Which type of epithelium is characterized by flat cells and primarily facilitates diffusion?

Simple squamous epithelium is composed of a single layer of flat cells, which is key for its function in facilitating diffusion. The thinness of these cells allows for efficient movement of gases and other substances across the epithelial layer. This type of epithelium is commonly found lining structures such as alveoli in the lungs and blood vessels, where rapid transfer of oxygen, carbon dioxide, and nutrients is essential.

The flat shape of the cells reduces the distance that molecules must travel, making diffusion much more efficient than in other types of epithelium. For instance, in contrast to cuboidal or columnar epithelium, which possess a larger volume and a more complex structure, simple squamous epithelium's configuration is specifically adapted for quick and effective exchange processes.