Basal lamina

From Freepedia

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

The two layers of the basal lamina sit on top of the lamina reticularis, which is synthesized by cells from the underlying connective tissues. These three layers are collectively referred to as the basement membrane.

Some organs do not have a lamina reticularis, such as the glomerulus in the kidneys.

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.

1 Kierszenbaum, AL. Histology and Cell Biology: An Introduction to Pathology. Mosby, Inc, MO: 2002. Chapter 4.