The glycocalyx, also known as the pericellular human anatomy and physiology mckinley pdf, is a glycoprotein and glycolipid covering that surrounds the cell membranes of some bacteria, epithelia and other cells. Most animal epithelial cells have a fuzz-like coat on the external surface of their plasma membranes.
The glycocalyx is a type of identifier that the body uses to distinguish between its own healthy cells and transplanted tissues, diseased cells, or invading organisms. Included in the glycocalyx are cell-adhesion molecules that enable cells to adhere to each other and guide the movement of cells during embryonic development. The slime on the outside of a fish is an example of glycocalyx. The term was initially applied to the polysaccharide matrix coating epithelial cells, but its functions have been discovered to go well beyond that. The glycocalyx is located on the apical surface of vascular endothelial cells which line the lumen. The enzymes and proteins listed above serve to reinforce the glycocalyx barrier against vascular and other diseases. Another main function of the glycocalyx within the vascular endothelium is that it shields the vascular walls from direct exposure to blood flow, while serving as a vascular permeability barrier.
Research has shown that the glycocalyx, which is located on the apical surface of endothelial cells, is composed of a negatively charged network of proteoglycans, glycoproteins, and glycolipids. Because the glycocalyx is so prominent throughout the cardiovascular system, disruption to this structure has detrimental effects that can cause disease. Certain stimuli that cause atheroma may lead to enhanced sensitivity of vasculature. Initial dysfunction of the glycocalyx can be caused by hyperglycemia or oxidized LDL which then causes atherothrombosis. Experiments have been performed in order to test precisely how the glycocalyx can be altered or damaged. One particular study used an isolated perfused heart model designed to facilitate detection of the state of the vascular barrier portion, and sought to cause insult-induced shedding of the glycocalyx to ascertain the cause and effect relationship between glycocalyx shedding and vascular permeability. Fluid shear stress is also a potential problem if the glycocalyx is degraded for any reason.
Another similar experiment was carried out to determine what kinds of stimuli cause fluid shear stress. The initial measurement was taken with intravital microscopy, which showed a slow-moving plasma layer, the glycocalyx, of 1 micrometer thick. The glycocalyx exists in bacteria as either a capsule or a slime layer. The difference between a capsule and a slime layer is that in a capsule polysaccharides are firmly attached to the cell wall, while in a slime layer the glycoproteins are loosely attached to the cell wall. Bacteria growing in natural ecosystems, such as in soil, bovine intestines, or the human urinary tract, is surrounded by some sort of glycocalyx-enclosed microcolony. A glycocalyx can also be found on the apical portion of microvilli within the digestive tract, especially within the small intestine. Physiology: The unity of form and function.
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The endothelial glycocalyx: composition, functions, and visualization. Haematological Disorders-Drug Targets, 2009, 9, p. Fluid shear stress directly stimulates synthesis of the endothelial glycocalyx : perturbations by hyperglycemia. Bacterial Glycocalyx in Nature and Disease. PIV Reveals a Hydrodynamically Relevant Endothelial Surface Layer in Venules In Vivo – Smith et al. The glycocalyx of the sperm surface. This page was last edited on 2 March 2018, at 10:27.