PATHOLOGY

Detailed explanation-1: -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. They are so small that red blood cells need to flow through them single file.

Detailed explanation-2: -Capillaries are small, normally around 3-4µm, but some capillaries can be 30-40 µm in diameter. The largest capillaries are found in the liver. (capillar comes from the greek for hairlike).

Detailed explanation-3: -Explanation: Capillaries are one cell thick so that diffusion of gases and other substances like urea, nutrients, water, etc becomes easier.

Detailed explanation-4: -But other blood vessels, such as capillaries, are extremely small. They range from 2 to 12 micrometers, which is even less than the diameter of a human hair.