What is endothelium?(Part 1)

Nature of endothelium

Endothelium is also called tunica intima, and it is the innermost layer of your artery and your other blood vessels {Refer to Powertec (146)}. As part of your artery,  you will surely arrive at a conclusion that its main function is to support your arterial wall. To some extent, it does, but it has other functions much more important than being support of your artery. This will be the center of discussion in this article.

Functions of endothelium

Aside from serving as the innermost lining of your artery, the endothelium has the following more important functions:

  1. Maintenance of the vascular tone. It produces the substance nitric oxide which is responsible for the dilation of your artery. It also produces endothelin and angiotensin II which are responsible for the constriction of your artery[1]. For all of these reasons, the endotheliumcontrols the diameter of your artery, increasing or decreasing it as needed. If there is a need to increase your blood pressure to a certain degree, then your endothelium increases it by effecting constriction of your arteries; if there is a need to lower it, then your endothelium will dilate your arteries. Your endothelium does this spontaneously without your knowing it and without waiting for you.
  2. Inhibition and stimulation of smooth muscle cell proliferation and migration[1]. The smooth muscle cells should be located at the right places. If their multiplication and migration are not controlled, then they will wreak havoc to your cardiovascular For this reason, the endothelium balances these two processes. If, however, your endothelium is being injured by an abnormality in your body, it may react spontaneously to allow the proliferation and migration of smooth muscle cells to protect itself.
  3. Inhibition and stimulation of thrombogenesis and fibrinolysis[1].Thrombogenesis refers to the formation of obstructions in your blood vessels, particularly in the arteries. Fibrinolysis, on the other hand, refers to the dissolution and dis-aggregation of possible obstructions.

From the foregoing discussion, it can be gleaned that if the endothelium is damaged, the balances that it does so that no opposing force will predominate will be damaged as well, and you will have a lot of problems.

Factors injurious to the endothelium

High blood pressure

Being the innermost lining of the artery, the endothelium takes the brunt of the flowing blood. If the blood pressure is very much elevated compared to the normal ranges, it will injure the endothelium, and this injury is the beginning of a process which will develop into atherosclerosis, then leading to hypertension {Refer to Powertec 146}.

High level of LDL-cholesterol

When the level of your LDL-cholesterol is very much above the normal ranges, it suppresses the endothelium to produce nitric oxide[1]—a substance whose one function is to dilate the blood vessels. In the absence of sufficient nitric oxide, your blood vessels, specifically the arteries, constrict leading to hypertension, which will, in turn, lead to the development of, or aggravate existing, atherosclerosis.

Ways of preventing injury to the endothelium

Control the high blood pressure

You should know your current blood pressure. You are very much negligent of your health if at this time you still do not know your current blood pressure! If your blood pressure is above the normal ranges, you need to consult a medical doctor so that you will be prescribed with the necessary medications. In addition, you will be requested to have blood and urine examinations whose results will provide your medical doctor with an idea on the severity of your medical condition. It is not enough that your blood pressure is controlled; in addition, other aggravating factors, such as abnormalities in your blood chemistry, need to be corrected, so that your hypertension will not get worse.

(To be continued)


  1. Davigon J, Ganz, Peter. Atherosclerosis: evolving vascular biology and clinical implications, role of endothelial dysfunction in atherosclerosis. Circulation. 2004;109: III-27-III-32. doi:10.1161/01.CIR. 0000131515.03336.f8.
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