Basement Membrane

Underlying most epithelia is the basement membrane (basal lamina). The basement membrane provides structural and metabolic support to epithelia. It is usually 30 - 60 nm thick and made up of a feltwork composed of collagenous and non-collagenous glycoproteins and proteoglycans. Integrins on the basal surface of epithlial cells interact with proteins of the basement membrane. This layer can best be seen in silver-stained sections or in those stained with the periodic acid Schiff (PAS) procedure