Blood

• Plasma proteins


  • Albumins
  • Alfa Beta Globulins
  • Gamma Globulins
  • Fibrinogens
• Blood is the body's only fluid tissue
• Composition of blood


  • Plasma
  • Erythrocytes, or red blood cells (RBCs)
  • Leukocytes, or white blood cells (WBCs)
  • Thrombocytes, or platelets

  
• Plasma


  • ~90% water, 10% solutes
  • Solutes include ions, hormones, gases, plasma proteins
• Plasma proteins


  • Albumin: draws water to maintain blood osmolarity and volume, transports and buffers plasma pH
  • Globulins: transport molecules and antibodies
  • Fibrinogens: blood clotting
• Hypoproteinemia is a pathological condition related to plasma proteins
• Formed elements


  • Only WBCs are complete cells
  • RBCs have no nuclei or organelles, and platelets are just cell fragments
  • Most formed elements survive in the bloodstream for only a few days
  • Most blood cells do not divide but are renewed by cells in bone marrow
• Erythrocytes (RBCs)


  • Primary function is oxygen/carbon dioxide transport
  • Secondary function is blood pH regulation
  • Biconcave discs, anucleated, essentially no organelles: must do anaerobic respiration
  • 97% filled with hemoglobin (Hb), a protein that functions in gas transport
  • Able to change shape as necessary
• Hemoglobin


  • Normal concentration is 12-18 g/100 ml blood
  • Hemoglobin reversibly binds with oxygen and 98.5% of all oxygen in the blood is bound to hemoglobin
  • Hemoglobin is composed of the protein globin, made up of two alpha and two beta chains, each bound to a heme group
  • Each heme group bears an atom of iron, which can bind to one oxygen molecule
  • Each hemoglobin molecule can transport up to four molecules of oxygen
• Hemoglobin forms


  • Oxyhemoglobin: hemoglobin bound to oxygen, bright red color
  • Deoxyhemoglobin: hemoglobin after oxygen diffuses into tissues, dark red color
  • Carbaminohemoglobin: hemoglobin bound to carbon dioxide, 20%
  • Carboxyhemoglobin: hemoglobin bound to carbon monoxide, 5-15% (higher in smokers!)
  • Fetal Hemoglobin: contains 2 alpha and 2 gamma globin molecules, greater affinity for oxygen, gas exchange occurs across placenta
• Erythropoiesis (RBC production)


  1. Takes about 15 days to develop, life span: ~ 120 days

  2. Hematopoiesis occurs in the bone marrow, spleen, liver, and thymus before birth

  3. Hematopoiesis occurs in the adult red bone marrow of the axial skeleton and girdles, epiphyses of the humerus and femur

  4. Hematopoietic Stem Cells give rise to all formed elements

  5. Requires: iron, amino acids, folic acid, Vit. B12, Vit. C, copper

  6. Testosterone stimulates RBC production
• Hormonal control of erythropoiesis

  • Erythropoietin (EPO) release by the kidneys is triggered by hypoxemia, decreased oxygen availability, increased tissue demand for oxygen
  • Enhanced erythropoiesis increases the RBC count in circulating blood and oxygen carrying ability of the blood
• Hemolysis (Destruction of old RBCs)


  1. Old erythrocytes become rigid and fragile, and their hemoglobin begins to degenerate

  2. Dying erythrocytes are engulfed by macrophages

  3. Heme and globin are separated and the iron is salvaged for reuse in the liver and spleen, globins recycled into more proteins

  4. Heme is ultimately degraded to bilirubin and excreted
• Anemia types and polycythemia types are pathological conditions related to the life cycle of red blood cells

  
• Blood transfusions


  • Packed red cells (cells with plasma removed) are usually transfused
  • Important to match donor's antigens (RBCs only) and recipient's antibodies
  • In most cases, the same blood type is used in transfusions
  • Loss of 30% or more of blood results in severe shock which can be fatal
• Blood groups


  • Humans have 30 varieties of naturally occurring RBC antigens
  • The antigens of the ABO and Rh blood groups cause vigorous transfusion reactions when they are improperly transfused
  • Other blood groups (MNS, Duffy, Kell, Kidd, and Lewis) are mainly used for legalities
• ABO blood groups


  • Two antigens (A and B) on the surface of the RBCs
  • Two antibodies in the plasma (anti-A and anti-B)
  • Presence or absence of these antigens is used to classify blood groups
• Rh blood group


  • Presence of the Rh antigen on RBCs is indicated as Rh+
  • Anti-Rh antibodies
• Blood typing is used to determine blood group
• r blood groups (MNS, Duffy, Kell, Kidd, and Lewis) are mainly used for legalities
• Blood Groups


  • ABO
  • Rh
• ABO blood groups


  • Two antigens (A and B) on the surface of the RBCs
  • Two antibodies in the plasma (anti-A and anti-B)
• ABO blood group antigens

  • Unique to the individual
  • Recognized as foreign if transfused into another individual
• Presence or absence of ABO antigens


  Used to classify blood groups
• Rh antigen


  Presence on RBCs is indicated as Rh+
• Anti-Rh antibodies


  • Not spontaneously formed in Rh- individuals
  • Only formed if an Rh- individual receives Rh+ blood
• A second exposure to Rh+ blood will result in a typical transfusion reaction
• Hemolytic Disease of the Newborn (HDN) is a patho check-in
• Leukocytes (WBCs) are the only blood components that are complete cells (nucleated, many organelles)
• Leukocytes


  • Defensive Cells (primarily phagocytic)
  • Only ~1% of the total blood volume (4,500-11,000/µL)
  • Can leave capillaries via diapedesis and are directed to sites of infection by chemotaxis
  • Move through tissue spaces—not confined to vessel
• Leukocytosis


  WBC count over 11,000 per microliter
• Leukocyte Disorders is a patho check-in
• Types of Leukocytes (WBCs)

  • Granulocytes (Basophils, Eosinophils, Neutrophils)
  • Agranulocytes (Monocytes, Lymphocytes)
• Granulocytes


  • Lobed nuclei with granules in cytoplasm
• Agranulocytes


  • Simple nucleus without granules
• Neutrophils


  • Most common WBC (50-70%) in blood
  • #1 WBC at site of an infection
  • Take up both acidic and basic dyes = stain purple
  • Motile, phagocytic, contain many lysosomes (granules)
  • Increase with bacterial infection, decrease during viral infection
• Eosinophils


  • Account for 2–4% of WBCs
  • Have red-staining, bilobed nuclei
  • Have red to crimson (acidophilic) large, coarse, lysosome-like granules
  • Phagocytize cells infected with parasitic worms
  • Lessen the severity of allergies
• Basophils


  • Rarest of WBCs: account for 0.5-1% of WBCs
  • Have U- or S-shaped nuclei with purplish-blue granules in cytoplasm
  • Are functionally similar to mast cells: secrete histamine and heparin
• Agranulocytes


  • Includes lymphocytes and monocytes
  • Lack visible cytoplasmic granules
  • Are similar structurally, but are functionally distinct
• Lymphocytes


  • Account for 25-33% or more of WBCs
  • Have large, dark-purple, circular nuclei with a thin rim of blue cytoplasm
  • Are found mostly enmeshed in lymphoid tissue
  • There are two types: T cells and B cells