The anatomy of m. genioglossus in the 15-week human fetus.

The attachments, course, and interrelationships of M. genioglossus were examined in 28 fifteen-week human fetal specimens. Observations were made from histologic sections of the tongue cut in one of the three standard planes of section. The anterior-most genioglossal fibers insert near the tip of the tongue at the level of the anterior extent of the median septum. Within the central mass of the tongue, some fibers of this muscle characteristically decussate across midline, a limited number below the level of the septum and a considerably larger number above it. Posteriorly, a few of the most posterior and inferior fibers of M. genioglossus could be traced to an attachment on the thickened perichondrium on the superior edge of the hyoid anlage. In other respects, the disposition of genioglossal fibers at this stage of development resembles closely that description generally given for the adult structure.