MUSCLES OF THE PHARYXX. 



187 



the greater number of 

 passing forwards slightly 



Fig. 163. 



stylo-maxillary ligament, to which in some 

 its fibres are attached by a thin aponeurosis 

 downwards, it is inserted 

 along the side and under part 

 of the tongue as far as the tip, 

 its fibres decussating, and be- 

 coming blended with those of 

 the hyo-glossus and palato- 

 glossus muscles. 



This muscle lies deeply beneath 

 the parotid gland, and is crossed 

 by the gustatory nerve. It arises 

 occasionally from the inner side of 

 the angle of the lower jaw ; and 

 cases have been observed in which 

 it was altogether absent. 



Fig. 163. VIEW OB- PART OE THR 

 LEFT SIDE OF THE HEAD AND 

 THROAT, TO SHOW THE DEEP MUS- 

 CLES OF THE CHEEK, PHARYNX, 

 &0. (modified from Cloquet). ^ 



The pharynx has been distended 

 by stuffing, a, external pterygoid 

 process ; 6, styloid process, with 

 short portions of the three styloid 

 muscles attached ; c, body of the 

 lower jaw, which has been divided 

 at the place where the pterygo- 

 maxillary ligament + is attached ; 

 d, body of the hyoid bone; e, 

 thyroid cartilage ; /, cricoid carti- 

 lage ; g, interval between the first 

 and second ring of the trachea ; 1, 

 outer part of the orbicularis oris muscle ; 2, buccinator ; 3, superior constrictor of the 

 pharynx ; 4, middle constrictor ; 5, inferior constrictor ; 6, oesophagus ; 7, points by 

 three lines to the lower parts of the stylo-glossus, stylo-hyoid, and stylo-pharyngeus 

 muscles respectively ; 8, mylo-hyoid ; 9, hyo-glossus, of which a small part is removed 

 posteriorly to show the attachment of the middle constrictor ; 10, thyro-byoid. 



ACTIONS. The genio-glossus muscle has a complicated action, one part protruding 

 and another retracting the tongue, while a third depresses the middle portion of the 

 organ. Protrusion is effected by contraction chiefly of its posterior, and retraction 

 by contraction of its anterior fibres, and the middle part, or nearly the whole muscle, 

 acts as the depressor. In deglutition the stylo-glossus muscle raises the sides of the 

 tongue spasmodically backwards and upwards, while the hyo-glossus opposes that 

 action. In other circumstances the first muscle assists in forming a hollow, while 

 the second tends to producing a convexity in the dorsum of the tongue. 



MUSCLES OF THE PHARYNX AND SOFT PALATE. 



THE PHARYNX, the dilated superior part of the alimentary tube, extending 

 from the base of the skull to the oesophagus, presents at the sides and pos- 

 teriorly a continuous wall, in great part formed and supported by distinct 

 muscles resting in front of the vertebral column, and is open in front 

 towards the nasal cavity, the mouth, and the larynx, 



The constrictors of the pharynx are three thin expanded muscles which 

 invest the pharyngeal wall, overlapping one another upwards, so that the 

 lowest is most superficial. 



