1. It is red in color because it contains hemoglobin. 100 ml of blood contains 15-16 grams of hemoglobin. Each red blood cell contains 29 picograms of hemoglobin.
2. It is round, bi-concave and disk-like.
3. Its diameter is about 7.5 µm and thickness is 2.0-2.5 µm.
4. Its periphery is smooth and thick and the middle is thin. Center thickness is 1.0 µm.
5. Mammalian red blood cells do not have a nucleus (exception—camel).
6. Its average lifespan is 120 days or 4 months. During this time it covers a distance of 1100 km.
7. It contains 60-70% water and 30-40% solids (90% of the solids are hemoglobin).
8. It helps in making bilirubin and biliverdin.