ABSTRACT
The lungs are the site of gaseous exchange, enabling delivery of oxygen to the blood and removal of carbon dioxide from it. To efficiently perform this function, the lungs are connected to the outside environment via the trachea, mouth and nose. Because of this direct connection to the external environment, mechanisms are needed to help remove inhaled particles such as toxins and pathogens. One such mechanism is the trapping of particles within the protective mucus layer that sits above the airway epithelium. The co-ordinated beating of multiple motile cilia in the airways enables directed flow of mucus away from the lower regions of the lungs and up towards the mouth and nose, from where it can be safely removed. In addition to the important role played by motile cilia, cells in the lungs also contain non-motile, primary cilia. Currently, much less is known about the role of primary cilia in the lungs, though evidence is beginning to emerge. Here we describe the cellular structure of the lungs with an emphasis on the development of primary (non-motile) and motile cilia. We also consider the relationships between cilia and lung disease, when cilia structure/function is directly affected for example as occurs in primary ciliary dyskinesia and also when cilia are indirectly impaired for example in asthma or cystic fibrosis.
