[Three-dimensional architecture of the intrinsic tongue muscles using a modified alkaline maceration method]

The three-dimensional architecture of the intrinsic tongue muscle fibers using the anterior part of the rabbit tongue was studied by scanning electron microscopy with a modified chemical-maceration method. The tongue tissues fixed with 10% formalin solution were treated with 1% OsO4 solution at 5 minutes for hardening of the specimen surface. Subsequently, they were immersed in 6N-NaOH solution for 30 minutes at 60 degrees C for the removal of connective tissues followed by dissection of muscle fibers under a binocular microscope to clarify the structure of the intrinsic tongue muscles. The specimens were treated with tannic acid and OsO4 (conductive staining method; Murakami, 1974), and observed with a SEM. Muscular fiber bundles of the transverse and vertical muscles of the tongue changed their direction at the alignment on the sites where the bundles enter the longitudinal muscles from the innermost surface to form monolayers of muscular bundles extending anteroposteriorly. These muscular bundles formed tunnel-like structures each of which covered a longitudinal muscle bundle. It was considered that these tunnel-like structures support the contraction of the longitudinal muscles as the "muscular sheath".