The nose is the major portal of air exchange between the internal and external environment. Nasal functions include warming, lubricating, humidifying, filtering, stimulating, and regulating airflow. The roof of the nose also contains olfactory epithelium. In humans, the sense of smell contributes to the perception of taste, warns of impending hazards, and affects social interactions.
The nose is the preferred primary route of breathing. Many infants are obligate nose breathers and have difficulty compensating by oral breathing if their nose is obstructed. Occlusion of the nose in such an infant may cause serious airway difficulties. This characteristic generally persists until 6 months of age.
The first sign of nasal development occurs at about 3 to 4 weeks of fetal life. It begins with nasal pits forming on the developing face that then invaginate to form the nasal sacs. The oronasal membrane separates the nasal sacs from the primitive oral cavity. The primitive nasal choanae communicate with the oral cavity when the membrane ruptures during the eighth week of gestation. As the membranous nasal cavities develop, neural crest cells migrate from the anterior skull base and proliferate in the facial processes to form the bony/cartilaginous skull base and nasal vaults, which are completely formed by the end of the 10th week.
The upper third of the nose is supported by paired nasal bones and the frontal process of the maxilla. The middle third of the nose is supported by upper lateral cartilages attached to the undersurface of the nasal bones. The lower third of the nose is supported by lower lateral cartilages. Within the nose, paired inferior, middle, and superior turbinates arise primarily from the lateral nasal walls. The area of drainage below each turbinate is the respective meatus (Fig. 365-1). The turbinates are highly vascular structures that play a primary role in humidifying, warming, and filtering airflow. The nasal valve is the narrowest portion of the nasal passage and is located inside the anterior aspect of the nose. The valve helps control nasal airflow and affects the subjective sensation of the adequacy of nasal airflow. In neonates, as much as half of the total airway resistance occurs in the nose, and small amounts of additional obstruction can substantially affect airway patency.
Internal nasal anatomy and sinus development. A: Coronal view representing the middle of the nose, demonstrating the developmental stages of the maxillary (lettered in red) and frontal (lettered in blue) sinuses. B: Sagittal view of the lateral nasal wall, demonstrating the ethmoid sinuses, the developmental stages of the sphenoid sinus (lettered in green), and the ostium of the maxillary sinus. Ethmoidal cells are a contiguous honeycomb, located lateral to the lateral wall of the nose with multiple ostium. The roof of the nasal cavity separates the nasal ...