Muscles, movement and a fractured condyle

Correct answer: B. Anteromedially

• A. There is no muscular vector drawing the fragment straight up.
• B. Correct. The lateral pterygoid inserts into the pterygoid fovea on the anterior condylar neck and into the articular disc. When the neck fractures, that muscle pulls the proximal fragment anteriorly and medially, which is why displaced condylar fragments are so consistently found in that position.
• C. Straight posterior displacement is not the pattern; the lateral pterygoid pulls forward, and its medial course adds the medial component.
• D. Posterolateral displacement would require a posterior and lateral pull, and no muscle acts on the condyle in that direction.

Correct answer: D. Both the buccinator and the medial pterygoid

• A. Both muscles have maxillary attachments, so this cannot be right.
• B. The medial pterygoid's superficial head attaches to the tuberosity, but again this is not the only correct option.
• C. The buccinator does attach to the maxilla, but it is not the only one of the pair that does.
• D. Correct as this question is keyed. The buccinator arises in part from the alveolar process of the maxilla opposite the molars, and the medial pterygoid has an accessory superficial head arising from the maxillary tuberosity and the pyramidal process of the palatine bone. Both therefore have a maxillary attachment.

Note: The medial pterygoid's main deep head arises from the medial surface of the lateral pterygoid plate and inserts on the mandibular angle. Its small superficial head is the maxillary attachment being tested here.

Correct answer: A. Lateral pterygoid

• A. Correct, and this is the exception. The inferior head of the lateral pterygoid is the principal muscle of opening, protruding the mandible and pulling the condyle and disc forward down the articular eminence. Its superior head stabilises the disc during closure but the muscle as a whole is not a closer.
• B. The masseter is a powerful elevator and the strongest muscle of mastication by force per cross-sectional area.
• C. The medial pterygoid elevates the mandible, working with the masseter as a functional sling around the angle.
• D. Temporalis elevates the mandible, and its posterior fibres retrude it.

Correct answer: D. The posterior fibres of temporalis

• A. The inferior head of lateral pterygoid protrudes the mandible, which is the opposite movement.
• B. The anterior temporalis fibres are near vertical and elevate the mandible.
• C. The superficial masseter fibres run downward and backward, so they elevate and slightly protrude.
• D. Correct. The posterior fibres of temporalis run almost horizontally forward to the coronoid process, so their line of pull draws the mandible backward. They are assisted in retrusion by the deep masseter fibres and the digastric.

Correct answer: D. Rotation occurs in the lower compartment first, followed by translation in the upper compartment

• A. This reverses the two compartments. Translation belongs to the upper joint space.
• B. The upper compartment is a gliding joint, not a rotational one.
• C. Pure hinge rotation without translation is what produces the first stage of opening, so translation is not the only movement.
• D. Correct. The TMJ is divided by the disc into two functional compartments. The lower, between condyle and disc, is the rotational or hinge compartment and accounts for roughly the first 20 to 25 mm of opening. The upper, between disc and glenoid fossa, is the translational or gliding compartment that carries the condyle-disc assembly forward down the eminence for wider opening.

Note: The recall recorded a bare choice between rotation and translation. Rotation is correct for opening about the condylar axis, but the full answer is that the two movements are sequential and occupy different joint compartments.

Correct answer: C. The ramus of the mandible

• A. The submandibular gland relates to the body of the mandible, lying in the submandibular triangle and hooking around the posterior border of mylohyoid.
• B. The styloid process and the muscles arising from it form part of the deep boundary of the parotid bed, but the gland wraps the ramus.
• C. Correct. The parotid occupies the retromandibular fossa and wraps around the posterior border of the ramus, with a superficial lobe lateral to it and a deep lobe medial. Between them run the facial nerve, the retromandibular vein and the external carotid artery, which is why identifying the nerve is the central problem of parotid surgery.
• D. The zygomatic arch is the superior boundary of the parotid region, not the structure it envelops.