The nasal cavities are paired chambers that function to filter, warm, and humidify inspired air. Vibrissae (short, stiff hairs) and mucous secretions trap inhaled particulate matter that is then swept by the action of the ciliated respiratory epithelium away from the respiratory passages. Blood-filled venules in the respiratory mucosa help warm the inspired air, and glandular secretions help moisten it.

• Examine the nasal cavities in this slide of fetal mouse head. Note their division by the nasal septum and the projecting turbinates (conchae), which protrude into the cavities and serve to increase surface area and air turbulence.
• In the nasal mucosa covering the cartilage, identify the following features: pseudostratified columnar, ciliated epithelium and venules and serous-mucous glands in the underlying CT. At the dorsal surface of the nasal cavities, the lining epithelium is modified as olfactory epithelium. However, it does not yet appear to be fully differentiated in this fetal tissue.
• Next, examine this sample of olfactory epithelium. Note the thick pseudostratified columnar, ciliated olfactory epithelium. This epithelium contains containing olfactory neurons, containing olfactory receptors that transmit the sense of smell. Identify Bowman’s olfactory glands, nerve tissue, and blood vessels in the olfactory mucosa. Compare it to the respiratory epithelium, which is also present in this slide and seen below.

Next is the larynx.