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Concept
Membrane basale
Résumé
The basement membrane, also known as base membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between epithelial tissues including mesothelium and endothelium, and the underlying connective tissue.
As seen with the electron microscope, the basement membrane is composed of two layers, the basal lamina and the reticular lamina. The underlying connective tissue attaches to the basal lamina with collagen VII anchoring fibrils and fibrillin microfibrils.
The basal lamina layer can further be subdivided into two layers based on their visual appearance in electron microscopy. The lighter-colored layer closer to the epithelium is called the lamina lucida, while the denser-colored layer closer to the connective tissue is called the lamina densa. The electron-dense lamina densa layer is about 30–70 nanometers thick and consists of an underlying network of reticular collagen IV fibrils which average 30 nanometers in diameter and 0.1–2 micrometers in thickness and are coated with the heparan sulfate-rich proteoglycan perlecan. In addition to collagen, this supportive matrix contains intrinsic macromolecular components. The lamina lucida layer is made up of laminin, integrins, entactins, and dystroglycans. Integrins are a key component of hemidesmosomes which serve to anchor the epithelium to the underlying basement membrane.
To represent the above in a visually organised manner, the basement membrane is organized as follows:
Epithelial/mesothelial/endothelial tissue (outer layer)
Basement membrane
Basal lamina
Lamina lucida
laminin
integrins (hemidesmosomes)
nidogens
dystroglycans
Lamina densa
collagen IV (coated with perlecan, rich in heparan sulfate)
Attaching proteins (between the basal and reticular laminae)
collagen VII (anchoring fibrils)
fibrillin (microfibrils)
Lamina reticularis
collagen III (as reticular fibers)
Connective tissue (Lamina propria)
The primary function of the basement membrane is to anchor down the epithelium to its loose connective tissue (the dermis or lamina propria) underneath.
Source officielle
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Proximité ontologique