ANATOMY

Detailed explanation-1: -During gas exchange oxygen moves from the lungs to the bloodstream. At the same time carbon dioxide passes from the blood to the lungs. This happens in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli.

Detailed explanation-2: -Capillaries are so tiny that we can only see them with a microscope-they are thinner than a hair and smaller than a dot on a piece of paper.

Detailed explanation-3: -Arterioles carry blood and oxygen into the smallest blood vessels, the capillaries. Capillaries are so small they can only be seen under a microscope. The walls of the capillaries are permeable to oxygen and carbon dioxide.

Detailed explanation-4: -Because of their small size, the capillaries are sometimes called the microcirculation. They are also called the exchange vessels, because the exchange of water and solutes between the bloodstream and the interstitial fluid takes place across the walls of the capillaries.

Detailed explanation-5: -Capillaries-these are the sites of gas exchange between the tissues.