Blood Chapter 21

• Components of Blood


  • Erythrocytes
  • Buffy coat
  • Plasma
• Formed elements


  Erythrocytes, leukocytes, and platelets
• Whole blood


  • Can be centrifuged to reveal three components: Erythrocytes (44%), Buffy coat (1%), Plasma (55%)
• Functions of Blood


  • Transportation
  • Regulation
  • Protection
• Transportation


  Blood transports oxygen, carbon dioxide, hormones, nutrients, wastes
• Regulation


  Blood helps maintain temperature, pH, fluid levels in cardiovascular system
• Protection


  Leukocytes guard against infection by triggering immune response to antigens, Blood carries antibodies
• Formed elements in the blood

  • Erythrocytes
  • Leukocytes
  • Platelets
• Hematocrit


  Percentage of the volume of all formed elements in the blood, clinically it is percentage volume of erythrocytes only
• Erythrocytes


  Commonly called red blood cells, not true cells as they lack nucleus and organelles, 7.5 μm in diameter, biconcave disc shape, line up in single file termed a roulea as they pass through small blood vessels
• Hemoglobin


  Every erythrocyte contains about 280 million molecules, transports oxygen and carbon dioxide, "Oxygenated" when maximally loaded with oxygen, "Deoxygenated" when some oxygen is lost and carbon dioxide gained, each molecule consists of four globin polypeptides (two alpha and two beta chains) and four heme groups containing iron (Fe2+) ions for oxygen binding
• Erythrocyte life cycle


  1. Old erythrocytes are phagocytized in liver and spleen

  2. Heme group is converted into biliverdin which is then converted to bilirubin

  3. Iron is transported by transferrin to liver and stored by ferritin

  4. Erythrocyte proteins are broken down into free amino acids
• Leukocytes


  White blood cells, possess a nucleus and organelles, larger than erythrocytes, help initiate an immune response and defend the body against pathogens
• Types of leukocytes


  • Granulocytes: Neutrophils, Eosinophils, Basophils
  • Agranulocytes: Lymphocytes, Monocytes
• Diapedesis


  Process of leukocytes squeezing through vessel wall to exit bloodstream and get to tissue
• Chemotaxis


  Process of leukocytes moving towards chemicals that are found at sites of infection
• Platelets


  Small, irregular, membrane-enclosed cell fragments, do not have a nucleus, produced in red marrow from cells called megakaryocytes, involved in blood clotting
• Thrombocytopenia


  Abnormally small number of platelets
• Erythropoiesis


  Production of erythrocytes, about 3 million per second, rate controlled by levels of hormone erythropoietin, occurs in red bone marrow