Final answer:
Simple squamous epithelium is the single cell layer that lines the serous membranes in the body, providing a protective surface and facilitating the rapid passage of substances.
Step-by-step explanation:
The single cell layer of the epithelium that forms the lining of the serous membrane is known as simple squamous epithelium. This epithelial tissue is characterized by thin, flat cells with flat nuclei, and is found where rapid passage of chemical compounds is necessary, such as in the alveoli of lungs for gas exchange, in certain segments of kidney tubules, and in the lining of capillaries. The mesothelium is a type of simple squamous epithelium which specifically covers the serous membranes lining the body cavities and internal organs, with its primary function being to provide a smooth and protective surface while secreting a lubricating fluid.