Endothelial cell

Endothelial cell. A type of flattened cell that lines the inside of the blood vessels and especially the capillaries , forming part of its wall. It was discovered by a scientist named David Romo Erazo , thanks to his studies.

Summary

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• 1 Features
• 2 Morphology
• 3 Functions
  • 1 inflammation
• 4 Sources

characteristics

The endothelial cell lines the blood vessel and has an elongated configuration with its axis in the direction of blood flow. It has an approximate length of 25 to 50 micrometers and a width of 10 to 15 micrometers. Two types of junctions between endothelial cells have been described: some narrow (tigh) and others weak (gap).

Tight joints are more common in the arteries than in the veins. The type joints (gap) are not found in the capillaries. The importance of the unions lies in their ability to limit the transport of substances and molecules through the endothelial layer, the element that generates the main function of the endothelium as a mechanical barrier.

Morphology

The nucleus of the endothelial cells is very flattened and therefore appears elliptical in the sections viewed under a microscope. The thicker, nuclear region of the cell protrudes into the lumen. The peripheral and thinner portion of the cell is tremendously thin, and the membranes that look at light or tissue are separated by a layer of cytoplasm 0.2 to 0.4 microns thick.

There is a Golgi complex and a few mitochondria in the region near the nucleus , while in the peripheral thin region of the cytoplasm there are tortuous tubular elements of the endoplasmic reticulum . Lysosomes are rare , but multivesicular bodies are not uncommon.

A striking feature of endothelial cells is the presence of a large population of plasma-necked vesicles, about 70 nanometers in diameter, with a thin neck, which are present on both cell surfaces and open to light and extravascular space.

The luminal surface of cells is normally smooth in profile, but often the edges of neighboring cells may overlap, and then a ridge or tongue may project into the light for a short distance. Desmosomes and zonula adherens are usually missing , but there is a small occluder junction that in cryofracture preparations shows one to three parallel intramembrane cords on face E.

On the extraluminal or external surface, the endothelial cells are in contact with the basement membrane and substances such as collagen , proteglycans , heparan sulfate , integrins; in the luminal part, the endothelial cells in contact with the blood have mucopolysaccharides , glycoproteins , fibrinogen and some fibrin.

In the human body, the entire vascular endothelium can weigh about 1.5 kilograms and covers an area of ​​about 600 square meters.

Features

Endothelial cells form the vascular endothelium which is a simple, flat (single-layer cell) epithelium that lines the inside of the blood vessels and heart.

Endothelial cells have various functions in homeostasis, including the following:

1. They form a smooth surface that facilitates the laminar flow of blood and prevents the adhesion of blood cells.
2. They form a permeability barrier for nutrient exchange between plasma and the cell gap, while regulating the transport of substances between the two.
3. They regulate angiogenesis and vascular remodeling.
4. They contribute to the formation and maintenance of the extracellular matrix.
5. They produce growth factors in response to vascular damage, especially influencing the proliferation of vascular smooth muscle.
6. They produce substances that regulate platelet aggregation, coagulation fenrreacion and fibrinolysis.
7. They synthesize and degrade various hormones.
8. They participate in the immune response by generating cytokines that modulate the activity of lymphocytes.
9. They release agents that act paracrine on adjacent smooth muscle cells, regulating their contraction.

The vascular endothelium produces and releases vasodilator and vasoconstrictor substances.

Vasodilators include: nitric oxide (NO) (formerly known as endothelium-derived relaxant factor or EDRF), endothelium-derived hyperpolarizing factor (EDHF), and prostacyclin . Vasoconstrictor substances include: endothelin and thromboxane A2.

Inflammation

The last decades have been very productive in understanding the endothelial cell and its function during the inflammatory process. Previously, the endothelium was viewed as a simple physical barrier that separated blood from the underlying tissues.

Although its structure is apparently simple, it is currently known to be a highly specialized and metabolically very active organ; it plays a very important role not only in maintaining vascular tone and permeability but also in leukocyte trafficking and in modulating homeostasis and thrombosis .

The endothelial cell participates in all phases of acute or chronic inflammation; it produces vasodilation mediators such as nitric oxide and prostacyclin and expresses adhesion molecules that facilitate leukocyte adherence and transmigration. The initial event in acute inflammation is vasodilation with subsequent increase in vascular permeability and exudation of neutrophils; although vasodilation mediators can arise from plasma, leukocytes, or platelets. The endothelium as an organ that regulates vascular tone contributes to this process.