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.
For other uses, see Capillary (disambiguation). Capillaries (/ËkÃ¦páµ»lÉriz/ in US; /kÉËpÉªlÉriz/ in UK) are the smallest of a body's blood vessels (and lymph vessels) that make up the microcirculation. Their endothelial linings are only one cell layer thick.