462 



THE MUSCULAR SYSTEM. 



It is directed downwards and somewhat posteriorly, along the inferior border of 

 the genioglossus, to be inserted into the anterior surface of the body of the hyoid 

 bone. The muscles of opposite sides are often fused together. 



The muscle is placed deeper than the anterior belly of the digastric muscle and 

 the mylo-hyoid, and is in contact with the inferior border of the genioglossus 

 muscle. 



Nerve-Supply. It is supplied by the hypoglossal nerve, but its nerve can be traced back 

 to an origin from the communication between that nerve and the first and second cervical 

 nerves. 



Actions. The digastric, stylo-hyoid, mylo-hyoid, and genio-hyoid muscles are all elevators 

 of the hyoid bone. The posterior belly of the digastric and stylo-hyoid also retract, while the 

 anterior belly of the digastric and the genio-hyoid protract it. The anterior belly of the digastric, 

 mylo-hyoid, and genio-hyoid also assist in opening the mouth. 



M. trans versus M. verticalis 

 linguae linguae 



M> 



The Muscles of the Tongue. 



The muscular substance of the tongue consists of two symmetrical series of 

 muscles placed on either side of a membranous raphe in the median plane. The 



series comprise (1) extrinsic 

 muscles arising from the soft 

 palate, styloid process, hyoid 

 bone and mandible, and 

 (2) intrinsic muscles proper 

 to the tongue itself. Each 

 set consists of four series of 

 muscles. 



A. The extrinsic mus- 

 cles are four in number:; 

 (1) genioglossus, (2) hyo- 

 glossus, (3) styloglossus, and? 

 (4) glossopalatinus. 

 Profmrta^^lf^^vmimmimm JfllUlf M - G-enioglossus.- 



lingute' 



artery .V^j 



Septum 



M. longitudffife 



Fat 



FIG. 411. A, TRANSVERSE, AND B, LONGITUDINAL VERTICAL 

 SECTIONS THROUGH THE TONGUE (Krause). 



The genioglossus muscle 

 (O.T. geniohyoglossus 



M. transversus (Fig. 408, p. 459) is an ex 

 trinsic muscle of the tongu< 

 as well as a supra -hyoi< 

 muscle. 



It is a fan-shaped muscl 

 arising by its apex froi 

 the superior of the two mental spines, behind the symphysis of the mandibl 

 (Fig. 410, p. 461). 



From that origin the muscular fibres diverge ; the lowest fibres are directe 

 downwards and backwards, to be inserted into the body of the hyoid bone ; th 

 highest fibres curve forwards, to be attached to the tip of the tongue ; the intei 

 mediate fibres are attached to the substance of the tongue in its whole lengt 

 between the base and tip. 



The muscles of opposite sides are separated by the median raphe of the tongu : 

 On the lateral aspect, of each, are the hyoglossus and mylo-hyoid muscles. 



M. Hyoglossus. The hyoglossus muscle is also an extrinsic muscle of tl 

 tongue as well as a supra-hyoid muscle. 



It arises from the body and great cornu of the hyoid bone. 

 It is directed upwards and forwards, to be inserted into the side of the tongi 

 its fibres interlacing with the fibres of the styloglossus. 



The muscle is quadrilateral, and lies between the genioglossus and mylo-hyc 

 muscles, separated from the latter by the mucous membrane of the floor of t 

 mouth, the sublingual and part of the submaxillary glands, the lingual and hyj 

 glossal nerves, and the submaxillary duct. 



The chondroglossus is a small separated slip of the hyoglossus, not always present. 



