1146 



THE DIGESTIVE SYSTEM. 



From the posterior surface of the glosso-palatine arch a thin triangular fold 

 of mucous membrane, called the plica triangularis, passes backwards. Its base 

 corresponds to the glosso-palatine arch, its superior border is free, and passes down- 

 wards and backwards, frequently overlapping the tonsil. Its lower border is attached 

 to the side of the tongue. It covers, medially, the inferior part of the tonsillar fossa. 



The palatine tonsil presents very different forms in different individuals. 



It may project from the fossa into the cavity of the pharynx, or it may be 

 flat and limited to the tonsillar fossa. In some cases the plica triangularis is 

 fused with the free surface of the tonsil, and the lymph tissue may in some cases 

 be developed on the medial surface of that plica. 



Internal jugular vein 

 Accessory nerve 

 Digastric muscle 

 I 



Hypoglossal nerve 



Internal carotid artery 

 Vagus nerve 



Stylo-hyoid 



Glosso- 



pharyngeal nerve 



Parotid gland - 

 Posterior facial 

 vein 



External carotid 



artery 

 Styloglossus 



Ascending 

 palatine artery 



Internal pterygoid 



Epiglottis 



Glosso-epiglottic 

 fold 



Masseter 



Pharyngeal portion 

 of tongue 



Fungiform papil 

 Buccinator 



Sympathetic trunk 



Ascending pharyngeal artery 

 Dens 



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Retro-pharyngeal 

 lymph gland 



Superior 

 constrictor muscle 



Pharyngo-palatine 

 arch 



Palatine tonsil 



Pharyn go- epiglottic 

 fold 



Glosso-palatine 

 arch 



JS^Srv Vallate papillae 



Raphe of tongue 

 Conical papillae 



Fungiform papi 



FIG. 905. HORIZONTAL SECTION THROUGH MOUTH AND PHARYNX AT THE LEVEL OF THE PALATINE TONSILS. 



The stylopharyngeus, which is shown immediately to the medial side of the external carotid artery, and the 

 prevertebral muscles, are not indicated by reference lines. 



The palatine tonsils are oval in shape, with the long axes directed vertically. 

 and each presents a medial and a lateral surface, and a superior and inferior pole, 

 and an anterior and posterior margin. 



The medial surface is prominent and free, studded with small pit-like depressions 

 called the fossulse or crypts of the tonsil. 



The lateral, or attached surface, is enclosed in a distinct fibrous capsule, connected 

 with the pharyngo-basilar fascia, and this capsule separates the tonsil from the 

 superior constrictor muscle of the pharynx. 



The superior pole is rounded and blunt, and presents numerous fossulae. 

 inferior pole projects downwards towards the tongue. The 'anterior margin loofo 

 towards the glosso-palatine arch, and is often overlapped by the plica triangularis 

 the posterior margin is directed towards the pharyngo-palatine arch. 



