Page "Red blood cell" Paragraph 24

Mammalian erythrocytes are typically shaped as biconcave disks: flattened and depressed in the center, with a dumbbell-shaped cross section, and a torus-shaped rim on the edge of the disk.

This distinctive biconcave shape optimises the flow properties of blood in the large vessels, such as maximization of laminar flow and minimization of platelet scatter, which suppresses their atherogenic activity in those large vessels.

However, there are some exceptions concerning shape in the artiodactyl order ( even-toed ungulates including cattle, deer, and their relatives ), which displays a wide variety of bizarre erythrocyte morphologies: small and highly ovaloid cells in llamas and camels ( family Camelidae ), tiny spherical cells in mouse deer ( family Tragulidae ), and cells which assume fusiform, lanceolate, crescentic, and irregularly polygonal and other angular forms in red deer and wapiti ( family Cervidae ).

Members of this order have clearly evolved a mode of red blood cell development substantially different from the mammalian norm.

Overall, mammalian erythrocytes are remarkably flexible and deformable so as to squeeze through tiny capillaries, as well as to maximize their apposing surface by assuming a cigar shape, where they efficiently release their oxygen load.