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Red Blood Cells or Erythrocytes

Red Blood Cells ( RBC ) or Erythrocytes

  • Red blood cells or erythrocytes containing the oxygen carrying protein hemoglobin, Which pigment gives whole blood to red colour.
  • Healthy adult male has about 5.4 (µl ) a healthy adult female has about 4.8 (µ l ) ( One drop of blood is 50 µl ).

Anatomy :

  • Rbc are biconcave disc with diameter of 7.8 µm ( micrometer ), mature Rbc have a simple structure no nucleus.
  • The plasma membrane is both strong and flexible. Which allow them to deform without rupturing as they squeeze through narrow capillaries.
  • Certain glycolipids in the plasma membrane of Rbc are antigens that account for the various blood groups such as the ABO and Rh groups.
  • Rbc lack of a nucleus and other organells and neither reproduce or carry on extensive metabolic activities. The cytosol of Rbc contain hemoglobin molecules.
  • The biconcave disc has a much greater surface area for the diffusion of gas molecules.

Physiology :

  • Rbc are highly specialized for their oxygen transport function. Because mature Rbc have no nucleus and lack of mitochondria. It generates ATP anaerobically ( Without Oxygen ).
  • The shape of Rbc facilitates its function a biconcave disc has a much greater surface area for diffusion of molecules into and out of the Rbc.
  • Each Rbc contain about 280 million hemoglobin molecules. A hemoglobin molecule consists of a protein called globin, composed of 4 ply peptide chains ( 2 alpha and 2 beta chains ).
  • A ring like non protein pigment is called the heme is bound to each of the four chains. At the center of each heme ring is an iron ( Fe2+) that can combine reversibly with one oxygen molecule.
  • Each hemoglobin molecule to bind with oxygen O2 molecules. Each oxygen ( O2 ) molecules picked from the lungs is bound to an iron ion. The iron O2 reactions reverses hemoglobin releases O2. Which diffuses first into the interstitial fluid and than into cells.
  • Hemoglobin also transports about 23% of the total CO2 a waste product of metabolism. Blood flowing capillaries picks up the CO2. Some which combine with amino acid in the globin part of hemoglobin. As blood flow through lungs the carbondiaxide is released from Hb and than exhaled.
  • Hemoglobin also plays a role in the regulation of blood flow and blood pressure. The gaseous hormones ( NO ) nitric oxide produced by the endothelia cells that line  blood vessels binds to hemoglobin, under some circumstances hemoglobin release NO. 
  • The released Nitric Oxide ( NO ) causes vasodilation ( An increase in blood vessel diameter ). It occur when the smooth muscle in the vessel wall relaxes.
  • Vasodilation improves blood flow and enhances oxygen delivery to cells near the site of Nitric Oxide ( NO ) release.


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