PATHOLOGY

Detailed explanation-1: -One cell thick vessels are the blood vessels that join arteries and veins are the tiniest and most abundant blood vessels, called capillaries. They primarily serve the purpose of exchanging materials between the blood and tissue cells.

Detailed explanation-2: -Endothelial cells form a single cell layer that lines all blood vessels and regulates exchanges between the bloodstream and the surrounding tissues. Signals from endothelial cells organize the growth and development of connective tissue cells that form the surrounding layers of the blood-vessel wall.

Detailed explanation-3: -Capillary Structure. Capillaries are very thin, approximately 5 micrometers in diameter and composed of only two layers of cells. The inner layer is made up of endothelial cells with an outer layer of epithelial cells.