circuit > pulmonary • Work done by left ventricle pumping to systemic is 5-7X greater • Makes left ventricle more muscular (and 3-4X thicker) 13-37

  38. Heart Valves 13-38

  39. Atrioventricular Valves • Blood flows from atria into ventricles thru 1-way atrioventricular (AV) valves • Between right atrium and ventricle is tricuspid valve • Between left atrium and ventricle is bicuspid or mitral valve 13-39

  40. Atrioventricular Valves continued • Opening and closing of valves results from pressure differences • High pressure of ventricular contraction is prevented from everting AV valves by contraction of papillary muscles which are connected to AVs by chorda tendinea 13-40

  41. Semilunar Valves • During ventricular contraction blood is pumped through aortic and pulmonary semilunar valves • Close during relaxation 13-41

  42. Cardiac Cycle 13-42

  43. Cardiac Cycle • Is repeating pattern of contraction and relaxation of heart • Systole refers to contraction phase • Diastole refers to relaxation phase • Both atria contract simultaneously; ventricles follow 0.1-0.2 sec later 13-43

  44. Cardiac Cycle • End-diastolic volume is volume of blood in ventricles at end of diastole • Stroke volume is amount of blood ejected from ventricles during systole • End-systolic volume is amount of blood left in ventricles at end of systole 13-44

  45. Cardiac Cycle continued • As ventricles contract, pressure rises, closing AV valves • Called isovolumetric contraction because all valves are closed • When pressure in ventricles exceeds that in aorta, semilunar valves open and ejection begins • As pressure in ventricle falls below that in aorta, back pressure closes semilunars • All valves are closed and ventricles undergo isovolumetricrelaxation • When pressure in ventricles falls below atria, AVs open and ventricles fill • Atrial systole sends its blood into ventricles 13-45

  46. 13-46

  47. Heart Sounds • Closing of AV and semilunar valves produces sounds that can be heard thru stethoscope • Lub (1st sound) produced by closing of AV valves • Dub (2nd sound) produced by closing of semilunars 13-47

  48. Heart Murmurs • Are abnormal sounds produced by abnormal patterns of blood flow in heart • Many caused by defective heart valves • Can be of congenital origin • In rheumatic fever, damage can be from antibodies made in response to strep infection 13-48

  49. Heart Murmurs continued • In mitral stenosis, mitral valve becomes thickened and calcified, impairing blood flow from left atrium to left ventricle • Accumulation of blood in left ventricle can cause pulmonary hypertension • Valves are incompetent when don't close properly • Can be from damage to papillary muscles 13-49

  50. Heart Murmurs continued • Murmurs caused by septal defects are usually congenital • Due to holes in septum between left and right sides of heart • Pressure causes blood to pass from left to right 13-50

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