INFERIOR MAXILLARY REGION. 325 



the aperture of the nose, and the Compressor Nasi appears to press upon the 

 nose so as to increase its breadth, and thus tends rather to open than to close 

 the nostrils. The Depressor Alae Nasi is a direct antagonist of the preceding 

 muscles, drawing the ala of the nose downwards, and thereby constricting the 

 aperture of the nares. 



6. SUPERIOR MAXILLARY REGION. (Fig. 215.) 



Levator Labii Superioris. Zygomaticus major. 



Levator Anguli Oris. Zygomaticus minor. 



The Levator Labii Superioris is a thin muscle of a quadrilateral form. It 

 arises from the lower margin of the orbit immediately above the infraorbital 

 foramen, some of its fibres being attached to the superior maxilla, others to the 

 malar bone ; its fibres converge to be inserted into the muscular substance of 

 the upper lip. 



Relations. By its superficial surface, with the lower segment of the Orbicu- 

 laris Palpebrarum ; below, it is subcutaneous. By its deep surface, it conceals 

 the origin of the Compressor Nasi and Levator Anguli Oris muscles, and the 

 infraorbital vessels and nerves, as they escape from the infraorbital foramen. 



The Levator Anguli Oris arises from the canine fossa, immediately below the 

 infraorbital foramen ; its fibres incline downwards and a little outwards, to be 

 inserted into the angle of the mouth, intermingling with those of the Zygoma- 

 tici, the Depressor Anguli Oris, and the Orbicularis. 



Relations. By its superficial surface, with the Levator Labii Superioris and 

 the infraorbital vessels and nerves. By its deep surface, with the superior 

 maxilla, the Buccinator, and the mucous membrane. 



The Zygomaticus major is a slender fasciculus, which arises from the malar 

 bone, in front of the zygomatic suture, and, descending obliquely downwards 

 and inwards, is inserted into the angle of the mouth, where it blends with the 

 fibres of the Orbicularis and Depressor Anguli Oris. 



Relations. By its superficial surface, with the subcutaneous adipose tissue. 

 By its deep surface, with the malar bone, and the Masseter and Buccinator 

 muscles. 



The Zygomaticus minor arises from the malar bone, immediately behind the 

 maxillary suture, and, passing downwards and inwards, is continuous with the 

 outer margin of the Levator Labii Superioris. It lies in front of the preceding. 



Relations. By its superficial surface, with the integument and the Orbicularis 

 Palpebrarum above. By its deep surface, with the Levator Anguli Oris. 



Nerves. This group of muscles is supplied by the facial nerve. 



Actions. The Levator Labii Superioris is the proper elevator of the upper 

 lip, carrying it at the same time a little outwards. The Levator Anguli Oris 

 raises the angle of the mouth and draws it inwards ; whilst the Zygomatici 

 raise the upper lip and draw it somewhat outwards, as in laughing. 



7. INFERIOR MAXILLARY REGION. (Fig. 215.) 



Levator Labii Inferioris (Levator Menti). 

 Depressor Labii Inferioris (Quadratus Menti). 

 Depressor Anguli Oris (Triangularis Menti). 



Dissection. The muscles in this region may be dissected by making a vertical incision 

 through the integument from the margin of the lower lip to the chin ; a second incision should 

 then be carried along the margin of the lower jaw as far as the angle, and the integument care- 

 fully removed in the direction shown in Fig. 214. 



The Levator Labii Inferioris (Levator Menti} is to be dissected by everting the 

 lower lip and raising the mucous membrane. It is a small conical fasciculus, 

 placed on the side of the frsenum of the lower lip. It arises from the incisive 

 fossa, external to the symphysis of the lower jaw : its fibres descend to be in- 

 serted into the integument of the chin. 



