THE HEAD AND NECK 



1237 



opening of Wharton's duct, and near to this is the opening of the 

 duct of Rivini or of Bartholin, which comes from the outermost 

 lobule of the sublingual gland. A little posterior to this is a fold 

 of the mucous membrane, at either side, produced by the upper 

 border of the subjacent sublingual gland. This fold is known as 

 the plica sublingualis, and it extends from the side of the tongue 

 to the dental arch. It is upon this plica that the majority of the 

 ducts of Walther (sublingual ducts) open. 



The lips are covered by skin externally, and mucous membrane 

 internally. Between these two layers are the muscular fibres 



Descending Palatine Artery 



.Palatal Raph6 



.Uvula 

 [''' _.Post. Pillar of Fauces 



-Ant. Pillar of Fauces 



Tonsil 



I Posterior Wall of Pharynx^ '^ 



Dorsum of Tongue 



Fig. 503. — The Buccal Cavity and Isthmus Faucium. 

 (The Maxillae are widely separated). 



of the orbicularis oris, blended with which are the fibres of 

 the buccinator, and, in the case of the upper lip, fibres of the 

 depressor anguli oris, whilst in the case of the lower lip there are 

 the fibres of the levator anguli oris. Between the mucous mem- 

 brane and the muscular element there are a number of small race- 

 mose glands, called the labial glands, the ducts of which open on 

 the inner surface of each lip. The tortuous coronary arteries are 

 embedded in each lip, and those of opposite sides anastomose at the 

 median line. 



Between the upper lip and the columella nasi there is a groove, 

 called the philtrum. 



The lymphatic vessels of the npper lip pass, on either side, to the 

 submaxillary lymphatic glands. The Ijonphatic vessels of the 

 lateral portion of the lower lip also pass, on either side, to the sub- 

 maxillary lymphatic glands; and those of the mesial portion pass to 

 the submental, or suprahyoid, gland of the corresponding side. 



