The word erythrocyte is derived from the Greek words erythros meaning red and kytos meaning cell. The biconcave disk-like cells of red color of blood are called red blood cells or hematids or erythrocytes or RBCs. In the human body, red blood cells travel around the body once every 60 seconds. The body contains 20-30 trillion red blood cells which are 70% of all cells in the body. A percentage measurement of the volume of red blood cells in the blood is called hematocrit (HCT). If it is deficient in the body, it causes anemia and if it is more, it causes polycythemia. Children have the highest number of red blood cells in their blood.
