660 



DISSECTION OF THE PHARYNX. 



Seven aper- 

 tures, viz. 



Posterior 

 nares. 



Eustachian 

 tube 



cartilagi- 

 nous part ; 



pharyngeal 

 opening ; 



construc- 

 tion. 



Fauces. 



Isthmus of 

 the fauces. 



Upper 

 opening of 

 larynx. 



On raising the soft palate, the opening into the mouth isthmus 

 faucium (H) is exposed, bounded laterally by a mucous fold which 

 descends to the tongue and is named the anterior pillar of the fauces ; 

 while between the anterior and posterior pillars on each side is 

 hollow containing the tonsil (K). 



Next in order, below the mouth, comes the aperture of the 

 larynx (N) with the epiglottis projecting above it. Lowest of al] 

 is the opening (o) from the pharynx into the (esophagus. 



The apertures into the pharynx are seven in number, and have 

 the following position and boundaries : 



The posterior openings of the nasal fossce (choanae ; G) are oval in form, 

 and measure about an inch from above downwards, but only half an 

 inch across. Each is constructed in the dried skull by the sphenoid, 

 with the vomer and palate bones above, by the palate below, by tht 

 vomer internally, and by the internal pterygoid plate on the outer sid 



The EUSTACHIAN TUBE (p) is a canal, partly osseous, partly cartih 

 ginous, by which the tympanic cavity of the ear communicates wit] 

 the external air." 



If the mucous membrane be removed from the tube on the right 

 side, the cartilaginous part is seen to be nearly an inch long. It is 

 fixed above to a groove between the petrous part of the temporal 

 and the sphenoid bones, and ends in front by a wide opening on 

 the inner side of the internal pterygoid plate, on a level with the 

 posterior extremity of the inferior spongy bone of the nose (fig. 237, 

 p. 670). Its opening in the pharynx is oval in form, and the inner 

 margin projects forwards, giving rise to a trumpet-shaped mouth. 



This part of the tube is constructed of a triangular piece of yellow 

 fibro-cartilage, which is bent downwards on each side so as to enclose 

 a narrow space. The inner portion is larger than the outer, and 

 increases in breadth from behind forwards. On its outer side the tube 

 is completed by fibrous tissue. The cartilage is covered on its inner 

 side by mucous membrane, and through the tube the mucous lining 

 of the cavity of the tympanum is continuous with that of the pharynx. 



The space included between the root of the tongue and the soft 

 palate is called the fauces. It is wider below than above ; and on 

 each side lies the tonsil. 



The ISTHMUS FAUCIUM (H) is the narrowed aperture of communica- 

 tion between the mouth and the pharynx. It is bounded above by 

 the soft palate, below by the tongue, and on the sides by the anterior 

 pillars of the soft palate. Its size varies with the movements of these 

 parts, and it can be closed by the meeting of the soft palate and the 

 tongue. 



The APERTURE OF THE LARYNX (N) is wide in front, where it is 

 bounded by the epiglottis, and pointed behind between the arytenoid 

 cartilages. The sides are sloped from before backwards, and are 

 formed by folds (aryteno-epiglottidean) of the mucous membrane 

 extending between the arytenoid cartilages and the epiglottis. 

 Behind it is limited by the cornicula laryngis, and by the arytenoid 

 muscle covered by mucous membrane. During respiration this 



