Ch19 Blood Sum 09

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Ch19 Blood Sum 09

  1. 1. Ch. 19 Blood The Cardiovascular System <ul><li>A circulating transport system: </li></ul><ul><ul><li>a pump (the heart) </li></ul></ul><ul><ul><li>a conducting system (blood vessels) </li></ul></ul><ul><ul><li>a fluid medium (blood) </li></ul></ul>Functions of the Cardiovascular System <ul><li>To transport materials to and from cells: </li></ul><ul><ul><li>oxygen and carbon dioxide </li></ul></ul><ul><ul><li>nutrients </li></ul></ul><ul><ul><li>hormones </li></ul></ul><ul><ul><li>immune system components </li></ul></ul><ul><ul><li>waste products </li></ul></ul>
  2. 2. Blood <ul><li>Is specialized fluid of connective tissue </li></ul><ul><li>Contains cells suspended in a fluid matrix </li></ul>5 Functions of Blood <ul><li>Transport of dissolved substances </li></ul><ul><ul><li>Gases-O2 from lungs to tissues </li></ul></ul><ul><ul><li>Nutrients-from digestive tract, storage, or liver </li></ul></ul><ul><ul><li>Hormones-such as from endocrine glands to target cells </li></ul></ul><ul><ul><li>Waste products-from cells to kidneys </li></ul></ul><ul><li>Regulation of pH and ions </li></ul>
  3. 3. <ul><li>Regulation of pH and ions </li></ul><ul><ul><ul><ul><li>Ions – either add or subtract i.e. Ca or K by diffusion w/ interstitial fluid & blood </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Absorbs & neutralize acid </li></ul></ul></ul></ul><ul><ul><ul><li>- i.e lactic acid from skeletal muscles </li></ul></ul></ul><ul><li>Restriction of fluid losses at injury sites </li></ul><ul><ul><li>- Clotting </li></ul></ul><ul><li>Defense against toxins and pathogens </li></ul><ul><ul><li>- WBC – transported by blood to fight infection & remove debris </li></ul></ul><ul><li>Stabilization of body temperature </li></ul><ul><ul><li>- Heat loss via skin if hot </li></ul></ul><ul><ul><li>- Heat retention to brain and other vital organs via shunting </li></ul></ul>
  4. 4. Whole Blood <ul><li>Plasma : </li></ul><ul><ul><li>Fluid proteins in solution </li></ul></ul><ul><ul><li>Like interstitial fluid </li></ul></ul><ul><li>Formed elements : </li></ul><ul><ul><li>all cells and cell fragments </li></ul></ul>Plasma <ul><li>Water </li></ul><ul><li>Dissolved plasma proteins </li></ul><ul><li>Other solutes </li></ul><ul><li>similar to, & exchanges fluids with, interstitial fluid </li></ul><ul><li>Is matrix of formed elements </li></ul>
  5. 5. 3 Types of Formed Elements <ul><li>Red blood cells ( RBCs ) or erythrocytes : </li></ul><ul><ul><li>transport oxygen </li></ul></ul><ul><li>White blood cells ( WBCs ) or leukocytes : </li></ul><ul><ul><li>part of the immune system </li></ul></ul><ul><li>Platelets : cell fragments involved in clotting </li></ul>Hemopoiesis <ul><li>Process of producing formed elements </li></ul><ul><li>By myeloid and lymphoid stem cells </li></ul>Fractionation <ul><li>Process of separating whole blood for clinical analysis: </li></ul><ul><ul><li>into plasma and formed elements </li></ul></ul>
  6. 6. 3 General Characteristics of Blood <ul><li>38°C (100.4°F) is normal temperature </li></ul><ul><li>High viscosity </li></ul><ul><li>Slightly alkaline pH (7.35–7.45) </li></ul>Blood Volume <ul><li>Blood volume (liters) = 7% of body weight (kilograms): </li></ul><ul><ul><li>adult male: 5 to 6 liters </li></ul></ul><ul><ul><li>adult female: 4 to 5 liters </li></ul></ul>
  7. 7. Plasma <ul><li>Makes up 50–60% of blood volume </li></ul><ul><li>More than 90% of plasma is water </li></ul>Figure 19–1b
  8. 8. Extracellular Fluids <ul><li>Interstitial fluid (IF) and plasma </li></ul><ul><li>Materials plasma and IF exchange across capillary walls: </li></ul><ul><ul><li>water </li></ul></ul><ul><ul><li>ions </li></ul></ul><ul><ul><li>small solutes </li></ul></ul>Differences between Plasma and IF <ul><li>Levels of O 2 and CO 2 </li></ul><ul><li>Dissolved proteins: </li></ul><ul><ul><li>plasma proteins do not pass through capillary walls </li></ul></ul>
  9. 9. 3 Classes of Plasma Proteins <ul><li>Albumins (60%) </li></ul><ul><li>Globulins (35%) </li></ul><ul><li>Fibrinogen (4%) </li></ul>Albumins <ul><li>Transport substances: </li></ul><ul><ul><li>fatty acids </li></ul></ul><ul><ul><li>thyroid hormones </li></ul></ul><ul><ul><li>steroid hormones </li></ul></ul>Fibrinogen <ul><li>Molecules form clots </li></ul><ul><li>Produce long, insoluble strands of fibrin </li></ul><ul><li>If remove clotting proteins, = serum </li></ul>
  10. 10. Globulins <ul><li>Antibodies , also called immunoglobulins </li></ul><ul><ul><li>- Attack foreign bodies </li></ul></ul><ul><li>Transport globulins (small molecules): </li></ul><ul><ul><li>hormone-binding proteins – thyroid binding protein binds thyroid hormones; transcortin binds acth (adrenocorticoytropic hormone), stimulates thyroid </li></ul></ul><ul><ul><li>Metalloproteins- i.e. transferrin for Fe </li></ul></ul><ul><ul><li>apolipoproteins ( lipoproteins ) </li></ul></ul><ul><ul><li>steroid-binding proteins – i.e. testosterone binding hormone binds & transports testosterone </li></ul></ul>
  11. 11. Serum <ul><li>Liquid part of a blood sample in which dissolved fibrinogen has converted to solid fibrin </li></ul>Other Plasma Proteins <ul><li>1% of plasma: </li></ul><ul><ul><li>changing quantities of specialized plasma proteins </li></ul></ul><ul><ul><li>enzymes, hormones, and prohormones </li></ul></ul><ul><ul><ul><li>TSH, FSH, LH, insulin, prolactin </li></ul></ul></ul>Origins of Plasma Proteins <ul><li>90% made in liver </li></ul><ul><ul><li>All albumin and fibrinogen </li></ul></ul><ul><li>Antibodies made by plasma cells made by lymphocytes </li></ul><ul><li>Peptide hormones made by endocrine organs </li></ul>
  12. 12. Red Blood Cells <ul><li>Red blood cells (RBCs) make up 99.9% of blood’s formed elements </li></ul>Measuring RBCs <ul><li>Red blood cell count: </li></ul><ul><ul><li>reports # of RBCs in 1 microliter whole blood </li></ul></ul><ul><li>Hematocrit (packed cell volume, PCV): </li></ul><ul><ul><li>percentage of RBCs in centrifuged whole blood </li></ul></ul>Normal Blood Counts <ul><li>RBC : male: 4.5–6.3 million, female: 4.–5.5 million </li></ul><ul><li>Hematocrit : </li></ul><ul><ul><li>male: 40–54%, female: 37–47% </li></ul></ul><ul><ul><li>Why different? Males have androgens </li></ul></ul><ul><ul><li>that stimulate RBC production </li></ul></ul>
  13. 13. RBC Structure <ul><li>Small and highly specialized disc </li></ul><ul><li>Thin in middle and thicker at edge </li></ul>Figure 19–2d Importance of RBC - Shape and Size <ul><li>High surface-to-volume ratio: </li></ul><ul><ul><li>quickly absorbs and releases oxygen </li></ul></ul><ul><li>Discs form stacks: </li></ul><ul><ul><li>smoothes flow through narrow blood vessels </li></ul></ul><ul><li>Discs bend and flex entering small capillaries: </li></ul><ul><ul><li>7.8 µ m RBC passes through 4 µ m capillary </li></ul></ul>
  14. 14. Lifespan of RBCs <ul><li>Lack nuclei, mitochondria, and ribosomes </li></ul><ul><li>Live about 120 days </li></ul>Hemoglobin (Hb) <ul><li>Protein molecule, transports respiratory gases </li></ul><ul><li>Responsible for cells ability to transport O2 and CO2 </li></ul><ul><li>Normal hemoglobin: </li></ul><ul><ul><li>14–18 g/dl whole blood - males </li></ul></ul><ul><ul><li>12-16 g/dl “” - females </li></ul></ul>
  15. 15. Hemoglobin Structure <ul><li>Complex quaternary structure </li></ul>Figure 19–3 <ul><li>4 globular protein subunits: </li></ul><ul><ul><li>each with 1 molecule of heme </li></ul></ul><ul><ul><li>each heme contains 1 iron ion </li></ul></ul><ul><li>Iron ions easily: </li></ul><ul><ul><li>associate with oxygen ( oxyhemoglobin ) </li></ul></ul><ul><ul><li>or dissociate from oxygen ( deoxyhemoglobin ) </li></ul></ul>
  16. 16. Fetal Hemoglobin <ul><li>Strong form of hemoglobin found in embryo/fetus </li></ul><ul><li>Takes oxygen from mother’s hemoglobin at the placenta begins last 7 months in utero and continues over the first year </li></ul><ul><li>FH can be stimulated in adults with SCA or thalassemia – only adult from of hemaglobin is abnormal </li></ul>Hemoglobin Function <ul><li>Each RBC has 280 million Hb molecules </li></ul><ul><li>Each Hb molecule has 4 heme units </li></ul><ul><li>So each RBC potentially has more 1 billion O 2 molecules </li></ul>
  17. 17. Carbaminohemoglobin <ul><li>With low oxygen (peripheral capillaries): </li></ul><ul><ul><li>hemoglobin releases oxygen which makes plasma CO2 elevated </li></ul></ul><ul><ul><li>Alpha and beta chains binds carbon dioxide and carries it to lungs </li></ul></ul><ul><ul><li>Carbaminohemoglobin is formed </li></ul></ul><ul><ul><li>RBC then absorb O2 and releases CO2 </li></ul></ul>Anemia <ul><li>Hematocrit or hemoglobin levels are below normal </li></ul><ul><li>Is caused by several conditions </li></ul>
  18. 18. Recycling RBCs <ul><li>1% of circulating RBCs wear out per day: </li></ul><ul><ul><li>about 3 million RBCs per second </li></ul></ul><ul><li>Macrophages of liver, spleen, and bone marrow: </li></ul><ul><ul><li>monitor RBCs </li></ul></ul><ul><ul><li>engulf RBCs before membranes rupture (hemolyze) </li></ul></ul>Figure 19–4
  19. 19. Diagnosing Disorders <ul><li>Hemoglobinuria : </li></ul><ul><ul><li>hemoglobin breakdown products in urine due to excess hemolysis in blood stream </li></ul></ul><ul><li>Hematuria : </li></ul><ul><ul><li>whole red blood cells in urine due to kidney or tissue damage </li></ul></ul>Hemoglobin Recycling <ul><li>Phagocytes break hemoglobin into components: </li></ul><ul><ul><li>globular proteins to amino acids </li></ul></ul><ul><ul><li>heme to biliverdin </li></ul></ul><ul><ul><li>iron </li></ul></ul>
  20. 20. Iron Recycling <ul><li>To transport proteins ( transferrin ) </li></ul><ul><li>To storage proteins ( feritin and hemosiderin ) </li></ul>Breakdown of Biliverdin <ul><li>Biliverdin (green) is converted to bilirubin (yellow) </li></ul><ul><li>Bilirubin is: </li></ul><ul><ul><li>excreted by liver (bile) </li></ul></ul><ul><ul><li>jaundice is caused by bilirubin buildup </li></ul></ul><ul><ul><li>converted by intestinal bacteria to urobilins and stercobilins </li></ul></ul>
  21. 21. RBC Maturation <ul><li>Red blood cell formation </li></ul><ul><li>Occurs only in red bone marrow (myeloid tissue) </li></ul><ul><li>Stem cells mature to become RBCs </li></ul>Figure 19–5 Erythropoiesis Hemocytoblasts <ul><li>Stem cells in bone marrow divide to produce: </li></ul><ul><ul><li>myeloid stem cells : </li></ul></ul><ul><ul><ul><li>become RBCs, some WBCs </li></ul></ul></ul><ul><ul><li>lymphoid stem cells : </li></ul></ul><ul><ul><ul><li>become lymphocytes </li></ul></ul></ul>
  22. 22. Stages of RBC Maturation <ul><li>Myeloid stem cell </li></ul><ul><li>Proerythroblast </li></ul><ul><li>Erythroblasts </li></ul><ul><li>Reticulocyte </li></ul><ul><li>Mature RBC </li></ul>Components <ul><li>Building red blood cells requires: </li></ul><ul><ul><li>amino acids </li></ul></ul><ul><ul><li>iron </li></ul></ul><ul><ul><li>vitamins B 12 , B 6 , and folic acid </li></ul></ul>
  23. 23. Pernicious Anemia <ul><li>Low RBC production </li></ul><ul><li>Due to unavailability of vitamin B 12 </li></ul>Stimulating Hormones <ul><li>Erythropoietin (EPO) </li></ul><ul><li>Also called erythropoiesis-stimulating hormone: </li></ul><ul><ul><li>secreted when oxygen in peripheral tissues is low ( hypoxia ) </li></ul></ul><ul><ul><li>due to disease or high altitude </li></ul></ul>
  24. 24. RBC Tests Table 19–1
  25. 25. Surface Antigens <ul><li>Are cell surface proteins that identify cells to immune system </li></ul><ul><ul><li>Triggers immune response </li></ul></ul><ul><li>Normal cells are ignored and foreign cells attacked </li></ul><ul><ul><li>Each cell has surface AG (antigens) </li></ul></ul><ul><ul><li>Allows for recognition of self </li></ul></ul>Blood Types <ul><li>Are genetically determined </li></ul><ul><li>By presence or absence of RBC surface antigens A , B , Rh </li></ul>
  26. 26. 4 Basic Blood Types <ul><li>A (surface antigen A) </li></ul><ul><li>B (surface antigen B) </li></ul><ul><li>AB (antigens A and B) </li></ul><ul><li>O (neither A nor B) </li></ul>Figure 19–6a
  27. 27. Agglutinogens <ul><li>Antigens on surface of RBCs </li></ul><ul><li>Screened by immune system </li></ul><ul><li>Plasma antibodies attack ( agglutinate ) foreign antigens </li></ul>Blood Plasma Antibodies <ul><li>Type A: type B antibodies </li></ul><ul><li>Type B: type A antibodies </li></ul><ul><li>Type O: both A and B antibodies </li></ul><ul><li>Type AB: neither A nor B </li></ul>
  28. 28. The Rh Factor <ul><li>Also called D antigen </li></ul><ul><li>Either Rh positive (Rh + ) or Rh negative (Rh — ) </li></ul><ul><li>Only sensitized Rh — blood has anti-Rh antibodies </li></ul><ul><li>So . . . </li></ul><ul><ul><li>Rh+ mom has Rh- baby - no problems ever </li></ul></ul><ul><ul><li>Rh- mom + Rh+ dad = Rh+ baby – no problem for pregnancy </li></ul></ul><ul><ul><li>Blood will mix around delivery & mom will make anti-Rh AB </li></ul></ul><ul><ul><li>Second baby that is Rh+ will be attacked by mom’s anti-Rh AB can cause death at or before delivery </li></ul></ul><ul><li>Known as Hemolytic Disease of the Newborn or erythroblastalis fetalis </li></ul><ul><li>Newborn born with this is anemic and jaundiced </li></ul><ul><li>May have to have complete transfusion </li></ul><ul><li>RhoGam – to mom prevents production of anti-Rh AB last 3 months of pregnancy and before and after delivery </li></ul>
  29. 29. Cross-Reaction <ul><li>Also called transfusion reaction </li></ul><ul><li>Plasma antibody meets its specific surface antigen </li></ul><ul><li>Blood will agglutinate and hemolyze </li></ul><ul><li>If donor and recipient blood types not compatible </li></ul>Figure 19–6b
  30. 30. White Blood Cells ( WBCs ) <ul><li>Also called leukocytes </li></ul><ul><li>Do not have hemoglobin </li></ul><ul><li>Have nuclei and other organelles </li></ul>WBC Functions <ul><li>Defend against pathogens </li></ul><ul><li>Remove toxins and wastes </li></ul><ul><li>Attack abnormal cells </li></ul>WBC Movement <ul><li>Most WBCs in connective tissue proper & lymphatic system organs </li></ul><ul><li>Small numbers in blood: 6000 to 9000 per microliter </li></ul>
  31. 31. Circulating WBCs <ul><li>Migrate out of bloodstream </li></ul><ul><ul><li>- Margination-activated WBCs adhere to vessel walls, then can squeeze thru (emigration or diapedesis) </li></ul></ul><ul><li>Have amoeboid movement </li></ul><ul><ul><li>- Gliding movement, needs ATP and Ca </li></ul></ul><ul><ul><li>- Movement of emigration </li></ul></ul><ul><li>Attracted to chemical stimuli ( positive chemotaxis ) </li></ul><ul><ul><li>- Chemicals guide WBC to invading pathogens, damaged tissues, and other WBC </li></ul></ul><ul><li>Some are phagocytic: </li></ul><ul><ul><li>neutrophils, eosinophils (microphages), and monocytes (macrophage) </li></ul></ul><ul><ul><li>Engulf waste and pathogens </li></ul></ul>
  32. 32. Types of WBCs <ul><li>Neutrophils </li></ul><ul><li>Eosinophils </li></ul><ul><li>Basophils </li></ul><ul><li>Monocytes </li></ul><ul><li>Lymphocytes </li></ul>Figure 19–9
  33. 33. Neutrophils <ul><li>Also called polymorphonuclear leukocytes </li></ul><ul><li>50–70% of circulating WBCs </li></ul><ul><li>12 um in dia </li></ul><ul><li>10 hour life span - eats 12-24 bacteria first </li></ul><ul><li>Very dense 2-5 segment nucleus </li></ul><ul><li>Pale cytoplasm granules with lysosomal enzymes & bactericides (hydrogen peroxide and superoxide) </li></ul>Neutrophil Action <ul><li>Very active, first to attack bacteria, fungi, and some viruses </li></ul><ul><li>Engulf pathogens </li></ul><ul><li>Digest pathogens </li></ul><ul><li>Release prostaglandins (hormones) and leukotrienes (calls other cells). Contributes to local inflammation </li></ul><ul><li>Form pus (dead neutrophils, cell debris and waste) </li></ul>
  34. 34. Eosinophils <ul><li>Also called acidophils </li></ul><ul><li>2–4% of circulating WBCs </li></ul><ul><li>12 um dia </li></ul><ul><li>2 lobed nucleus </li></ul><ul><li>Attack large parasites, then toxic compounds: nitric oxide & cytotoxic enzymes </li></ul>Eosinophil Actions <ul><li>Are sensitive to allergens </li></ul><ul><li>Control inflammation with enzymes that counteract inflammatory effects of neutrophils and mast cells </li></ul>
  35. 35. Basophils <ul><li>Are less than 1% of circulating WBCs </li></ul><ul><li>Are small - <8-10 um diameter </li></ul><ul><li>Migrate to site via capallaries </li></ul><ul><li>Accumulate in damaged tissue </li></ul>Basophil Actions <ul><li>Release chemicals that attract basophils and eosinophils </li></ul><ul><li>Granuales discharged into interstitial fluid. They contain: </li></ul><ul><li>histamine : </li></ul><ul><ul><li>dilates blood vessels </li></ul></ul><ul><li>heparin : </li></ul><ul><ul><li>prevents blood clotting </li></ul></ul><ul><ul><li>Both enhance inflammation </li></ul></ul>
  36. 36. Monocytes <ul><li>+= 15 um diam </li></ul><ul><li>2–8% of circulating WBCs </li></ul><ul><li>Are large and spherical </li></ul><ul><li>Large or kidney nucleus </li></ul><ul><li>Enter peripheral tissues and become macrophages after 24 hours – aggressive </li></ul>Macrophage Actions <ul><li>Engulf large particles and pathogens </li></ul><ul><li>Secrete substances that attract immune system cells and fibroblasts to injured area </li></ul>
  37. 37. Lymphocytes <ul><li>20–30% of circulating WBCs </li></ul><ul><li>Very small, but larger than RBCs </li></ul><ul><li>Large round nucleus w/ thin cytopalmic halo </li></ul><ul><li>Migrate in and out of blood </li></ul><ul><li>Mostly in connective tissues & lymphatic organs </li></ul>Lymphocyte Actions <ul><li>Are part of the body’s specific defense system </li></ul><ul><li>3 classes </li></ul><ul><li>T cells </li></ul><ul><li>B cells </li></ul><ul><li>Natural killer (NK) cells </li></ul>
  38. 38. T cells <ul><li>Cell-mediated immunity </li></ul><ul><li>Attack foreign cells directly </li></ul><ul><li>Coordinates immune response </li></ul>B cells <ul><li>Humoral immunity </li></ul><ul><ul><li>Produce and distribute AB </li></ul></ul><ul><li>Differentiate into plasma cells </li></ul><ul><ul><li>Synthesize and distribute antibodies </li></ul></ul>Natural Killer Cells (NK) <ul><li>Immune survelliance </li></ul><ul><li>Detect and destroy abnormal tissue cells (cancers) </li></ul>
  39. 39. WBC Disorders <ul><li>Leukopenia : abnormally low WBC count </li></ul><ul><li>Leukocytosis : abnormally high WBC count </li></ul><ul><li>Leukemia : extremely high WBC count </li></ul>WBC Production <ul><li>All blood cells originate from hemocytoblasts: </li></ul><ul><ul><li>which produce myeloid stem cells and lymphoid stem cells </li></ul></ul>
  40. 40. Myeloid Stem Cells <ul><li>Differentiate into progenitor cells : </li></ul><ul><ul><li>which produce all WBCs except lymphocytes </li></ul></ul>Lymphocytes <ul><li>Are produced by lymphoid stem cells </li></ul><ul><li>Lymphopoiesis : the production of lymphocytes </li></ul>WBC Development <ul><li>WBCs, except monocytes: develop fully in bone marrow </li></ul><ul><li>Monocytes: develop into macrophages in peripheral tissues </li></ul>
  41. 41. Other Lymphopoiesis <ul><li>Some lymphoid stem cells migrate to peripheral lymphoid tissues (thymus, spleen, lymph nodes) </li></ul><ul><li>Also produce lymphocytes </li></ul>
  42. 42. Summary: Formed Elements of Blood Table 19–3
  43. 43. Platelets <ul><li>Cell fragments involved in human clotting system - 4um dia and 1 um thick – “sticky” </li></ul><ul><li>Nonmammalian vertebrates have t hrombocytes (nucleated cells) </li></ul>Platelet Circulation <ul><li>Circulates for 9–12 days </li></ul><ul><li>Dead removed by phagocytosis in spleen </li></ul><ul><li>2/3 are reserved for emergencies </li></ul>Platelet Counts <ul><li>150,000 to 500,000 per microliter </li></ul><ul><li>Thrombocytopenia : abnormally low platelet count </li></ul><ul><li>Thrombocytosis : abnormally high platelet count </li></ul>
  44. 44. 3 Functions of Platelets <ul><li>Release important clotting chemicals </li></ul><ul><li>Temporarily patch damaged vessel walls </li></ul><ul><li>Actively contract tissue after clot formation </li></ul>Platelet Production <ul><li>Also called thrombocytopoiesis : occurs in bone marrow </li></ul>Megakaryocytes <ul><li>Giant cells </li></ul><ul><li>Manufacture platelets from cytoplasm </li></ul><ul><li>Each cell produces ~4000 platelets </li></ul>
  45. 45. Hemostasis <ul><li>The cessation of bleeding: </li></ul><ul><ul><li>vascular phase </li></ul></ul><ul><ul><li>platelet phase </li></ul></ul><ul><ul><li>coagulation phase </li></ul></ul>
  46. 46. <ul><li>Endothelial cells contract </li></ul><ul><li>Contraction is due to </li></ul><ul><li>1. Endothelial cells and </li></ul><ul><li> platelets releasing chemicals </li></ul><ul><li>2. pain receptors initiate reflexes </li></ul><ul><ul><li>stimulate smooth muscle contraction </li></ul></ul><ul><li>Endothelial cell membranes become “sticky”: </li></ul><ul><li>- seal off blood flow </li></ul><ul><li>Von Willebrand factor (large plasma protein) synthesized by endothelial cells causes the stickiness by binding to proteins and cells </li></ul>The Vascular Phase <ul><li>A cut triggers immediate response = vascular spasm </li></ul><ul><li>20 to 30-minute contraction </li></ul>
  47. 47. The Platelet Phase <ul><li>Begins within 15 seconds after injury </li></ul>Figure 19–11b <ul><li>Platelet adhesion (attachment): </li></ul><ul><ul><li>to sticky endothelial surfaces </li></ul></ul><ul><ul><li>to basal laminae </li></ul></ul><ul><ul><li>to exposed collagen fibers </li></ul></ul><ul><li>Platelet aggregation (stick together): </li></ul><ul><ul><li>forms platelet plug which closes small breaks </li></ul></ul>
  48. 48. Activated Platelets Release Clotting Compounds <ul><li>Granules in Platelets break down and release </li></ul><ul><ul><li>Adenosine diphosphate (ADP) – aggregating agent (more platelets) </li></ul></ul><ul><ul><li>Thromboxane A 2 and serotonin – enhance vascular spasm </li></ul></ul>
  49. 49. This is a positive feedback cycle that activates and attracts more and more platelets to the area. Within 1 minute a platelet plug is built Platelet Plug: Size Restriction <ul><li>Prostacyclin : </li></ul><ul><ul><li>released by endothelial cells </li></ul></ul><ul><ul><li>inhibits platelet aggregation </li></ul></ul><ul><li>Inhibitory compounds: </li></ul><ul><ul><li>released by other white blood cells </li></ul></ul>
  50. 50. The Coagulation Phase <ul><li>Begins 30 seconds or more after the injury </li></ul>Figure 19–12a <ul><li>Blood clotting ( coagulation ): </li></ul><ul><ul><li>Involves a series of steps </li></ul></ul><ul><ul><li>converts circulating fibrinogen into insoluble fibrin </li></ul></ul><ul><li>Blood Clot </li></ul><ul><ul><li>Fibrin network </li></ul></ul><ul><ul><li>Covers platelet plug </li></ul></ul><ul><ul><li>Traps blood cells </li></ul></ul><ul><ul><li>Seals off area </li></ul></ul><ul><li>Clotting factors </li></ul><ul><ul><li>Also called procoagulants </li></ul></ul><ul><ul><li>Proteins or ions in plasma </li></ul></ul><ul><ul><li>Required for normal clotting </li></ul></ul>
  51. 51. Cascade Reactions <ul><li>During coagulation phase </li></ul><ul><li>Chain reactions of enzymes and proenzymes </li></ul><ul><li>Form 3 pathways </li></ul>3 Coagulation Pathways <ul><li>Extrinsic pathway : </li></ul><ul><ul><li>begins in the vessel wall </li></ul></ul><ul><ul><li>outside blood stream </li></ul></ul><ul><li>Intrinsic pathway : </li></ul><ul><ul><li>begins with circulating proenzymes </li></ul></ul><ul><ul><li>within bloodstream </li></ul></ul><ul><li>Common pathway: </li></ul><ul><ul><li>where intrinsic and extrinsic pathways converge </li></ul></ul>
  52. 52. 3 Coagulation Pathways The Extrinsic Pathway <ul><li>Damaged cells release tissue factor (TF) </li></ul><ul><li>TF + other compounds = enzyme complex </li></ul><ul><li>Activates Factor X </li></ul>The Intrinsic Pathway <ul><li>Activation of enzymes by collagen </li></ul><ul><li>Platelets release factors ( e.g., PF–3 ) </li></ul><ul><li>Series of reactions activate Factor X </li></ul>
  53. 53. The Common Pathway <ul><li>Enzymes activate Factor X </li></ul><ul><li>Forms enzyme prothrombinase </li></ul><ul><li>Converts prothrombin to thrombin </li></ul><ul><li>Thrombin converts fibrinogen to fibrin </li></ul><ul><ul><li>Thrombin stimulates formation of tissue factor </li></ul></ul><ul><ul><ul><li>stimulates release of PF-3: </li></ul></ul></ul><ul><ul><ul><li>forms positive feedback loop (intrinsic and extrinsic): </li></ul></ul></ul><ul><ul><ul><ul><li>accelerates clotting </li></ul></ul></ul></ul>Clotting: Area Restriction <ul><li>Anticoagulants (plasma proteins): antithrombin-III & alpha-2-macroglobulin </li></ul><ul><li>Heparin </li></ul><ul><li>Protein C (activated by thrombomodulin ) </li></ul><ul><li>Prostacyclin </li></ul>
  54. 54. Other Factors <ul><li>Calcium ions (Ca 2+ ) and vitamin K are both essential to the clotting process </li></ul>Clot Retraction <ul><li>After clot has formed: </li></ul><ul><ul><li>Platelets contract and pull torn area together </li></ul></ul><ul><li>Takes 30–60 minutes </li></ul>Fibrinolysis <ul><li>Slow process of dissolving clot: </li></ul><ul><ul><li>thrombin and tissue plasminogen activator (t-PA) : activate plasminogen </li></ul></ul><ul><li>Plasminogen produces plasmin : digests fibrin strands </li></ul>
  55. 55. Disorders of Hemostasis <ul><li>Thrombembolic disorders – clots too easily </li></ul><ul><ul><li>Thrombus – clot that develops and persists in an unbroken blood vessel (may prevent blood flow and cause tissue death) - Coronary thrombosis </li></ul></ul><ul><ul><li>Embolus – thrombus that breaks away from the vessel wall and travels through bloodstream </li></ul></ul><ul><ul><li>Embolism – obstructs a vessel (pulmonary embolism) </li></ul></ul><ul><ul><li>Bedridden patients, long flights (slow moving blood) </li></ul></ul><ul><li>Bleeding Disorders – prevent normal clotting </li></ul><ul><ul><li>Thrombocytopenia – platelet numbers low </li></ul></ul><ul><ul><li>Impaired liver function – not able to synthesize coagulants </li></ul></ul><ul><ul><li>Hemophilias – several hereditary conditions (person doesn’t make the clotting factors correctly </li></ul></ul>

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