T.M. Joint: Temporomandibular Anatomy Quiz

Temporomandibular Joint (TMJ)

• Type: Biaxial condylar synovial joint
• Located between the head of the mandible and the mandibular fossa and articular tubercle

Articular Surfaces

• Fibrous capsule attached to:
  • Above: Margins of the mandibular fossa and articular tubercle
  • Below: Neck of the mandible
• Thickened laterally to form the temporomandibular ligament

Ligaments

• Temporomandibular ligament:
  • Triangular, thickened band of the lateral part of the capsule
  • Attached above to the articular tubercle and below to the lateral and posterior surfaces of the neck of the mandible
• Stylo-mandibular ligament:
  • From the anterior border of the styloid process to the angle and posterior border of the mandible
  • Separates the parotid from the submandibular gland
• Spheno-mandibular ligament:
  • From the spine of the sphenoid to the lingula of the mandible
• Pterygo-mandibular ligament:
  • From the pterygoid hamulus to the posterior end of the mylohyoid line of the mandible

Articular Disc

• Oval plate of dense fibrous tissue separating the joint cavity into upper and lower compartments
• Upper surface: Concavo-convex
• Lower surface: Concave
• Attached to the fibrous capsule all around and receives the insertion of the lateral pterygoid muscle

Nerve Supply and Blood Supply

• Nerve supply: Fine branches from the auriculo-temporal nerve and nerve to masseter
• Blood supply:
  • Maxillary artery
  • Superficial temporal artery

Movements of the Mandible (TMJ)

• Depression (opening the mouth):
  • Combined movement of simple hinge movement and gliding movement of the head
  • Mainly produced by lateral pterygoid muscles assisted by gravity
• Elevation (closing the mouth, occlusal position):
  • Reversed movements to depression
  • Produced by medial pterygoid, temporalis, and masseter muscles
• Protraction (forward movement):
  • Produced by lateral and medial pterygoids and superficial fibers of the masseter muscle
• Retraction (backward movement):
  • Produced by posterior fibers of the temporalis muscle
• Side to side movement (for grinding and chewing):
  • Produced by medial and lateral pterygoid muscles acting alternately

Temporal and Infratemporal Fossae

• Temporal Fossa:
  • Region on the side of the head below the temporal lines and above the zygomatic arch
  • Contents: Temporalis muscle, deep temporal vessels, and nerves
• Infratemporal Fossa:
  • Region below and medial to the zygomatic arch, behind the maxilla, and deep to the ramus of the mandible
  • Contents:
    • Muscles of mastication: Temporalis, medial and lateral pterygoid muscles
    • Blood vessels: Maxillary artery and its branches, pterygoid venous plexus
    • Nerves: Mandibular nerve, otic ganglion, and chorda tympani
    • Ligaments: Sphenomandibular ligament

Muscles of Mastication

• Temporalis:
  • Fan-shaped muscle with three sets of fibers (anterior, middle, and posterior)
  • Origin: Temporal fossa, temporal fascia, and inferior temporal line
  • Insertion: Tip and medial surface of the coronoid process and anterior border of the ramus of the mandible
• Masseter:
  • Origin: Temporal fossa, temporal fascia, and inferior temporal line
  • Insertion: Tip and medial surface of the coronoid process and anterior border of the ramus of the mandible
  • Actions: Elevation of the mandible by anterior fibers and retraction by posterior fibers