Endothelium
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Endothelium | |
---|---|
microvessel showing endothelial cells, which encircle an erythrocyte (E), forming the innermost layer of the vessel, the tunica intima. | |
Details | |
System | Circulatory system |
Location | Lining of the inner surface of blood vessels and lymphatic vessels |
Identifiers | |
MeSH | D004727 |
TH | H2.00.02.0.02003 |
FMA | 63916 |
Anatomical terms of microanatomy] |
The endothelium (pl.: endothelia) is a single layer of
Endothelial cells in direct contact with blood are called vascular endothelial cells whereas those in direct contact with
These cells have unique functions that include fluid filtration, such as in the glomerulus of the kidney, blood vessel tone, hemostasis, neutrophil recruitment, and hormone trafficking. Endothelium of the interior surfaces of the heart chambers is called endocardium. An impaired function can lead to serious health issues throughout the body.
Structure
The endothelium is a thin layer of single flat (
Endothelium is of
Terminology
The
Function
The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. This forms a barrier between vessels and tissues and control the flow of substances and fluid into and out of a tissue. This controls the passage of materials and the transit of white blood cells into and out of the bloodstream. Excessive or prolonged increases in permeability of the endothelium, as in cases of chronic inflammation, may lead to tissue swelling (edema). Altered barrier function is also implicated in cancer extravasation.[6]
Endothelial cells are involved in many other aspects of vessel function, including:
- Blood clotting (thrombosis and fibrinolysis). The endothelium normally provides a surface on which blood does not clot, because it contains and expresses substances that prevent clotting, including heparan sulfate which acts as a cofactor for activating antithrombin, a protein that inactivates several factors in the coagulation cascade.
- Inflammation.[7] Endothelial cells actively signal to white blood cells of the immune system[8] during inflammation
- Formation of new blood vessels (angiogenesis).
- Constriction and enlargement of the blood vessel, called vasoconstriction and vasodilation, and hence the control of blood pressure
Blood vessel formation
The endothelium is involved in the formation of new blood vessels, called
The general outline of angiogenesis is
- activating signals binding to surface receptors of vascular endothelial cells.
- activated endothelial cells release proteases leading to the degradation of the basement membrane
- endothelial cells are freed to migrate from the existing blood vessels and begin to proliferate to form extensions towards the source of the angiogenic stimulus.
Host immune response
Endothelial cells express a variety of immune genes in an organ-specific manner.[12] These genes include critical immune mediators and proteins that facilitate cellular communication with hematopoietic immune cells.[13] Endothelial cells encode important features of the structural cell immune response in the epigenome and can therefore respond swiftly to immunological challenges. The contribution to host immunity by non-hematopoietic cells, such as endothelium, is called “structural immunity”.[14]
Clinical significance
Endothelial dysfunction is a result of changes in endothelial function.
One of the main mechanisms of endothelial dysfunction is the diminishing of
Angiosarcoma is cancer of the endothelium and is rare with only 300 cases per year in the US.[27] However it generally has poor prognosis with a five-year survival rate of 35%.[28]
Research
Endothelium in cancer
It has been recognised that endothelial cells building tumour vasculature have distinct morphological characteristics, different origin compared to physiological endothelium, and distinct molecular signature, which gives an opportunity for implementation of new biomarkers of tumour angiogenesis and could provide new anti-angiogenic druggable targets.[29]
Endothelium in diet
A
A Mediterranean diet has been found to improve endothelial function in adults which can reduce risk of cardiovascular disease.[32][33] Walnut consumption improves endothelial function.[34][35]
Endothelium in Covid-19
In April 2020, the presence of viral elements in endothelial cells of 3 patients who had died of
History
In 1958, A. S. Todd of the University of St Andrews demonstrated that endothelium in human blood vessels have fibrinolytic activity.[38][39]
See also
- Apelin
- Caveolae
- Cellular dewetting
- Endothelial activation
- Endothelial microparticle
- Endothelial progenitor cell
- Endothelium-derived relaxing factor (EDRF)
- Robert F. Furchgott (1998 Nobel prize for discovery of EDRF)
- Platelet activation
- Susac's syndrome
- Tunica intima
- VE-cadherin
- Weibel–Palade body
- Angiocrine growth factors
- Endothelial Cell Tropism
References
- ^ a b "Endothelium" at Dorland's Medical Dictionary
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- ^ "Endothelial cell". BioPortal. Stanford University. Archived from the original on 2013-10-02. Retrieved 2013-09-28.
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- ^ "Angiosarcoma - National Cancer Institute". www.cancer.gov. 2019-02-27. Retrieved 2021-08-10.
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External links
- Anatomy photo: Circulatory/vessels/capillaries1/capillaries3 - Comparative Organology at University of California, Davis, "Capillaries, non-fenestrated (EM, Low)"
- Histology image: 21402ooa – Histology Learning System at Boston University