The marginal part consists of the fibres immediately adjacent to the vermilion border, responsible for eversion and thinning of the lip margin. These are the fibres repaired in vermilion border lacerations.
| Origin | Modiolus at each lip corner — fibres from adjacent facial muscles converge |
|---|---|
| Insertion | Skin of the lip margins — dermis of the vermilion border |
| Nerve Supply | Facial nerve — buccal branches (VII) |
| Blood Supply | Facial artery — superior and inferior labial arteries |
| Actions | Everts the lip margins — thins and everts the red lip; Produces lip purse for kissing and whistling |
|---|
Precise alignment of the marginal orbicularis oris fibres at the vermilion border is the key to an aesthetic lip laceration repair. Misalignment by even 1 mm produces a visible step deformity. In cleft lip repair, the orbicularis oris muscle (including the marginal part) must be fully freed from its abnormal attachments and reoriented to re-create a functional oral sphincter.
Visible as the sharp vermilion border definition during lip puckering.
Vermilion border step deformity from imprecise marginal orbicularis alignment in lip laceration closure, requiring careful re-repair with loupe magnification.
