[1] This type of epithelium is often permeable and occurs where small molecules need to pass quickly through membranes via filtration or diffusion.

Simple squamous epithelia are found in endothelium (lining of blood and lymph capillaries), mesothelium (coelomic epithelium/peritoneum), alveoli of lungs, glomeruli, and other tissues where rapid diffusion is required.

[2] Within the cardiovascular system such as lining capillaries or the inside of the heart, simple squamous epithelium is specifically called the endothelium.

It is also called pavement epithelium due to its tile-like appearance.

Simple squamous epithelium falls under the physiological category of exchange epithelium due to its ability to rapidly transport molecules across the tissue layer.