MYOFIBROUS ORGANIZATION OF THE ANTERIOR NECK MUSCLES (Mm. HYOIDEI)

Transverse muscle sections from 14 adult humans (10 males and 4 females) were studied for estimations on myofibrous organization of hyoid muscles, the number and the size and density of muscle fibers. The samples were embedded in celloidin and double-stained with hematoxylin and eosin, and the results were compared with those on other human muscles. The following results were obtained: 1) In the area of the transverse section of muscle belly, geniohyoid was the largest (an average of 101.5 sq. mm) . Superior omohyoid, inferior omohyoid and sternohyoid were in the range of the smallest area group, with an average of approximately 20 sq. mm. The range of hyoid muscles belonged to hand and foot muscles. 2) The number of muscle fibers per sq. mm. of geniohyoid and mylohyoid was approximately 800 per sq. mm. on the the average, and the female range for this parameter was larger than that for the male. In addition, other muscles were approximately 600 sq. mm. in size. No sex difference could be established. These muscles were as large as the masseter, in which the ranges were narrow in comparison to hand and foot muscles. 3) The total number of muscle fibers in geniohyoid was 80, 000, which was the largest by far. Mylohyoid, anterior belly of digastric and thyrohyoid were ranked in the second group, and stylohyoid, superior omohyoid and inferior omohyoid fell into the group having the smallest number, 40, 000 on the average. 4) Mean muscle fiber size was approximately 1, 000 μm². Data on this were generally greater in males than in females. The size distribution pattern had a tendency toward a multi-peaked pattern with advanced age. The range of muscle fiber mean size was approximately equal to that of hand muscle, was smaller than foot muscle and larger than masseter. 5) On muscle fiber density, geniohyoid and mylohyoid muscle had a density of about 80%, others were from 60 to 70% on the average. These findings were higher than those for masseter' but lower than those for rectus abdominis'.