The perpendicular plate is a vertical sheet of bone situated deep within the facial skeleton and cranium. It is a central, thin partition whose primary purpose is to separate the body’s major air passages. This bony lamina functions as a dividing wall within the skull’s interior architecture.
Part of the Ethmoid Bone
The perpendicular plate is an upward extension of the ethmoid bone, a single, unpaired bone nestled deeply within the skull at the roof of the nasal cavity. The ethmoid bone is positioned between the two orbits, contributing to both the cranial base and the facial structure. The perpendicular plate descends from the horizontal cribriform plate, effectively bisecting the ethmoid bone vertically.
The ethmoid bone is complex, consisting of this vertical plate, the cribriform plate, and two lateral masses. It articulates with thirteen other bones, serving as a nexus point in the central facial skeleton.
Forming the Bony Nasal Septum
The perpendicular plate contributes to the bony nasal septum, the partition that divides the nasal cavity into distinct left and right chambers. It is a thin plate that descends vertically, forming the superior portion of this medial wall and the upper half of the bony scaffolding.
Inferiorly, the plate articulates with the vomer bone, which forms the posteroinferior part of the bony septum. Anteriorly, the lower edge connects with the septal cartilage, a flexible structure that forms the front part of the nose. This tripartite connection establishes the complete midline partition and rigid skeletal division of the nasal airway.
Defining Boundaries of the Nasal Cavity
The superior attachment of the perpendicular plate helps define the nasal cavity’s roof and its relationship to the braincase. It extends downward from the cribriform plate, the horizontal component of the ethmoid bone that separates the nasal cavity from the anterior cranial fossa.
The plate also articulates with several surrounding bones, establishing boundaries beyond the nasal septum. Its superior anterior border connects with the spine of the frontal bone and the crest of the nasal bones. Posteriorly, its upper half articulates with the sphenoidal crest of the sphenoid bone. This wide-ranging articulation stabilizes the central facial region and anchors the ethmoid bone complex within the skull.