Basal lamina

Basal lamina is a layer of extracellular material separating epithelial tissue from connective tissue. The thickness of the basal lamina is 30-100 nm.

Function

 * This is a selective barrier between epithelial and connective tissue that is important for the interaction, placement and orientation of epithelial cells.
 * If it is disturbed, there is invasion of epithelial cells into connective tissue (in cancers) or vice versa (e.g. in the growth of blood vessels).
 * The basal lamina may contain pores where functional communication between the two tissues is needed (e.g. intestinal villi, Peyer's patches).

Construction
It contains two layers:


 * 1) Lamina lucida
 * 2) *A light layer that adheres to the base of the epithelial cell.
 * 3) *It is attached to cells by hemidesmosomes and anchoring filaments (molecules of integral membrane proteins integrins).
 * 4) *It consists mainly of laminin.
 * 5) Lamina densa - electron-dense layer 20-90 nm thick.
 * 6) *It has a felt-like character.
 * 7) *The lamina reticularis is connected to the lamina dense by a system of anchoring fibrils.
 * 8) *The lamina densa consists mainly of collagen type IV.

Lamina reticularis - a thin layer of reticular fibers and microfibrils of elastic fibers.


 * Lamina reticularis is a product of fibrous tissue cells.
 * It consists of:
 * collagen III (reticular fibers),
 * collagen VII (anchoring fibrils),
 * fibrillin (microfibrils of elastic fibers).

The term basal lamina is often confused with the term basement membrane. Basal membrane = lamina basalis + lamina reticularis.


 * In the light microscope we do not see the basal lamina, but the basement membrane.

Related Articles

 * Epithelium
 * Tissue