What is the name of the layer of cells that constitutes the outer portion of the skin and other membranes?

The outer portion of the skin and other membranes is indeed referred to as the epithelium. This layer serves as a protective barrier that covers the surface of the body and lines various cavities and organs. The epithelium consists of tightly packed cells that provide protection against environmental hazards, pathogens, and dehydration.

Moreover, it plays essential roles in functions like absorption, secretion, and sensation. Different types of epithelial tissue can be found throughout the body, tailored to their specific functions, such as the skin (keratinized epithelium) or the lining of internal organs (various forms of simple and stratified epithelium).

The dermis, in contrast, is the layer beneath the epithelium that contains connective tissues, blood vessels, and nerve endings, whereas the hypodermis lies beneath the dermis and primarily consists of fat and connective tissue, providing insulation and cushioning. Sublayers is a term that does not specifically identify any one layer of skin but rather refers to layers of various tissues throughout the body in a general sense.