Frontal Bone Markings.
The frontal bone (os frontale) is the cranial bone that surrounds the anterior portion of brain.
It is divided into vertical and horizontal parts. The vertical or squamous part (squama frontalis) is a broad, flattened extension that forms the forehead.
The horizontal or orbital part (pars orbitalis) consists of two plates that form the roofs of the orbits and nasal caivities.
a. Superciliary arch or supraorbital ridge (arcus superciliaris frontalis) is a smooth, arched, elevation above the orbit, which forms the eyebrow ridge.
b. Glabella (glabella frontalis) is a smooth prominence located above the nasal bones (or nose) and between the superciliary arches (or eyebrow ridges).
c. Supraorbital notch or foramen (incisura supraorbitalis frontalis; foramen supraorbitae frontalis) is a notch or small hole located along the superior margin of the orbit. It serves as a passageway for the supraorbital vessels and nerve.
d. Orbital surface or plate (facies orbitalis frontalis) is a horizontal extension that forms the roof of the orbit and nasal cavity.
e. Zygomatic process (processus zygomaticus frontalis) is an inferior extension of the squamous part of the frontal bone that joins with the frontal process of the zygomatic bone.
f. Frontal sinus (sinus frontalis) is a large cavity located above the orbit and deep to the superciliary arch. The cavity secretes mucous into the nasal cavity, lightens the skull, and resonates the voice.