Red Blood Corpuscles

• Diameter- 6.9-7.4µ
• Thickness- 2.2µ at the periphery, 1µ centrally
• Surface area- 140sq µ
• Volume- 85-90cu µ
• They are biconcave in shape which play the following roles:

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  1. Equal and rapid diffusion of substances into the cells
  2. Large surface area for removal of substances
  3. Reducing tension on the cell membrane
  4. Allows the cell to squeeze through thin capillaries
• Normal RBC count is 4-5.5 lakh cells/ cu mm
• Number reduces in anemia and is elevated in polycythemia
• RBCs with variation in size-Anisocytes
• RBCs with variation in shape- Poikilocytes
• Lifespan of the RBC- 120 days
• Synthesis of RBCs occurs by the process of Erythropoiesis
• Site of Erythropoiesis  in fetal life

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  1. Mesoblastic stage- In the mesoderm of the yolk sac for the first 2 months of INTRAUTERINE LIFE
  2. Hepatic- In the liver, from the third month of IU life
  3. Myeloid- In the red bone marrow and the liver, during the last three months of IU life
• Site of Erythropoiesis  in Post natal life-

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  1. Upto 5-6 years- All the bones in the body
  2. 6th to 20th year- Long bones and flat bones
  3. After 20 years- Only flat bones
• Stages of Erthropoiesis:

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  1. Proerythroblast
  2. Early normoblast- Also called basophilic normoblast
  3. Intermediate normoblast- Hb appears at the stage, polychromophilicnormoblast
  4. Late normoblast- Presence of pyknotic nucleus, and orthochromophilic cytoplasm
  5. Reticulocyte- Immediate precursor to the mature RBC, 1% of the RBC population
  6. Mature erythrocyte