How are red blood cells well adapted to their function?

Firstly red blood cells have very few organelles, losing many of them such as the nucleus in order to maximise the amount of haemoglobin they can hold. Furthermore they are relitavely thin meaning they have a high surface area to volume ratio so that they can maximise oxygen absorption. Finally red blood cells have a biconcaved shape making them more flexible so that they can squeeze through the smaller blood vessels such as the capillaries and carry oxygen to the extrimities of the body.