THE KURUME MEDICAL JOURNAL Vol.27, P.233-237, 1980 ON THE SHAPE OF THE MUSCLES OF THE TONGUE OF EUMECES LATISCUTATUS LATISCUTATUS MICHIO MIYAZAKI" AND TAKAYUKI NAKAMURA The First Department of Anatomy Kurume University school of Medicine. Kurume, and The First Department of Oral Anatomy Fukuoka Dental College, Fukuoka, 814, Japan Received for publication October 5, 1980 Due to the difference in the method of food catch and intake even in the same kind of animals the tongue and the muscles of the tongue are different in shape, respectively. Accordingly, morphological comparisons were perf or- med between the muscles of the tongue of the amphibia, the reptiles, and the fish and those of Eumeces latiscutatus latiscutatus examined belonging to the reptiles. INTRODUCTION the neck. After decalcification, neu- tralization, washing, and dehydration It is well known that the method of as usual, the tissues were imbeded in food catch and intake of every kind of paraffin, and serial sections of 10ƒÊ animals depends upon the function of were prepared, double-stained with the muscles of the tongue. Thereupon, Hematoxylin-Eosin, and examined. the muscles of the tongue of a newt, a bull frog, and a Xenopus loevis be- longing to the amphibia, of a gecko FINDINGS belonging to the reptiles, and of a Bokophthalmus pectinirostris belonging The Os hyoideum of Eumeces latiscu- to the fish have so far been investiga- tatus latiscutatus lies on the ventral ted morphologically and comparative aspect of the mandibula. It consists of anatomically and their function con- the basihyal bone which is cartilaginous sidered. This time, on the shape of and a part of whose tip intrudes into the muscles of the tongue of Eumeces the tongue and of 2 pairs of the pro- latiscutatus latiscutatus belonging to cesses projecting from this before and the reptiles a report will be made. behind: the cornu anterius and the cornu posterius. On the other hand, regarding the MATERIALS AND METHOD muscle groups of the tongue partici- pating in the tongue movement on the Materials used were Eumeces la- region of the tongue there are the Mm. tiscutatus latiscutatus living through- hyoidei laterales such as the M. genio- out Japan except for a part of Hokkaido glossus, M. geniohyoideus, M. hyoglossus after fixation in a 10% formalin solu- and M. sternohyoideus, and the Mm. tion. The animals were beheaded from hyoidei mediales such as the M. trans- 233 234 MIYAZAKI AND NAKAMURA versus linguae, M. longitudinalis linguae, the hyoid body to its tip, the bilateral and M. verticalis linguae. muscle bundles draw a little outward from the median plane and gradually A detailed report of these muscle dwindle away. Moreover, this is a groups of the tongue is as follows: muscle which pulls the tongue backward, 1. M. genioglossus and among the muscles penetrating The M. genioglossus, as seen in Figs. the tongue it seems to be the most 3 and 4, arises from the medial side well-developed and function the most of the tip of the mandibula, running effectively. back along the dorsal aspect of the M. geniohyoideus, and intrudes into the 4. M. sternohyoideus tongue from the body of the tongue to The M. sternohyodeus, which is its root obliquely along the lateral side regarded as a continuation of the M. of the M. hyoglossus. However, this rectus abdominis, arises from the muscle which pulls the tongue out of ventral side of the sternum, passing the mouth functionally is poor in the by the lateral side of the trachea, and development. attaches to the medial surface of the hyoid bone. This is also a muscle which 2. M. geniohyoideus pulls the hyoid bone backward. The M. geniohyoideus, as seen in Figs. 3, 4, 5, and 6, arises from the 5. M. transversus linguae posterior surface of the fore end of The M. transverses linguae, as seen the mandibula (sulcus mentalis), run- in Figs. 1, 2, 3, 5, and 6, is observable ning back between the M. genioglossus below within the M. hyoglossus at the and the M. inframandibulae, and pas- origin of the root of the tongue. It sing through under the M. hyoglossus arises from the upper part of the medial from the body of the tongue to its side of this muscle, runs forward, and back, becomes a somewhat flattened spreads toward the upper part of the muscle bundle and attaches to the lat- lateral side. As it approaches the tip eral side of the tongue. This is also a of the tongue, it gradually becomes muscle which pulls the tongue out of one muscle band. Thus, it begins with the mouth like the M. genioglossus. the upper part of the M. hyoglossus (the lower part of the M. longitudinalis) 3. M. hyoglossus and ends with the tip of the tongue. The M. hyoglossus, as given in Figs. 1-6, arises from the lateral side of the 6. M. longitudinalis linguae cor nu pos teri us of the hyoid bone, The M. longitudinalis linguae, as seen running forward as a pair of the mus- in Figs. 1-5, is only observable in the cle bundle, right and left. After pas- back of the tongue and in the lower sing by the lateral side of the carti- surface of the lateral side. The muscle lagines laryngis, it penetrates the bundle in the back of the tongue arises tongue at its origin. When it reaches from the rear of the hyoid bone and the tip of the tongue, the bilateral ends after running through from the muscle bundles gather in the median upper partof the M. transversus lin- plane and present a shape embracing guae to the apex lingue, while the mus- the body of the hyoid bone, which is a cle bundle observable in the lower sur- tubulous hyoid muscle surrounding this face of the lateral side arises from the muscle. And then, as it moves from lower aspect of the M. transversus lin- SHAPE OF THE TONGUE MUSCLE 235 guae at the origin of the hyoid root along the dorsal aspect of the M. in- and runs forward along the lower sur- f ramandibulae, and further, after face of the bilateral side of the tongue. passing through under the M. hyoglossus, Especially, a pair of the muscle bundles attaches to the lateral side of the hyoid nearest the M. hyoglossus, as they bone. approach the tip of the tongue, adhere 3. The M. hyoglossus arises from to the lower surface of this muscle and the lateral aspect of the cornu poster- becomes one muscle bundle. However, ius of the hyoid bone and runs forward . other muscle bundles end with the apex After passing by the lateral side of linguae. the cartilagines laryngis it penetrates the tongue at the origin of its root , 7. M. verticalis linguae reaching the apex linguae without The M. verticalis linguae, as seen bifurcating. On the way, a tubulous in Figs. 5 and 6, arises from the medial hyoid muscle which seems to embrace side of the M. hyoglossus at the origin this muscle, appears. This muscle is a of the hyoid root before or after the retractor and as a muscle penetrating appearance of the M. transversus lin- the tongue it is the most favorable in guae, or it arises from the bilateral the development. sides. They are, in both cases , a mus- 4. The M. sternohyoideus is regarded cle running vertically. as a continuation of the M. rectus The former runs forward, adhering abdominis. It arises from the ventral to the muscle arising from the lower side of the sternum passing forward, part of the ventral side of the hyoid it reaches the medial side of the hyoid bone, and runs toward the apex lin- bone. guae between the M. hyoglossus, end- 5. The M. transversus linguae arises ing nearly with the disappearance of from the upper part of the medial side the hyoid bone, while the latter in- of the M. hyoglossus at the origin of trudes from the back of the tongue the root of the tongue. Running for- into the muscle bundles of the M . ward, it gradually spreads out and longitudinalis linguae below and ends ends with the apex linguae after pass- with the apex linguae. ing by along the upper part of this muscle. 6. The M. longitudinalis linguae a- CONCLUSION rises from the back of the tongue or from the lower part of the lateral side The muscles of the tongue of Eumeces at the origin of its root and runs to- latiscutatus latiscutatus were investiga- ward the apex linguae above or below ted histologically. The results obtained the transversal muscle band, respec- are as follows: tively. Partially, a pair of the muscle 1. The M. genioglossus arises from bundle seen on the innermost side under the medial side of the tip of the man- the transversal (on the side of the M. dibula, running back along the dorsal hyoglossus) adheres to the lower part aspect of the M. geniohyoideus . Fol- of this muscle. lowing the course from the body of the 7. The M. verticalis linguae arises tongue to its root it intrudes obliquely from the upper part of the medial side into the tongue. of the M. hyoglossus or from its lat- 2. The M. geniohyoideus arises from eral side at the origin of the tongue the sulcus mentalis, running backward root before or after the appearance of 236 MIYAZAKI AND NAKAMURA the M. transversus linguae. The former that, as seen in a newt or in snakes runs forward between the M. hyoglos- in Formosa reported by Konishi, a sus and ends with the disappearance tubulous muscle of the tongue was of the hyoid bone, while the latter confirmed around the M.