Temporomandibular Joint (TMJ)
Introduction
- Temporomandibular Joint (TMJ): Joint between the temporal bone and mandible.
- "Temporo" refers to the temporal bone.
- "Mandibular" refers to the mandible.
Type of Joint
- Condylar Variety of Synovial Joint
- Condylar process of the mandible fits into the temporal bone.
Articulating Surfaces
- Upper Surface: Mandibular fossa of the temporal bone.
- Lower Surface: Condylar process of mandible.
Ligaments
- Fibrous Capsule: Covers the joint.
- Lateral Temporomandibular Ligament: Located between the temporal and mandible bones.
- Stylomandibular Ligament: Situated between the styloid process and mandible.
- Sphenomandibular Ligament: Attaches from sphenoid bone to mandible.
Articular Disc
- Structure: Disc-like structure between articulating surfaces.
- Divides the joint into upper and lower compartments.
- Upper compartment: Permits gliding movement.
- Lower compartment: Permits rotary and gliding movements.
- Function: Reduces friction, acts as a shock absorber, and lubricates the joint.
- Regions: Anterior, anterior thick band, intermediate region, posterior thick band, and bilaminar region (contains venous plexuses).
Relations
- Anteriorly: Lateral pterygoid muscle, masseteric nerve, and vessels.
- Posteriorly: Parotid gland, external auditory meatus, superficial temporal vessels, auriculo-temporal nerve.
- Medially: Spine of sphenoid, sphenomandibular ligament, auriculotemporal nerve, chorda tympani nerve, middle meningeal artery.
- Laterally: Skin, fascia, parotid gland, facial nerve.
- Superiorly: Middle cranial fossa.
- Inferiorly: Maxillary artery and vein.
Nerve, Blood, and Lymphatic Supply
- Nerve Supply: Auriculotemporal nerve and Masseteric nerve.
- Blood Supply: Superficial temporal artery and Maxillary artery.
- Lymphatic Drainage: Upper cervical lymph nodes.
Movements of TMJ
- Depression: Opening of the mouth.
- Elevation: Closing of the mouth.
- Protrusion: Protraction of the chin.
- Retrusion: Retraction of the chin.
- Lateral (Side-to-side) Movements: Chewing or grinding.
- Upper Compartment: Movements between upper articular surface and articular disc.
- Lower Compartment: Movements between disc and head of mandibular condyle.
Muscles Involved in Movements
- Depression: Lateral pterygoid muscle.
- Elevation: Masseter, anterior vertical middle oblique fibers of temporalis, medial pterygoid muscles.
- Protrusion: Lateral and medial pterygoid, superficial oblique fibers of masseter.
- Retraction: Posterior horizontal fibers of temporalis, deep vertical fibers of masseter.
- Lateral Movement: Chewing assisted by opposite side lateral and medial pterygoid.
Clinical Anatomy
- Dislocation of Mandible: During excessive mouth opening.
- Derangement of Articular Disc: Due to injury like overclosure or malocclusion.
- Surgical Consideration: Preserve VII nerve (facial nerve) and auriculotemporal nerve.
Important Questions
- Describe TMJ under:
- Type
- Articular surfaces
- Ligaments
- Movements
- Nerve and blood supply
- Write a short note on movements of the TMJ.
Conclusion: TMJ is crucial for mandibular movements, and understanding its anatomy and function is essential for diagnosing and treating related disorders.