MUSCULAR SVSTEiM. 91 



Attachments. — Superiorly, to the broad depression upon the 

 side of the fore angle of the superior maxillary bone; inferiorly, 

 to the alveolar processes of the lower jaw, and the bone in front 

 of them; internally, to the buccal membrane; anteriorly, to the 

 side of the lip and angle of the mouth. 



Relations. — Externally, with the zygomaticus, inferior division 

 of the levator labiisuperioris al^eque nasi, dilatatornaris lateralis, 

 panniculus carnosus, and skin ; internally, with the raasseter, 

 buccal membrane, and two anterior upper molar teeth. 



Direction. — Transverse and penniform : the superior fibres di- 

 verge from their maxillary attachment; those below run obliquely, 

 forwards and downwards. 



Structure. — Fleshy. 



Action. — To render the buccal membrane tense, and also to 

 assist in elevating the angle of the mouth and side of the lip. 



BUCCINATOR. — Alveolo-labialis. 



Situation. — In the space between the jaws. 



Figure.— 'BroQ.d, flat, approaching the triangular. 



Attachments. — Posteriorly, to the border of the lower jaw in the 

 space between the last molar tooth and the root of the coronoid 

 process, and to the tuberosity of the superior maxilla; superiorly 

 and inferiorly, to the outer walls of the alveolar cavities for the 

 molar teeth ; anteriorly, to the angle of the mouth ; and inter- 

 nally, to the buccal membrane. 



Relations. — Externally, with the masseter, caninus, pannicu- 

 lus, and skin, and with the facial artery and vein and parotid 

 duct ; internally, with the buccal membrane ; postero-inferiorly, 

 with the buccal nerve, artery, and varicose vein ; antero-inferiorly, 

 with the depressor labii inferioris and inferior labial bloodves- 

 sels ; postero-superiorly, with the temporal vein. 



Direction. — Longitudinal, from behind forwards. 



Structure. — With the exception of its posterior or narrow ex- 

 tremity, which contains some slips of tendon, and a few tendi- 

 nous fibres which are visible about the angle of the mouth, it is 

 entirely fleshy. 



Action. — To aid in tightening the buccal membrane, and retract 

 the angle of the mouth. 



, DEPRESSOR LABII INFERIORIS. — MaxUlo-lahialis. 



Situation. — Along the side of the lower jaw. 

 Figure. — Elongated, flattened, pyramidal, ba:5C turneil back- 

 wards. 



