blood

• Functions of blood


  • Transportation
  • Protection
  • Homeostasis
• Blood transportation functions


  • Gases: Oxygen & Carbon Dioxide
  • Formed elements
  • Absorbed nutrients
  • Hormones
  • Removal of waste products
• Blood protection functions


  • Immune response
  • Hemostasis: clotting response to bleeding
• Blood homeostasis functions


  • Body Temperature / Distributes heat
  • pH levels of tissues
  • Fluid levels
• Hematocrit


  Percentage by volume of elements in blood

  
• Plasma


  ~55% of blood volume, 92% water, 8% solutes

  
• Plasma proteins


  • Albumin (60%) - maintain osmotic pressure
  • Globulins (36%) - transport lipids, vitamins, antibodies
  • Fibrinogen (4%) - blood clotting
  • Other solutes (~1%)
• Erythrocytes (Red Blood Cells)

  • Biconcave disc shape - increases surface area for diffusion
  • Lack nucleus at maturity - more room for hemoglobin
  • Transport O2 and some CO2

  
• Hemoglobin


  4 heme groups - bind to oxygen, 4 globin - bind to carbon dioxide, 1 molecule can loosely bind to 4 molecules of oxygen

  
• Erythropoiesis


  1. RBC's formed in red bone marrow (epiphyses)

  2. Stimulated by erythropoietin released by kidneys in low oxygen conditions

  3. Life span: Men ~120 days, Women ~109 days

  4. Removal by macrophages in spleen and liver, heme reused, globin broken down

  
• Leukocytes (White Blood Cells)


  • Nucleated, large, longer life span (~10 months), capable of amoeboid movement
  • 2 major categories: Granulocytes and Agranulocytes

  
• Granulocytes


  • Neutrophils (50-80%)
  • Eosinophils (1-4%)
  • Basophils (<1%)

  
• Agranulocytes


  • Monocytes (2-8%)
  • Lymphocytes (20-40%)

  
• Thrombocytes (Platelets)


  Fragments of megakaryocytes, involved in hemostasis: blood clot formation

  
• Hemostasis


  Tissue damage initiates spasm in tunica media, vasoconstriction, platelets bind to exposed collagen fibers forming a "plug", activated platelets release ADP & thromboxane A2 to activate more platelets, release of serotonin to maintain blood vessel spasm
• Coagulation


  Soluble Fibrinogen converted into Fibrin threads, Fibrin catches & binds platelets and RBC's, Intrinsic & Extrinsic Pathways
• Common Pathway


  Clotting factor X (prothrombin converting factor) is activated in the presence of Ca+2 and phospholipids, converts prothrombin into thrombin, Thrombin converts soluble fibrinogen into insoluble fibrin, Fibrin traps RBC's to form clot
• Clot Dissolution


  Clotting factor XII activates kallikrein, Kallikrein converts plasminogen to form plasmin, Plasmin breaks down fibrin to dissolve clot
• Preventing Blood Clots


  • Aspirin: inhibits thromboxane A2 production, slows down platelet plug formation and intrinsic pathway
  • Antithrombins: prevents conversion of prothrombin into thrombin, reduces potential for spontaneous clot formation, aided by heparin