The endothelium is the layer of flattened cells of mesenchymal origin lining the wall of the blood and lymph vessels and capillaries, ensuring processes of exchange between blood and tissues. Is a continuous membrane consisting of a layer of endothelial cells associated intercellular "cement". The endothelium of blood capillaries some authorities is interrupted due to the presence of submicroscopic intracellular "long" (in the kidneys, endocrine glands, intestine) or wide intercellular gaps (in the liver, spleen, bone marrow).

Ploskostei the preparation of the inner lining artery muscle type: 1 - endothelium cells; 2 - cells porandamaalingud layer; 3 - the boundaries between endothelial cells (Schelkunova).

Endothelium [from Greek. endon - inside + (EPI)teli] - layer flattened cells of mesenchymal origin lining the wall of the blood and lymph vessels. In the embryogenesis endothelium first arises from the special cell differentiation of mesenchyme, forming a closed single layer of cells in the blood islets, located in the wall of the yolk SAC and the chorion to 2-3 weeks of fetal development. The majority of authors considers endothelium product particularly differentiated cells in the mesenchyme. Some authors refer endothelium a highly specific type of epithelial tissues (angioedemanew). Endothelium cells are thin plates, closely adjacent to each other and forming a solid single layer layer (Fig.). The length of endothelial cells from 5 MK to 175 MK, thickness in oraloader areas from 200 + 1-2 MK. Winding borders of the cells are well impregnants silver nitrate. Polygonal shape of the cells varied, depending on the size of the vessel and the degree of its expansion. The kernel of endothelial cells are oval, long diameter are located along dlinnie vessel. Endothelium cells often contain one core, sometimes 2-3, there are simplasta with 10 or more cores. In endothelial cells found pinocytosis bubbles diameter 500-1000+, located near the outer and inner surface. On the surface of endothelial addressed to the flow of the blood, are submicroscopic villi. In the cytoplasm of endothelium identified endoplasmic network with numerous granules RNA its membranes, small mitochondria. Intercellular spaces of a width of 100 + intercellular cement does not contain. There scaly the overlap of the two neighboring endothelial cells. Micropores diameter 300-400 + found in the endothelium of the capillaries of the glomerulus, CVS intestine, endocrine glands. The endothelium of blood capillaries surrounded basal membrane of the missing in the endothelium lymphatic capillaries. In the endothelium identified glycogen, vitamin C, alkaline phosphatase. The most differentiated endothelium of the endocardium and large vessels, less - capillary endothelium. Endothelium cells divide by mitosis and amitiza. When reparative regeneration restoration of endothelium is through mitoticescoe dividing cells at the edge of wounds and napoletane them on the damaged surface. The restoration of the endothelium also made little differentiated mesenchymal elements located in the subendothelial layer. The formation of new capillaries is due to the merger kidney-shaped outgrowths of endothelium with each other. Endothelium lining listed in the capillaries of the liver, bone marrow, spleen and sinuses lymph nodes, has a pronounced ability to accumulate alien colloids from the blood and lymph. This endothelium related to elements of the reticuloendothelial system (see). Through the endothelium is to exchange of substances between the blood or lymph) and tissue fluids.