Bone up on your Cranial Anatomy: bones of the skull, jaw as appendage
Here's an overview for those of you interested in learning about the head – its geography and organization. This is the architectural underpinning that the jaw, neck and facial musculature rests on.
The Head and its Appendage, the Jaw
Given the many bones and muscles we tackle as beginning massage students, it’s understandable that we approach the head as a single unit. Once we have a closer look, however, we see that the head is composed of three anatomical areas: the neuro-cranium, the viscero-cranium, and the mandible.
The neuro-cranium is simply the round ball that holds the brain. It has a dense “base,” which is a nest for the brain with many openings for nerves and blood vessels, and a thin “vault,” which caps the brain and distributes the force of any bumps or blows. If you imagine wearing a cap, the edge of the cap would outline the place where the base and the dome meet.
The viscero-cranium is the bony scaffolding of the face, from nose to mouth and ear to ear. Structurally, the face hangs from a set of sutures just at the bridge of the nose and behind the eyes, and it includes most of our sinuses and special senses. Like the bones of the vault, the bones in the face are designed to disperse most impact forces superficially, rather than into the nerve- and vessel-rich area of the sinuses and cranial base.
The mandible is the lower jaw: a dense bone that hangs from the cranial base, like the chin strap of an old motorcycle helmet. Connected to the rest of the head by the temporo-mandibular joints (TMJ), the jaw is highly mobile and performs a variety of functions. So, looking at someone face-to-face we can see all three aspects of the head: the neuro-cranium at the forehead, the viscero-cranium from the eyes to the upper teeth, and the lower jaw at the chin. This perspective becomes very useful when assessing the alignment of each aspect in relation to each other and the neck.
Since we’re accustomed to considering the face as a whole, we don’t tend to think of the jaw as an highly mobile appendage of the head. However, just as the arms and legs are appendages that can either support or drag on the torso, the mandible can rest in balance…or not, which strains the head and upper neck. This heavy bone and related myofasciae form a functional unit which plays an important role in our overall balance.