:: Section 2
In order to evaluate aerosol deposition, first we need to learn our respiratory system. The system is typically divided into three regions (from the viewpoint of respiratory deposition): Head Airways region, Lung Airways Region and Pulmonary Region.
The head airways region is also called extra thoracic or nasopharyngeal region, and it includes nose, mouth, pharynx and larynx. The lung airways region is also called tracheobronchial region, and it is from the trachea to the terminal bronchioles. In this region, the trachea subdivides into smaller and smaller branches just like an inverted tree. From the trachea to the alveolar surface, there are 23 airway branchings. The pulmonary region is also called alveolar region. This is where gas exchange takes place. If fully unfolded, the surface area for this gas exchange region is about 75m2, approximately half of a singles tennis court!
The following animation show the anatomy of our respiratory system.
Which region is more vulnerable to external materials?