MUSCLES OF FACIAL EXPRESSION

The muscles of facial expression are located within the subcutaneous tissue of the face. They originate from bone or fascia and insert onto the skin and muscles. As they contract, the muscles pull on the skin to exert their effects. Facial expressions produced are secondary functions of these muscles

Occipitofrontalis. This is a bundle of muscle that includes 2 bellies of frontal muscle and 2 bellies of occipital muscle connected by aponeurosis. Frontal part originate from the aponeurosis and insert on upper part of the orbicularis oculi and skin of the eyebrow. It is innervated by temporal branch of the facial nerve.

Action. The frontal part raise the eyebrows and the skin over the root of the nose and at the same time draw the scalp forward forming the transverse wrinkles.

Orbital group

Nasal group

Oral group

These includes mainly 3 muscles

orbicularis oculli

Levator palpebrae superioris

Corrugator supercilli

Orbicularis oculi. is a broad, flat muscle that encircles the palpebral fissure. The muscle originates from the medial orbital rim and medial palpebral ligament. The muscle consists of two parts: the thicker orbital part; which is the outer circle which runs over the orbit and forms loops return to the origin, and the thinner, palpebral part which encircles the palpebral fissure and forms the upper and lower lids

Contraction of palpebral part alone results in gentle closure of the lids while contraction of both palpebral and orbital parts results in forceful closure of the lids

Actions

Palpebral part – gently closes the eyelids.

Orbital part – tightly closes the eyelids.

Corrugator supercili. This muscle attaches to superciliary arch and inserts to the skin of eye brow. The muscle lies deep to O.Oculi muscle. Contraction of this muscle draws the eyebrows medially and inferiorly to produces vertical wrinkles known as “frown lines

Action. It draw the eyebrows downwards and medially producing vertical wrinkles of the forehead

Levator palpebrae superioris. This muscle originate from the sphenoid bone and insert into the superior tarsus and conjunctica.

Innervation. Branch of oculomotor nerve

Action. Elevate upper eyelid

It includes

Procerus

Depressor septi

Nasalis

Dilator naris

Levator labii superioris alaequae nasi

Procerus muscle. It originate from the fascia covering the lower part of the nasal bone and upper part of the lateral nasal cartilage to insert into the skin over the lower part of the forehead between the two eyebrows. Innervated by facial nerve and its contraction draws the medial angle of the eyebrows to form the transverse wrinkles over the bridge of the nose.

Nasalis is a paired muscle that covers the dorsum of the nose. It consists of two parts; alar and transverse. The alar part is also called dilator naris, and the transverse part is known also as the compressor naris.

Contraction of Nasalis muscle can cause “bunny lines” on the nasal dorsum.

The compressor nasi and depressor septi are the sphincter muscles, while the dilator naris and levator labii superioris alaeque nasi are the dilator muscles of nasal apertures

Depress the cartilaginous part of the nose, draws the ala towards the septum

Depressor septi

Antagonist to other muscles of the nose, draws the ala of nose downwards and constricts the nares

Dilators

Enlarge the aperture of the nose

Levator labii superioris alaequae nasi

Secondary dilator of naris

The oral muscles of facial expression are responsible for the movements of the mouth and lips. They are required in singing and whistling and add emphasis to vocal communication.

The group consists of the orbicularis oris, buccinator, and various smaller muscles

Buccinator muscle. The buccinator muscle originates from the outer surface of the alveolar margins of the maxilla superiorly and mandible inferiorly opposite the molar teeth and from the pterygomandibular ligament posteriorly. The muscle fibers pass forward, forming the muscle layer of the cheek. The parotid duct pierces the muscle to open in oral buccal mucosa. The buccinator muscle blends with the orbicularis oris muscle.

The buccinator compresses the cheeks and lips against the teeth, thus positioning the food for efficient chewing. The compression action also is important in producing sucking as in neonates feeding. Cheek compression is also important in producing blowing actions, as in blowing the musical instruments.

Action

Mastication/chewing

Sucking

Blowing musical instruments

Orbicularis oris. The orbicularis oris forms the bulk of upper and lower lips. The muscle is a circular sphincter of the mouth and originates from the midline of maxilla and mandible to be inserted in the skin of upper and lower lips.

Attachments – Arises from the maxilla and from the other muscles of the cheek. It inserts onto the skin and mucous membrane of the lips.

Innervation – Buccal branches of the facial nerve

A series of small muscles that blend with O. Oris muscle and radiate out from the lips make up the dilator muscles and lower depressor muscles, their action is to separate the lips; this movement is usually accompanied by opening of the jaws. These muscles are divided into two groups

Lower group

Upper group

depressor anguli oris,

depressor labii inferioris,

mentalis.

Upper group

risorius,

zygomaticus major,

zygomaticus minor,

Levator anguli oris

NA

MUSCLE

ORIGIN

INSERTION

INNERVATION

ACTION

1

Levator labii superioris

Maxillary and zygomatic bone

upper lip

Facial nerve

Elevate the upper lip

2

Zygomaticus major

Arise from the zygomatic bone

Angle of the mouth

Facial nerve

Pull the angle of the mouth upward and lateral(help in smiling)

3

Zygomaticus minor

Anterior aspect of the lateral surface of zygomatic bone

Upper lip medial to angle of the mouth

Facial nerve

Elevate the upper lip(help in smiling)

4

Risorius muscle

Fascia over masseter muscle

Skin of the angle of mouth

Facial nerve

Retracts the angle of the mouth and helps in producing unpleasant expression

5.

Levator anguli oris

canine fossa in maxilla below the infraorbital foramen

inserts into the modiolus at the angle of mouth

Facial nerve

Elevate the angle of the mouth

6

Depressor anguli oris

mandible, lateral to Depressor Labii Inferioris

modiolus on angle of the mouth.

Facial nerve

Contraction causes the angle of the lower lip to depress

7

Depressor labii inferioris

mandible inferior to mental foramen

inserts on the skin and mucosa of the lower lip

Facial nerve

Contraction depresses the lower lip

8

Mentalis muscle

Incisive fossa of the mandible

Integument of the chin

Facial nerve

Raises and protrude the lower lip and at the same time wrinkles the skin of the chin expressing doubt

9

Platysma

Upper parts of the pectoral and deltoid fasciae

Anterior fiber; to the base of the mandible

Posterior fiber; to the skin of the lower face and lip and may be continuous with the risorius

Facial nerve

Depress mandible

Pulls the angle of the mouth downwards as in horror or surprise

Grays anatomy textbook

Moore clinically oriented anatomy