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Frontal Bone

The frontal bone is a large, unpaired bone that starts out developmentally as two halves that fuse together, along the metopic suture. The frontal bone articulates with the right and left parietal bones, the zygomatic bones, the sphenoid bone, the ethmoid bones, lacrimal bones, maxillary bones, and the nasal bones. The frontal bone is made up of three parts: the squamous, orbital and nasal parts. The squamous portion is the largest and smoothest. On either side of the midline are two rounded elevations, called the frontal eminences.  Beneath these are two superciliary arches joined in the middle by the glabella. Laterally, the supraorbital margins form the orbital rim and contain the supraorbital notch which transmits the supraorbital vessels and nerves.

Inferior to the glabella lie the nasal notch and spine, which articulate with the nasal bones and the perpendicular plate of the ethmoid. The cranial surface of the squamous portion of the frontal bone contains the sagittal sulcus, in which the sagittal venous sinus resides. The edges of the sulcus extend inferiorly to form the frontal crest, to which the falx cerebri attaches. The orbital portion of the frontal bone is formed by two orbital plates joined by the ethmoidal notch, which is filled by the cribriform plate of the ethmoid. The inferior surface of each orbital plate contains a small depression under the zygomatic process called the lacrimal fossa. The orbital portion of the frontal bone contains the frontal sinuses and the frontonasal ducts