Erythrocytes are red blood cells (RBCs)
– They are the most numerous formed cell
– They are flat, red disks with no nucleus
• Erythrocytes begin in as erythroblasts and are released as immature reticulocytes
• Hemoglobin in erythrocytes carries oxygen and carbon dioxide
– erythr/o- = red
– -cyte = cell

Erythrocytes cannot divide or repair themselves because they have no nucleus
– They deteriorate and die in about 120 days
– Erythrocytes must constantly be replenished
• When there are too few erythrocytes, erythropoietin prompts their production
• The spleen removes old erythrocytes and recycles their iron and amino acids

Notice the characteristic red color of erythrocytes (red blood cells) and their unique “doughnut” shape. Each erythrocyte has a depressed center and no cell nucleus.

Because there is no nucleus, an erythrocyte eventually deteriorates and dies after 120 days