The Muscles of Mastication

Masseter

The masseter muscle is the most powerful muscle of mastication. It is quadrangular in shape and has two parts: deep and superficial.

It lies superficial to the pterygoids and temporalis muscles.

• Attachments:
  • The superficial part originates from maxillary process of the zygomatic bone.
  • The deep part originates from the zygomatic arch of the temporal bone.
  • Both parts attach to the ramus of the mandible.
• Actions: Elevation of the mandible (closes the mouth).
• Innervation: Mandibular nerve (V₃).

By TeachMeSeries Ltd (2025)

Fig 1
The masseter muscle. Only the superficial head is visible

Temporalis

The temporalis muscle originates from the temporal fossa – a shallow depression on the lateral aspect of the skull.

The muscle is covered by tough fascia which can be harvested surgically and used to repair a perforated tympanic membrane (an operation known as a myringoplasty).

• Attachments: Originates from the temporal fossa of the skull and attaches onto the coronoid process of the mandible.
• Actions: Elevation of the mandible (closing the mouth). Also performs retraction of the mandible (moving the jaw posteriorly).
• Innervation: Mandibular nerve (V₃).

By TeachMeSeries Ltd (2025)

Fig 2
The temporalis muscle.

Medial Pterygoid

The medial pterygoid muscle has a quadrangular shape with two heads: deep and superficial. It is located inferiorly to the lateral pterygoid.

• Attachments:
  • The superficial head originates from the maxillary tuberosity and the pyramidal process of palatine bone.
  • The deep head originates from the medial aspect of the lateral pterygoid plate of the sphenoid bone.
  • Both heads attach to the ramus of the mandible near the angle of mandible.
• Actions: Elevation of the mandible (closing the mouth).
• Innervation: Mandibular nerve (V₃).

Lateral Pterygoid

The lateral pterygoid muscle has a triangular shape with two heads: superior and inferior. It has horizontally orientated muscle fibres, and thus is the major protractor of the mandible.

• Attachments:
  • The superior head originates from the greater wing of the sphenoid.
  • The inferior head originates from the lateral pterygoid plate of the sphenoid.
  • The two heads converge into a tendon which attaches to the neck of the mandible.
• Actions:
  • Bilateral action – protraction of the mandible and depression of the chin.
  • Unilateral action  – ‘side to side’ movement of the jaw.
• Innervation: Mandibular nerve (V₃).

By TeachMeSeries Ltd (2025)

Fig 3
The medial and lateral pterygoids.