Which blood cells do not have a nucleus?

Erythrocytes, or red blood cells, are unique among blood cells because they do not contain a nucleus. This absence of a nucleus allows them to maximize the space available for hemoglobin, the protein responsible for transporting oxygen throughout the body. The primary function of erythrocytes is to efficiently carry oxygen to tissues and remove carbon dioxide from them, which is enhanced by their biconcave shape and lack of organelles, allowing for greater flexibility and surface area.

In contrast, leukocytes, or white blood cells, contain nuclei and are integral to the immune response, playing a crucial role in defending the body against infections. Platelets, which are small cell fragments involved in clotting, are also anucleate; however, they are not true cells in the way that erythrocytes and leukocytes are, and their primary function is related to hemostasis rather than oxygen transport. Lastly, basophils are a type of leukocyte that does possess a nucleus and is involved in inflammatory responses and the release of histamine. Therefore, the identification of erythrocytes as the blood cells lacking a nucleus underscores their specialized role in oxygen transport in the circulatory system.