Muscle fiber types of human orbicularis oculi muscle

초록

The aim of this study was to elucidate the muscle type of the orbicularis oculi muscle in humans using immunostaining. The eyelids of 5 Korean adult cadavers were used. A 1:1000 mouse monoclonal anti-skeletal myosin antibody solution (fast) was used for immunostaining. On sagittal sections, pre-septal, upper pre-tarsal, mid-pre-tarsal, lower pre-tarsal, and ciliary parts were selected and 0.38mm x 0.38mm rectangular areas were photographed. The number and size of the muscle fibers in each part were evaluated by the image analyzer program and calculated per unit area (1mm2). Fast fibers (87.8 ± 3.7%) occupied a significantly larger portion of the muscle (p=0.000) than non-fast fibers (12.2 ± 3.7%). Among the 3 areas (pre-septal, pre-tarsal, and ciliary parts), the ciliary part had a significantly (p=0.019) higher portion (91.7%) of fast fibers than the pre-tarsal part (86.6%). The diameter of the fast fibers (17.7 ± 2.6μm) was significantly greater (p= 0.000) than the non-fast fibers (13.0 ± 2.1μm). Our results showed that the eyelid has a higher proportion of fast muscle fibers than the mouth. Closing of the eyelids is faster than the mouth; however, the duration or power associated with closing of the mouth is stronger than closing of the eyelids.