After branching off of the nasociliary nerve, the anterior ethmoidal nerve enters the anterior ethmoidal foramen and send sensory fibers to the middle and anterior ethmoidal air cells.
2.
They are partially closed, in front and below, by two thin, curved plates of bone, the sphenoidal conchae, leaving in the articulated skull a round opening at the upper part of each sinus by which it communicates with the upper and back part of the nasal cavity and occasionally with the posterior ethmoidal air cells.