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Temporomandibular Joint (TMJ) Dysfunction and Emotional Stress

Muscles pretaining to TMJ

Muscles of mastication

All the following muscles are innervated by mandibular division of trigeminal nerve

• Masseter
  Origin: superficial fibres attach to the zygomatic process of the maxilla, and to the anterior two-thirds of the lower border of the zygomatic arch; deep fibres attach to the posterior third of the lower border and to the whole of the medial surface of the zygomatic arch.
  Insertion: superficial fibres attach at the angle and lower half of the lateral surface of the ramus of the mandible; deep fibres attach to the coronoid process of the mandible.
  Action: elevation and protraction of mandible

• Temporalis
  Origin: temporal fossa and deep surface of the temporal fascia.
  Insertion: the medial surface, apex, and anterior border of the coronoid process, and the anterior border of the ramus of the mandible nearly as far forward as the last molar tooth.
  Action: elevation of the mandible

• Medial pterygoid
  Origin: deep fibres attach to the medial surface of the lateral pterygoid plate and the grooved surface of the pyramidal process of the palatine bone; superficial fibres attach to the lateral surfaces of the pyramidal process of the palatine and tuberosity of the maxilla.
  Insertion: the inferior and posterior part of the medial surface of the ramus and angle of the mandible.
  Action: Bilateral contraction elevates and protracts mandible; unilateral contraction diducts mandible to contralateral side.

• Lateral pterygoid
  Origin: superior fibres attach to the lower part of the lateral surface of the great wing of the sphenoid and from the infratemporal crest; inferior fibres attach to the lateral surface of the lateral pterygoid plate.
  Insertion: into a depression in front of the neck of the condyle of the mandible, and into the front margin of the articular disk of the temporomandibular articulation.
  Action: Bilateral contraction protracts and depresses mandible; unilateral contraction creates side to side movement.

Suprahyoid muscles

• Digastric
  Origin: mastoid notch of the temporal bone
  Insertion: digastric fossa of the mandible, fastened to the greater horn of hyoid by fibrous loop, which is sometimes lined by a mucous sheath.
  Action: rises hyoid or depresses mandible
  Innervation: posterior belly by digastric branch of facial nerve; anterior belly by mylohyoid branch of trigeminal nerve

• Stylohyoid
  Origin: Styloid process of temporal bone
  Insertion: body and greater horn of hyoid – split by fibrous loop of the digastric attachment
  Action: draws hyoid and tongue superiorly and posteriorly.
  Innervation: styloid branch of facial nerve

• Mylohyoid
  Origin: mylohyoid line of the mandible.
  Insertion: the body of the hyoid bone and median fibrous raphé extending from the symphysis mentis to the hyoid bone, where it joints at an angle with the fibres of the opposite muscle.
  Action: elevation of the hyoid and posterior translation of mandible.
  Innervation: mylohyoid branch of trigeminal nerve.

• Geniohyoid
  Origin: inferior mental spine of the mandible
  Insertion: anterior surface of the body of the hyoid bone
  Action: draws tongue forward.
  Innervation: ventral rami of C1 and C2 spinal nerves through hypoglossal nerve.
  

Other muscles indirectly involved in TMJ

• Tensor tympani
  Origin: cartilaginous portion of the auditory tube and the adjoining part of the great wing of the sphenoid.
  Insertion: the manubrium of the malleus.
  Action: pull the malleus medially, tensing the tympanic membrane.
  Innervation: branches of the mandibular division of the trigeminal nerve, by way of the otic ganglion.

• Tensor veli palatini.
  Origin: scaphoid fossa at the base of the medial pterygoid plate, from the spina angularis of the sphenoid and from the lateral wall of the cartilage of the auditory tube.
  Insertion: aponeurosis at palatine bone.
  Action: elevates, retracts and lateral deviates soft palate with mastication; opens Eustachian tube.
  Innervation: mandibular division of the trigeminal nerve.