256 



Anatomy of Skeleton 



the posterior part of the region, however, the muscle is carried on over the facial vessels, 

 and usually blends here with the Risorius muscle. 



The mucous membrane on the outside of the alveolus belongs to the alveolo-labial 

 or extra-dental sulcus, and it can be seen (Fig. 204) on the bone that the sulcus becomes 



shallower as it is traced back- 

 wards : the Buccinator is attached 

 opposite the molars, nearer the line 

 of the teeth than the muscles 

 further forward. 



Behind the last molar the 

 mucous membrane becomes con- 

 tinuous with that on the inner 

 side of the jaw by a narrow strip 

 crossing the extreme back part of 

 the alveolus. This strip lies 

 between the last tooth and the 

 attachment to the bone of the 

 pterygo - mandibular ligament, 

 which passes downwards and out- 

 wards to this point from the bony 

 region formed by the lower end of 

 the internal pterygoid plate and the 

 tuberosity of the palate. 



The Buccinator arises from 

 the front aspect of the ligament, 

 and its line of origin extends on to 

 the jaw (Fig. 204) forwards and 

 outwards from the point of attach- 

 ment : the upper Constrictor 

 reaches the jaw along the back 

 aspect of the ligament, obtains 

 a few fibres of origin from the 

 bone behind and internal to the 

 attachment, and then passes along 

 the mucous membrane to the 

 tongue. The diagram in Fig. 206 shows the arrangement of the structures in this 

 region, and the path of the lingual nerve is seen below, behind, and outside the fibres 

 of the Constrictor, and then below the mucous membrane to reach the tongue. 



FIG. 204. Attachments and relations of mandible. Upper figure shows the inner side of the right half of 

 the bone. The parallel lines indicate the regions in relation with the inner and outer Pterygoid 

 muscles ; between the former and the bone several structures are seen (compare Fig. 207), but the 

 external Pterygoid is in direct contact with the jaw and the Temporal insertion, the masseteric 

 vessels alone intervening between it and the bone. The outer aspect (lower figure) shows the 

 ramus covered by Masseter with the exception of a small area above and behind where the parotid 

 lies on the bone. The body is divided by the Buccinator and oblique line into an upper and front part * 

 covered by mucous membrane, and a lower and back part covered by facial muscles, deep to which the 

 facial vessels cross the bone and pass on to the Buccinator. The arrows mark the borders of the 

 Temporal tendon ; observe the extent of its insertion. 



The same diagram also shows that the ramus of the jaw with its attached muscles 

 is placed in contact with the side wall of the pharynx. The Internal Pterygoid is 

 the deepest of these muscles, and is therefore the one in immediate contact with the 



FIG. 203. A diagrammatic sketch to show how the salivary 

 glands of the floor of the mouth come into relation with 

 the lower jaw. The mass of the tongue is supposed to 

 have been removed, the hyoid divided through the 

 body, and the left half of the mandible and Mylo- 

 hyoid viewed from the inner side. The major portion 

 of the submaxillary gland is seen to lie on the outer side 

 of the Hyoglossus, which has been cut across near its 

 origin, and the posterior part of the gland comes into 

 relation with the Internal Pterygoid insertion ; the 

 front part of the gland reaches the edge of Mylo-hyoid 

 and passes partly below and external to it and partly 

 above and internal to it. It is the former of these 

 two parts, the " superficial part," which alone lies in 

 contact with the bone ; the " deep part " lies in the 

 sulcus between Hyoglossus and Mylo-hyoid. The 

 sublingual gland, on the other hand, touches the bone 

 further forward, above the origin of the muscle. 



