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 (55% of total blood)
  • Formed Elements (45% of total blood)
• Plasma


  Pale, yellow liquid that surrounds cells. 91% water, 7% proteins, and 2% other
• Plasma Proteins


  • 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


  The process that produces formed elements (blood cellular components)
• In the fetus, hematopoiesis occurs in several tissues, including the liver, thymus, spleen, lymph nodes, and red bone marrow
• After birth, hematopoiesis is confined primarily to red bone marrow, but some white blood cells are produced in lymphatic tissues
• Stem cells/Hemocytoblasts


  All the formed elements of blood are derived from a single population of these cells
• 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)

  • Disk-shaped with thick edges
  • Nucleus is lost during development
  • Live for 120 days
• Erythrocyte function


  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
• Oxyhemoglobin


  Hemoglobin with an O2 attached
• Red Blood Cell Production

  Shown in Figure 11.6
• 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. Heme is converted to bilirubin

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

  6. Hemoglobin's iron is recycled
• Leukocytes (White Blood Cells)


  • Lack hemoglobin
  • Larger than erythrocytes
  • Contain a nucleus
• Leukocyte functions


  • Fight infections
  • 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/Thrombocytes


  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.
• Platelet function


  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 production of new blood or by a transfusion.
• Mechanisms to Prevent Blood Loss

  • Vascular spasm
  • Platelet plugs
  • Blood clotting (coagulation)
• Vascular Spasm


  Temporary constriction of blood vessel, stimulated by chemicals released by cells of the damaged blood vessel wall and by platelets
• Platelet Plug Formation


  1. Platelet adhesion occurs first, when platelets stick to the exposed collagen in the damaged blood vessel wall

  2. After platelets adhere to collagen, they become activated, change shape, and release chemicals

  3. In platelet aggregation, fibrinogen forms bridges between the fibrinogen receptors of numerous platelets, resulting in a platelet plug
• Blood Clotting


  Blood can be transformed from a liquid to a gel, forming a network of thread-like proteins called fibrin that trap blood cells and fluid
• Steps in Clot Formation

  1. Injury to a blood vessel causes inactive clotting factors to become activated due to exposed connective tissue or release of thromboplastin

  2. Prothrombinase (clotting factor) is formed and acts upon prothrombin

  3. Prothrombin is switched to its active form thrombin

  4. Thrombin activates fibrinogen into its active form fibrin

  5. Fibrin forms a network that traps blood (clots)
• Figure 11.11 shows the clot formation process
• Transfusion Reactions/Agglutination


  Clumping of blood cells, which is bad
• 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 O
  • Type A
  • Type B
  • Type AB
• 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 (universal donor)
• Rh Positive


  Having Rh antigens