ORBICULARIS ORIS 



435 



flesliy slips from the maxilla and mandible — the musculi incisivi, as they are 

 called — pass outwards and forwards to join the deep surface of the transverse fibres 

 near the corners of the mouth. 



Nerve-supply. — The buccal and supramaxillary branches of the lower division 

 of tlie facial, which enter the facial part of the muscle near its outer border. 



Action. — (1) To bring together tlie lips and to oppose all the other mu.scles 

 which converge upon the mouth, and tend to draw it open in various directions. 

 It thus acts negatively, and prevents the expression of any emotion, as when the 

 lips are pursed up. If the upper fibres alone act, the upper lip will be drawn 



Fig. 311. — The Deeper Layer of the Muscles of the Face axd Neck. 



Corrugator 

 Bupercilii 



Fyramidalia 



Levator labii 

 superioris 

 alaeque nasi 

 Levator labii 

 superioris 

 Compressor 

 narium 

 Levator anguli 

 oris 

 Naso-labialis 

 Depressor alae 

 nasi 

 Orbicularis oris 



Buccinator 



Depressor 



angull oris 



Depressor labii 



inferioris 

 Levator menti 

 Mylo-hyoid 



Anterior belly of 

 digastric 



Temporal 



ZygomaticuB 

 major 



Splenius capitis 



Stylo-hyoid 



Sterno-mastoid 



Scalenus anticus 



downwards; if the lower, the lower lip will be drawn upwards. If the fibres of 

 the labial portion contract strongly, the corners of the mouth are approximated. 

 (2) To shoot out the lips: this will chiefly depend upon the contraction of the 

 facial portion and the musculi incisivi. (3)'To press the lips against the teeth: the 

 plane of the muscle being curved, with the concavity against the arches formed by 

 the front tectli, its contraction will carry the food backwards into the oral cavity. 



Relations. — In front of the lal)ial portion is the bright red skin of the ])rola- 

 bium; and in front of the facial ]iortion lie the angular and labial series of muscles, 

 together with some suljcutaneous fat. 



