- 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 O2 (oxyhaemoglobin) & CO2 (carbaminohaemoglobin)
- 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.