Which cells in the blood do not have a nucleus?

Erythrocytes, or red blood cells, are the specialized cells in the blood that do not have a nucleus. During their development in the bone marrow, erythrocytes undergo a process called enucleation, where they lose their nucleus. This adaptation allows them to maximize space for hemoglobin, the protein responsible for oxygen transport. Without a nucleus, erythrocytes can carry more oxygen to tissues, making them vital for respiratory and metabolic functions.

Leukocytes, or white blood cells, and thrombocytes, which are platelets, retain their nuclei and play roles in the immune response and blood clotting, respectively. Plasma cells are a type of white blood cell that produce antibodies, and they also possess a nucleus. This characteristic of erythrocytes highlights their unique role in the circulatory system, distinguishing them from other blood cell types.