Muscles of the Face

Summary

• There are two types of muscles in the face
  1. Mimetic Muscles 
     • These are the muscles of facial expression
     • Innervate by CNVII (facial nerve)
  2. Muscles of Mastication 
     • These are used in mastication (i.e. chewing)
     • Innervated by CNV (trigeminal nerve)

Mimetic Muscles

• These muscles act to manipulate skin/muscle
  • Therefore attach from bone to skin/fascia

• Collectively, they have a sphincter-like activity in two key areas:
  1. Around the mouth
     • Orbicularis oris
     • Buccinator – also puffs out the cheeks
     • Risorius
     • Levators/depressors – there are several of these
  2. Around the eyes
     • Occipito-frontalis
     •  Orbicularis oculi – 3 parts
       1. Orbital part (squeezes eye shut)
       2. Palpebral part (gentle eye closure)
       3. Lacrimal part (tear release)
     • Levator palpebrae superioris
       • CNIII
       • Positioned in the upper eyelid
     • Procerus
       • Used in frowning

     • 

• Modiolus  – this is a chiasma of several muscles (seen as dimples)

• Innervation of the mimetic muscle is done by the five branches of CNVII (Ten Zulus Brought My Cat)
  • Trochlear
  • Zygomatic
  • Buccal
  • Mandibular
  • Cervical

Muscles of Mastication

• There are 5 muscles of mastication
  • All five are supplied by the three branches of CNV (trigeminal nerve)

    

1. Masseter
   • Attachments: from angle + ramus of mandible => zygomatic arch
   • Function: Elevation
   • 

     

2. Temporalis
   • Attachments: Temporal fossa => Coronoid process
   • Function: Elevation + retraction
   • 

     

3. Medial Pterygoid
   • Attachments:Medial angle of mandible => Medial aspect of Lateral Pterygoid Plate (LPP)
   • Function: Elevation + side-to-side movement

   • 

4. Lateral Pterygoid
   • Attachments: Condyle of mandible => Lateral aspect of LPP
   • Function: Depression + protraction
   • 

     

5. Digastric (anterior belly) – sometimes considered separate to the MofM
   • Attachments: Digastric belly => Mastoid notch of the temporal bone
   • Function: Depression along with infrahyoids

Actions of the muscles of mastication

1. Elevation
   • Masseter
   • Temporalis
   • Medial pterygoid
2. Depression
   • Gravity
   • Suprahyoid
   • Infrahyoid
3. Protrusion (moving the mandible forward)
   • Lateral Pterygoid
   • (Medial pterygoid)
4. Retrusion (moving the mandible back and bringing lower teeth in front of upper teeth)
   • Posterior Temporalis
   • Masseter
5. Grinding (side-to-side)
   ○ Unilateral action of pterygoid muscles