all right in previous discussions we've talked  about the immovable joints of the skull or the  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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  
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
later about the four muscles of mastication that  will actually allow for these movements to occur