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 cannot compensate 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 from 6 weeks to 6 months of age.
The first sign of nasal development occurs at about 3 to 4 weeks
of fetal life.1 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. 370-1). 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 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 (lettering 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 ...