ZYGOMATICUS MINOR— DEPRESSOR LAB 11 INFERIORIS 439 



Nerve-supply. — The iiifraorl)ital branch of the upper division of the facial 

 nerve, which sends filaments to the outer part of the deep surface of the muscle. 



Action. — (1) To raise and dilate the nostril; (2) to raise the inner half of the 

 u])i>cr lip. 



Relations. — Superficially, the skin and orbicularis palpebrarum; deeply, the 

 compressor narium and levator anguli oris. 



2. LEVATOR LABII SUPERIORIS 



The levator labii superioris — named from its action — is a nearly scjuare slieet, 

 and it belongs to the superficial layer of muscles. 



Origin.— The front of the maxilla just below the margin of the orbit, and from 

 the adjacent part of the malar bone. 



Insertion. — The deep surface of the skin and the subjacent muscular tissue 

 near the upper edge of the inner half of the upper prolaljium. 



Structure. — Its fibres, arising fleshy, descend parallel to one another and 

 almost vertically to their insertion, where they interlace with the fibres of the 

 orbicularis oris. It freci[uently receives at its outer border some bundles of fibres 

 from the orbicularis palpeln'arum. 



Nerve-supply. — The infraorbital branch of the upper division of the facial 

 nerve, which sends filaments to the outer part of its deep surface. 



Action. — To raise the inner half of the upper lip. This muscle, with its two 

 fellows, the preceding and following, is especially used in the expression of grief, 

 and to some extent of anger also, as when the lip is raised and somewhat everted 

 so as to show the canine tooth. In crying, the action of these muscles is strongly 

 displayed, for when the eyes are closed by the orbiculares palpebrarum, at the same 

 time the mouth is made square by the elevation of the inner half of the lip, while 

 the outer half is drawn down by the depressor anguli oris. 



Relations. — Superficially, the skin and orbicularis palpebrarum; deeply, the 

 levator anguli oris, the infraorbital vessels and nerve. 



3. ZYGOMATICUS MINOR 



The zygomaticus minor — named from its association with the zygomaticus 

 major and its smaller size — is a small riljbon-shaped band, often absent, and 

 belonging to the superficial layer of facial muscles. 



Origin. — The lower part of the front of the malar bone close to its junction 

 with the maxilla. 



Insertion. — The deep surface of the skin and the subjacent muscular tissue at 

 a point upon the upper border of the prolabium of the upper lip about midway 

 between tlie middle line and the outer corner of the mouth. 



Structure. — Arising fleshy, the small band of parallel filu-es which is upon its 

 inner margin closely connected Avith the preceding muscle, passes downwards and 

 inwards to its insertion, which interlaces with the fil:)res of the orbicularis oris. 



Nerve-supply. — The infraorbital branch of the upper division of the facial 

 nerve, which sends fih\ments to the deep surface of the muscle. 



Action. — To raise and somewhat evert the part of the upper lip to which it is 

 attached. 



Relations. — Superficially, the skin and orbicularis palpebrarum; deeply, the 

 levator anguli oris, facial portion of the orbicularis oris, and the infraorljital branch 

 of the facial nerve. 



4. DEPRESSOR LABII INFERIORIS 



The depressor labii inferioris, or quadratus menti — named from its action, 

 or shape, and its connection with the lower lip and chin (rnentum) — is a nearly 

 square sheet, and belongs to the second layer of the facial muscles. 



Origin.— The outer aspect of the lower border of the body of the mandible 

 below the canine and bicuspid teeth. 



