What are three ways that red blood cells are significantly different to other specialised animal cells?

Red blood cells are intricately designed to carry out the extremely important function of delivering oxygen to where it is required in the body.Firstly, red blood cells have a significantly different shape to most other specialised cells. The flexible, biconcave disc shape allows easy movement through very narrow blood vessels and maximises surface area for more efficient oxygen uptake.Secondly, they are unique by the fact that they do not contain a nucleus. Red blood cells lack a nucleus to increase the space inside the cell for oxygen.Lastly, red blood cells contain haemoglobin, an important protein that binds oxygen molecules to transport them around the body.These are the three major factors that make red blood cells so different to other specialised cells in the body.