1. Recognize major parts of the respiratory track: trachea, bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar duct, and alveoli.
2. Understand the blood-air interface in the alveolus and know the function of the type 1 and 2 pneumocyte and alveolar macrophage.
The respiratory system functions in the exchange of gases between the external and internal environments. Major parts of the system include the nasal cavity, larynx, trachea, bronchi, and pulmonary alveoli. Some regions of the respiratory system are specialized for conduction of gases and other areas of the system function primarily in the exchange of gases. In both regions mechanisms exist to filter the gases. The function of each part of the respiratory system is reflected in the structure of its wall: the type of epithelium and its apical modifications, intraepithelial and subepithelial glands, cartilaginous rings and plates, smooth muscle and elastic tissue, and the relationship of capillary endothelium to alveolar epithelium.
|Trachea||Cartilage rings, pseudostratified ciliated epithelium with goblet cells, glands in submucosa|
|Bronchi ciliated||Plates of cartilage, smooth muscle, pseudostratified epithelium with goblet cells, glands may be present|
|larger bronchioles||Pseudostratified ciliated epithelium with goblet cells|
|smaller bronchioles||Simple columnar or cuboidal, ciliated epithelium|
|terminal bronchioles||Simple cuboidal ciliated epithelium with nonciliated Clara cells|
|Respiratory bronchioles||Alveoli form outpocketings from walls of bronchiole, smooth muscle in nonrespiratory portions of walls|
|initial segment||Both ciliated and Clara cells|
|distal segment||Clara cells predominate|
|Alveolar ducts and alveoli||Squamous epithelium (type I pneumocytes), surfactant cells (type II pneumocytes), macrophages|