Endothelial cells are the only structure found in all parts of the circulatory system.
a. true
b. false

a. True

Explanation:

Endothelial cells

These cells are found in all the parts of the circulatory system , these are about a cell thick , and composes a wall known as the edothelium , which lines all the blood vessels , i.e. , the arterioles , veins , capillaries , arteries , venules .

Beneath the endothelial cells , there is a layer of smooth muscle cells .

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