The epithelial lining of the gas exchange system is adapted to provide defence against pathogens. List the structures in the gas exchange system that possess a ciliated epithelial lining.
Identify the cells in ciliated epithelium that synthesise and release mucus.
Pneumonia, an infectious disease of the lungs, may be caused by Streptococcus pneumoniae. Most healthy people who inhale air containing these bacteria do not become ill because alveolar macrophages act on them. Outline the mode of action of an alveolar macrophage when S. pneumoniae is present.
Irritants in tobacco smoke can contribute to emphysema, one of the chronic obstructive pulmonary disorders (COPD). In emphysema, the alveoli lose their recoil on expiration and can burst. Suggest how the structure of the alveolar wall changes so that an alveolus bursts.
Some alveolar cells produce a surfactant that helps prevent collapse of the alveoli on exhalation. Too much surfactant reduces the efficiency of gas exchange in the alveoli. A glycoprotein called GM-CSF is released by some cells of the immune system when there is too much surfactant in the alveoli. Excess surfactant is then broken down by alveolar macrophages. Receptors for GM-CSF are found on the cell surface membranes of alveolar macrophages. Explain how maintaining the correct amount of surfactant in the alveoli is the outcome of a cell signalling mechanism.