CorpusHuman Anatomy
MuscularMuscle group

Muscles of facial expression

Also known as: mimetic muscles, facial muscles, second pharyngeal arch muscles

Thin subcutaneous muscles derived from the 2nd pharyngeal arch. They move the skin of the face and scalp, open and close the eyes and mouth, and create facial expression. All are supplied by the facial nerve (CN VII).

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Overview

The mimetic muscles lie in the superficial fascia. Most arise from bone or fascia and insert into skin, so contracting them wrinkles and moves the face. They are arranged around the openings of the face as sphincters and dilators: orbicularis oculi around the eye, orbicularis oris around the mouth, and nasalis at the nose. Many lip muscles converge on the modiolus, a fibromuscular knot just lateral to the angle of the mouth. Platysma and occipitofrontalis extend this sheet over the neck and scalp. Buccinator is also a mimetic muscle, although it lies deep in the cheek and works mainly in chewing.

All develop from the mesenchyme of the 2nd pharyngeal arch and keep its nerve, the facial nerve. After leaving the stylomastoid foramen, CN VII passes through the parotid gland and divides into five branches: temporal, zygomatic, buccal, marginal mandibular and cervical. Sensation from the face, in contrast, is carried by the trigeminal nerve (CN V).

Parts & subdivisions

  1. Scalp
    Occipitofrontalis (with the epicranial aponeurosis) and temporoparietalis.
  2. Orbital group
    Orbicularis oculi, corrugator supercilii, procerus.
  3. Nasal group
    Nasalis (transverse and alar parts), depressor septi nasi.
  4. Oral group — elevators
    Levator labii superioris (and alaeque nasi), zygomaticus major and minor, levator anguli oris, risorius.
  5. Oral group — sphincter and depressors
    Orbicularis oris, depressor anguli oris, depressor labii inferioris, mentalis.
  6. Cheek
    Buccinator.
  7. Neck
    Platysma.
  8. Auricular muscles
    Anterior, superior and posterior auricular muscles (vestigial in humans).

Anatomy

Innervation

Facial nerve (CN VII): temporal, zygomatic, buccal, marginal mandibular and cervical branches, plus the posterior auricular nerve.

Nerve roots

Cranial nerve VII (facial motor nucleus, pons); no spinal roots

Arterial supply

Mainly the facial artery (superior and inferior labial, angular branches) and the superficial temporal artery (transverse facial branch), plus branches of the ophthalmic and maxillary arteries.

Development

2nd (hyoid) pharyngeal arch mesoderm, together with stapedius, stylohyoid and the posterior belly of digastric.

Function

  • Non-verbal communication through facial expression
  • Protect the eye (blinking, forced closure) and spread the tear film
  • Control the oral opening for speech, eating, sucking and whistling
  • Keep food out of the vestibule of the mouth during chewing (buccinator)

Clinical significance

Bell palsy (LMN facial palsy)

Idiopathic inflammation of CN VII in the facial canal paralyses the whole of one side of the face, including the forehead. The patient cannot close the eye (risk of exposure keratitis), cannot raise the eyebrow and has a drooping mouth. Hyperacusis (stapedius) and loss of taste over the anterior two-thirds of the tongue occur if the lesion is proximal. Early corticosteroids improve recovery.

UMN (central) facial palsy

In a stroke affecting the cortex or the corticobulbar tract, the forehead is spared, because the upper facial motor nucleus receives input from both hemispheres. Only the contralateral lower face is weak.

Mnemonics

Facial nerve branches

"Two Zebras Bit My Cookie": temporal, zygomatic, buccal, marginal mandibular, cervical.

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.