The squamous part of the frontal bone is the superior (approximately two thirds) portion when viewed in standard anatomical orientation. There are two surfaces of the squamous part of the frontal bone: the external surface, and the internal surface.
The external surface is convex and usually exhibits, in the lower part of the middle line, the remains of the frontal suture
; in infancy this suture divides the frontal bone into two and later fuses. A condition where fusion has not taken place, may persist throughout life and is referred to as a ''metopic suture''.
On either side of this suture, about 3 cm. above the supraorbital margin, is a rounded elevation, the frontal eminence
These eminences vary in size in different individuals, are occasionally unsymmetrical, and are especially prominent in young skulls; the surface of the bone above them is smooth, and covered by the
The epicranial aponeurosis (aponeurosis epicranialis, galea aponeurotica) is an aponeurosis (a tough layer of dense fibrous tissue). It covers the upper part of the skull in humans and many other animals.
In humans, the epicrania ...
Below the frontal eminences, and separated from them by a shallow groove, are two arched elevations, the superciliary arches
; these are prominent medially
, and are joined to one another by a smooth elevation named the glabella
. They are larger in the male than in the female, and their degree of prominence depends to some extent on the size of the frontal air sinuses
; prominent ridges are, however, occasionally associated with small air sinuses.
Beneath each superciliary arch is a curved and prominent margin, the supraorbital margin
, which forms the upper boundary of the base of the
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a ...
, and separates the squamous part from the orbital portion of the bone.
The lateral part of this margin is sharp and prominent, affording to the eye, in that situation, considerable protection from injury; the medial part is rounded.
At the junction of its medial and intermediate thirds is a notch, sometimes converted into a foramen
, the supraorbital notch
or foramen, which transmits the supraorbital vessels and nerve.
A small aperture in the upper part of the notch transmits a vein from the diploë
to join the supraorbital vein
The supraorbital margin ends laterally in the
The zygomatic processes are three processes (protrusions) from other bones of the skull which each articulate with the zygomatic bone. The three processes are:
* Zygomatic process of frontal bone from the frontal bone
* Zygomatic process of ...
, which is strong and prominent, and articulates with the
In the human skull, the zygomatic bone (from grc, ζῠγόν, zugón, yoke), also called cheekbone or malar bone, is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. It is ...
Running upward and backward from this process is a well-marked line, the
The parietal bones () are two bones in the skull which, when joined at a fibrous joint, form the sides and roof of the cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is nam ...
, which divides into the upper and lower temporal lines, continuous, in the articulated skull, with the corresponding lines on the parietal bone.
The area below and behind the temporal line forms the anterior part of the
The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines and terminating below the level of the zygomatic arch.
* Medial: frontal bone, parietal bone, temporal bone, and sphenoid ...
, and gives origin to the temporalis muscle
Between the supraorbital margins the squamous part projects downward to a level below that of the zygomatic processes. It meets the nasal bone
where it presents a rough, uneven serrated notch known as the
The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, part ...
, and this articulates on either side of the middle line with the nasal bone, and laterally with the
frontal process of the maxilla
The frontal process of maxilla is a strong plate, which projects upward, medialward, and backward from the maxilla, forming part of the lateral boundary of the nose.
Its ''lateral surface'' is smooth, continuous with the anterior surface of the b ...
and with the lacrimal
. This part is sometimes called the nasal part of frontal bone
The term nasion
is applied to the middle of the frontonasal suture. From the center of the notch the nasal process projects downward and forward beneath the nasal bones and frontal processes of the
The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The ...
e, and supports the bridge of the nose.
The nasal process ends below in a sharp spine, and on either side of this is a small grooved surface which enters into the formation of the roof of the corresponding nasal cavity.
The spine forms part of the
In biology, a septum ( Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate.
* Interat ...
of the nose, articulating in front with the crest of the nasal bones and behind with the perpendicular plate of the ethmoid
The internal surface of the squamous part is concave and presents in the upper part of the middle line a vertical groove, the sagittal sulcus
, the edges of which unite below to form a ridge, the frontal crest; the sulcus
lodges the superior sagittal sinus, while its margins and the crest afford attachment to the
The falx cerebri (also known as the cerebral falx) is a large, crescent-shaped fold of dura mater that descends vertically into the longitudinal fissure between the cerebral hemispheres of the human brain,Saladin K. "Anatomy & Physiology: The U ...
The crest ends below in a small notch which is converted into a foramen, the foramen cecum
, by articulation with the ethmoid
This foramen varies in size in different subjects, and is frequently impervious; when open, it transmits a vein from the nose to the superior sagittal sinus
On either side of the middle line the bone presents depressions for the convolutions of the brain, and numerous small furrows for the anterior branches of the middle meningeal vessels.
Several small, irregular fossæ may also be seen on either side of the sagittal sulcus
, for the reception of the arachnoid granulations
Bones of the head and neck