Ethmoidal notch

The ethmoidal notch of the frontal bone is a quadrilateral-shaped, midline gap located on the inferior surface of the frontal bone, separating its two orbital plates. When the frontal bone is joined with the ethmoid bone beneath it, the cribriform plate of the ethmoidal bone slots into this ethmoidal notch. This plate forms the roof of the nasal cavity and allows the olfactory nerve fibers to pass through.

The ethmoid bone, which is a single bone, has ethmoidal air cells along its edges. These thick edges make up the side walls of the nasal cavities or the inner walls of the eye sockets. Now, near the edges of the ethmoidal notch, thin strips of the orbital plate on both sides extend over the ethmoidal sides, creating a roof over the ethmoidal air cells within the ethmoid bone.

Two transverse grooves cross the edges of the ethmoidal notch. When bony notch connects with the ethmoid bone, these grooves become the anterior and posterior ethmoidal canals. The outer ends of these canals open into the medial wall of the eye socket, while the inner ends open into the anterior cranial fossa, at the border of the cribriform plate and ethmoidal notch of the frontal bone. The anterior canal carries the nasociliary nerve and anterior ethmoidal vessels, while the posterior canal transports the posterior ethmoidal nerve and vessels.