 Next, we'll talk about pulmonology. Let's start out with some basic anatomy of the lungs. The first thing you see in this image is the conducting zone. The conducting zone are the large airways that consist of the nose, the pharynx, and then down further in the larynx, the trachea, and it branches off into the bronchi. The small airways consist of bronchioles that further divide into terminal bronchioles, as you see here. The purpose of the conducting zone is to warm, humidify, and filter the air that enters our respiratory system. It does not, however, participate in gas exchange. This is why we call this region the anatomic dead space. The conducting zone is made up of several different types of cells. First, cartilage and goblet cells extend from the beginning of the respiratory tract down to the end of the bronchi. After that, we have pseudo-stratified, ciliated columnar cells that will primarily make up the epithelium of the bronchus, and they extend to the beginning of the terminal bronchioles. At that point in time, then they will transition into cuboidal cells. The purpose of cilia in these cells is to clear out the mucus and the debris from the lungs. As we cough, and as we go about our normal respiratory function, that cilia and the mucus will pass any debris or any foreign bodies out of the small airways of the respiratory tract and bring it up so that we can cough it out. The respiratory zone is beyond the conducting zone and consists of respiratory bronchioles, alveolar ducts, and alveoli. This is going to be in the periphery of the lung and the very, very small airways that we see in those regions. This is where gas exchange occurs. Most of the time, these are made up of cuboidal cells, and specifically in the respiratory bronchioles, but we do get to simple squamous cells in the alveoli. The reason the alveoli are made up of simple squamous cells is because they participate in the gas exchange, which needs to occur on a very thin membrane. We do not have cilia in the alveoli. They terminate in the respiratory bronchioles. Any problems or foreign bodies that get as far down into the alveoli are cleared out by alveolar macrophages. We do not have cilia in the alveoli. They terminate in the respiratory bronchioles. The lack of cilia to clear out any foreign bodies or debris or dust deep in the lungs is the process and is the function of alveolar macrophages. These macrophages also will participate in immune response.