Simple squamous epithelium
Simple squamous epithelium is composed of a single layer of thin cells that are much wider than they are tall. This epithelium presents a minimal barrier to passive diffusion and, therefore, lines surfaces across which metabolites or gases can move rapidly. This epithelium also lines surfaces that require minimal protection, as shown here. Kidney 1000x
The simple squamous epithelium at the black arrows serves a lining function with no transport occurring across its surface. The simple squamous epithelia at the green arrows line capillaries where large amounts of transport and diffusion occur.
Simple cuboidal epithelium >
Simple cuboidal epithelia frequently form the walls of ducts or tubules, as seen here. Cuboidal cells usually possess spherical nuclei, while the cells themselves vary from nearly cube-shaped to rectangular.