Blood Corpuscles (Red Blood Cells)

RBCs (Erythrocytes)

  • Biconcave, disk shaped, colourless (red due to haemoglobin), spongy, flat at center & thick & round at periphery.
  • 2 micron in size.


  • About 4.5 to 5 million / mm3 but in infants 6 – 7 million / mm3
  • Its count lowers by 5% during sleep & increases during pregnancy & emotional upsets.
  • People living at high altitudes have 30 % more RBCs.
  • Abnormal increase in number of RBCs is called Polycythaemia.
  • Abnormal decrease in number of RBCs is called Erythropenia.

Production & Death

  • Produced in bone marrow of long bones (ribs, breast & ilium of hip girdle)
  • In embryo it is produced in liver & spleen
  • Produced bone marrow of all bones in children up to 5 years.
  • Destroyed in spleen, liver & bone marrow in which iron part retained & protein part excreted as bile pigments.
  • About 20,000,000 RBCs destroyed per minute or 1% of total RBCs per day in adult human being.


  • Contain haemoglobin [ Haemin (iron part) & globin (protein)] which carries O(oxyhaemoglobin) & CO2 (carbaminohaemoglobin)

Special features

  • Small size enables them to move through very fine capillaries
  • Concavities on both side provide larger surface area for absorption of O2
  • Make a stable compounds with CO (carboxyhaemoglobin) which cuts down the ability of haemoglobin to carry oxygen.
  • Have no nuclei due to which they are concave
  • Lack of mitochondria enables them to transport oxygen & nutrients unconsumed to the tissues.
  • Lack of EPR increases their flexibility for movement in narrow capillaries.