Biconcave shape of RBC’s is helpful because:
Easily passage through capillaries
Roulex formation.
Increased surface area for a given diameter.
None.
Guyton-419
Normal red blood cells, are biconcave discs having a mean diameter of about 7.8 micrometres and a thickness of 2.5 micrometres at the thickest point and 1 micrometre or less in the centre. The shapes of red blood cells can change remarkably as the cells squeeze through capillaries.