222 THE DIGESTIVE SYSTEM 



also connected with the anterior auricular lymph glands, which 

 lie superficial to the parotid. The lymph vessels of the mandi- 

 bular teeth also join the submaxillary lymph glands, but some 

 pass directly to the upper anterior group of the deep cervical 

 glands. These glands are associated with the upper part of 

 the internal jugular vein. 



THE SALIVARY GLANDS 



The Parotid is the largest of the three chief salivary glands. 

 It lies in a somewhat wedge-shaped recess, which is bounded 

 posteriorly by the anterior border of the sterno-mastoid, 

 anteriorly by the posterior border of the ramus and the 

 condyle of the mandible, and superiorly by the floor of the 

 external acoustic meatus. The anterior part of the gland 

 passes forwards into the face, overlapping the masseter muscle, 

 and is termed the facial process (Fig. 85). 



The parotid duct emerges from the facial process and, after 

 passing forwards across the masseter, it turns medially to pierce 

 the buccinator muscle. It then passes forwards for a short 

 distance in the submucous tissue of the cheek and pierces the 

 mucous membrane opposite the second molar tooth of the 

 maxilla. Its orifice is sometimes marked by a small papilla, 

 which may be felt with the tip of the tongue. The course of 

 the duct corresponds, on the surface, to the middle third of 

 a line drawn from the lower border of the external acoustic 

 meatus to a point midway between the red margin of the 

 upper lip and the ala of the nose. 



As the openings in the buccinator and in the mucous 

 membrane through which the duct passes are not placed 

 opposite one another, a valve-like arrangement is provided to 

 prevent the backward passage of air or fluid. Despite this 

 arrangement, the duct occasionally becomes greatly inflated 

 and forms a distinct tumour in the cheek. The condition 

 occurs most commonly in glass-blowers, who have to exercise 

 considerable expulsive force in the performance of their craft. 



