L3.2.1: Erythrocytes

• ERYTHROCYTES

  ● Red Blood Cells (RBCs)

  ● Main function is to carry oxygen
• ERYTHROCYTES

  ● Differ from other blood cells

  ○ Anucleate (no nucleus)

  ○ Contain few organelles; lack mitochondria

  ○ Make ATP by anaerobic means

  ○ Essentially “bags” of hemoglobin (Hb)

  ○ Shaped like biconcave discs (looking like miniature doughnuts when viewed with a microscope)
• ERYTHROCYTES

  ● Normal count is 5 million RCBs per mm3 of blood

  ● HEMOGLOBIN — an iron-bearing protein

  ○ Binds oxygen

  ○ Each hemoglobin molecule can bind 4 oxygen molecules

  ○ Each erythrocyte has 250 million hemoglobin molecules

  ○ Normal blood contains 12-18 g of hemoglobin per 100 milliliters of blood
• NOTE: Hemoglobin also binds with a small amount of carbon dioxide but not at the same binding site as oxygen.
• HOMEOSTATIC IMBALANCES

  ● ANEMIA — “lacking blood”; decrease in the oxygen-carrying ability of the blood due to:

  ○ Lower than normal number of RBCs

  ○ Abnormal or deficient hemoglobin content in the RBCs
• HOMEOSTATIC IMBALANCES

  ● POLYCYTHEMIA — disorder from excessive or abnormal increase of RBCs due to:

  ○ Polycythemia vera (bone marrow cancer)

  ○ Secondary polycythemia (life at higher altitudes because air is thinner and less oxygen is available)

  ○ Increase in RBCs slow blood flow and increases blood viscosity
• TYPES OF ANEMIA

  Decreased RBC numbers

  • Hemorrhagic
  • Hemolytic
  • Pernicious
  • Aplastic

  Inadequate hemoglobin content

  • Iron-deficiency

  Abnormal hemoglobin in RBCs

  • Sickle Cell (SCA)
• Hemorrhagic

  Sudden hemorrhage
• Hemolytic

  Lysis of RBC as a result of bacterial infections
• Pernicious

  Lack of vitamin B12 (lack of intrinsic factor required for absorption of the vitamin or intrinsic factor is formed by stomach mucosa cells)
• Aplastic

  Depression/destruction of bone marrow by cancer, radiation, or certain medications
• Iron-deficiency

  • Lack of iron in the diet or slow/prolonged bleeding, which depletes iron reserves needed to make hemoglobin
  • RBCs are small and pale because they lack hemoglobin
• Sickle Cell (SCA)

  • Genetic defect leads to abnormal hemoglobin, which becomes sharp and sickle-shaped under conditions of increased oxygen use by the body
  • Occurs mainly in people of African descent (Malaria is prevalent in Africa. Apparently, individuals with sickle cell gene have better chance of surviving where malaria is prevalent.)
• The term “lysis” refers to the breakdown or destruction of cells. “Hemolysis” specifically means the destruction of red blood cells.
• Sickle cell trait (SCT) is manifested by individuals carrying only one sickling gene. They do not display the symptoms but can pass on the sickling gene to their offspring.
• Blood doping is commonly done by athletes; the infusion of a person’s own RBCs back into their bloodstream to increase the amount of Hb in the bloodstream