blood

• Functions of blood


  • Transport of gases, nutrients and waste products
  • Transport of processed molecules
  • Transport of regulatory molecules
  • Regulation of pH and osmosis
  • Maintenance of body temperature
  • Protection against foreign substances
  • Clot formation
• Composition of blood


  • Plasma
  • Formed elements
• Plasma


  55% total of blood, pale yellow liquid that surrounds the cells, 91% water, 7% protein, 2% other
• Formed elements


  45% of total blood, cells and cell fragments (erythrocytes, leukocytes, thrombocytes)
• % of erythrocytes volume to the total blood volume, normal values 47% ± 5% in males, 42% ± 5% in females

  HEMATOCRIT
• Normal blood pH


  Between 7.35 and 7.45
• Plasma proteins


  • Albumin (58% of plasma proteins)
  • Globulins (38% of plasma proteins)
  • Fibrinogens (4% of plasma proteins)
• Albumin


  Helps maintain water balance, maintains plasma osmotic pressure, can hold back water
• Globulins


  Helps immune system, transportation of some hormones and mineral salts
• Fibrinogens


  Aids in clot formation
• Hematopoiesis


  1. Occurs in fetal liver, thymus, spleen, lymph nodes, and red bone marrow

  2. After birth, primarily in red bone marrow

  3. Stem cells differentiate to give rise to different cell lines
• Stem cells


  • Single population of cells that give rise to all formed elements of blood
• Erythrocyte production


  1. Decreased blood O2 levels cause kidneys to increase erythropoietin production

  2. Erythropoietin stimulates red bone marrow to produce more erythrocytes

  3. Increased erythrocytes increase blood O2 levels
• Erythrocytes


  Red blood cells, disk-shaped with thick edges, flexible, lose nucleus during development, live for 120 days, undergo hemolysis and deposited in spleen
• Hemoglobin


  Main component of erythrocytes, responsible for red pigment, transports O2, composed of heme molecule with iron atom
• Hemoglobin does not exist free in plasma to protect it from breaking into fragments and to prevent it from making blood more viscous and raising osmotic pressure
• Oxyhemoglobin


  Hemoglobin with an O2 attached
• Types of leukocytes


  • Granulocytes (neutrophils, eosinophils, basophils)
  • Agranulocytes (monocytes, lymphocytes)
• Neutrophils


  • Most common, most numerous, first line of recognition and defense, phagocytes
• Eosinophils


  • Reduce inflammation, destroy parasites, increase during allergies and infections
• Basophils


  • Least common, release histamine and heparin
• Monocytes


  • Largest sized white blood cells, help protect against bacteria, produce macrophages
• Lymphocytes


  • Immune response, T cells and B cells
• Platelets


  Minute fragments of cells, produced from megakaryocytes in red bone marrow, play important role in preventing blood loss
• Preventing blood loss


  1. Vascular spasm

  2. Platelet plug formation

  3. Blood clotting (coagulation)
• Vascular spasm


  Temporary constriction of blood vessel, reduces blood loss
• Platelet plug formation


  1. Platelet adhesion to exposed collagen

  2. Platelet activation and release of chemicals

  3. Platelet aggregation forming a plug
• Blood clotting


  1. Injury activates clotting factors

  2. Prothrombinase formed and acts on prothrombin

  3. Prothrombin converted to thrombin

  4. Thrombin activates fibrinogen into fibrin

  5. Fibrin forms a network trapping blood
• Anticoagulants


  Prevent clots from forming, examples are heparin and antithrombin
• Clot retraction and fibrinolysis

  1. Clot retraction condenses clot and squeezes out serum

  2. Fibrinolysis is the process of dissolving the clot
• ABO blood groups


  • Type A
  • Type B
  • Type AB
  • Type O
• ABO blood group antigens

  Type A antigen, Type B antigen
• ABO blood group antibodies

  Anti-A antibodies in type B blood, Anti-B antibodies in type A blood, Neither in type AB, Both in type O
• ABO blood group distribution in Caucasians in the US: O 47%, A 41%, B 9%, AB 3%. In African-Americans: O 46%, A 27%, B 20%, AB 7%
• Rh blood group


  Rh positive means having Rh antigens, 95-85% of population is Rh+
• Rh incompatibility in pregnancy

  1. Rh- mother exposed to Rh+ fetal blood produces antibodies

  2. Repeated exposure causes reaction
• Hemolytic disease of newborn

  Occurs when Rh- mother produces anti-Rh antibodies that cross placenta and cause agglutination and hemolysis of fetal erythrocytes
• RhoGAM treatment prevents hemolytic disease of newborn in Rh- mothers
• Diagnostic blood tests


  • Complete blood count
  • Hematocrit
  • Hemoglobin
  • Blood typing
  • Prothrombin time
  • White blood cell count
  • White blood cell differential count
• White blood cell disorders

  • Leukopenia (low count)
  • Leukocytosis (high count)