Fig. 8.

Axial sections of the human tongue. The 3D model of the human tongue in the lateral view with the level of five axial sections marked. Sections are arranged from superior to inferior and labeled in mm relative to the most superior part of the tongue. In the 2 mm section the plane passes through the SL. The SL is composed of longitudinally arranged muscle fascicles, yet they interweave so extensively that this longitudinal orientation is not evident in it’s gross appearance. At the 4 mm level most of the tongue is the TV with the SL which is seen around the edges. In the axial plane the transverse muscle is sectioned lengthwise and is more evident then the vertical muscle. Fascicles of the transverse muscle originate from the midline septum and insert into the lateral boundaries of the tongue. A darker area next to the septum reflects the presence of GG muscle fascicles, which compose the vertical muscle in this area and are notably denser than the remainder of the vertical muscle. The 10 mm level passes through middle of the tongue and all tongue muscles are present. Note that in this specimen a regional expansion of the lateral tongue has filled the defect left by the loss of molar teeth (arrowhead). The GG is sharply delineated as a separate entity; it is shaped like a wedge and is composed of thick fascicles arranged in rows. Lateral to the GG the CL is quite prominent. Although this axial plane is below most of the TV, due to the tongue’s curve the TV is seen in the tongue base. A thin rim of SL is present anteriorly and posteriorly. The HG is cut in cross section and appears as a planar muscle with well defined dark muscle fascicles. Finally, the SG is seen close to its origin from the stylohyoid bone on the right side. However in the left side, which is at a lower level, some fascicles of the SG appear to pass through the HG to become transverse muscle fascicles (arrow). At the 12 mm level the most notable changes are that the courses of the IL and SG are seen. The SG has a posterior part that blends into and possible passes through the HG, and an anterior part that joins with the IL to form most of the CL. At the 20 mm level the entire course of the horizontal GG can be seen.