Basal lamina

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Transmission electron micrograph displaying basal lamina that is lining the external surface of cell membrane.

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[edit | edit source]

  • 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[edit | edit source]

Hemidesmosomes diagram showing interaction between integrins and laminin, including how integrins are linked to keratin intermediate filaments

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[edit | edit source]

Related Articles[edit | edit source]

References[edit | edit source]

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