Epithelium: Starts as “respiratory epithelium” in the nose (pseudostratified columnar ciliated epithelium with goblet cells) and loses its complexity to become simple squamous cells in the alveoli to allow for free gas exchange.
Larynx: respiratory epithelium
Note: Epithelium on true vocal cords is stratified squamous for toughness to abrasion and dessication
Trachea: respiratory epithelium
Bronchi: respiratory epithelium
Bronchioles: simple columnar to simple cuboidal ciliated
Glands: Goblet cells secrete mucus which is used to line the upper airways and prevent infections/dessication; would inhibit gas exchange in the conduction zone and are therefore not needed (macrophages live in the alveoli to kill pathogens). Seromucous glands are primarily concerned with keeping serous membranes lubricated so that potential space is maintained for regular expansion/contraction.
Larynx: goblet cells and seromucous glands
2. Clara cells: these cells are simple cuboidal cells found in the epithelia of interpulmonary bronchioles and terminal bronchioles. Their function is still unknown, but it is thought that they are important in detoxifying gases (by secreting CCSP).
3. Surfactant: surfactant is made by type II pneumocytes in the alveoli of the lungs. The function of surfactant is to reduce surface tension of water covering alveoli and also to keep alveoli from sticking to each other. Lack of surfactant causes respiratory distress syndrome in the newborn, the largest cause of premature birth death in the US.
Note: Survanta is an inhaled drug made of bovine lung extract that is used to keep surfactant on alveoli until premature babies can produce their own