Morphological study of the human chondroglossus muscle in Japanese.

The chondroglossus muscle was macroscopically studied to clarify its fundamental morphology. This muscle was present in all of the 100 tongue halves examined in Japanese cadavers. In 14% of the specimens, however, the muscular fibers were sparse and vestigial. Originating mainly from the medial side of the lesser cornu of the hyoid bone, the chondroglossus muscle passed upward to penetrate the inferior longitudinal muscle of the tongue, and immediately entered the genioglossus muscle. Ascending inside the genioglossus muscle, it's bundles spread, taking a broom head or a fan-like shape. Thereafter it reached the submucosal layer in the root of the tongue, changed the direction from upward to forward, and terminated diffusely, never going past the sulcus terminalis. The origin, course, and spreading manner of the chondroglossus muscle were quite different from those of the hyoglossus muscle. The nerve fiber supplying the chondroglossus muscle was a ramus from the first lateral branch of the hypoglossal nerve. It should be considered a separate extrinsic lingual muscle independent of the hyoglossus muscle, although they have a phylogenetically close relationship.