They can only bee seen under a microscope. Capillaries connect the smallest arteris with the smalest vaines. They make up a complete network of blood vessels through all parts of the body. The largest capillaries are in the bone marrow. The smallest capillaries are in the brain and lining of the intestine.
Capillaries have thin walls.
Food which are carried in the blood strem are able to pass through thier walls into the tissues. Waste materials from the tissues also pass through capillaries . In the capillaries of the lungs, oxygen goes though the walls into the heart, and carbon dioxide goes out though the capillaries back into the lunges befor you exhale. Other waste products pass through tiny capillaries into the kidneys, intestine, and skin. This concludes my report on the capillaries .