The endothelium is a single layer of cells called endothelial cells that line all blood vessels and lymphatic vessels in the body. It forms the inner cellular lining of the blood vessels (arteries, veins, and capillaries) and the lymphatic system, making direct contact with the blood/lymph and the circulating cells. The endothelium is considered one of the largest organs in the body and is vital to the functioning of all organs and tissues.
The main functions of the endothelium include:
- Control of blood fluidity, platelet aggregation, and vascular tone: Endothelial cells synthesize and release substances that regulate blood flow, such as nitric oxide, metabolites of arachidonic acid, various peptides, adenosine, purines, and reactive oxygen species.
- Regulation of immunology, inflammation, and angiogenesis: The endothelium plays a role in the immune response, inflammation, and the formation of new blood vessels.
- Metabolism and endocrine function: Endothelial cells are involved in the metabolism of various substances and the production of vasoactive hormones, such as angiotensin II.
- Maintenance of vascular integrity and permeability: The endothelium forms a barrier between the bloodstream and the surrounding tissues, controlling the passage of materials and the transit of white blood cells.
- Endothelial dysfunction: Impaired endothelial function can lead to serious health issues throughout the body, including cardiovascular diseases, stroke, and atherosclerosis.
