Basement membrane - Definition and Overview

The basal lamina (previously called basement membrane) is a layer on which epithelium sits. This layer is approximately 40-50 nm thick and composed of the lumina lucida and the lumina densa. The lumina lucida is adjacent to the epithelial cells and composed of laminin (a proteoglycan) and collagen (Type IV). The lumina densa is composed of collagen (Type VII).

Anchoring fibers extend into the underlying extracellular matrix and loop around collagen bundles. Although found beneath all basal laminae, they are especially numerous in stratified squamous cells of the skin.

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