Question

can you think of any reason why it might be more advantageous for the external epithelium (i.e. the skin) to be comprised of squamous cells rather than cuboidal or columnar?

Answer 1

Squamous cells allow for passive diffusion and are flattened i.e. cells are wider than their height. Which allows them to form several layers as found in the skin in the form of keratinized stratified squamous cells. This arrangemnet allows them to easily protect the body from external environment and if damaged only top layers need to be regenerated.

Whereas the size of the cuboidal cells are equal in height and width and columnar cells are almost four times longer than their width. They cannot be regenrated and cannot form several layers as a protection to the body.