Answer
The skin is subjected to almost constant friction, which wears away the surface cells, and is charged with preventing the entry of damaging agents and with preventing water loss from the body. A stratified squamous epithelium with its many layers is much better adapted to stand up to abrasion than is simple epithelium (single-layer cells); also the stratified epithelia regenerate more efficiently than simple epithelia. Finally, keratin is a tough waterproofing protein that fills the bill for preventing desiccation and acting as a physical barrier to injurious agents. Because a mucosa is a wet membrane, it would be ineffective in preventing water loss from the deeper tissues of the body.
Work Step by Step
The skin is subjected to almost constant friction, which wears away the surface cells, and is charged with preventing the entry of damaging agents and with preventing water loss from the body. A stratified squamous epithelium with its many layers is much better adapted to stand up to abrasion than is simple epithelium (single-layer cells); also the stratified epithelia regenerate more efficiently than simple epithelia. Finally, keratin is a tough waterproofing protein that fills the bill for preventing desiccation and acting as a physical barrier to injurious agents. Because a mucosa is a wet membrane, it would be ineffective in preventing water loss from the deeper tissues of the body.
