What are the two layers of the basement membrane, and what makes each layer?
- Basal Lamina
- Reticular Lamina
Most epithelial cells are separated from the connective tissue by a sheet of extracellular material called Basement Membrane. The basement membrane is usually visible with the light microscope. It is formed by the association of two layers : Basal lamina and reticular lamina.
Basal lamina is visible only with the electron microscope, and about 20-100 nm in thickness. It consists of a delicate network of fine fibrils (lamina densa). In addition the basal lamina may have an electron-lucent layer on one or both sides of the lamina densa . This layer is called lamina rara or lamina lucida . The main components of basal lamina are type 4 collagen, the glycoproteins laminin and entacin, and proteoglycans.
Reticular lamina is fromed by reticular fibers , as the name suggests. The reticular lamina is usually thicker than the basal lamina.
Some facts on the basement membrane :