PATHOLOGY

Detailed explanation-1: -Capillaries are the connection of the smallest branches of arteries and veins. The capillary walls are one cell thick. Capillaries allow molecules to pass through across the capillary walls. This exchange of materials is not possible across the walls of other types of blood vessels because the walls are too thick.

Detailed explanation-2: -Explanation: Capillaries are one cell thick so that diffusion of gases and other substances like urea, nutrients, water, etc becomes easier.

Detailed explanation-3: -Capillaries are tiny, extremely thin-walled vessels that act as a bridge between arteries (which carry blood away from the heart) and veins (which carry blood back to the heart).