Red blood cells (RBCs) are non-nucleated, round, biconcave, disc-shaped cells They are 6.7 to 7.7μ in diameter, approximating the size of the nucleus of a small normal lymphocyte.
In stained blood films, only the flattened surfaces of the RBCs are seen. Therefore, they appear circular with an area of central pallor corresponding to the indented area. The central pallor occupies about one-third of the diameter of the cell. RBCs contain hemoglobin and stain pink to brick-red.