556 



DISSECTION OF THE FACE. 



large and 



small : 



Risorius 

 muscle : 



Buccinator 

 muscle : 



origin ; 



insertion at 

 corner of 

 the mouth ; 



parts in con 

 tact with it : 



use on 

 aperture, 



on cheek, 



in expelling 

 air. 



Orbicular 

 muscle of 

 lips includes 

 fibres of 

 buccinator, 



longer and larger than the other ; they are therefore named major 

 and minor. 



The zygomaticus major arises from the outer part of the malar 

 bone, and is inserted into the skin and mucous membrane at the 

 angle of the mouth. 



The zygomaticus minor arises from the malar bone in front of 

 the major, and blends with the elevator of the upper lip. This 

 muscle is often absent. 



Action. The large muscle draws upwards and backwards the 

 corner of the mouth, as in laughing ; and the small one assists the 

 levator labii superioris in raising the upper lip. 



The RISORIUS MUSCLE (fig. 185, p. 501) is a thin bundle of 

 fibres, sometimes divided into two or more parts, which arises 

 externally from the fascia over the masseter muscle, and is connected 

 internally with the apex of the depressor aiiguli oris. 



Action. It retracts the corner of the mouth in smiling. 



The BUCCINATOR ( tig. 203) is the flat and thin muscle of the 

 cheek, and occupies the interval between the jaws. It arises from 

 the outer surface of the alveolar borders of the upper and lower 

 maxillae, as far forwards in each as the first molar tooth ; and in 

 the interval between the jaws behind it is attached to a tendinous 

 band known as the pterygo-maxillary ligament. From this origin 

 the fibres are directed forwards to the lips, where they pass into the 

 orbicularis ; most of the upper fibres descend to the lower lip 

 while many lower ones ascend to the upper lip, a decussation taking 

 place at the corner of the mouth. The highest and lowest fibres 

 enter the corresponding lip. 



On the cutaneous surface of the buccinator are the different 

 muscles converging to the angle of the mouth ; and crossing the 

 upper part is the duct of the parotid gland, which perforates the 

 muscle opposite the second upper molar tooth. Internally the 

 muscle is lined by the mucous membrane of the mouth, and ex- 

 ternally it is covered by a fascia (bucco-pharyngeal) that is con- 

 tinued over the pharynx behind. By its intermaxillary origin 

 the buccinator corresponds with the attachment of the superior 

 constrictor of the pharynx. 



Action. By one muscle the corner of the mouth is retracted, and 

 by the action of both the aperture of the mouth is widened trans- 

 versely. 



In mastication the cheek is pressed against the arches of the 

 teeth and food cannot accumulate in the interval, while the corner 

 of the mouth is fixed by the orbicularis. 



In the expulsion of air from the month, as in whistling, the 

 muscle is contracted so as to prevent bulging of the cheek ; but in 

 the use of a blow-pipe it is stretched over the volume of air 

 contained in the mouth, and maintains a continuous stream by its 

 contraction during expiration. 



The ORBICULARIS ORIS is mainly formed by the prolongation of 

 the fibres of the levator and depressor angulis oris and buccinator 

 muscles. The buccinator fibres lie next to the mucous membrane, 



