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% of total blood, pale yellow liquid that surrounds cells, 91% water, 7% proteins, and 2% other
• Formed elements


  45% of total blood, cells and cell fragments, erythrocytes, leukocytes, thrombocytes
• Plasma proteins


  • Albumin
  • Globulins
  • Fibrinogen
• Albumin


  58% of plasma proteins, helps maintain water balance
• Globulins


  38% of plasma proteins, helps immune system
• Fibrinogen


  4% of plasma proteins, aids in clot formation
• Hematopoiesis


  1. Hematopoiesis is the process that produces formed elements

  2. In the fetus, hematopoiesis occurs in several tissues, including the liver, thymus, spleen, lymph nodes, and red bone marrow

  3. After birth, hematopoiesis is confined primarily to red bone marrow, but some white blood cells are produced in lymphatic tissues

  4. All the formed elements of blood are derived from a single population of cells called stem cells, or hemocytoblasts

  5. These stem cells differentiate to give rise to different cell lines, each of which ends with the formation of a particular type of formed element
• Erythrocytes


  Red blood cells (RBC), disk-shaped with thick edges, nucleus is lost during development, live for 120 days, function is to transport O2 to tissues
• Hemoglobin


  Main component of erythrocytes, transports O2, each globin protein is attached to a heme molecule, each heme contains one iron atom, O2 binds to iron, oxyhemoglobin is hemoglobin with an O2 attached
• Production of erythrocytes


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

  2. Erythropoietin stimulates red bone marrow to produce more erythrocytes

  3. Increased erythrocytes cause an increase in blood O2 levels
• Fate of old erythrocytes and hemoglobin

  1. Old red blood cells are removed from blood by macrophages in spleen and liver

  2. Hemoglobin is broken down

  3. Globin is broken down into amino acids

  4. Hemoglobin's iron is recycled

  5. Heme is converted to bilirubin

  6. Bilirubin is taken up by liver and released into small intestine as part of bile
• Leukocytes


  White blood cells (WBC), lack hemoglobin, larger than erythrocytes, contain a nucleus, functions are to fight infections and remove dead cells and debris by phagocytosis
• Types of leukocytes


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


  Most common, remain in blood for 10 to 12 hours then move to tissues, phagocytes
• Eosinophils


  Reduce inflammation, destroy parasites
• Basophils


  Least common, release histamine and heparin
• Monocytes


  Largest sized white blood cells, produce macrophages
• Lymphocytes


  Immune response, several different types (T cells and B cells), lead to production of antibodies
• Platelets


  Minute fragments of cells, each consisting of a small amount of cytoplasm surrounded by a cell membrane, produced in the red bone marrow from large cells called megakaryocytes, play an important role in preventing blood loss
• When blood vessels are damaged, blood can leak into other tissues and disrupt normal function
• Blood that is lost must be replaced by the production of new blood or by a transfusion
• Blood clot


  Network of thread-like proteins called fibrin that trap blood cells and fluid, depends on clotting factors
• Clotting factors


  Proteins in plasma, only activated following injury, made in liver, require vitamin K
• Clot formation


  Injury causes enough clotting factors to be activated that anticoagulants can't work in that particular area of the body
• Anticoagulants


  Prevent clots from forming, examples are heparin and antithrombin
• Antigens


  Molecules on surface of erythrocytes
• Antibodies


  Proteins in plasma that bind to specific antigens
• Blood groups


  Named according to antigen (ABO)
• ABO blood groups


  • Type A blood has type A antigens
  • Type B blood has type B antigens
  • Type AB blood has both types of antigens
  • Type O blood has neither A nor B antigens
• Antibodies in ABO blood groups


  • Plasma from type A blood contains anti-B antibodies
  • Plasma from type B blood contains anti-A antibodies
  • Type AB blood plasma has neither type of antibody
  • Type O blood plasma has both anti-A and anti-B antibodies
• Agglutination reaction


  Clumping of blood cells (bad)
• Blood donor and recipient according to ABO blood types


  • O are universal donors because they have no antigens
  • Type A can receive A and O blood
  • Type B can receive B and O blood
  • Type AB are universal recipients, can receive A, B, AB or O blood
  • Type O can only receive O blood
• Rh blood group


  Rh positive means you have Rh antigens, 95 to 85% of the population is Rh+, antibodies only develop if an Rh- person is exposed to Rh+ blood by transfusion or from mother to fetus
• Rh incompatibility in pregnancy

  1. If mother is Rh- and fetus is Rh+ the mother can be exposed to Rh+ blood if fetal blood leaks through placenta and mixes with mother's blood

  2. First time this occurs mother's blood produces antibodies against antigens

  3. Any repeated mixing of blood causes a reaction
• Hemolytic disease of newborn


  Occurs when mother produces anti-Rh antibodies that cross placenta and agglutination, and hemolysis of fetal erythrocytes occurs, can be fatal to fetus, prevented if mother is treated with RhoGAM which contains antibodies against Rh antigens
• Diagnostic blood tests


  • Complete blood count
  • Hematocrit
  • Hemoglobin
  • Prothrombin time
  • White blood cell count
  • White blood cell differential count
• Complete blood count


  Provides information such as RBC count, hemoglobin, hematocrit, and WBC count
• Hematocrit


  Percentage of total blood volume composed of RBC