Muscles of Mastication Quiz

Muscles of Mastication

• The muscles of mastication move the mandible, enabling chewing and grinding
• The mandible can move in five ways: forward (protrusion), backward (retraction), up/close (elevation), down/open (depression), and side-to-side (rotation)
• Understanding these muscles is important for diagnosing and treating conditions like TMJ disorders, or post-treatment discomfort from interventions like impacted dental block.

Masseter Muscle

• A thick, quadrilateral muscle with two parts (superficial and deep)
• Origin (Superficial): Anterior two-thirds of the lower border of the zygomatic arch
• Origin (Deep): Posterior third of the lower border and the whole of the medial surface of the zygomatic arch
• Insertion (Both): Outer surface of the ramus of the mandible (superior to the superficial part).
• Action: Closing the mouth/elevates the mandible.
• Nerve Supply: Masseteric nerve (anterior division of the mandibular nerve).
• Blood Supply: Facial branch of the superficial temporal artery and masseteric branch of the maxillary artery.

Temporalis Muscle

• A fan-shaped muscle on either side of the head
• Origin: The whole of the temporal fossa, bounded at the top by the inferior temporal line.
• Insertion: The top and medial surface of the coronoid process, and the anterior border of the ramus of the mandible.
• Action: Elevates the mandible, and retracts the head of the condyle back into the glenoid fossa (backwards motion).
• Nerve Supply: Anterior and posterior deep temporal nerves (anterior division of the mandibular nerve).
• Blood Supply: Middle temporal branch of the superficial temporal artery. Deep temporal branches of the maxillary artery.

Lateral Pterygoid Muscle

• A short, thick, triangular muscle with two heads (upper and lower)
• Origin (Upper Head): Infratemporal surface and crest of the greater wing of the sphenoid bone.
• Origin (Lower Head): Lateral surface of the lateral pterygoid plate of the sphenoid bone.
• Insertion: Pterygoid fovea on the anterior aspect of the neck of the mandible.
• Action: Bilateral Contraction opens and protrudes the mouth. Unilateral action produces grinding or side-to-side movement.
• Nerve Supply: Lateral pterygoid nerve (anterior branch of the mandibular nerve).
• Blood Supply: Pterygoid branches of the maxillary artery.

Medial Pterygoid Muscle

• A thick, quadrilateral muscle with two heads (large deep and small superficial)
• Origin (Large Deep Head): Medial surface of the lateral pterygoid plate of the sphenoid bone.
• Origin (Small Superficial Head): Tuberosity of the maxilla and pyramidal process of the palatine bone.
• Insertion: Medial surface of the ramus and angle of the mandible (below and behind the inferior dental foramen).
• Action: Elevates the mandible and, in conjunction with the lateral pterygoid muscle, protrudes the mandible.
• Nerve Supply: Medial pterygoid branch of the mandibular nerve.
• Blood Supply: Pterygoid branches of the maxillary artery.

Digastric Muscle

• Composed of two bellies (anterior and posterior)
• Origin (Anterior Belly): Digastric fossa on the lower border of the mandible.
• Origin (Posterior Belly): Digastric notch on the mastoid process of the temporal bone.
• Insertion: Meets at the intermediate tendon above the hyoid bone, attached to the body of the hyoid bone via a fibrous sling
• Action: Depression of the mandible, elevates the hyoid bone during chewing and swallowing
• Nerve Supply: Anterior Belly- mylohyoid nerve, Posterior Belly- digastric branch of the facial nerve VII.
• Blood Supply:
• Anterior Belly- submental branch of facial artery.
• Posterior Belly– posterior auricular/occipital artery.

Buccinator Muscle

• Forms part of the cheek
• Origin: Pterygomandibularraphe, buccal alveolar bone, molars
• Insertion: Blends with the Orbicularis Oris at the corners of the mouth.
• Action: Pulls corner of the mouth back, compresses cheek against buccal surfaces of molars, regulates the vestibular region with the tongue.
• Nerve Supply: Facial nerve, buccal branch.
• Blood Supply: Facial & maxillary arteries.

Geniohyoid Muscle

• Located above the medial part of the mylohyoid line.
• Origin: Inferior genial tubercle
• Insertion: Body of the hyoid bone
• Action: Aids in deglutition and opening the mouth (depresses mandible),
• Nerve Supply: Hypoglossal nerve
• Blood Supply: Sublingual branch of the lingual artery

Genioglossus Muscle

• Origin: Superior genial tubercle on the inner surface of the mandible
• Insertion: Dorsum of the tongue (forming large fan-shaped muscle) Superior fibres—tip of the tongue, Inferior fibres—body of the hyoid bone
• Action: Depresses the tongue, Inferior fibres retract the tongue, Superior fibres protrude the tongue,
• Nerve Supply: Hypoglossal nerve.
• Blood Supply: Sublingual branch of the lingual artery and submental branch of the facial artery

Summary Table

• A summary table should be compiled to consolidate the information about each muscle- using the information above.