In severe deoxygenation, NO-sensitive cells in the medulla oblongata respond to this release by increasing the rate and depth of breathing. The smooth muscle in the walls of the bronchioles is very sensitive to the concentration of carbon dioxide. A rising level of CO 2 causes the bronchioles to dilate. This lowers the resistance in the airways and thus increases the flow of air in and out. Diseases of the Lungs Pneumonia Pneumonia is an infection of the alveoli.
Tissue fluids accumulate in the alveoli reducing the surface area exposed to air.
If enough alveoli are affected, the patient may need supplemental oxygen. In asthma, periodic constriction of the bronchi and bronchioles makes it more difficult to breathe in and, especially, out. Attacks of asthma can be triggered by airborne irritants such as chemical fumes and cigarette smoke airborne particles to which the patient is allergic . Link to discussion of allergic asthma. In this disorder, the delicate walls of the alveoli break down, reducing the gas exchange area of the lungs.