Temporal bone and TMJ Anatomy Lecture Notes

Temporomandibular Joint (TMJ) Lecture Notes

Course Information

  • Institution: Edith Cowan University (ECU), Australia

  • Course: SON1101 - Sectional Anatomy and Comparative Imaging 1

  • Lecture: Week 3, Lecture 3

Lecture Aim

  • Discuss the following topics related to the Temporomandibular Joint (TMJ):

    • The bony anatomy of the TMJ

    • Articular disk and ligaments of the TMJ

    • Muscular anatomy of the TMJ

    • Detailed learning outcomes

Bony Anatomy of the TMJ

  • The TMJ is classified as a modified hinge joint that facilitates mastication (chewing).

  • Articulating surfaces:

    • Mandibular fossa: Part of the temporal bone; forms the superior articulating surface.

    • Articular eminence: Anterior boundary of the joint; prevents the forward displacement of the mandibular condyle.

Articular Disk of the TMJ

  • The articular disk (commonly referred to as the meniscus) is shaped like a bowtie and is positioned between the mandibular condyle and fossa.

  • Functions:

    • Acts as a shock absorber during jaw movements.

  • Components of the meniscus:

    • Anterior band: Attaches to the lateral pterygoid muscle.

    • Posterior band: Has fibrous connections to the temporal bone and the posterior aspect of the condyle.

  • The articular disk is not tightly bound to the fossa, allowing it to move anteriorly with the condyle.

Ligaments of the TMJ

  • Several ligaments support the TMJ and maintain the position of the articular disk:

    • Collateral ligament: Attaches to the medial and lateral surfaces of the condyle.

    • Temporomandibular ligament (lateral ligament):

    • Extends from the articular eminence and zygomatic process to the posterior aspects of the articular disk, condylar head, and neck.

    • Provides lateral stability and restricts posterior movement of the condyle and articular disk.

Muscles Involved in TMJ Function

  • Muscles of Mastication: There are four primary muscles on each side of the TMJ responsible for the movement of the mandible:

    • Temporalis Muscle:

    • Shape: Fan-shaped

    • Origin: Temporal fossa

    • Insertion: Coronoid process and anterior ramus of the mandible

    • Function: Elevates the mandible.

    • Masseter Muscle:

    • Description: The strongest muscle of the jaw.

    • Origin: Zygomatic arch

    • Insertion: Ramus and angle of the mandible

    • Function: Elevates the mandible.

    • Pterygoid Muscles:

    • Medial Pterygoid Muscle:

      • Origin: Pterygoid processes of the sphenoid bone

      • Insertion: Angle of the mandible

      • Function: Closes the jaw.

    • Lateral Pterygoid Muscle:

      • Origin: Pterygoid processes of the sphenoid bone

      • Insertion: Condylar process of the mandible

      • Function: Opens the jaw and allows for protrusion and lateral movement of the mandible.

Imaging of the TMJ

  • MRI of TMJ:

    • Can be used to visualize the TMJ in various states (mouth closed vs. mouth open):

    • Mouth Closed:

      • Features: Glenoid fossa, articular disk, condyle.

    • Mouth Open:

      • Changes in position of the articular disk.

  • CT Imaging: Details of the TMJ and associated muscles can be observed using axial CT scans that highlight the structures surrounding the joint

  • Ultrasound: Provides additional imaging perspectives on the TMJ.

References

  • Kelley, Lorrie L., and Connie Petersen.

    • Title: Sectional Anatomy for Imaging Professionals - E-Book, Mosby, 2018.

  • Mayo Clinic, TMJ Symptoms and Causes.

  • Tanteri, G., Prandi, R., Lodo, P., Margolo, N., Carnazza, G. (2020). TMJ and MRI Anatomy.

  • Various research articles on TMJ anatomy and imaging methods, including comparisons between ultrasound and MRI.

Questions

  • Any questions?