00:01
Now, we have the
muscles of mastication.
00:04
And we have four pairs
of muscles of mastication.
00:08
The first one highlighted
in red here is the masseter.
00:13
The masseter is originating
from the maxillary process
of the zygomatic bone,
as well as the zygomatic arch.
00:21
Its insertion is here to
the ramus of the mandible.
00:27
All muscles of mastication
will be innervated
by branches of the trigeminal nerve,
and the masseter is innervated
by the masseteric nerve,
the anterior trunk of
the mandibular nerve,
which is a branch
of the trigeminal.
00:43
When the masseter shortens or tracks
it's going to elevate the mandible,
thus closing the jaw,
and it can also produce
some minor jaw protrusion.
00:54
So it can move
the mandibular jaw
outwards or forward
just a little bit.
01:03
The temporalis is the
next muscle of mastication
and you see it
highlighted in red.
01:11
It's originating from the floor,
the temporal fossa
in the overlying temporal fascia.
01:18
It's insertion is to the coronoid
process and ramus of the mandible.
01:26
Temporal branches
of the anterior trunk
of the mandibular nerve
serve as its innervation.
01:34
And when it contracts,
it will elevate the mandible,
thus closing the jaw,
and the horizontal fibers
are going to be
primarily retractors
of the mandible.
01:46
So they will pull
the mandibular jaw inward.
01:56
Next, here we have the
lateral pterygoid muscle.
02:00
And here we see
the lateral pterygoid on the left
highlighted in red.
02:08
Kind of has two points of origin
from the skull:
one, is from the infraotemporal
surface and crafts
to the greater wing
of the sphenoid.
02:18
And then the other point of origin
of the lateral pterygoid
is going to be the lateral surface
of the lateral pterygoid plate.
02:25
So hence its name
because of this partial origin
from the pterygoid plate.
02:32
Insertion is going to be
on the joint capsule
and articular disc of the
temporal mandibular joint,
or excuse me
temporal mandibular joint,
and it also has a partial insertion
on the neck of the condyliod process
of the mandible.
02:51
Innervation is by the
lateral pterygoid nerve,
which is from the anterior trunk
of the mandibular nerve against,
again a division that trigeminal.
03:02
And its action when it contracts
is to protract the mandible,
as well as to depress the chin.
03:11
It also produces lateral side
to side movements of the jaw
as well during
chewing or mastication.
03:20
Lastly,
we have another pterygoid muscle
but this one is more immediately
located, highlighted in red.
03:28
It has two points of origin.
03:30
One is from the medial surface
of the lateral pterygoid plate
and pyramidal process
of the palatine bone.
03:37
It also has a point of origin
from the maxillary tuberosity.
03:43
The insertion is
to the ramus of the mandible.
03:49
And its innervation is
the medial pterygoid nerve,
which is a branch
of the anterior trunk
of the mandibular nerve.
03:57
And lastly,
the action of the medial pterygoid
when it contracts
is to elevate the mandible
and then produce
protrusion of the mandible.