Muscles of Facial Expression Study Notes

MUSCLES OF FACIAL EXPRESSION

Introduction

  • Facial muscles develop from the 2nd Pharyngeal arch of the embryo.
  • Arranged in groups around the openings of:
    • Mouth
    • Nose
    • Eyes
    • Ears
    • Scalp
    • Neck
  • Function: Act as dilators and constrictors of these openings.
  • Responsible for facial expression through contraction.
  • Innervation: All facial muscles are innervated by Cranial Nerve VII (CN:7).

Topographical Classification of Muscles

Epicranial Muscles
  • Occipitofrontalis (frontal part)
Circumorbital & Palpebral Muscles
  • Orbicularis Oculi
  • Corrugator
  • Levator Palpebrae Superioris
Nasal Group
  • Procerus
  • Nasalis
  • Depressor Septi
Oral Group
  • Levator, Depressor, and Retractors of Upper and Lower Lip
  • Orbicularis Oris
  • Buccinator

Detailed Muscles of Facial Expression

Occipitofrontalis
  • Origin: Subcutaneous tissue and skin of eyebrow.
  • Insertion: Epicranial aponeurosis.
  • Action: Raises the eyebrow upwards.
Orbicularis Oculi
  • Types: Orbital part and Palpebral part.
  • Origin:
    • Orbital part: Frontal process of maxilla and medial palpebral ligament; surrounds the orbital margin.
    • Palpebral part: Bone above and below medial palpebral ligament.
    • Lacrimal part: Upper part of lacrimal crest and lateral surface of lacrimal bone.
  • Insertion: Skin around the margin of orbit and lateral palpebral raphe.
  • Action:
    • Blinking of 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 supraorbital margin.
  • Action: Pulls eyebrow medially and downward, forming vertical wrinkle.
Levator Palpebrae Superioris
  • Origin: Inferior surface of lesser wing of sphenoid.
  • Insertion:
    • Upper lamina: Skin of upper eyelid.
    • Middle lamina: Superior tarsus.
    • Lower lamina: Superior conjunctival fornix.
  • Action: Elevates upper eyelid (opening of 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 nose with the opposite muscle.
  • Action:
    • Transverse part: Compresses the nasal aperture.
    • Alar part: Dilates the nasal aperture.
Oral Group Muscles
Levator Labii Superioris
  • 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 upper lip.
Levator Anguli Oris
  • Origin: Canine fossa of maxilla.
  • Insertion: Angle of mouth.
  • Action: Raises the angle of mouth.
Zygomatic Major
  • Origin: Zygomatic bone.
  • Insertion: Angle of mouth.
  • Action: Pulls angle of mouth upward and laterally (e.g., 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 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 of mandible.
  • Insertion: Skin of the chin.
  • Action: Puckers the chin.
Buccinator
  • Origin:
    • Upper fibers: Outer surface of alveolar process of 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 teeth against the gums; enables 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 and puckering of lip.

Expression and Associated Muscles

  • 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 mostly supplied by branches of the:
    • Facial Artery
    • Superficial Temporal Artery
    • Maxillary Artery

Bell's Palsy

  • Possible symptoms of Bell's Palsy may include:
    • Smoothing of the forehead
    • Eyebrow droop
    • Facial paralysis, twitching, or weakness
    • Droopy eyelid, dry eye, or excessive tearing
    • Drooping corner of the mouth, dry mouth, impaired taste.