What is the role of red blood cells in our body?

Red blood cells are vital for us to stay alive as they carry out an extremely important role in our body - oxygen transport. Red blood cells are the carrier of oxygen around our body in the blood stream, and the mechanism by which our organs, muscles, and tissues get the supply of oxygen they need to function. 

Red blood cells are able to carry oxygen because of a special protein called haemoglobin. The haemoglobin is present throughout the red blood cell, giving it its characteristic red colour. The red blood cell itself is concave in shape, similar to a doughnut but without the hole going all the way through. This gives the red blood cell greater surface area allowing it to carry more oxygen. Its shape also allows it to fit through narrow capillaries and blood vessels in our body. It's important to note that red blood cells have no nucleus, but they have a cell membrane - a very thin cell membrane! This allows easy diffusion of oxygen into oxygen-poor environments where the oxygen is needed.