Which site is lined by simple squamous epithelium?

• A. Kidney glomeruli
• B. Lining of stomach
• C. Lining of urinary bladder
• D. Ducts of glands

Answer: (A)

Simple squamous epithelium is a single, very thin layer of flat cells that lines surfaces where rapid diffusion or filtration is needed. In the kidney, the walls of the glomerular capillaries are lined by this thin endothelium, allowing fluids and small solutes to pass through quickly during filtration. The Bowman's capsule’s parietal layer is also made of simple squamous epithelium, which fits the idea of a porous, filtration-focused lining. By contrast, the stomach lining is made of simple columnar epithelium for secretion and absorption, the urinary bladder is lined by transitional epithelium that allows stretch, and glandular ducts are typically lined by simple cuboidal or stratified epithelium depending on function. Therefore, the site lined by simple squamous epithelium is the kidney glomeruli.