SN2
SHORT NOTE
5M
★ High-yield
Describe the temporomandibular joint with its movements. Add a note on its dislocation.
Type and Articulation
The temporomandibular joint is a synovial, condylar (modified hinge) joint between the head of the mandible and the mandibular fossa and articular tubercle of the temporal bone.
- Its articular surfaces are covered with fibrocartilage, not hyaline cartilage — unusual among synovial joints, and shared with the sternoclavicular and acromioclavicular joints
- An articular disc divides the cavity into upper and lower compartments
Ligaments
| Ligament | Attachment | Function |
|---|---|---|
| Lateral (temporomandibular) | Articular tubercle to the neck of the mandible | The chief ligament; prevents posterior dislocation |
| Sphenomandibular | Spine of the sphenoid to the lingula | Accessory; a remnant of MECKEL cartilage; acts as a swinging hinge |
| Stylomandibular | Styloid process to the angle of the mandible | Accessory |
Movements
| Movement | Compartment | Muscles |
|---|---|---|
| Depression (opening) | Lower — hinge; then upper — gliding | Lateral pterygoid, digastric, geniohyoid, mylohyoid; assisted by gravity |
| Elevation (closing) | Both | Temporalis, masseter, medial pterygoid |
| Protrusion | Upper | Lateral and medial pterygoids |
| Retraction | Upper | Posterior fibres of temporalis |
| Side-to-side (chewing) | Both | Pterygoids of alternate sides |
Nerve and Blood Supply
- Nerves — auriculotemporal and masseteric branches of the mandibular nerve (V3) — consistent with Hilton's law
- Arteries — superficial temporal and maxillary arteries
Applied Aspects
- Anterior dislocation — from a wide yawn, a blow, or dental extraction. The head passes in front of the articular tubercle and spasm of the elevators holds it there; the mouth cannot be closed
- Reduction — the thumbs are placed on the lower molars and the mandible pressed downward and backward; the thumbs must be wrapped, as the jaw snaps shut
- Posterior dislocation is prevented by the lateral ligament and the postglenoid tubercle; a severe blow fractures the neck of the mandible instead
- Referred pain to the ear — the auriculotemporal nerve supplies both the joint and the external auditory meatus, so temporomandibular dysfunction is a common cause of "earache" with a normal ear
- Temporomandibular dysfunction syndrome — pain, clicking and limited opening, usually from bruxism or malocclusion; treated conservatively
- The joint is examined by placing a finger in the external auditory meatus and asking the patient to open and close the mouth
All questions in Head & Neck
- Q1Describe the triangles of the neck with their boundaries and contents. Add a note on the posterior triangle and its applied anatomy. ★
- Q2Describe the thyroid gland under relations, blood supply and nerve relations. Add a note on the applied anatomy of thyroidectomy. ★
- Q3Describe the parotid gland under bed, structures within it, duct and nerve supply. Add a note on its applied anatomy. ★
- Q4Describe the larynx under cartilages, cavity, muscles and nerve supply. Add a note on vocal cord palsy. ★
- Q5Describe the cavernous sinus with its contents and connections. Add a note on cavernous sinus thrombosis and the dangerous area of the face. ★
- SN1Describe the course and branches of the facial nerve. Differentiate upper from lower motor neurone facial palsy. ★
- SN2Describe the temporomandibular joint with its movements. Add a note on its dislocation. ★
- SN3Describe the submandibular gland with its relations, duct and nerve supply. ★
- SN4Describe the layers of the deep cervical fascia and the fascial spaces of the neck. ★
- SN5Describe the tongue with its papillae, muscles and nerve supply. Add a note on hypoglossal nerve palsy. ★
- SN6Describe the layers of the scalp with their clinical importance. ★
- SN7Describe the trigeminal nerve with its divisions and distribution. Add a note on the associated parasympathetic ganglia.