Lower face injection anatomy: jawline, chin, perioral
Jawline, chin and perioral region — where the arteries are close, the muscles are functional, and errors are immediately visible.
The lower third combines a dense arterial supply with constant functional demand. Errors here are visible in conversation, not just in photographs.
Muscles
Orbicularis oris forms the sphincter of the mouth. Into it insert the elevators — levator labii superioris, zygomaticus major and minor — and the depressors: depressor anguli oris (DAO), depressor labii inferioris, mentalis.
Each participates in speech and eating, so weakening any of them has functional consequences. The DAO is a common toxin target for a downturned mouth corner, but it sits directly adjacent to the depressor labii inferioris; diffusion between them produces an asymmetric smile that lasts months.
Mentalis hyperactivity gives the chin its dimpled appearance. Masseter hypertrophy widens the lower face and responds to toxin, with the caveat that sustained reduction changes bite mechanics.
Arteries
The facial artery crosses the mandible at the anterior border of masseter — one of the few places on the face where the pulse is readily palpable, and therefore a landmark worth using. It then runs toward the nose, giving off the inferior and superior labial arteries.
The labial arteries run within or just deep to orbicularis oris, most often on the posterior aspect of the lip near the wet-dry border. Their depth varies between individuals. This is the anatomical reason routine lip filler carries a genuine occlusion risk.
Ligaments and the jowl
The mandibular retaining ligament tethers soft tissue near the parasymphysis. Tissue lateral to it descends while tissue at the tether stays, producing the prejowl sulcus and the jowl beside it. The jowl is a boundary effect. Filling the sulcus without addressing the descent adds weight to a region already carrying too much.
The mental foramen
Sits on the mandible between the premolars, transmitting the mental nerve and vessels. Volume placed over it can compress the nerve and produce lip and chin numbness. It is also the target for a mental block, which is a far more comfortable route to perioral anaesthesia than repeated infiltration.
Practical implications
- Palpate the facial artery at the mandibular border before working along the jawline.
- In the lip, stay superficial to the labial arteries, inject slowly, keep aliquots small.
- For the DAO, favour concentrated product and precise placement over volume and spread.
- Assess whether a jowl is descent or volume before choosing what to do about it.
