618 lec - blood

• Blood


  Fluid connective tissue that constantly circulates around the body, propelled by the pumping action of the heart, and transports oxygen, nutrients, hormones, heat, antibodies, immune cells, clotting factors, and waste materials
• Whole blood


  • Comprised of formed elements (red blood cells, white blood cells, and platelets) and plasma

  
• Plasma


  The liquid (yellow) portion of the blood, with water as the main constituent (90-92%) and other components like proteins, inorganic salts/ions, nutrients, waste products, regulatory substances, and gases

  
• Plasma proteins


  • Albumins
  • Globulins
  • Clotting factors
• Other plasma components


  • Electrolytes
  • Nutrients
  • Waste products
  • Hormones
  • Gases
• Cellular content of blood

  • Three types: erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets)

  
• Hemopoiesis/Hematopoiesis


  1. Process of blood cell formation from pluripotent stem cells (hemocytoblast)

  2. Includes erythropoiesis, thrombopoiesis, and leukopoiesis

  
• Erythrocytes (red blood cells)


  • Most abundant type of blood cell (about 99% of all blood cells)
  • Biconcave discs without nucleus
  • Main function is to transport oxygen
• Erythropoiesis


  Process of erythrocyte development from stem cells (about 7 days)

  
• Hemoglobin


  A large, complex molecule containing a globular protein (globin) and a pigmented iron-containing complex called heme/haem, which can bind to oxygen
• Hemoglobin binds to oxygen

  Forms oxyhemoglobin
• Factors affecting oxygen transport

  • Low pH
  • Low oxygen levels in tissues (hypoxia)
  • Temperature
• Control of erythropoiesis


  1. Rate of RBC production = Rate of RBC destruction

  2. Erythropoietin (produced mainly by the kidney) regulates red blood cell production

  
• Hypoxia


  Low oxygen levels in tissues
• Hypoxemia


  Low oxygen levels in the blood
• Hemolysis


  Breakdown or destruction of red blood cells carried out by macrophages in the spleen, bone marrow and liver

  
• Hypoxemia


  Low oxygen levels in your blood
• Hypoxia


  Low oxygen levels in your tissues
• Negative Feedback Correction of Hypoxemia


  Figure 12
• Hemolysis


  Breakdown or destruction of RBCs carried out by macrophages in the spleen, bone marrow and liver
• As erythrocytes age, their cell membranes become more fragile and so more susceptible to hemolysis
• Iron released by hemolysis is returned to the bone marrow to form new hemoglobin molecules
• Biliverdin is formed from the heme of the hemoglobin, reduced to the yellow pigment bilirubin, and excreted in bile
• Life cycle of the erythrocyte

  Figure 8
• Blood typing


  Based on the presence of ABO and Rhesus (Rh) antigens (inherited) on the surface of cells
• Antibodies


  Dissolved proteins in plasma that react to foreign antigens in a process called agglutination
• Antibodies for the ABO group are acquired as a child
• Antibodies for Rh antigens are acquired only through an exposure to the antigen
• Rhesus (Rh) antigen or Rhesus factor


  RBC membrane antigen
• Rhesus-positive (Rh+) individuals


  Have Rh antigen and do not therefore make anti-Rhesus antibodies
• Rhesus-negative (Rh-) individuals


  Capable of making anti-Rh antibodies, but are stimulated to do so only in certain circumstances, e.g. in pregnancy, or as the result of an incompatible blood transfusion
• Blood typing


  Determining a blood type and transfusion compatibility by mixing a drop of blood with sera containing known antibodies
• In a transfusion, the donor's cells must survive the recipient's antibodies


  Transfusion reaction occurs if mismatched blood agglutinates
• Rh− mothers need to be concerned about blood incompatibility with Rh+ babies, which can lead to hemolytic disease of the newborn (HDN)
• Leukocytes (white blood cells/WBCs)


  • Have an important function in defense and immunity
  • Detect foreign or abnormal (antigenic) material and destroy it, through a range of defense mechanisms
  • Largest blood cells but they account for only about 1% of the blood volume
  • Contain nuclei and some have granules in their cytoplasm
  • Rising white cell numbers in the bloodstream (leukocytosis) usually indicate a physiological problem, e.g. infection, trauma or malignancy

  
• Types of leukocytes


  • Granulocytes (polymorphonuclear leukocytes)
  • Agranulocytes
• Granulopoiesis


  Formation of granulocytes
• All granulocytes have multilobed nuclei in their cytoplasm
• Granulocytes are named based on the dyes they take up when stained in the laboratory
• Granulocytes (granular leukocytes)


  Figure 14