Surgical Anatomy of the Deep Neck: Layers, Landmarks and Danger Zones

Deep neck contouring is safe when the surgeon always knows which layer the instruments are in and what lies immediately beneath it. The anatomy is not complicated; it is compact. That is exactly why it is easier to learn at the dissection table than from a diagram.

The layers, from skin to floor of mouth

1. Skin and subcutaneous fat. The plane of liposuction and of skin redraping.
2. Platysma. A thin muscle sheet whose medial borders diverge to a variable degree in the submental region.
3. Subplatysmal fat. The deep fat between the medial platysmal borders, over the anterior bellies of the digastric.
4. Anterior digastric bellies. Paired muscles running from the mandible towards the hyoid, framing the submental triangle.
5. Mylohyoid. The muscular floor beneath the digastric; deeper structures of the floor of the mouth lie beyond it.
6. Submandibular gland. In the submandibular triangle, partly wrapping around the posterior border of the mylohyoid.

The hyoid bone sits beneath it all as the skeletal reference point for the cervicomental angle.

Nerves that define the danger zones

• Marginal mandibular branch of the facial nerve. Runs deep to the platysma near the mandibular border and can lie below it in some patients. It is at risk during subplatysmal dissection along the jawline and over the gland. Injury weakens the lower lip depressors.
• Cervical branch of the facial nerve. Supplies the platysma. Its injury can also produce an asymmetry of the lower lip, which is why lower lip weakness after neck surgery is not always a marginal mandibular injury.
• Lingual nerve and the submandibular duct. On the deep aspect of the gland. They matter whenever the gland is reduced or mobilised.
• Great auricular nerve. Crosses the sternocleidomastoid laterally and matters during lateral neck dissection and skin flap elevation.

Vessels

• Facial artery and vein. Closely related to the submandibular gland and crossing the mandibular border; central to bleeding risk in gland surgery.
• Anterior jugular veins. In the subplatysmal plane of the anterior neck; easy to encounter during central dissection.

Bleeding control is not a detail in this region: hematoma and airway compromise lead the list of complications discussed on Day 01. In the 2025 series of 83 partial gland excisions with a vessel-sealing device, no intraglandular bleeding or postoperative hematoma was reported, while transient lower lip weakness occurred in 7 patients, all recovering within six months. See Submandibular gland management in deep plane neck lift.

Landmarks worth trusting

• The mandibular border and the anterior border of the masseter as the region where the facial vessels and the marginal mandibular branch converge.
• The medial borders of the platysma as the doorway to the subplatysmal space.
• The anterior digastric bellies as the lateral walls of central deep contouring.
• The hyoid as the deep reference for the angle and for where the platysma will be adapted.

Where this is taught at All About The Neck

• Day 01, 10:15. Surgical anatomy of the neck: layers, landmarks and danger zones, including subcutaneous and subplatysmal planes, digastric and mylohyoid relationships, facial vessels, and the marginal mandibular and cervical branches.
• Day 02, 09:30 to 12:45. Access and superficial dissection, entering the deep neck, digastric, mylohyoid and hyoid relationships, and mapping the submandibular region with faculty prosection of the duct and adjacent neural anatomy.
• Day 02, 16:45. Danger-zone review and complication scenarios on the specimen.