By Elizabeth A. Murray, Mount St. Joseph University
The teaching of gross anatomy has long relied on the dissection of humans and other animals. But for now we will focus on the Anatomage software system; a technology that can be referred to as a virtual autopsy table. This software was initially based upon data gathered by the Visible Human Project through the University of Colorado School of Medicine.
Bones of the Brain Case
Taking the cadaver down to the bones, let’s start with the skull. There are eight bones of the brain case–the frontal bone, and laterally the parietal bone, the temporal bone, and between all of those there is sphenoid bone.
Posteriorly, there is occipital bone, then there is the opposite side parietal bone, the temporal bone on this side and back to that sphenoid bone. But that’s only seven bones. The ethmoid bone, the final bone of the cranial region, can be seen inside the skull.
Sutures of the Skull
The sutures of the skull are the joints between individual skull bones. So, if we tilt down, we can see the coronal suture between the frontal bone and the two parietal bones. If we continue to tilt, we can see the sagittal suture on the midline between the two parietal bones.
If we want a bird’s-eye view of that, we can go to the top of the skull, and we can see the sagittal suture between the two parietal bones, the coronal suture between the parietal bones and the frontal bone, and if we tilt posteriorly, we can see the lambdoid suture or lambdoidal suture between the occipital bone and the two paired parietal bones.
And the pterion is not a precise spot, it’s more of a four corners region, where the temporal bone, the parietal bone, the frontal bone, and the sphenoid bone all converge. So, it’s a region of the thinnest area of bone in the skull.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Facial Bones
Out of the 14 bones of the facial region, two are unpaired and the rest are all paired bones.
The obvious mandible, the lower jaw, is a singular bone that has an alveolar ridge that houses the lower teeth. And here’s the maxilla, Anatomage presents them both at the same time, but there is a left and a right maxillary bone, or maxillae. And those house the upper teeth in their alveolar ridge.
We can see the right and left nasal bones, as well as, in the corner of the eye, we can see the lacrimal bone. Each lacrimal bone is very small, they are the smallest bones of the face, but it’s covered over here slightly by the lacrimal sack and duct.
Then we can see the zygomatic bones on either side, right and left. And if we go internally into the nasal cavity, we see the right nasal concha; the left is on the opposite side and between them sits the vomer bone.
The vomer is the other unpaired bone of the facial region. The upper region of the nasal cavity has a perpendicular plate made of the ethmoid bone, as well as some lateral masses that house the sinuses. And the ethmoid bone can be seen in the eye orbit as well, but it is a bone of the brain case, not of the facial region.
The Palatine Bones
The palatine bones are hard to find in a full skull, but they make up a small portion of the lateral nasal wall most posteriorly and a small portion of the posterior palate. The more anterior part of the palate is made up by the maxillary bones. And we can easily see how the maxilla makes up most of the lateral nasal wall and also how the nasal concha hangs from that maxillary bone. There is a superior and middle mate nasal concha that are part of the ethmoid bone.
This projection behind the palatine bone are the so-called pterygoid plates of the sphenoid bone. The sphenoid bone is a bone of the brain case region, but it really makes its way all around different portions of the skull.
The Temporomandibular Joint
The temporomandibular joint, or TMJ, is the only movable joint in the skull. None of the sutures have any independent movement. So, here’s the temporomandibular joint where the head or condyle of the mandible sits into the temporal fossil on the temporal bone. The anterior portion is called the coronoid portion of the mandible, and this is the area of movement. There’s an articular disc there that allows for that movement.
Anterior to the TMJ is the zygomatic arch, which is made partly by the temporal bone and partly by the zygomatic bone. So, the zygomatic arch can be easily palpated on yourself.
The Hyoid Bone
And if we want to look at some other bony landmarks, we can see the supraorbital foramen in the frontal bone, we see the infraorbital foramen in the maxillary bone, and we see the mental foramen on either side of the mandible. These are for sensory nerves that supply the face. In the posterior orbit, we can see how the sphenoid bone contributes to much of the anatomy of the posterior aspects of the eye sockets, as well as the pterygoid plates.
Another bone that is important for its muscle attachment sites is the hyoid bone. It must be remembered that this is an unusual bone because it’s the only bone in the body that doesn’t directly articulate with any other bone. The hyoid bone is a small and delicate bone but has many attachment sites, including to both the mastoid and styloid processes of the skull. It’s also connected down by muscles to the sternum.
Common Questions about Skull Bones
The Anatomage is a software system; a technology that can be referred to as a virtual autopsy table. This software was initially based upon data gathered by the Visible Human Project through the University of Colorado School of Medicine.
Out of the 14 bones of the facial region, two are unpaired and the rest are all paired bones.
The hyoid bone is an unusual bone because it’s the only bone in the body that doesn’t directly articulate with any other bone.
