Lungs allow rapid gas exchange between the atmosphere and the blood. Air is drawn into the lungs via the trachea due to low pressure in the lungs, created by the movement of the ribs and diaphragm. The trachea divided into two bronchi which carry air to and from each lung. Within each lung there is a tree-like system of tubes ending in narrow tubes, bronchioles, attached to tiny balloon-like alveoli. The alveoli are the sites of gas exchange.
Everyone normally has a thin coating of mucus in these tubes, produced continuously from goblet cells in the walls of the airways. Any dust, debris or microorganisms that enter the airways become trapped in the mucus. This is continually removed by the wave-like beating of cilia that cover the epithelial cells lining the tubes of the gas exchange system. However, people with CF, have mucus that is drier than usual resulting in a sticky mucus layer that the cilia find difficult to move.
This sticky mucus in the lungs has two major effects on health, It increases the chances of lung infection and it makes as exchange less efficient, particularly in the later stages of the disease.
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