Applied Anatomy Study Of Localizations Of Zygomatic Branch And Marginal Mandibular Branch Of Facial Nerve To Muscles

Objectives: To indentify localizations and surface marks of the zygomatic branch of facial nerve(ZB) to the musculus zygomaticus and the marginal mandibular branch of facial nerve(MMB) to the depressor anguli oris.Methods: 10 (20 sides) 10% formalin-fixed specimens of adult cadaveric head were used to make microscopic observation which contained the course,anatomical relation and distribution of ZB and MMB . Their innervating pattern and location where they enter musculus zygomaticus and depressor anguli oris were measured respectively. Coordinate systemⅠ(regarding of the horizontal line threading labial commissure as X-axis, the vertical line threading external canthus at the same side as Y-axis) and coordinate systemⅡ(regarding the labial commissure as original point, the horizontal and vertical lines threading original point as X and Y-axis respectively) were established. The locations of the terminal branches which pass through muscles of ZB in coordinate systemⅠand MMB in coordinate systemⅡwere measured and recorded respectively, while surface positioning were made.Results: Zygomatic branch of facial nerve which came out of the parotid from its anterior superior edge was mainly divided into two branches (rated 65%, 13 sides). Orbicularis oculi muscle was innervated by the superficial branch ramus superfacialis which passed through the surface of head side of major zygomatic muscle; the ramus profundus which entered the major zygomatic muscle through its deep plate in the upper half part was the main branch, divided into 2-6 branches,(average 3.40±1.06). The number of nerve branches entering the muscle was 3-8(average 6.00±1.49). Among the total, with regarding the intersection of suprema branch(Z1) and the outer edge of major zygomatic muscle as point"A", the intersection of the most inferior branch(Z2) and the outer edge of major zygomatic muscle as point"B", the connection line"AB"was the surface projection of localizations of ZB to musculus zygomaticus. Marginal mandibular branch of facial nerve which originated from the inferior division of facial nerve, 80% came out of the parotid from its anterior inferior edge passing through the superior edge of mandibular angle and posterior border of masseter, mainly one branch (rated 60%), the majority (rated 60%) of them course along upper direction of mandible's inferior border, after spanning the face blood vessel ,divided into 2-8 branches, (average3.5±1.78), entering deep plate of depressor anguli oris, innervating this muscle in claw-shaped or clump-shaped way. Among the total, the intersection of suprema branch(M1) and the outer edge of depressor anguli oris as point"a", the intersection of the most inferior branch(M2) and the outer edge of depressor anguli oris as point"b", the connection line"ab"was the surface projection of localization of MMB to depressor anguli oris. Numbers of branches entering this muscle was 5-11(average 8.0±2.52). The marginal mandibular branch interanastomos with buccal branch of facial nerve and mental nerve by tiny communicating branches.Conclusion: In the face surgery operations, it is safe to undermine on 2/3 depth below the major zygomatic muscle and for avoiding injuring the ZB, it is necessary to avoid undermining below the zygomatic plane, especially on the 1/2 depth; while undermining on 1/2 depth below major zygomatic muscle, it is good to operate through deep plane of this muscle to avoid injuring the buccal branch of facial nerve. Pathway of MMB relates much with inferior border of mandible and facial artery. The branch of MMB enters the deep plane of depressor anguli oris 30mm from the lateral vertical of angle of mouth and interanastomos with mental nerve around mental foramen, so we should take care it in operation to reduce post-operation complications.