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The endothelium is a thin layer of single flat cells that line the interior surface of blood vessels and lymphatic vessels.[1]Endothelium is of mesodermal origin. Both blood and lymphatic capillaries are composed of a single layer of endothelial cells called a monolayer.
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.
Within the cardiovascular system such as lining capillaries or the inside of the heart, simple squamous epithelium is specifically called the endothelium. [3] Cells are flat with flattened and oblong nuclei. It is also called pavement epithelium due to its tile-like appearance. This epithelium is associated with filtration and diffusion.
The more metabolically active a tissue is, the more capillaries are required to supply nutrients and carry away products of metabolism. There are two types of capillaries: true capillaries, which branch from arterioles and provide exchange between tissue and the capillary blood, and sinusoids , a type of open-pore capillary found in the liver ...
The ependyma is made up of ependymal cells called ependymocytes, a type of glial cell. These cells line the ventricles in the brain and the central canal of the spinal cord, which become filled with cerebrospinal fluid. These are nervous tissue cells with simple columnar shape, much like that of some mucosal epithelial cells. [2]
The blood–brain barrier is formed by the brain capillary endothelium and excludes from the brain 100% of large-molecule neurotherapeutics and more than 98% of all small-molecule drugs. [28] Overcoming the difficulty of delivering therapeutic agents to specific regions of the brain presents a major challenge to treatment of most brain disorders.
Aging is associated with blood flow changes in the brain. These changes may be linked to an increased risk of neurodegenerative conditions.. A new mouse study maps how these changes vary ...
In the perivascular spaces, the pia mater begins as mesothelial lining on the outer surface, but the cells then fade to be replaced by neuroglia elements. [9] Although the pia mater is primarily structurally similar throughout, it spans both the spinal cord's neural tissue and runs down the fissures of the cerebral cortex in the brain. It is ...