PATHOLOGY

Detailed explanation-1: -Capillaries have walls only one endothelial cell thick, meaning their walls are very thin. This makes them well adapted for gas exchange, as substances only have to diffuse over a short distance.

Detailed explanation-2: -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-3: -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.