hi let's talk about the osteology of the oral cavity before we move to the skull we should
begin with the hyoid bone the hyoid bone has a couple of main features so there are the greater
horns or the greater cornu the lesser horns and then the the body or the corpus of the hyoid bones
it's these greater cornua that we're concerned about with respect to the oral cavity because
they're going to be the attachment site for the high of glosses muscle one on either side going
up from the hyoid bone into the tongue so it's one of the extrinsic sets of tongue muscles now moving
into the skull specifically the mandible of the skull and this is a posterior view of the mandible
we can see here's the body of the mandible and there are the rami of the mandible here are the
mandibular teeth and the angles of the mandible so here is the the mental or the posterior view
of the the chin region so let's let's see what what there is to to be hold here so looking
specifically at the posterior aspect of the the mental region we can see two pairs of spines so
these are called mental spines and there's a superior pair these are going to be much more
evident and then an inferior pair these are going to be much less evident the the superior pair here
are the attachment sites for the genioglossus muscle whereas the inferior pair are the
attachment sites for the geniohyoid muscles so genioglossus is another pair of extrinsic
tongue muscles running from the the genu the bend of the the mandible to
the tongue and then the geniohyoid runs from the genu of the mandible to the hyoid bone so
these are exquisitely well named muscles there's there's a lot there's a lot in a
muscles name now we have a couple of Fossae or indentations within the bone so anteriorly here
we have the digastric Fossae these digastric Fossae are the anterior attachment sites for
the anterior bellies of the digastric muscles so digastric Fossae for the anterior bellies
of the digastric muscles that that kind of makes sense and when we think about the the
osteology in this in this region so we have these layers here so genioglossus geniohyoid
and then the anterior belly of digastricus and then we're going to another set of muscles
the mylohyoid muscles and those are going to attach to the mylohyoid lines here and there
and then they'll meet their counterpart along the at the midline of the of the floor of the
oral cavity in a raphe so we have this this layering of genioglossus geniohyoid mylohyoid
and then anterior belly of the digastricus which we should we should see this born out in the
muscles as well so superior to the mylohyoid line we're going to have a fossa and these
Fossae are going to accommodate the sublingual glands these are the sublingual Fossae and then
inferior to that mylohyoid line we're going to have an indentation that's going to accommodate
the deep parts of the submandibular glands and these are they submandibular Fossae so all all
is fairly straightforward here in terms of the the anatomical arrangements of these Fossae and
spines and lines with respect to the orientation of their muscles now let's take a view of the
mandible recalling that the main parts of the mandible are the body which we can see here and
then the ramus of the mandible my apologies for any squealing of this pen within the body of the
the mandible the the portion of the body that is going to support the teeth this is the alveolar
arch there's also an alveolar arch on the maxilla as well to support the maxillary teeth and this
this lateral aspect of the alveolar arch here is known as the buccal plate and that buccal plate
is very delicate compared to the lingual plate so the lingual plate would be on the tongue side or
the lingual side of the mandible and so as you're performing your extractions as you leverage the
the buccal plate is in danger of fracturing the lingual plate tends to be much more robust and
is unlikely to fracture during an extraction but that that buccal plate may so that buccal plate
is not to be confused with the buccal shelf which we can see here as this indentation so
there's just a flattened Ridge there that buccal shelf if you can imagine the long buccal nerve
of the buccal nerve sometimes called the long buccal nerve which is a branch of v3 on its
way out from the infer temporal fossa to the the buccal facial space is is moving along that line
so that's a good landmark for finding that that long buccal nerve so that that's how paintable
we also have the mylohyoid groove of the ramus so this is a medial view of
the mandible so again this would be the the ramus and coming down here is this
mylohyoid groove the mylohyoid groove is a groove which accommodates the nerve to the
mylohyoid muscle so here's the mylohyoid line coming down here here is where the
inferior alveolar nerve the IAN enters into the mandible but then it gives off
that nerve to the mylohyoid muscle there and that mylohyoid groove accommodates that nerve
finally let's talk a little bit about teeth there are teeth of the maxilla and teeth of
the mandible adult humans typically have 32 teeth and the numbering convention you know we would
start with number one it for the the right third maxillary molar and we would come all the way over
to 16 which would be the left third maxillary molar and then we go down to 17 would be the
left third mandibular molar and then over to 32 which would be the right third mandibular molar
but we also give these teeth names and so when we name these teeth and divide them up we usually do
so by quadrant so if we're to just draw a line down the middle we would see that we have in
each quadrant a central incisor a lateral incisor a canine a first premolar second premolar and then
first second and third molars which we can't see owing to the the anterior view of this particular
skull humans by virtue of how they've evolved generally are going to not necessarily have
space to accommodate their their third molars these tend to erupt later in life towards the
end of teens early 20s so we call them wisdom teeth and what that age has to do with wisdom
I'll never know but it certainly didn't arrive for me at that age so let's look at the at the
mandible here so we've got a pretty good view of the the mandibular teeth so this would be tooth
number 17 that would be a third molar that would be a second molar and there will be a first molar
so those are your mandibular molars here would be that second premolar and the first premolar
here is the canine and then for this here are the incisors
that's the medial and then that's lateral and then we go from 17 all the way over
here to 32 and we can see that these teeth are in this alveolar arch in the alveolar
process of the arch surrounds the the roots of the teeth we also have a nice view here
of the the buccal shelf as we go so these are some of the the osteological features
that that you'll encounter in the oral cavity thank you very much for your time