Atelectasis (/ËÃ¦táµ»ËlÉktÉsáµ»s/ uses combining forms of atel- + ectasis, from Greek: á¼ÏÎµÎ»Î®Ï, incomplete + á¼ÎºÏÎ±ÏÎ¹Ï, extension) is the collapse or closure of a lung resulting in reduced or absent gas exchange.
A single capillary is so small that it allows only one blood cell to flow through it at a time. The capillary walls are also very small, only one cell thick. These thin walls easily allow water, oxygen, carbon dioxide, and other nutrient and waste substances to exchange between blood cells and the surrounding tissue.
Science Videos. Science Main Index. Capillaries are the smallest blood vessels in the body. They allow water, oxygen, carbon dioxide, and other nutrient and waste substances to exchange between blood and surrounding tissues. Read on to learn more about capillaries, and what they do in your body.cience Videos. Science Main Index. Capillaries are the smallest blood vessels in the body. They allow water, oxygen, carbon dioxide, and other nutrient and waste substances to exchange between blood and surrounding tissues. Read on to learn more about capillaries, and what they do in your body.