Erythrocytes are also known as red blood cells that deliver oxygen to and remove carbon dioxide from tissues. Erythrocytes have a limited life span and as they age, their membranes become more fragile leading to a loss of function and swelling. This damage occurs as the fragile cells pass through narrow capillaries, which occurs in the spleen. The life span of the erythrocyte varies from 70-160 days in domestic species. The average lifespan of RBCs in human is 120 days.