Discocytes

Discocytes are red blood cells that exhibit a biconcave disc shape. This morphology, often described as the normal erythrocyte form in humans and many other mammals, produces a central pallor when viewed under light microscopy and contributes to a characteristic smooth, doughnut-like appearance.

The discocyte shape is supported by a composite membrane cytoskeleton, including spectrin, actin, ankyrin, and band 3, anchored to the lipid bilayer. The geometry increases the surface area-to-volume ratio, facilitating gas exchange and enabling the cell to deform as it traverses capillaries smaller than its resting diameter. The cells are typically anucleate and lack most organelles, a feature linked to their long, flexible lifespan.

Clinical relevance: The discocyte is the standard shape; deviations from this form—such as stomatocytes, echinocytes, or spherocytes—can appear in various disease states and are described as poikilocytosis. Comparative hematology notes that red blood cell shapes vary across species; in non-mammalian vertebrates, red cells are often nucleated and may differ in overall morphology.