Hi, this is Dr. Kingston,
and in this video I'll be talking about
the innervation of the cheeks , teeth, and gingivae
The objective here is exactly the same as the title.
So your cheeks are probably very familiar to you.
But anatomically the cheeks are
defined as the skin,
the buccinator muscle fibers and the mucosa
that make up the lateral wall of the oral cavity.
They receive motor innervation for that
buccinator muscle from the facial nerve,
because it is a muscle of facial expression and
sensory innervation for the skin
and mucosa from the buccal nerve,
which is a branch of
the mandibular nerve in the infratemporal fossa.
So here's the mandibular nerve and we can follow
that buccal nerve right down on to the cheek there.
The buccinator muscle deep to the buccal fat pad,
which we see right there,
and it is technically a muscle of
facial expression that tenses the cheeks.
It's innervated by the facial nerve and everything.
But you really make use of
it when you're eating something.
So it's position deep within the cheek here,
allows it to hold
the cheek right up against
the buccal surface of the teeth.
This means that as you're chewing,
the food that's being ground up on your molars
doesn't slip off and fall into the oral vestibule.
And speaking of teeth and chewing,
all teeth are going to receive
somatic sensory innervation from the trigeminal nerve.
The maxillary teeth are innervated by
branches of the maxillary division and
the mandibular teeth are innervated by
branches of the mandibular division.
The innervation of the maxillary teeth is
split up among three branches from the maxillary nerve.
So here is trigeminal,
here is the maxillary nerve.
First branch here is the posterior superior alveolar,
which heads into the maxilla itself.
where it's going to travel down to
the alveolar process and spread out in
a superior dental plexus
that's going to send branches to individual teeth.
This is going to supply
the molars for the maxillary tooth row.
Our other two branches here,
the middle superior alveolar and the anterior
superior alveolar, branch from the infraorbital nerve,
which is the terminal extension
here of the maxillary nerve.
The middle superior alveolar is going to innervate
the premolars and the first molar.
And the anterior superior alveolar
is going to innervate those anterior teeth,
the incisors and canines.
Note here that both of these nerves are going to
come down into the alveolar process and
again spread out into
that dental plexus that will then
send branches to individual teeth.
The mandibular division of trigeminal,
so back up here, is going to pass
through foramen ovale and into the infratemporal fossa,
where it's going to give off a branch
called the inferior alveolar nerve.
And that is going to travel inferiorly and enter
into the mandible through a little hole
called the mandibular foramen.
It's then going to pass through the bone
down into the alveolar process,
where it's going to form a inferior dental plexus
that will send branches up to individual teeth here.
Now, all the mandibular teeth are
innervated by the inferior alveolar nerve,
but the molars and premolars get innervation
specifically from branches named
dental branches. And the incisors,
the canine, and part of that first premolar are
innervated by what are called incisive branches.
The main differentiation between
the dental branches and
the incisive branches is this little guy here.
This mental nerve is going to emerge from
the mental foramen out onto the face as a sensory nerve.
Anything that comes off before that is a Dental Branch.
Anything that comes off after that,
his branch here is going to be an incisive nerve.
The innovation of the gingivae is slightly more
complicated because there's two sides of the gingiva.
So we have a buccal side and a lingual side,
and these are separated by this tooth row.
The solution that your body has to
this is that the gingivae share
sensory innervation with neighboring structures
on either side of the tooth row.
I put together a little chart here to help you remember
what structures share innervation with the gingivae.
Most gingivae is going to share
the innervation of its neighboring mucosa.
The only exception to this are
the buccal and labial gingivae of the maxilla.
So these guys up here.
And these are also going to get some innervation
from the nerves that
serve the teeth that sit right near them.
This means that the buccal gingiva for
the maxillary molars here
comes from both the buccal nerve,
so this little branch over here of the mandibular nerve,
and the posterior superior alveolar nerve
that we saw earlier.
All right.
The premolars are served both by
the infraorbital nerve and
the middle superior alveolar nerve.
And the canine and incisors are
served by the infraorbital nerve
and the anterior superior alveolar.
Now, the general pattern here is that
the maxillary gingivae are innervated by branches of
the maxillary division of trigeminal and
the mandibular gingivae are
innervated by the mandibular division.
So obviously we have
a pretty glaring exception to this here with
the buccal nerve innervating
some of the maxillary gingivae.
But in all other regions,
this pattern will hold. The maxillary lingual gingiva,
so lingual is the side over here by the tongue,
are butted up against the hard palate,
which is innervated by
the greater palatine nerve posterior to
the canines and the nasopalatine anterior to them.
So both of those are branches of the maxillary nerve.
For the mandibular teeth,
the buccal nerve again is going to
innovate the gingivae lateral to the molars.
And for the anterior teeth, It's the mental nerve.
The lingual nerve, on the lingual gingiva
here, also innervates the whole of the oral flora mucosa.
And so it's just a little jump
upward to hit the lingual gingiva here as well.
That brings us to the end
of our discussion of innervation.
So here is your practice question.
The answer here is C.
You should target the inferior
alveolar nerve for this procedure.
This question might have been a little bit tricky.
So number 1, that inferior first premolar
has a split innervation between
the dental branches of the inferior alveolar and
the incisive branches of the inferior alveolar.
But that is not the only reason why
the inferior alveolar nerve as
a whole is a correct answer here.
Remember that these dental branches
and incisive branches exist
within the alveolar process of the mandible here,
so they're actually quite difficult to access.
The inferior alveolar nerve,
though, the nerve that these all branch
from is much easier to access,
especially with an anesthetic.
It is going to enter into
the mandibular bone here at the mandibular foramen.
And the mandibular foramen is very closely
associated with this little spike
of bone here called the lingula.
And this is a palpable structure within
your own mouth and within
your patient's mouth in the future.
So you would direct your needle with
anesthetic toward this lingula and
anesthetize the inferior alveolar nerve
as it enters into the mandible.
That is the end.
Thank you for watching.