Inferior view of horizontal orbital part of frontal bone. There are two parts of the frontal bone. The larger vertically directed squamous portion forms the forehead and anterior part of the neurocranium, and the horizontal orbital part forms the roof of the orbit and ethmoid sinuses and most of the floor of the anterior cranial fossa. The junction of these two parts form the superior orbital margins. The supraorbital notch or foramen is located along this rim at the junction of its medial one-third and lateral two-thirds. It transmits the supraorbital neurovasculature from the orbit to the upper eyelid, forehead, and anterior scalp. The ethmoid notch is a rectangular-shaped space in the midline between the orbital plates of the frontal bone and receives the cribriform plate and orbital plates of the ethmoid bone. The roofs of the ethmoid air cells or sinuses are visible on the undersurface of the orbital plates of the frontal bone. The anterior part of the ethmoid notch is filled in by a stepped portion of the external nose, including the septal cartilage and lateral nasal cartilages. (Image courtesy of AL Rhoton, Jr.)