THE HI'. AH AND NECK. 



99 



//6>7t.' is the pharyngecU plexus formed and wJiat docs it supply f 



Tliis plexus is formed by the union of branches from 



1. The superior cervical ganglion of the sympathetic. 



2. The glosso-pharyngeal nerve, the ninth cranial nerve. 



3. The pneumogastric or vagus nerve, the tenth cranial nerve. 



4. The superior laryngeal nerve, a branch of the vagus. 



This plexus supplies the mucous membrane and muscles of the pharynx and 

 all the muscles of the soft palate except the tensor palati, which receives its 

 nerve-supply from the otic ganglion. 



The pharyngeal plexus may be seen on your dissection on the outer surface 

 of the middle and inferior constrictors of the pharynx. 



What functions may be rationally attributed to the soft palate as a ivlwlc ? 



Its principal function seems to be to direct food to the stomach and protect 

 the other cavities communicating with the pharynx from invasion by the food, 

 (i) The anterior pillars of the fauces and the tongue prevent regurgitation into 

 the mouth. (2) The posterior pillars of the fauces prevent regurgitation into 

 the nose through the posterior nares. (3) The epiglottis protects the larynx. 

 (4) The levator palati forms a temporary roof over the pharynx during deglu- 

 tition, and thereby protects the Eustachian tube. (5) The tensor palati opens 

 the Eustachian tube during deglutition. 



THE PHARYNX. 



This cavity is situated behind the nose, mouth, and larynx. It connects the 

 mouth with the oesophagus. It is in communication with : 



1. The larynx, which is guarded by the epiglottis. 



2. The oesophagus, its downward continuation to the stomach. 



3. The tympanum, through the Eustachian tube. 



4. The nose, by the posterior nares. 



5. The mouth, being partially shut off by the fauces. The proper muscles 

 of the pharynx are: (i) The superior constrictor pharyngis. (2) The middle 

 constrictor pharyngis. (3) The inferior constrictor pharyngis. (4) The stylo- 

 pharyngis muscle. (5) The palato-pharyngeus muscle. 



The inferior constrictor you will find arising from (i) the cricoid cartilage ; 

 (2) the oblique line of the thyroid; (3) the inferior cornu of the thyroid. It 

 is inserted into the fibrous raphe. (Fig. 62.) 



The middle constrictor arises from the cornua of the hyoid bone, and from 

 the stylo-hyoid ligament. (Fig. 62.) It is inserted into the median raphe, the 

 fibres being disposed as follows : (i) The inferior fibres extend downward and 

 are overlapped by the inferior constrictor ; (2) the superior fibres extend upward 

 and overlap the superior constrictor in part ; (3) the middle fibres extend hori- 

 zontally. (Fig. 62.) 



The superior constrictor muscle of the pharynx (Fig. 62) is pale and 

 thin in comparison with the inferior constrictor. The reason of this will be 

 appreciated when you understand the mechanism of deglutition. Growth is the 

 correlative of function : the function of the inferior constrictor is vigorous con- 

 traction, hence its roborous fibres ; on the other hand, the function of the superior 

 constrictor is a retaining bag, hence its predominance of connective over muscular 

 tissue. 



This muscle has the following origins, u;hk:U ae ,\vcl ; sl)<-un>iri figure. 62 : (i) 

 From the internal pterygoid plate, lovcr tluVd, and .its ha.rii'.lar process; (2) 



