So I just looked this up in a few of my texts (robins, big picture histology, etc). Found the following. Goblet cells are replaced in the later bronchiole by clara/club cells (non-ciliated bronchiolar secretory cells), tall dome-shaped cells containing secretary granules, which are unique to bronchioles. They secrete stuff that is protective of the bronchiolar epithelium and reduce the viscosity of surface mucus, degrade airborne toxins, and divid to regenerate ciliated and nonciliated cell of the bronchiolar epithelium. These continue down to the respiratory bronchioles. In the alveoli there are the following cells: 1. type I pneumocytes: these are super thin flattened cells. they present 10% of the cells in the lung but they cover about 97% of the surface. they are connected by tight junctions. They are squamous cells. 2. Type II pneumocytes- large cuboidal cells that secret surfactant. they have the multilamellar bodies. they cover 3-5% of the alveolar surface. they also divide and regenerate the type I pneumocytes. 3. alveolar macrophages: not part of the epithelium per se. they are derived of course from monocytes in the blood and are the most numerous cell in the lung. they are known as dust cells, because they trap inhaled particulates. they eventually migrate or are washed to bronchioles where they adhere to mucus and are carried to the mouth for disposal. There are multiple recent articles confirming that in fact "club cells" are the same as "clara cells." Name was changed as mentioned earlier because Clara was a Nazi and thus the name was changed to club cells. Hopefully that helps. As a clinical correlate in the flu the club cells have tryptase which can cleave the hemagluttinin of influenza A and activate allowing it to cause sx's and such.
