The squamous cell epithelium forms a barrier between the body and the exterior environment, according to Rutgers University. These cells also provide protection for the underlying tissues.
Squamous cell epithelium refers to the thin layer of cells that line all inner and outer surfaces of the body, informs Rutgers University. Flattened epithelium that consists of only a single layer of cells is called simple squamous epithelium. Epithelium composed of more than one layer of cells is called stratified epithelium.
Simple squamous epithelium lines internal body surfaces that are not usually exposed to irritation, explains Rutgers University. This includes structures, such as the heart, lungs and blood vessels, adds Davidson College. The cells are connected to each other through tight junctions, forming a selective barrier that is permeable only to small molecules. In the lungs, simple squamous epithelium allows oxygen and carbon dioxide gases to diffuse between the air and the bloodstream.
Stratified squamous epithelium is found in body surfaces exposed to significant amount of wear, describes State University of New York Downstate Medical Center. This includes the skin and passageways that lead to the outside of the body, such as the nose and anus. These cells similarly create a barrier between the body and the outside world, but the added cellular layers protect the underlying structures from physical trauma and chemical damage, notes Davidson College.