Jaw and Tongue Muscles in Instrumental Phonetics

Jaw Muscles

  • Functional Importance

    • Critical for mastication (chewing) and speech.

    • Categorized into two groups:

    • Elevators (lifters) - raise the jaw.

    • Depressors (lowerers) - lower the jaw.

Key Jaw Muscles

Masseter Muscle

  • Primary Function: Elevates the mandible (jaw closing).

  • Origin: Zygomatic arch.

  • Insertion: Ramus and angle of the mandible.

  • Parts: Divided into two parts:

    • Deep head

    • Shallow head

Temporalis Muscle

  • Function: Elevates and retracts the mandible (fast closing).

  • Origin: Temporal fossa (a shallow depression on the lateral side of the skull).

  • Insertion: Coronoid process of the mandible.

  • Anatomical Features:

    • Fan-like shape allows wide range of jaw movements.

    • Vertical (anterior) fibers elevate the mandible.

    • Horizontal (posterior) fibers retract the mandible.

Pterygoid Muscles

  • Composed of two muscles:

    • Medial Pterygoid:

    • Origin: Sphenoid bone, palatine bone, maxilla.

    • Insertion: Inner surface of the mandible.

    • Function: Elevates the mandible (similar to the masseter).

    • Lateral Pterygoid:

    • Origin: Sphenoid bone, maxilla.

    • Insertion: TMJ disc and condyle of the mandible.

    • Function: Controls side-to-side movement and protrusion of the jaw.

Jaw Depressor Muscles

  • Include:

    • Anterior belly of the digastric muscle.

    • Mylohyoid.

    • Geniohyoid.

  • Function: Responsible for lowering the mandible and stabilizing the hyoid bone, aiding in tongue movements.

Extrinsic Tongue Muscles

  • Role: Key for speech movements; connect the tongue to surrounding structures.

  • Major Muscles:

    • Genioglossus:

    • Origin: Mental spine of the mandible.

    • Insertion: Throughout the tongue, from tip to root.

    • Actions: Protracts, depresses; can groove the tongue.

    • Divisions:

      • Anterior section: Lowers and retracts tongue front.

      • Middle section: Lowers and pulls forward tongue body; creates groove.

      • Posterior section: Pulls tongue root forward.

    • Palatoglossus:

    • Origin: Palatine aponeurosis.

    • Insertion: Sides of the tongue body.

    • Actions: Elevates the tongue, assists in constrictions.

    • Hyoglossus:

    • Origin: Greater horn of the hyoid bone.

    • Insertion: Sides of the tongue.

    • Action: Pulls the tongue down and back.

    • Styloglossus:

    • Origin: Styloid process of the temporal bone.

    • Insertion: Sides of the tongue, interlocks with intrinsic tongue muscles.

    • Actions: Traditionally raises and retracts the tongue; ongoing research into its speech role.