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The permeability of a capillary wall is determined by the type of capillary and the surface of the endothelial cells. A continuous, tightly spaced endothelial cell lining only permits the diffusion of small molecules. Larger molecules and blood cells require adequate space between cells or holes in the lining.
Differences in vascular permeability between normal tissue and a tumor. Vascular permeability, often in the form of capillary permeability or microvascular permeability, characterizes the capacity of a blood vessel wall to allow for the flow of small molecules (drugs, nutrients, water, ions) or even whole cells (lymphocytes on their way to the site of inflammation) in and out of the vessel.
The endothelium (pl.: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. [1] The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall.
Occludin is a transmembrane protein that regulates the permeability of epithelial and endothelial barriers. It was first identified in epithelial cells as a 65 kDa integral plasma-membrane protein localized at the tight junctions. [5]
TEM of rat kidney tissue shows a protein dense tight junction (three dark lines) at ~55,000x magnification.. Tight junctions provide endothelial and epithelial cells with barrier function, which can be further subdivided into protective barriers and functional barriers serving purposes such as material transport and maintenance of osmotic balance.
This barrier is composed of endothelial cells and ensures the protection and functionality of the brain and central nervous system. It has been found that pericytes are crucial to the postnatal formation of this barrier. Pericytes are responsible for tight junction formation and vesicle trafficking amongst endothelial cells.
Diffusion through the capillary walls depends on the permeability of the endothelial cells forming the capillary walls, which may be continuous, discontinuous, and fenestrated. [4] The Starling equation describes the roles of hydrostatic and osmotic pressures (the so-called Starling forces) in the movement of fluid across capillary endothelium ...
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. [1] [2] The basement membrane sits between epithelial tissues including mesothelium and endothelium, and the underlying connective tissue. [3] [4]