Top Epithelial Tissue Flashcards

Epithelial tissue (or just “epithelium”) is the thin layer of cells that surrounds an organ or cavity. It’s found all over the body, from the innermost alveoli of the lungs to the very top layer of your skin, and serves all kinds of functions depending on what kind of cells it’s made of and how they’re arranged. There are several different types of epithelial tissue, named for the different arrangements. Simple epithelium is a single layer of cells, whereas stratified epithelium is made up of several layers. In the epithelium of the lungs' alveoli, there’s a simple epithelium, since gases need to be exchanged across a thin membrane of cells. Your skin, on the other hand, is a stratified epithelium, made up of several layers of cells arranged in a stack.

Epithelium can also be described based on the shape of the cells: squamous (scale-like), cuboidal (cube-shaped) and columnar (column-shaped). These different shapes allow the cells to perform different functions. The different types of epithelium are named for both shape and arrangement: simple squamous, stratified squamous, simple cuboidal, stratified cuboidal, simple columnar, pseudostratified columnar (which is somewhat stratified), and transitional (which involves a mix of types).