Why are epithelia that are multilayered, not useful for absorption/secretion?
The thinker the layer, the harder it is to absorb things like saliva in your saliva glands, moister to keep you cool or secret oils out of your body. Thinner layers of skin like simple squamous cuboidal are more similar to a sponge than columnar (column) or Pseudostratified.
Why is single layered epithelium important for transport but not protection from abrasion?
The single-layered epithelium has secretory linings that allow for better absorption and secretion. A Pseudostratified columnar is meant to protect from abrasions.
Epithelia do not have vasculature; how do they get oxygen, glucose, etc...?
Epithelia do not contain blood vessels, however, the blood vessels are located very close to the epithelium that way exchange of material (i.e., oxygen-glucose, etc.) is possible.
What differentiates the location of keratinized vs. non-keratinized epithelium?
As keratinized cells reach the top layer of epithelia, they die; this occurs they take on a shape that protects the skin. Non-keratinized have nuclei and are living.