The anatomy and histology of the nasal cavity of the koala (Phascolarctos cinereus).

The anatomy of the nose of the koala was studied from fixed 0.5 cm thick sections of a whole head. Right and left nasal cavities are separated by a slender septum which does not exhibit 'swell bodies'. Dorsal and ventral conchae are simple curved plates without elaborate scrolls; the ventral concha is recurved to form a bulla. The nasal cavity communicates with confluent rostral maxillary and frontal air sinuses. A ventrocaudal maxillary sinus opens from the ventral meatus close to the choanae. There is a frontal sinus dorsocaudal to the ethmoid region which does not communicate with the nasal cavity. Nasal and oral cavities communicate via incisive ducts, opening just rostral to the vomeronasal ducts. The vomeronasal organ extends from the level of the fourth incisor to the first cheek tooth. The histology of the nasal area was examined by light and electron microscopy. Stratified squamous epithelium extends from the external nares to the incisive duct; nerve endings are frequent in association with its basal cells. Respiratory epithelium lines the nasal cavity proper, olfactory epithelium covers the ethmoturbinate bones, caudal dorsa concha and caudal septum, and sensory epithelium lines the medial aspect of the vomeronasal organ. Nasal secretions are provided by goblet cells and conchal and septal glands in respiratory areas, and by Bowman's and vomeronasal glands in the sensory areas. There are no lateral nasal glands, maxillary sinus glands or swell body glands.