The size of a dust mite is between 0.2 and 0.5 mm (200 to 500 μm),
The size of E. coli is between 0.5 to 3 microns (µm).
The size of the red blood cells is located between these two (7.2µm) (much smaller than mites but larger than E. coli)
A normal erythrocyte appears in profile as a biconcave disk, as a lighter center disk: it is a kind of pocket containing hemoglobin. This form gives it a high elasticity, which allows the transport of oxygen through some narrow capillaries. The normal diameter of red blood cells from the front varies from 6.7 to 7.7 micrometers (average 7.2 micrometers). They are in the form of biconcave disks (central region: 0.8 micrometer, peripheral region: 2.6 micrometers) most suitable for maximum fixation.
