QS Study

The temporomandibular joint (TMJ) acts as a sliding hinge, connecting our jawbone to our skull. It lets us move your jaw up and down and side to side, so you can talk, chew, and yawn. It is located anteriorly to the tragus of the ear, on the lateral aspect of the face.

Movements – Movements at this joint are produced by the muscles of mastication, and the hyoid muscles.

  • Protrusion.
  • Retraction.
  • Elevation.
  • Depression.
  • Side to side movement.

The upper part of the joint allows protrusion and retraction of the mandible – the anterior and posterior movements of the jaw. The lower part of the joint permits elevation and depression of the mandible; opening and closing the mouth.

Action:

Depression (Open mouth): Lateral pterygoid, Suprahyoid and Infrahyoid

Elevation (Close mouth): Temporalis, Masseter, and Medial pterygoid.

The protrusion (Protrude chin): Masseter (superficial fibers), Lateral pterygoid and Medial pterygoid.

Retrusion (Retrude chin): Temporalis and Masseter (deep fibres).

Side-to-side movements (grinding and chewing): Temporalis on the same side, Pterygoid muscles of opposite side and Masseter.

Muscles Producing Temporomandibular Joint 1

Fig: Muscles Producing Action on Temporomandibular Joint

Muscles producing movements –

(1) Protrusion By:

  • Medial pterygoid is responsible for protrusion (assisted by the medial pterygoid), and the posterior fibers of the temporalis perform retraction.
  • Lateral pterygoid is achieved by alternately protruding and retracting the mandible on each side.

(2) Retraction By: Posterior fibers of temporalis.

(3) Elevation By:

  • Masseter.
  • Temporalis and
  • Medial pterygoid of both sides.

The elevation is a very strong movement, caused by the contraction of the temporalis, masseter, and medial pterygoid muscles.

(4) Depression: By – Lateral pterygoid muscle. However, if there is resistance, the digastric, geniohyoid, and mylohyoid muscles assist.

(5) Side to side movement: By – Medial & lateral pterygoid muscles of each side acting alternately. These movements are performed by alternative contraction of medial and lateral pterygoids on every side.

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