Muscles of Facial Expression Study Notes

INTRODUCTION

  • Facial muscles develop from the 2nd Pharyngeal arch of the embryo.
  • Arrangement:
    • Muscles are grouped around the openings of the mouth, nose, eyes, ears, scalp, and neck.
    • They act as dilators and constrictors of these openings.
  • Function:
    • Muscle contractions are responsible for facial expressions, even for muscles located beyond the face.
  • Innervation:
    • All facial muscles are innervated by Cranial Nerve VII (CN: 7).

TOPOGRAPHICAL CLASSIFICATION

EPICRANIAL MUSCLES

  • Occipitofrontalis (frontal part)

CIRCUMORBITAL & PALPEBRAL MUSCLES

  • Orbicularis oculi
  • Corrugator
  • Levator palpebrae superioris

NASAL MUSCLES

  • Procerus
  • Nasalis
  • Depressor septi

ORAL GROUP MUSCLES

  • Elevators, depressors, and retractors of upper and lower lip:
    • Orbicularis oris
    • Buccinator

OCCIPITOFRONTALIS

FRONTAL PART

  • Origin: Subcutaneous tissue and skin of eyebrow.
  • Insertion: Epicranial aponeurosis.
  • Action: Raises the eyebrows upwards.

ORBICULARIS OCULI

ORIGIN

  • Orbital part: From the frontal process of the maxilla and medial palpebral ligament; surrounds the orbital margin.
  • Palpebral part: Bone above and below the medial palpebral ligament.
  • Lacrimal part: Upper part of lacrimal crest and lateral surface of the lacrimal bone.

INSERTION

  • Skin around the margin of the orbit and lateral palpebral raphae.

ACTION

  • Blinking of the eye:
    • Orbital part: Closes eyelid tightly.
    • Palpebral part: Gently closes eyelid.

CORRUGATOR SUPERCILII

ORIGIN

  • Medial end of supraciliary arch.

INSERTION

  • Skin in the middle of the supraorbital margin.

ACTION

  • Pulls eyebrow medially and downward; forms vertical wrinkle.

LEVATOR PALPEBRAE SUPERIORIS

ORIGIN

  • Inferior surface of the lesser wing of the sphenoid.

INSERTION

  • Upper lamina: skin of upper eyelid.
  • Middle lamina: superior tarsus.
  • Lower lamina: superior conjunctival fornix.

ACTION

  • Elevation of upper eyelid (opening of a closed eye).

NASAL GROUP MUSCLES

PROCERUS

ORIGIN

  • Nasal bone and lateral nasal cartilage.

INSERTION

  • Skin between eyebrows.

ACTION

  • Frowning.

NASALIS

ORIGIN

  • Transverse part: Anterior surface of maxilla near the nasal notch.
  • Alar part: From maxilla below, medial to transverse part.

INSERTION

  • Alar cartilage and continues over the bridge of the nose with opposite muscle.

ACTION

  • Transverse part: Compresses the nasal aperture.
  • Alar part: Dilates the nasal aperture.

ORAL GROUP OF MUSCLES

LEVATOR LABII SUPERIORIS

ALAEQUE NASI
  • ORIGIN: Lateral surface of frontal aspect of maxilla.
  • INSERTION:
    • Lateral slip: lateral part of upper lip.
    • Medial slip: Alar cartilage and skin of nose.
  • ACTION: Elevates the upper lip.

LEVATOR LABII SUPERIORIS

  • ORIGIN: Close to the infraorbital margin and above the infraorbital foramen.
  • INSERTION: Muscular substance of upper lip.
  • ACTION: Elevates and everts upper lip.

LEVATOR ANGULI ORIS

  • ORIGIN: Canine fossa of maxilla.
  • INSERTION: Angle of mouth.
  • ACTION: Raises the angle of the mouth.

ZYGOMATIC MAJOR

  • ORIGIN: Zygomatic bone.
  • INSERTION: Angle of mouth.
  • ACTION: Pulls angle of mouth upward and laterally (laughing, smiling).

ZYGOMATIC MINOR

  • ORIGIN: Zygomatic bone.
  • INSERTION: Skin of upper lip in lateral part.
  • ACTION: Elevates and everts upper lip; increases nasolabial furrow.

DEPRESSOR LABII INFERIORIS

  • ORIGIN: Oblique line of mandible.
  • INSERTION: Skin of lower lip.
  • ACTION: Pulls lower lip downwards and laterally.

DEPRESSOR ANGULI ORIS

  • ORIGIN: Posterior part of the oblique line of mandible.
  • INSERTION: Angle of mouth.
  • ACTION: Pulls angle of mouth downward and laterally.

RISORIUS

  • ORIGIN: Parotid fascia.
  • INSERTION: Angle of mouth.
  • ACTION: Grinning.

MENTALIS

  • ORIGIN: Incisive fossa (the dental hygienist's nightmare muscle).
  • INSERTION: Skin of the chin.
  • ACTION: Puckers the skin of the chin.

BUCCINATOR

ORIGIN
  • Upper fibers: Outer surface of the alveolar process of the maxilla.
  • Middle fibers: Pterygomandibular raphe.
  • Lower fibers: Mandible opposite to molars.
INSERTION
  • Upper fibers: Upper lip.
  • Lower fibers: Lower lip.
  • Middle fibers: Decussate to both the lips.
ACTION
  • Flattens the cheeks against the gums; aids in blowing out air through mouth.

ORBICULARIS ORIS

  • ORIGIN:
    • Extrinsic part: maxilla above incisor teeth.
    • Intrinsic part: Incisive fossa of maxilla and mandible.
  • INSERTION: Angle of mouth and skin of lip.
  • ACTION:
    • Closure of lip.
    • Protrusion of lip.
    • Puckering.

EXPRESSION

MUSCLES INVOLVED

  • Surprise: Frontalis
  • Frowning: Corrugator supercilii
  • Anger: Dilator naris, Depressor septi
  • Laughing, smiling: Zygomaticus major, minor
  • Sadness: Depressor anguli oris
  • Grinning: Risorius
  • Doubt: Mentalis
  • Whistling: Buccinator

BLOOD SUPPLY

  • The muscles of mastication are predominantly supplied by the branches of:
    • Facial artery.
    • Superficial temporal artery.
    • Maxillary artery.

BELL'S PALSY

Possible Symptoms of Bell's Palsy

  • Smoothing of the forehead.
  • Droopy eyelid.
  • Dry eye or excessive tears.
  • Eyebrow droop.
  • Facial paralysis, twitching, or weakness.
  • Drooping corner of mouth.
  • Dry mouth.
  • Impaired taste.