The morphology of the vertical and transverse intrinsic musculature of the tongue in the 15-week human fetus

Abstract

The attachments, courses and interrelationships of the transverse and vertical intrinsic muscle masses of the tongue were examined in 28 fifteen-week fetal specimens. Observations were made from 30-micron sections cut through the tongue in one of the three standard planes of section. Both sets of muscululature are qualitatively well-developed by this time period in fetal life. The transverse fibers were found to occupy the entire length of the tongue. They attach to the lamina propria of the lateral aspect of the body of the tongue and, in the root, to perimysial and adventitial connective tissue. In addition, some fibers were observed to be confluent with the mm. palatoglossus, tonsilloglossus and pharyngis superior. Medially, transverse fibers were found for the most part to terminate in the dense ventral aspect of the median septum. Vertical fibers are present from a point slightly posterior to the tip of the tongue to the level of the foramen cecum, beyond which they become sparse. All vertical fibers attach superiorly to the dorsal lamina propria. In the free part of the body, their ventral attachment, likewise, is to lamina propria. In the middle part of the tongue and, to a greater extent, in the root (as the inferior and lateral free surface decreases) these fibers attach in either the fascial plane underlying the transverse component or to the perimysium of longitudinally-running muscle bundles.