Ch. 20-Anatomy

• Blood


  A specialized fluid connective tissue
• Functions of the blood

  • Transport of dissolved gases
  • Distribution of nutrients
  • Transport of metabolic wastes
  • Delivery of enzymes & hormones
  • Stabilization of the pH & electrolyte composition of interstitial fluids
  • Prevention of fluid losses
  • Defense against toxins & pathogens
  • Stabilization of body temperature by absorbing & redistributing heat
• Components of the blood

  • Plasma: liquid matrix of blood
  • Formed elements: blood cells & cell fragments suspended in plasma
• Plasma


  Contributes 55% of the volume of whole blood, contains 92% water
• Differences between plasma and interstitial fluid

  Concentrations of dissolved oxygen & carbon dioxide, dissolved proteins
• Major classes of plasma proteins

  • Albumins
  • Globulins
  • Fibrinogen
• Albumins


  60% of plasma proteins, most abundant, major contributors to osmotic pressure, important in transport of fatty acids, steroid hormones, and other substances
• Globulins


  35% of plasma protein population, include immunoglobulins (antibodies) and transport globulins
• Fibrinogen


  4% of all plasma proteins, largest, essential for normal blood clotting
• Liver synthesizes and releases more than 90% of the plasma proteins
• Formed elements of the blood


  • Red blood cells
  • Leukocytes
  • Platelets
• Hematocrit


  Indicates the percentage of whole blood contributed by formed elements
• Red blood cells (RBCs)

  • Biconcave disc shape allows flexibility and ability to squeeze through small capillaries
  • Lack mitochondria, endoplasmic reticulum, ribosomes, and nuclei
• Hemoglobin


  Responsible for RBCs' ability to transport oxygen and carbon dioxide, gives blood its red color
• Blood types


  • Type A: has antigen A
  • Type B: has antigen B
  • Type AB: has both antigens A and B
  • Type O: has neither antigen A nor B
• Rh-positive


  Presence of Rh antigen on RBC surface
• Rh-negative


  Absence of Rh antigen on RBC surface
• Antibodies are present only if the individual has been sensitized by previous exposure to Rh-positive erythrocytes
• Major classes of leukocytes

  • Granular leukocytes (granulocytes)
  • Agranular leukocytes (agranulocytes)
• Leukopenia


  Inadequate number of leukocytes
• Leukocytosis


  Excessive number of leukocytes
• Lymphopenia


  Too few lymphocytes
• Lymphocytosis


  Usually high number of lymphocytes
• Neutrophils


  • Cytoplasm packed with granules containing lysosomal enzymes and bactericidal compounds
  • Very mobile, first to an injury site, specialize in attacking and digesting bacteria
  • Short life span of 12 hours
• Eosinophils


  • Attracted to foreign compounds that have reacted with circulating antibodies, increase dramatically during allergic reactions or parasitic infections, release enzymes to reduce inflammation
• Basophils


  • Migrate to injury sites, discharge granules containing histamine and heparin, increase inflammation response
• Monocytes


  Largest leukocytes, become macrophages outside the bloodstream, secrete substances that attract fibroblasts
• Lymphocytes


  Relatively small with little cytoplasm, part of the immune system, include T cells that directly attack foreign cells and B cells that differentiate into plasma cells that secrete antibodies
• Natural killer (NK) cells


  Responsible for immune surveillance and destruction of abnormal tissue cells, important in preventing cancer
• Platelets


  Flattened membrane-enclosed packets, manufactured by megakaryocytes in bone marrow, important for hemostasis and blood clotting
• Hemopoiesis


  1. Process of blood cell formation

  2. Pluripotent stem cells give rise to myeloid and lymphoid stem cells

  3. Myeloid stem cells form red blood cells and various leukocytes

  4. Lymphoid stem cells form lymphocytes
• Erythropoiesis


  Formation of red blood cells, regulated by erythropoietin (EPO) which stimulates increased cell division and maturation of RBCs
• Leukopoiesis


  Process where stem cells responsible for the production of white blood cells originate in the bone marrow, with lymphocytes also produced in the thymus
• Colony-stimulating factors (CSFs) are involved in the regulation of white blood cell populations, and are used commercially to stimulate WBC production in individuals undergoing cancer chemotherapy