304 



THE MUSCLES OF THE HEAD AND NECK. 



Varieties. The origin of the muscle is sometimes pierced by the lingual artery. Th 

 triticeo-glossiis is a small muscle which arises from the cartilage triticea in the thyro-hyoi 

 ligament, and passes upwards and forwards, lying on the inner side of the lingual artery, t 

 enter the tongue with the posterior part of the hyo-glossus. 



The ckondro-glossus is a small flattened muscular slip, sometimes described a 

 a part of the preceding muscle, from which it is separated, however, by the pharyn 

 geal fibres of the genio-glossus. It arises from the inner side of the base of th 

 small cornu and from part of the body of the hyoid bone, and its fibres are directe 

 upwards and forwards, spreading somewhat, to end on the dorsum of the tongue b 

 the side of the middle line. It is sometimes wanting. 



The stylo-glossus, the shortest of the three muscles which spring from th 

 styloid process, arises from the front of that process near its point, and from th 



Fig. 279. MUSCLES OF THE TONGUI 



PHARYNX, &C., OK THE LEFT SIDE. (Alle 



Thomson. ) ^ 



a, external pterygoid plate ; b, styloi 

 process ; c, section of lower jaw ; d, hyoi 

 bone ; e, thyroid cartilage ; /, cricoid cart 

 lage ; between d and e, the thyro-hyoid men 

 brane ; </, isthmus of thyroid body ; 1, styl< 

 glossus muscle ; 2, stylo-hyoid ; 3, styl< 

 pharyngeus ; 4, cat edge of mylo-hyoid ; ' 

 genio-hyoid ; 6, genio-glossus ; 7, hyo-glossus 

 8, lingualis inferior ; 9, part of superior coi 

 stricter of pharynx ; 10, back part of midd 

 constrictor ; 11, inferior constrictor ; 1' 

 upper part of oesophagus ; 13, crico-thyroi 

 muscle. 



stylo-maxillary ligament, to whic 

 in some cases the greater number c 

 its fibres are attached : passing foi 

 wards and slightly downwards an 

 inwards, it is inserted along the sid 

 and under part of the tongue as fa 

 as the tip, its fibres decussating 

 and becoming blended with those c 

 the hyo-glossus and palato-glossu 

 muscles. 



Relations. This muscle lies deepl 

 beneath the parotid gland and angle of the jaw, and is crossed by the lingual nerve. 



Varieties. Absence and doubling of the stylo-glossus have both been noted. The myl( 

 ylossus is a small accessory slip, which generally arises from the angle of the lower jaw, bn 

 has also been seen coming from the stylo-maxillary ligament. Occasionally the whole muscl 

 arises from one of these points. The name stylo-auricularis has been given to a sma' 

 muscular slip occasionally seen, springing from the cartilage of the external auditory meatu 

 close to its attachment to the bone, and ending below on the styloid process, or passing i 

 part or wholly into the stylo-glossus. A fibrous band is often found in this situation. 



Nerves. The muscles of this group are all supplied with branches from the hypogloss; 

 or twelfth cranial nerve. 



Actions. The genio-glouut muscle has a complicated action, the hinder part protrudin* 

 and the fore part retracting the tongue, while the middle part, or nearly the whole muscl< 

 acts as a depressor. The stylo-glossus draws the tongue backwards, and elevates its base. ] 

 thus comes into play in deglutition. The muscle of one side acting alone gives a laterE 

 direction to the fore part of the tongue. The hyo-glotsus and chondro-glossus retract an 

 depress the tongue. The genio-glossus and stylo-glossus acting together tend to make th 

 dorsum of the tongue concave, while the hyo-glossus produces a convexity. 



