The levator labii superioris alaeque nasi is the slender muscle right along the lateral margin
of the nose down to the lateral margin of the nostril and down to the superior labium
of the lip and you see the contralateral or the fellow here on the other side. This particular
muscle is going to originate from the frontal process of the maxilla. It then will insert
on the major alar cartilage of the nose as well as the skin of the upper lip is going to be
innervated by the zygomatic branches and the buccal branches of the facial nerve.
And when it is activated to contract, it will flare or dilate each nostril and it will also help
to elevate the upper lip. This flaring of the nostrils demonstrates anger or exertion
during physical activity when you want the nostrils to be dilated to help with airflow or in
inspiration. The levator labii superioris is a more substantial muscle than the other levator
labii superioris and we can see it highlighted in red. It is originating from the maxilla and
then like other muscles of facial expression it has insertion to the skin of the upper lip.
As before the zygomatic and the buccal branches contribute to its innervation. Again,
these are branches of the facial nerve and then the action of this particular muscle is to
open or dilate the mouth, elevate or evert the upper lip, and it also helps to deepen the
sulcus between the nose and the lip. The action has been described as showing signs of
sadness emotionally. We have a couple of zygomatic muscles. The first one here is the
zygomaticus major muscle highlighted here on the left side in red. As the name implies,
it does originate from the zygomatic bone and then based on where you see it inserts,
it is inserting on the angle of the mouth. And because of the zygomatic buccal location
of the muscle itself, the facial nerve branches zygomatic and buccal represent its
innervation. The action of the zygomaticus major is to dilate the mouth, elevate the labial
commissure, and this has bilateral versus unilateral action. If the action is bilateral, this
will help produce a smile. If it is unilateral, it will then result in producing a sneer expression.
Its counterpart is zygomaticus minor shown here in red. Here is the zygomaticus major
so you get to see the relationship of major to the minor. As the name implies, zygomatic
bones versus its origin and insertion is also to the skin of the upper lip. No surprise here.
Zygomatic and buccal branches of the facial nerve serve as nerves that supply the muscle
and some more actions to the major dilating the mouth, elevating and everting the upper
lip and then deepening the sulcus between the nose and the lip. This action can produce
the expression of sadness. Our next muscle is the levator anguli oris. This is a fairly small
muscle that you see associated with the superior part of the angle of the mouth. It is
It is originating from the maxilla bone right below the orbit and it is, as the name implies,
anguli it is going into the angle of the mouth. Zygomatic and buccal branches of the facial
nerve will innervate this particular muscle and when it shortens it will widen the oral
fissure while dilating the mouth. Risorius is shown right in through here. It is originating
from the fascia associated with the parotid glands. So this is simply the parotid fascia.
Insertion, as you can see here, is in to the angle of the mouth. Innervation because of its
location will be the buccal branches of the facial nerve. It will dilate and widen the mouth
when it contracts or shortens and it will also depress the labial commissures. Our next stop
is with the sphincter of the mouth shown here in red and this is the orbicularis oris. Its
origin is from the medial maxilla as well as the mandible. Also has partial origin from the
skin that surrounds the mouth and also the mouth angle. Insertion is to the superior and
inferior lips via the mucous membrane. Innervation is the buccal branch of facial to the
upper portion of the orbicularis oris and then the mandibular branch of the facial will
innervate the inferior aspect of the orbicularis oris. And when this muscle contracts, it will
serve as a sphincter of the mouth so close the mouth tightly and it will also protrude the
lips. And because of this lip protrusion, this is the kissing muscle, because this is the action
that you produce when you want to kiss someone. And then the sphincter-like action
of this muscle will resist distention when blowing. Here more inferiorly we have the
depressor labii inferioris and this is a bilateral muscle so you see both muscles right and left.
It's originating from the mandible as well as the platysma muscle and its insertion is to
the skin that's associated with the lower lip. Because of its inferior location in relationship
to the mandible, the mandibular branch of the facial nerve will be its nerve supply and
when this muscle contracts it will dilate the mouth as well as depress the lower lip and this
produces an expression of pouting or sadness. Related to the previous muscle is a
depressor inferiorly located. This is the depressor anguli oris in red, there will be one
on the right side as well. It's originating from the mandible and then inserting into the
angle of the mouth at this location. It is innervated by the buccal and mandibular branches.
The buccal will come here and innervate the more superior part of the muscle and then the
mandibular branches of the facial will innervate the lower portion of this muscle. And when
that contracts, it will dilate the mouth and then it will depress the labial commissures.
Here, we have a muscle in the medial location of the mandible. It is paired right and left.
This is the mentalis. It is originating from the mandible and then its insertion will be to
the skin of the chin. Because of its mandibular location, mandibular branch of facial nerve
and it will serve to elevate the lower lip as well as protrude the lower lip and this produces
a doubting type of expression. And our next muscle of facial expression and our last
muscle of facial expression is the platysma. This is a fairly expansive muscle that is
originating from the subcutaneous tissue in the supra and infraclavicular region so down in
in through here. Its insertion is superiorly located so that would be the base of the
mandible, angle of the mouth also to the orbicularis oris muscle and to skin related to the
cheek and the lower lip. Because of its more inferior location, the most inferior branches
of the facial nerve, the cervical branches, serve as the nerve supply to the platysma and
action when it contracts is to depress the mandible and it will also tend to stand at the
inferior face and then the skin related to the neck and this action produces some tension
and stress in the neck area.