An erythrocyte is another name for a red blood cell (RBC), which is technically a corpuscle (RBC) since it lacks a nucleus.
Structure and Function
These are small, biconcave cells measuring about 7-8 micrometres in diameter. Their principle function is to transport oxygen around the body. They contain haemoglobin, a protein pigment which carries the actual oxygen molecules. The structure and internal metabolism of an erythrocyte is exquisitely tailored to this purpose. The biconcave shape maximizes the surface area for oxygen exchange and is also flexible.
In adults, haematopoeisis takes place predominantly in the bone marrow of long bones. The precursor cell ("target cell" if it is released into the peripheral blood) ejects its nucleus during development, leaving more room for the payload of the corpuscle.
Red corpuscles have a life-span of 90-120 days. Senescent erythrocytes are broken down in the reticulo-endothelial system (principally the spleen and liver). The lifespan of the RBC determines the length of the period of the recent past over which an HbA1c measurement reflects glucose concentration by time.
The count, and percentage of blood volume (haematocrit) of red blood cells are often measured in a full blood count, but the more useful measurements are haemoglobin concentration and the size - the mean corpuscular volume (MCV), which may hint at the type of anaemia.