THE HEAD AND NECK 



iie>9 



The direction of the muscle is inwards, some of its fasciculi cilso 

 ascending. 



Action. — To draw the angle of the m.outh outwards and slightly 

 downwards. It is not a muscle of laughter, but is expressive of 

 scorn or pain. 



The muscle consists of a few scattered fasciculi, which are em- 

 bedded in the adipose tissue over the buccinator, and it is to be 

 regarded as a detached portion of the platysma myoides. 



Buccinator — Origin. — (i) The outer surfaces of the alveolar 

 borders of the superior and inferior maxillae, opposite the three 

 molar alveoli ; and (2) the anterior aspect of the pterygo-mandibular 

 ligament. 



Insertion. — ^The orbicularis oris at the angle of the mouth. 



Long Buccal Nerve (cut) 



Upper Head of External Pterygoid 



Capsule of Temporo- 

 mandibular Joint 



Lower Head of External 

 Pterj-goid 



Pteryeo-mandibular 

 Ligament 



i:;. . Stensen's Duct 



.Buccinator 



Internal Pterygoid 



Fig. 476. — The Pterygoid and Buccinator Muscles. 



The central fibres decussate, those from above entering the lower 

 lip, and those from below entering the upper lip. The highest and 

 lowest fibres take no part in this decussation, the highest passing 

 directly into the upper lip, and the lowest into the lower lip. 



Nerve-supply. — ^The short buccal nerves, which are derived from 

 (i) the infra-orbital branches of the temporo- facial division of the 

 facial, and (2) the buccal branches of the cervico-facial division 

 of the facial, nerve. 



Action. — (i) To draw the angle of the mouth outwards, and press 

 the lips against the teeth, thus preventing the food from accumulat- 

 ing between the lips and the teeth during mastication ; and (2) to 

 regulate the expulsion of air from the buccal cavity when the buccal 

 aperture is narrowed, as in playing the flute, or in whistling. 



The muscle is expanded over the cheek, but towards the angle 



74 



