alveolus

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One of the many thousands of tiny air sacs in the lungs. By the process of diffusion oxygen is transported from air in the alveoli into the blood, while carbon dioxide diffuses out of the blood and into the air in the alveoli. This process is called gas exchange. To aid this process, the alveoli have very thin walls, which are folded in order to increase their surface area and allow rapid gas exchange, and are surrounded by blood capillaries. The air in the alveoli is replenished as a result of breathing or ventilation. Smoking and exposure to other pollutants can cause the loss of the folds in the alveoli, which causes difficulties in breathing and the condition called emphysema.

Red represents the blood of Jesus. Effective date: c. 1862. >>