THE MUSCLES OF THE LIPS AND MOUTH. 



285 



THE MUSCLES OF THE LIPS AND MOUTH. 



Around the orifice of the mouth is situated the orbicularis muscle with con- 

 centric fibres, and this is joined by numerous other muscles which converge towards 

 the aperture, viz., superiorly, the common elevator of the lip and nose already 

 described, the proper elevator of the upper lip, the elevator of the angle of the 

 mouth and the zygomatic muscles, laterally, the risorius and buccinator muscles, 



Fig. 269. DEEP MUSCLES OF THE 



LEFT .SIDE OF THE HEAD AND 



NECK. (Allen Thomson, after 

 Bourgery. ) ^ 



, vertex of head ; b, superior 

 curved line of occipital bone ; c, 

 ramus of lower jaw ; c', its coro- 

 noid process ; d, hyoid bone ; e, 

 sternal end of clavicle ; e', acro- 

 mial end ; /, malar bone divided 

 to show the insertion of the tem- 

 poral muscle ; f divided zygoma, 

 and external ligament of the jaw ; 

 g, thyroid cartilage ; h, placed on 

 the lobule of the auricle, points 

 to the styloid process ; 1, temporal 

 muscle ; 2, corrugator supercilii ; 

 3, pyramidalis nasi ; 4, compressor 

 naris ; 5, levator labii superioris ; 

 6, levator anguli oris ; 7, outer 

 part of the orbicularis oris, the 

 part below the nose has been re- 

 moved ; 8, depressor alse nasi ; 9, 

 points to the buccinator muscle, 

 through which the parotid duct is 

 seen passing ; 10, depressor labii 

 inferioris ; 11, levator menti ; 12, 

 12, anterior and posterior bellies 

 of the digastric ; 13, stylo-hyoid 

 muscle ; 14, mylo-hyoid ; 15, hyo- 

 glossus, between which and 13, 

 is seen a part of the stylo-glossus ; 

 16, sterno- hyoid ; 17, on the cla- 

 vicle, indicates the posterior, and 

 17', the anterior belly of the omo- 

 hyoid ; 18, sterno-thyroid ; 19, 

 thyro-hyoid ; 20, 21, on the 

 sterno-mastoid muscle, point, the 

 first to the middle, the second to 

 the lower constrictor of the 

 pharynx ; 22, trapezius ; 23, 

 upper part of the complexus ; 24, 

 25, splenius ; 26, leva to r scapulae ; 

 27, middle scalenus ; +, posterior 

 scalenus ; 28, anterior scalenus. 



and inferiorly, the depressor of the angle of the mouth and that of the lower lip : 

 and lastly, acting indirectly on the lower lip is the levator menti. The converging 

 muscles will be first described, as the orbicularis is for the most part composed of 

 fibres prolonged from them. 



The levator labii superioris proprius muscle arises from the superior 

 maxillary bone immediately above the infraorbital foramen, and from the adjoining 

 surface of the malar bone ; it passes downwards and a little inwards to be inserted 

 into the skin of the upper lip. 



Relations. At its origin this muscle is overlapped by the orbicularis palpebrarum, but its 

 greater part is subcutaneous ; it partly conceals the levator anguli oris, and beneath it the 



