The perpendicular plate of ethmoid bone or lamina perpendicularis ossis ethmoidalis in Latin is a thin, flattened lamina that is quadrilateral in form. It descends from the horizontal cribriform plate to create the upper aspect of the nasal septum. It usually tends to deflect slightly away from the midline, and continues superior to this plate as the crista galli.
The ethmoid bone is a fragile bone that lies anterior to the cranial fossa and takes part in forming the medial walls of the orbit, the nasal septum, and the lateral walls and roof of the nasal cavity. It consists of a horizontal perforated cribriform plate, two lateral labyrinths containing ethmoid air cells, and a median perpendicular plate. The latter’s anterior border articulates with the nasal spine of the frontal bone as well as the nasal bones crests. Its posterior border articulates from above with the crest of the body of sphenoid, and with the vomer from below. Its thick inferior border attaches with the nasal septal cartilage. The perpendicular plate has smooth edges all in all, except from above. There, numerous grooves and canals lie. They transmit olfactory nerves filaments that lead to the medial foramina present in the cribriform plate.
In regards to ossification, the perpendicular plate begins to ossify from its median center during the first year, and then fuses with each of the labyrinths early during the second.
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