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

Links

Related Articles

• Epithelium
• Tissue

References

• VAJNER, Ludek – CARBON, George – KONRÁDOVÁ, Václava. Medical Histology. 1, Cytology and General Histology. 1st edition. Karolinum, 2010. 112 pp. ISBN 978-80-246-1860-9.