658 



DISSECTION OF THE PHARYNX. 



in swallow- 

 ing; 



of upper 

 constrictor. 



Pterygo- 

 maxillary 

 ligament. 



Dissection 

 to show 



longitudinal 

 muscles. 



Dissection. 



Interior of 

 pharynx. 



Objects to 

 be noted. 



same time will diminish the size of the pharynx ; and as the anterior 

 attachments of the lower muscles are nearer together than those o 

 the upper, the tube will be contracted more behind the larynx than 

 near the head. 



In swallowing, the object is first seized by the lower part of the 

 upper constrictor, and then forced on to the oesophagus by the succes 

 sive action of the middle and inferior constrictors. Since the back o 

 the pharynx is closely applied to the prevertebral muscles, iron 

 which it cannot be separated in the natural condition of the parts 

 the effect of the contraction of these muscles is to draw the tongue 

 hyoid bone and larynx backwards, as well as somewhat upward 

 owing to the oblique direction of the greater number of the fibres o 

 the middle and lower constrictors ; and the cavity, when empty, 

 compressed from before backwards. 



The upper part of the superior constrictor narrows the space above 

 the mouth, and assists in bringing together the posterior pillars 

 the soft palate. (See the action of the palato-pharyngeus, p. 664.) 



The pterygo-maxillary ligament is a thin fibrous band which passe 

 from the tip of the hamular process to the hinder end of the myh 

 hyoid ridge of the lower jaw, and gives origin in front to the middle 

 fibres of the buccinator and behind to the superior constrictor. It : 

 often partly concealed externally by the meeting of the fleshy fibre 

 of the two muscles. 



Dissection (fig. 233). By dividing the middle and inferior con 

 strictors midway between their origin and insertion, and reflecting 

 the parts forwards and backwards, the longitudinal fibres of th( 

 pharyngeal wall will be exposed. 



The LONGITUDINAL or ELEVATOR MUSCLES of the pharynx are the 

 stylo-pharyngeus and palato-pharyngeus. The stylo-pharynyeus has 

 already been described (p. 626), but it may now be followed to its 

 insertion. The palato-pharyngeus is only partially seen, and will be 

 described with the muscles of the soft palate. Its fibres appear 

 behind those of the stylo-pharyngeus, and descend to the lower part 

 of the pharynx, reaching backwards to the middle line. 



Dissection (fig. 233). Open the pharynx by an incision along th< 

 middle, and, al'ter removing the tow from the interior, keep it open 

 with hooks : a better view of the cavity will be obtained by partly 

 dividing the occipital attachment on each side. 



The INTERIOR OF THE PHARYNX is wider from side to side thai 

 from before backwards, and its greatest width is opposite the hyoic 

 bone ; from that spot it diminishes both upwards and downwards 

 but much more rapidly in the latter direction. In it the following 

 objects are to be noticed. 



At the top are situate the posterior apertures (G) of the nasa 

 fossae, which are separated by the septum nasi. Below them hangs 

 the soft palate, partly closing the opening into the mouth ; and from 

 its free margin a prominent fold of the mucous membrane, the 

 posterior pillar of the fauces (L), is continued downwards and back- 

 wards on each side of the pharynx. Immediately behind each nasal 



