Head and Neck Anatomy: Temporal and Infratemporal Regions

Temporal and Infratemporal Regions

• Muscles of mastication: 4 muscles that arise from the 1st branchial arch, inserted into the mandible, and take nerve supply from the mandibular nerve
• The 4 muscles of mastication are:
  • Temporalis
  • Masseter
  • Lateral Pterygoid
  • Medial Pterygoid

Temporalis Muscle

• Origin: temporal fascia, inserted into the tip, anterior border, and medial surface of the coronoid process
• Nerve supply: deep temporal nerves
• Action:
  • Elevation of the mandible
  • Retraction of the mandible
• Relations:
  • Superficial relations: superficial temporal vessels, auriculo-temporal nerve, zygomatic arch, and masseter muscle
  • Deep relations: maxillary artery and pterygoid plexus of veins, buccal nerve and artery, deep temporal vessels and nerve, and temporal fossa

Temporomandibular Joint (TMJ)

• Composed of:
  • Synovial membrane
  • Articular cartilage
  • Articular disc (an oval plate of fibrous tissue that divides the joint into upper and lower compartments)
  • Capsule (lined by synovial membrane)
  • Accessory ligaments:
    • Lateral temporomandibular ligament
    • Sphenomandibular ligament
    • Stylomandibular ligament
    • Pterygomandibular ligament
• Blood supply: superficial temporal artery and maxillary artery
• Nerve supply: auriculotemporal nerve

Movements of the Mandible

• Position at rest:
  • Slight interval between upper and lower teeth
  • Lower teeth lie slightly behind the level of the upper teeth
• Movements:
  • Protraction of the mandible by lateral and medial pterygoid muscles and masseter
  • Retraction of the mandible by posterior fibers of temporalis, digastric, and geniohyoid muscles
  • Depression of the mandible (opening of the mouth) by lateral pterygoid, platysma, digastric, mylohyoid, and geniohyoid muscles
  • Elevation of the mandible (closure of the mouth) by temporalis, masseter, and medial pterygoid muscles
  • Side to side movement of the mandible (grinding) by lateral and medial pterygoid muscles

Dislocation of the Mandible

• Anterior dislocation: mandible displaced in front of the eminence, causing compression of the blood vessels
• Dislocation is very dangerous and can be treated by using 2 fingers to depress the mandible downward and then backward

Masseter Muscle

• Origin: lower border and inner surface of zygomatic arch
• Insertion: lateral surface of ramus of mandible
• Action:
  • Elevation of the mandible
  • Protraction of the mandible
• Nerve supply: nerve to masseter

Lateral Pterygoid Muscle

• Origin: by 2 heads, upper head from infratemporal crest of greater wing of the sphenoid, and lower head from lateral surface of lateral pterygoid plate
• Insertion: fovea in front of the head of the mandible
• Action:
  • Protraction of the mandible
  • Depression of the mandible
  • Side to side movement
• Nerve supply: anterior division of the mandibular nerve

Medial Pterygoid Muscle

• Origin: by 2 heads, superficial head from maxillary tuberosity, and deep head from medial surface of lateral pterygoid plate
• Insertion: medial surface of the ramus of mandible
• Action:
  • Elevation of the mandible
  • Protraction of the mandible
  • Side to side movement
• Nerve supply: medial pterygoid nerve

This quiz covers the anatomy of the temporal and infratemporal regions, including the muscles of mastication, mandibular nerve, maxillary nerve, and temporomandibular region. It's a comprehensive quiz for students of anatomy and embryology.