Let’s start with simple epithelia. A simple epithelium is one cell layer thick, and the cells may be squamous, cuboidal, or columnar in shape. Depending on its location, this type of epithelium can function to line and protect an organ or participate in absorption and secretion. First, let's look at simple squamous epithelium.

• First examine the cornea of the eye, where simple squamous epithelia can be found as the inner lining of the cornea (arrow). Squamous epithelial cells are very thin and flat.

• The epithelium lining the lumen of blood vessels (endothelium) is also a good example of simple squamous epithelium. To the right is an image of a gallbladder with small vessels in the lamina propria (Lamina what?). See if you can locate some blood vessels with their lining of simple squamous epithelium in the connective tissue of the gallbladder.

• Another place where simple squamous epithelium (arrows) can be found is in the capsule of the renal corpuscles of the kidney where blood is filtered to produce urine. Locate some renal corpuscles with their capsule of simple squamous epithelium in this example.

Now for simple cuboidal epithelium.