Extracellular basement membrane

In biology, extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the cells in addition to performing various other important functions. ECM is the defining feature of connective tissue in animals. ECM includes the interstitial matrix and the basement membrane. 

The vitreous is a transparent extracellular matrix occupying the space between the posterior lens and the retina and, in the majority of vertebrate species, constitutes the major f)art of the volume of the eye. Embryo-logically it can be considered as the basement membrane of the retina. It provides a mechanical support for surrounding tissues and acts as a shock absorber by virtue of its viscoelastic properties (Balzas and Delinger, 1984). Vitreous consists mainly of water (98%) and colloids (0.1%) with ions and low molecular weight solutes making up the remainder. It is not fully developed at birth, and changes in both volume and chemical composition occur postnatally. 

Usher II is caused by mutations in at least four genes only one, usherin, has been identified. Usherin is an extracellular matrix protein of unknown function it is found in basement membranes in the eye and ear (and in other tissues as well). Similarly, at least two genes underlie Usher III, but only one (clarin-1) has been cloned. The function of clarin-1 is unknown. 

The basement membrane (BM) is a continuous layer of extracellular materials, forming a boundary between the basal layer of the epithelium and the connective tissues of the lamina propria and the submucosa. It can be subdivided into the lamina lucida,... 

Extracellular Matrix A meshwork-hke substance found within the extracellular space and in association with the basement membrane of the cell surface. It promotes cellular proliferation and provides a supporting structure to which cells or cell lysates in cultiu-e dishes adhere. [NIH]... 

The transition from mesenchyme to epithelium involves biochemical changes in the cells and the extracellular matrix, N-CAM expression on cell surfaces disappears, replaced by L-CAM (uvomorulin). Vimentin, a characteristic cytoskeletal component of mesenchyme, disappears, and cytokeratin, characteristic of epithelia, appears. There is a decrease in collagen I extracellularly and an increase in the basement membrane components laminin and collagen IV. 

Extracellular GAG, found in basement membrane and as a ubiquitous component of cell surfaces. 

The net surface charge of a cell and the associated electrical double layer are important in interactions between cells and may influence the development of extracellular structure such as basement membranes. The net negative charge on cells also gives rise to an experimentally measurable electrophoretic mobility. 

Berasain, P., Goni, F., McGonigle, S., Dowd, A., Dalton, J.P., Frangione, B. and Carmona, C. (1997) Proteinases secreted by Fasciola hepatica degrade extracellular matrix and basement membrane components. Journal of Parasitology 83, 1-5. 

Type IV collagen is a fundamental component of basement membranes (Fig. 1A). Basement membranes represent the portion of extracellular matrix that remains in direct contact with its formative cells. Basement membranes play an important role in cell adhesion, growth and differentiation, tissue repair, molecular ultrafiltration, cancer cell invasion, and metastasis. 

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