How are Capillaries made and adapted?

They come from the Arterioles branches which make them really small. In tissues, the network of those capillaries are called capillary beds. They carry the blood really close to each cell to exchange materials [eg Oxygen for Carbon Dioxide] Capillaries have permeable walls, which allows diffusion They are one cell thick, which increases massively the ratio for surface area to volume. They can be branched to Venules.