The orbicularis oris is the lip sphincter, formed by interlacing fibres from the surrounding facial muscles converging at the lips. Its contraction closes, protrudes, and shapes the lips for speech, swallowing, and expression. Cleft lip repair reconstructs the orbicularis oris by identifying and suturing the disrupted muscle layer across the cleft — this muscular repair is the critical step in cleft lip correction.
| Origin | No bony origin — the orbicularis oris is a complex of interlacing fibres from the facial muscles that converge at the lips (modiolus, perioral skin, and deep dermis) |
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| Insertion | Skin, mucosa, and modiolus of the upper and lower lips — the fibres encircle the mouth completely |
| Nerve Supply | Buccal and marginal mandibular branches of the facial nerve (VII) |
| Blood Supply | Superior and inferior labial arteries (from the facial artery) |
| Actions | Closes the mouth (lip compression); Protrudes the lips (pursing — whistling, kissing); Provides lip seal for swallowing and speech (bilabial consonants: B, P, M) |
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Primary cleft lip repair (Millard rotation-advancement technique) identifies and sutures the disrupted orbicularis oris muscle across the cleft — the muscle reconstruction is prioritised over skin tension. Incomplete muscular union produces the characteristic cleft lip scar band and flat philtrum. Orbicularis oris reconstruction in hemifacial microsomia and after tumour resection uses local advancement flaps.
The orbicularis oris is palpable as a firm ring encircling the mouth — its tone is assessed by lip compression against a spatula.
Orbicularis oris muscle continuity restored across the cleft as the primary step in lip repair producing normal lip seal and philtrum projection.
