Inferior view of the frontal bone. The frontal bone is derived from neural crest cells and develops via intramembranous ossification into two pieces that are separated by the frontal or metopic suture and anterior fontanelle. This midline suture extends from the nasion to the bregma and fuses during infancy and is usually obliterated by about 7 years of age to form a single 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 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 receives the cribriform plate of the ethmoid bone and the adjacent portions of the frontal bone form the roof of the ethmoid air cells or sinuses. (Image courtesy of AL Rhoton, Jr.)