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Encyclopedia > Basal lamina

The basal lamina (often erroneously called basement membrane) is a layer on which epithelium sits. This layer is composed of an electron-dense layer (lamina densa) between two electron-lucid layers (lamina lucida), and is approximately 40-50 nm thick (with exceptions such as the 100-200 nm glomerular basement membrane). The lamina densa is composed of type IV collagen. The lamina lucida is adjacent to the epithelial cells and contains the glycoprotein laminin. In zootomy, epithelium is a tissue composed of a layer of cells. ... A nanometre (American spelling: nanometer, symbol: nm) is 1. ... Nephron of the kidney A nephron is the basic structural and functional unit of the kidney. ... Tropocollagen triple helix. ... Cells in culture, stained for keratin (red) and DNA (green). ... A glycoprotein is a macromolecule composed of a protein and a carbohydrate (a sugar). ... Laminins are a family of heterotrimeric glycoproteins found in the basal lamina underlying epithelia. ...


Structure

The two layers of the basal lamina typically sit on top of the lamina reticularis, which is synthesized by cells from the underlying connective tissue and contains type IV collagen. The exception is when two epithelial layers abut one another (as in the alveoli of the lungs and glomeruli of the kidneys), in which the basal lamina of one epithelial layer fuses with that of the other. The alveoli (singular:alveolus), tiny hollow sacs which are continuous with the airways, are the sites of gas exchange with the blood. ... Glomerulus refers to two unrelated structures in the body, both named for their globular form. ...


Anchoring fibers composed of type VII collagen extend from the basal lamina into the underlying lamina reticularis and loop around collagen bundles. Although found beneath all basal laminae, they are especially numerous in stratified squamous cells of the skin. Squamous means covered with or formed of scales; scaly. ...


Basement membrane

The combination of the basal lamina and lamina reticularis or of two basal laminae is called the basement membrane. The term basement membrane is often confused with basal lamina. But whereas the basement membrane is visible under light microscopy, the basal lamina and lamina reticularis are only visible via electron microscopy. Microscopy is any technique for producing visible images of structures or details too small to otherwise be seen by the human eye. ...


The basal lamina is actually linked to the underlying type IV collagen; which makes up the basement membrane.


References

  • 1 Kierszenbaum, AL. Histology and Cell Biology: An Introduction to Pathology. Mosby, Inc, MO: 2002. Chapter 4.

  Results from FactBites:
 
CiteULike: Astrocytes secrete basal lamina after hemisection of rat spinal cord. (460 words)
Basal lamina is reconstructed over the lesioned surface of the spinal cord.
Ultrastructurally (3 days), basal lamina was polymerizing as small projections on the surface of astrocytic membranes facing the lesion, endothelia or pia.
By 5 days the basal lamina was a single membrane, folded multiple sheets or in swirls.
Dorlands Medical Dictionary (3781 words)
In the renal glomeruli and the pulmonary alveoli, it is bounded by the lamina rara externa and the lamina rara interna.
It consists of nine laminae (I–IX) that extend throughout the cord, roughly paralleling the dorsal and ventral columns of the gray substance, and a tenth region (lamina X) that surrounds the central canal and consists of the dorsal and ventral commissures and the central gelatinous substance.
(lam”ĭ-not´ə-me) [lamina + -tomy] division of the lamina of a vertebra.
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