Effective Gas Exchange

1.2 Conditions Needed For Effective Gas Exchange
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This essay is going to look at the conditions needed for gas exchange to happen effectively. Gas exchange is to do with the alveoli that are in the lungs, they have a large surface area and the average adult has around 600 million of them. The alveoli have one layer of flattened epithelial cells for its walls and this is the same with the walls of the capillaries. This then means that the gases only need to break through two thin cells. Water comes from the alveoli cells and then go into the alveoli itself this keeps it moist. The water causes the oxygen to dissolve, this happens before it diffuses through the cells into the blood, once the oxygen goes into the blood it then goes into the red blood cells, this is done by haemoglobin. The water consist of a substance called surfactant, the purpose of this is to reduce tension and to stop the alveoli collapsing, it is a soapy like substance. There is also something called phagocyte cells in the alveoli this is something that kills any bacteria that manages to get through the mucus. As the oxygen moves out of the alveoli up into the capillaries, the carbon dioxide moves from the capillaries into the alveoli ready to be exhaled