Re-evaluation of the orbicularis oculi muscle as revealed by the analysis of isolated muscle specimens.

Abstract

This study aimed to clarify the origin, insertion, and subdivision of the orbicularis oculi in detail with in situ specimens, as well as with isolated muscle specimens from the superficial and deep aspects. The periorbital muscles in fifteen cadavers fixed with formalin were examined in situ and/or in isolated muscle specimens, and evaluate their actions. The orbicularis oculi arose via the nasoglabellar aponeurosis, which was observable in the deep aspect of isolated specimens as a rigid sheet of connective tissue in the middle of both orbits and adhered to the dorsum nasi in situ (100%). The two subdivisions of the orbicularis oculi were demarcated at the lateral angle of the eye and exhibited different insertions. The fascicles of the upper and lower halves of the inner part met each other at the lateral canthus and formed a shallow groove between them as observed in situ, and terminated via the lateral palpebral raphe on the deep aspect of the muscle to the temporal fascia. The fascicles of the upper and lower halves of the outer part extended over the orbital margin and intermingled with each other to disperse in the temporal subcutaneous tissue. The nasoglabellar aponeurosis was structurally characterized as the common origin of the periorbital muscles. The present study confirmed that the inner and outer parts of the orbicularis oculi are distinguished by the difference of lateral termination and interpreted as having different function on the palpebral movement in each.