THE PHARYNX. 



1145 



(Fig. 903) presents a triangular area, sinus tonsillaris, bounded anteriorly by the 

 glosso-palatine arch, posteriorly by the pharyngo-palatine arch, and below by the 

 side of the tongue in its pharyngeal portion. This area is occupied in the greater 

 part of its extent by the tonsil. Above the tonsil there is a depression, the fossa 

 supratonsillaris (Fig. 903),- which is of considerable clinical interest. 



The arcus pharyngopalatinus (O.T. posterior pillar of the fauces) is a prominent 

 fold of mucous membrane, containing in its interior the pharyngopalatinus muscle. 

 It springs from the posterior edge of the soft palate, and, passing downwards and 

 slightly backwards, ends inferior ly on the side wall of the pharynx (Fig. 903). The 

 two pharyngo-palatine arches form the right and left boundaries of the pharyngo- 

 nasal isthmus, and the orifice can be 

 modified in size by the contraction of 

 the pharyngo-palatine muscles. 



The arcus glossopalatinus is de- 

 scribed on p. 1111. 



The isthmus pharyngonasalis is 

 the very oblique and somewhat tri- 

 angular orifice through which the oral 

 part communicates with the nasal part 

 of the pharynx (Fig. 904). It differs 

 considerably in size and shape in 

 different individuals, being in some so 

 small that the nasal part can be ex- 

 plored from the mouth only with very 

 great difficulty; whilst in others it 

 is of much larger dimensions (Fig. 

 905) and affords ample space for the 

 rhinoscopic examination of the nasal 

 part of the pharynx and the posterior 

 part of the nasal cavities. 



In general, it may be described 

 as triangular in shape, the sides corre- 

 sponding to the pharyngo-palatine TONSILS. 



arches, and the base, which is behind, Jt also shows the two palatine arches, and the pharyngo- 

 bpincr formpfl bv thp wmtprior wall of nasal isthmus, through which the nasal part, above, com- 



municates with the oral part of the pharynx, below. 



the pharynx. The apex of the triangle 



is directed towards the soft palate, and is encroached upon, and overlapped from 



below by the uvula, which assists in the closure of the orifice (Fig. 902). 



The philtrum 



Raphe of palate 



Uvula 



Pharyngo- 

 - palatine arch 

 Pharyngo- 

 nasal 

 isthmus 

 Palatine 

 tonsil 

 Glossp- 

 palatine arch 



Tongue 



FIG. 904. OPEN MOUTH SHOWING PALATE AND PALATINE 



By the contraction of the pharyngo-palatine muscles, which are enclosed within the 

 pharyngo-palatine arches, the sides of the isthmus can be approximated, like two curtains, 

 and its size correspondingly diminished. When, at the same time, the uvula and soft 

 palate are elevated, and the whole pharynx in this region is narrowed by the con- 

 traction of the superior constrictor, the aperture can be completely closed, and the 

 oral separated from the nasal part of the pharynx, as in the acts of swallowing and 

 vomiting. 



Tonsillse Palatinae. The palatine tonsils are two large, oval masses of lymph 

 tissue which are embedded in the side walls of the oral part of the pharynx, 

 between the glosso-palatine and pharyngo-palatine arches (Fig. 904). As already 

 pointed out, there is in this region a triangular interval (the sinus tonsillaris). 

 The greater part of this interval is occupied by the tonsil. In its superior part, 

 1 however, above the tonsil, there is usually found a variably developed depression 

 already referred to as the fossa supratonsillaris. 



The tonsillar sinus is bounded anteriorly by the glosso-palatine arch, passing 

 from the inferior surface of the soft palate to the side of the tongue. Posteriorly 

 it is bounded by the more vertical pharyngo-palatine arch, passing from the margin 

 of the uvula to the side wall of the pharynx. The inferior boundary is formed 

 by the margin of the tongue, while the narrpw apex above passes up to the side of 

 the soft palate. The tonsil occupies the inferior part of this sinus. 



