Muscles of the Xeck 



257 



Processus coronoideus 

 mandibnlae 



/- 



Ramus mandibnlae 



Os hvoideum 



M. mylohyoideus 



M. geniohyoideus 



303. Muscles of the floor of the mouth, 



viewed from behind and above. 

 (The imiscles of the tongue have been completely removed.) 



M. mylohyoideus (see also Figs. 298 and 300), unpaired. Form: flat, quadrangular, 

 broad, above, hullo wed out, like a trough. Position: stretches between the lower jaw and 

 the hyoid bone and thus forms the floor of the mouth; immediately adjacent to its lower 

 surface lies the anterior belly of the m. digastricus. Origin: hneae mylohyoideae mandibnlae. 

 Insertion: the fibers run parallel to one another on each side, backward, downward and 

 medianward and are attached for the most part to a medially situated connective-tissue raphe; 

 the posterior fibers go to the anterior surface of the corpus oss. hyoidei. Action: when the 

 hyoid bone is fixed, it depresses the lower jaw; when the lower jaw is fixed, it draws the hyoid 

 bone forward and ui)ward. Innervation: n. mylohyoideus (V. 3). 



M. geniohyoideus (see also Fig. 302). Fo'^rm:" flat-cylindrical, oblong. Position: on 

 the upper (buccal) side of the m. mylohyoideus, completely hidden by it from below; the 

 mm.-g'eniotiyoidei of the two sides are immediately adjacent to one another in the median plane. 

 < ) r i g i n : by a short tendon from the spina men talis inandibulae. Insertion: the fibers, diverging 

 a httle, extend to the anterior surface of the corpus oss. hyoidei. Action: when the hyoid 

 bone is fixed, it depresses the lower jaAv; when the lower jaw is fixed, it draws the hyoid bone 

 forward and upward. Innervation: n. h^'ijoglossus. 



Bursa [mucosa] subcutanea promineutiae laryugeae (see Fig. 302), often absent, 

 usually found only in men and only in older individuals ; it is unpaired and lies in the sub- 

 c\itaneous tissue in fi-ont of the upper part of the thyreoid cartilage. 



Bursa m. sternohyoidei (see Fig. 302), almost constant, is better developed in the 

 male than in the female and lies, if unpaired, in the median plane or, if paired, close to the 

 median plane upon the lig. hyothyreoidenm medium, between it on the one hand and the 

 m. stemohyoideus and the fascia colli on the other; it extends upward behind the hj'oid bone. 



Bursa m. thyreohyoidei (not shown in the drawing), stQl more constant than the 

 preceding, lies below the cornu majus oss. hyoidei, upon the membrana hyothjTeoidea, between 

 it and the upper end of the m. thyreohyoideus. 



