all right in previous discussions we've talked about the immovable joints of the skull or the
sutures and that is quite a few joints but we're going to talk about the only movable joint of the
skull which is your temporomandibular joint and colloquially we often refer to this as TMJ
now typically when people talk about TMJ they're talking about TMJ syndrome which we'll talk about
towards the end of this lecture this actually is the abbreviation for the bones that are composed
that compose this joint the temporo- and the mandibular so let's talk about what bones those
are so the two bones that are going to make up your TMJ joint are your temporal bone and your
mandible now specifically when we're talking about the temporal bone we're looking at an inferior
view here you can see this shallow area right past the zygomatic arch and the shallow area is
referred to as the mandibular fossa it's basically a divot that's going to allow for the mandibular
condyle of the mandible to fit or articulate with the skull so the skull is what's not moving the
mandible is the movable part of your TMJ joint so if you think about opening and closing your mouth
it's your mandible that's moving not your skull so there's no movable joints truly associated with
the skull now this is one of your first visits in terms of a dissection based atlas and that's what
you're going to be seeing in when we're talking about muscles and ligaments and great detail as
we go further so right here we're looking at an actual component of the TMJ and you can see right
here is your articular disc so the temporal bone is going to be right here your mandibles
right here your mandibular condyle and in between you're going to have a disc which is made up of
fibrocartilage now the articular disc in your TMJ is of particular importance because it divides the
joint into a superior compartment and an inferior compartment and there's going to be two completely
different types of movements that can occur here so let's talk about those movements in
just a moment so first we're going to talk about the clinical considerations that can occur here
now you can have a dislocated mandible now what that means is that your mandibular condyle pops
out of place and when you have this occur this actually will occur with the mandibular condyle
which typically sits right here will pop out and move anterior to your articular eminence so we
talked about the articular eminence when we're talking about bones it's basically that inferior
projection of the zygomatic arch so you'll have the mandibular condyle move inferiorly and then
anteriorly so that can happen with a blow to the side of the face sometimes if you have a weakening
of the ligaments in this region it can happen when you yawn very wide or if you're eating something
that's rather large it can happen just as easily in that particular situation as well now TMJ
syndrome which is what we typically think of when we think of TMJ is really amalgamation of
all kinds of different things it could just be a slight weakening of the ligaments in this region
it could have something to do with the articular disc of your TMJ joint it can have something to
do with a dislocation in addition to that as well so any type of damage or injury in this area can
be considered part of TMJ syndrome now typically what can help with TMJ syndrome is actually just
not using your temporomandibular joint so that's the more common clinical prescription for this
is to just stop using your TMJ joint allow for the structures of the joint to kind of relax
and become less inflamed so let's talk about the movements that can occur here now remember how
we talked about how that articular disc is actually going to divide the joint into two
different compartments so you're going to have the inferior compartment playing a bigger role
in terms of the more dominant movement at the TMJ which is elevation and depression so if you
think about that if you elevate that's closing your mouth depression is opening your mouth so
opening and closing so this is an example of a hinge joint now the superior compartment is
doing more of a sliding back and forth and that's what's referred to as protraction
and retraction so let's actually see what these movements are so we're going to start I believe
with protraction and retraction so really pay attention protraction think of jutting out your
chin and retraction going back to anatomical position so protraction jutting out retraction
re going back into anatomical position now in terms of the larger movement you have depression
and elevation so depression opening the mouth you can have various range of motion there elevation
going back to anatomical position so you can see the two main types of movements that can
occur depending on which compartment is actually moving based on that articular disc now we'll talk
later about the four muscles of mastication that will actually allow for these movements to occur