Skin is the main barrier between internal organs and the outside environment. The outer layer of skin is composed mostly of epithelial cells. Which is a characteristic of epithelial cells that makes them ideal for providing this type of protection?
Epithelial cells in the skin are stratified (layered) this helps so stuff can't get inside (bacteria/toxins/etc). The outer layers are also keratinized so they are hard enough to resist the friction
