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.
Arteries are thick walled,it is so because they carry blood with high pressure,so that the walls may not collapse.Veins are blue in color as the color of their impure blood. Their thickness is medium.On the other hand capillaries have very thin permeable walls because a lot of materials are transferred at their walls.he structures of arteries, capillaries, and veins are all different, because of their different functions. The only way that they are similar is because they are hollow, and â¦ have some elasticity.