- Basal lamina
The basal lamina is a layer of extracellular matrix on which
epithelium sits and which is secreted by the epithelial cells. It is often confused with thebasement membrane , and sometimes used inconsistently in the literature, see below.It is typically about 40-50
nanometre s thick (with exceptions such as the basal laminae that compose the 100-200 nanometre thickglomerular basement membrane ).Layers
The layers of the basal lamina ("BL") and those of the basement membrane ("BM") are described below:
Anchoring fibrils composed of type VII collagen extend from the basal lamina into the underlying reticular lamina and loop around collagen bundles. Although found beneath all basal laminae, they are especially numerous instratified squamous cells of the skin.These layers should not be confused with the
lamina propria , which is found outside the basal lamina. [BUHistology|22203loa]Basal lamina vs. basement membrane
The term "basal lamina" is usually used with
electron microscopy , while the term "basement membrane" is usually used withlight microscopy . The structure known as the basement membrane in light microscopy refers to the stained structure anchoring an epithelial layer. This encompasses the basal lamina secreted by epithelial cells and typically a reticular lamina secreted by other cells.The basal lamina "cannot" be distinguished under the light microscope, but under the higher magnification of an electron microscope, the basal lamina and lamina reticularis are visibly distinct structures.
Some theorize that the lamina lucida is an artifact created when preparing the tissue, and that the basement membrane is therefore equal to the lamina densa
in vivo . [cite journal | author = Chan F, Inoue S | title = Lamina lucida of basement membrane: an artefact | journal = Microsc Res Tech | volume = 28 | issue = 1 | pages = 48–59 | year = 1994 | pmid = 8061357 | doi = 10.1002/jemt.1070280106]Examples of basement membranes include:
*Basilar membrane
*Bruch's membrane
*Descemet's membrane
*Glomerular basement membrane ee also
*
Alveolar-capillary barrier
*Basolateral membrane
*Collagen
*Glomerular basement membrane
*Lamina propria References
* "1 Kierszenbaum, AL. Histology and Cell Biology: An Introduction to Pathology. Mosby, Inc, MO: 2002. Chapter 4."
Wikimedia Foundation. 2010.
