The bridge of the nose, formally known as the dorsum nasi, is the rigid, prominent structure extending from the area between the eyes down to the midpoint. This structure provides foundational support for the entire external nose, defining its profile and contour. The firm quality of the nasal bridge is due to its composition, which is entirely skeletal in its upper portion. This bony framework protects the underlying nasal cavity and anchors the nose to the rest of the facial skeleton. Understanding its composition is key to grasping how the nose maintains its shape and how it can be affected by trauma.
The Primary Skeletal Components of the Bridge
The composition of the nasal bridge centers on a pair of small, oblong elements called the nasal bones. These two bones are situated side-by-side at the upper and middle part of the face, where they meet to form the roof of the nasal cavity. They are the principal components that create the distinct structural prominence recognized as the bridge of the nose.
The two nasal bones join together along the midline of the face at a connection point known as the internasal suture. This articulation creates a protective, saddle-shaped bony vault that forms the hard, superior third of the external nose. Their outer surface is convex from side to side, giving the bridge its rounded appearance before it transitions into the supporting structures. The size and shape of these bones vary considerably among individuals, contributing to the wide range of nasal profiles seen across the population.
Supporting Structures and Boundaries
While the nasal bones form the immediate bridge, several other bones articulate with them to anchor this structure firmly to the skull, defining its boundaries. At the superior end, the bridge connects directly to the largest bone of the forehead, the frontal bone. This junction, where the nasal bones meet the frontal bone, is a key landmark known as the nasion, which marks the highest point of the bony nasal structure.
Laterally, the nasal bones articulate with the frontal processes of the maxilla, which are the upward-projecting plates of the upper jawbone. These processes extend superiorly alongside the nasal bones, providing strong lateral support and forming the sides of the bony vault. This connection ensures the bridge is fully integrated into the midface skeleton. Furthermore, the Perpendicular Plate of the Ethmoid bone, an internal structure, extends downward from the skull base to form the upper portion of the nasal septum. This internal plate articulates with the nasal bones from beneath, offering crucial central support that reinforces the structural stability of the bridge.
Distinguishing Bone from Cartilage
The rigid, unyielding feel of the upper nose contrasts sharply with the flexible nature of the lower nose, a difference explained by the transition from bone to cartilage. The nasal bones only form the superior third of the external nose, meaning the remaining two-thirds are supported by a complex arrangement of flexible cartilage. This distinction is particularly relevant because the bony bridge is prone to fracture, while the lower cartilaginous portion is more likely to bend or deform upon impact.
Cartilaginous Support
Immediately inferior to the nasal bones, the framework is continued by the paired lateral nasal cartilages. These are flat, wing-like pieces of hyaline cartilage that connect to the underside of the nasal bones and contribute to the middle third of the nose. The central support is provided by the septal cartilage, a flat, quadrilateral sheet that separates the two nasal passages. The flexibility of the lower nose, which includes the nostrils and the tip, is due to the presence of the greater alar cartilages. These cartilages are positioned below the lateral nasal cartilages and are responsible for shaping the nasal tip and the openings of the nostrils.