What shape do mature red blood cells take after losing their nucleus?

Mature red blood cells, or erythrocytes, adopt a biconcave disc shape after they lose their nucleus during the maturation process. This unique shape is critical for their primary function: the transport of oxygen and carbon dioxide throughout the body.

The biconcave design increases the surface area-to-volume ratio of the cells, which facilitates more efficient gas exchange. This structure allows the red blood cells to deform as they navigate through narrow capillaries, ensuring they can deliver oxygen to tissues and pick up carbon dioxide effectively.

Additionally, the shape helps with the flexibility and structural integrity of the red blood cells, enabling them to withstand the mechanical stresses they encounter as they flow through the circulatory system. Therefore, the biconcave disc shape is an evolutionary adaptation that enhances the functionality and efficiency of red blood cells in the circulatory system.