Let us now move on and discuss
some of these bones in more detail.
The first bone that we will
discuss is the frontal bone.
The frontal bone is the anteriormost
bone of a neural cranium.
It is shell shaped and corresponds
to the first frontal region of the face
more commonly known as the forehead or the fronts.
Additionally, the frontal bone is said to
have several different surfaces or parts,
the orbital, the nasal, the squamous and
although technically part of the squamous surface,
we can also differentiate the zygomatic process.
The squamous part is the
largest surface of the frontal bone.
This is specifically the portion
that corresponds to the forehead.
There are several important bony landmarks
located on the squamous surface of the frontal bone.
The first of which is the frontal tuber or tuberosity.
This landmark is located bilaterally
approximately three centimeters above the eyebrow
and it is a moderate prominence to which
muscles and connective tissues can attach.
Below the frontal tubers and
separated by a shallow groove
are located two curved elevations
known as the superciliary arches.
The superciliary arches are medially
prominent inner joined together
at the median elevated cranial
metric point known as the glabella.
As a side note in certain individuals, a persistent
line or suture extending from the glabella superiorly
can be seen on radiographs.
This line represents the fusion side
of the frontal bones embryologically
and if present, it is referred
to as the metopic suture.
Below this arch is located the supraorbital margin.
The margin acts as a boundary between the
squamous and the orbital surfaces of the frontal lobe.
On the medial end of this margin
is located a supraorbital foramen
which permits the passage of
the supraorbital nerve and vessels.
Medial to this foramen lies the
frontal notch which can only be found in
approximately 50% of skulls and permits the
passage of the supratrochlear nerve and vessels.
And lastly for this sectio,n let's discuss the
articulations of the squamous part of the frontal bone.
First, the lateral end of the
supraorbital margin tapers sharply.
It ends in a prominent zygomatic process
that articulates with the frontal process
of the zygomatic bone.
Also from the zygomatic process,
a curved posterosuperior line
arises which divides into
superior and inferior temporal lines.
What more, the area inferior to these lines is
known as the temporal surface of the frontal bone,
and it contributes to the formation of
the anterior part of the temporal fossa.
Second, the posterior margin which
articulates with the paired parietal bones,
and then third, the inferior margin that
articulates with the greater wing of the sphenoid.
And now we come to the last part
of the frontal bone, the orbital part.
There are two landmarks in the orbital
surface of the frontal bone that are of importance.
First of them is the fossa for the lacrimal gland.
This fossa is located on the anterolateral margin,
the orbital plate and houses the lacrimal gland.
Second is the trochlear fovea.
This landmark is located on the
anteromedial margin the orbital plate.
The trochlear fovea marks the
attachment of the fibrocartilaginous trochlea
through which the tendon of the
superior oblique muscle passes.
Furthermore, another point to
remember for future lectures is that
the orbital part of the frontal bone makes a
major contribution to the formation of the interior wall
of the anterior cranial fossa.
But more on that in future lectures