Simple squamous epithelium is made up of flattened squamous cells with irregular margins. This type of epithelium is found lining different cavities of the body, including the pleural, pericardial, and peritoneal cavities. It is also found lining glands and areas where passive diffusion occurs such as alveoli in the respiratory tract, and glomeruli in the kidney.

The main functions of the simple squamous epithelium include protection, diffusion, absorption, and filtration.