The Frontal Bone

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The frontal bone may be divided into two main portions, a vertical squamous portion which articulates with the paired parietals along the coronal suture and forms the forehead, and two orbital plates, which contribute to the ceiling and lateral walls of the left and right eye orbits. On the external surface the squamous portion frequently possesses a left and right frontal eminence. Additionally, the bone possesses two supra-orbital ridges (i.e., superciliary or brow ridges) which are bumps above each of the eye orbits. In early hominids these ridges formed a torus or large shelf-like process protruding from above the eyes. Associated with each superior orbital margin of the eye orbit the frontal bone may posses a supra-orbital notch or if completely surrounded by bone, a supra-orbital foramen. Above the fronto-nasal suture which allows articulation between the frontal and nasal bones there is generally a trace of the vertical metopic suture. In early life the metopic suture divided the frontal bone into left and right halfs. With in the bone, and above and the metopic suture, is the frontal sinus. The left and right frontal crest, begins at each zygomatic process of the frontal bone, and provides the anterior origin of the temporal line to which the left and right temporal muscle is attached.

Internally, the frontal bone possesses the median sagittal (i.e., sagittal-frontal) crest which separates the two frontal hemispheres of the brain.