Innervation of upper orbicularis oris muscle.

The aim of this study is to elucidate the innervation of upper orbicularis oris muscle. The upper lips of 17 hemifaces of Korean adult cadavers were dissected. The number of nerve branches crossing and entering the outer margin of pars peripheralis and pars marginalis were counted, respectively. The location of ramifying point of the buccal branch was measured. The nerve branches crossing the outer margin of pars peripheralis were about 4 (3.71 +/- 1.05) on each side of the face and branches crossing the outer margin of pars marginalis was 4.65 +/- 1.46. About four (4.06 +/- 0.83) branches entering the pars marginalis were found. Most ramifying points (14/17, 82%) located within a circle of 5 mm in radius diameter and the center was at 12 mm lateral and 26 mm superior to the mouth corner. An anatomical knowledge might be contributive to understand a wrinkle depletion of the upper lip and function of the orbicularis oris muscle.