460 



THE MUSCULAK SYSTEM. 



line of the thyreoid cartilage. The muscle is marked by an oblique tendinous 

 intersection in the middle of its length. 



M. Thyreohyoideus. The thyreo-hyoid muscle continues the line of the 

 preceding muscle to the hyoid bone. Short and quadrilateral, it arises from the 

 oblique line of the thyreoid cartilage. 



Passing over the thyreo-hyoid membrane, deep to the omo-hyoid and sterno- 

 hyoid, it is inserted into the body and great cornu of the hyoid bone. 



The levator glandulae thyreoideae is an occasional slip stretching between the hyoid bone 

 and the isthmus or pyramid of the thyreoid gland. 



STERNO-CLEIDO- 

 MASTOID 



SEMISPINALIS CAPITIS 



SPLENIUS CAPITIS 



LEVATOR SCAPULAE 



SCALENUS MED1US 

 SCALENUS ANTERIOR 



OMO-HYOID 

 TRAPEZIUS 



MYLO-HYOID 

 j- DIGASTRIC 

 HYOGLOSSUS 

 STYLO-HYOID 

 MIDDLE CONSTRICTO: 

 THYREO-HYOID 



INFERIOR 

 CONSTRICTOR 



^OMO-HYOID 

 INFERIOR 

 CONSTRICTOR 



STERNO-HYOID 

 STERNO-THYREOII . 



FIG. 409. THE MUSCLES OF THE SIDE OF THE NECK (anterior and posterior triangles). 



Nerve-Supply. TJae sterno-hyoid, sterno- thyreoid, and omo-hyoid are supplied by the ansa 

 hypoglossi ; the thyreo-hyoid, by a special branch from the hypoglossal nerve. Through the ansajM 

 hypoglossi the muscles are innervated by nerves which are ultimately derived from the first 

 three cervical nerves. The descendens hypoglossi is derived from the first two cervical nerves, 

 the descendens cervicis by the second and third ; and these two trunks combine to form the ' 

 ansa. The thyreo-hyoid muscle is innervated (through the hypoglossal) from the loop between if 

 the first and second cervical nerves. 



Actions. The sterno-hyoid, sterno-thyreoid, and omo-hyoid are depressors of the hyoid bone 

 The two former muscles are also accessory muscles of inspiration. The omo-hyoid is a feeble 

 elevator of the scapula. The thyreo-hyoid is, on the one hand, an elevator of the thyreoid cartilage 

 and acting with the previous muscles, on the other hand, it is a depressor of the hyoid bone. 



The supra-hyoid muscles comprise the digastric, stylo-hyoid, mylo-hyoid, anc 





