Red blood cells or RBCs play an important role by carrying oxygen throughout the body. The RBCs lacks nucleus and most organelles but they carries nutrients and the haemoglobin protein that make the blood red and carry oxygen. It is called as the red river of life as the red colour is due to the presence of haemoglobin that makes the blood red, it flows or circulates in the form of liquid in our body in same way like a river flows and known as life because blood carries oxygen which is required for breathing or survival,without oxygen a person would die.