152 SUPERIOR LABIAL GROUP. 



palpebrarum muscle, the facial artery, and the integument. By its 

 deep surface with the compressor nasi and alar cartilage. 



The levator labii superioris proprius is a thin quadrilateral muscle ; 

 it arises from the lower border of the orbit, and is inserted into the 

 integument of the upper lip. 



Relations. By its superficial surface with the lower segment of 

 the orbicularis palpebrarum, with the facial artery, and with the 

 integument. By its deep surface with the origins of the compressor 

 nasi and levator anguli oris muscle, and with the infra-orbital artery 

 and nerve. 



The levator anguli oris arises from the canine fossa of the supe- 

 rior maxillary bone, and passes outwards to be inserted into the 

 angle of the mouth, intermingling its fibres with those of the orbicu- 

 laris, zygomatici and depressor anguli oris. 



Relations. By its superficial surface with the levator labii supe- 

 rioris proprius, the branches of the infra-orbital artery and nerve, 

 and inferiorly with the integument. By its deep surface with the 

 superior maxillary bone and buccinator muscle. 



The zygomatic muscles are two slender fasciculi of fibres which 

 arise from the malar bone, and are inserted into the angle of the 

 mouth, where they are continuous with the other muscles attached 

 to this part. The zygomaticus minor is situated in front of the 

 major, and is continuous at its insertion with the levator labii supe- 

 rioris proprius ; it is not unfrequently wanting. 



Relations. The zygomaticus major muscle is in relation by its 

 superficial surface w r ith the low r er segment of the orbicularis palpe- 

 brarum above, and the fat of the cheek and integument for the rest 

 of its extent. By its deep surface with the malar bone, the masseter, 

 and buccinator muscle, and the facial vessels. The zygomaticus 

 minor being in front of the major, has no relation with the masseter 

 muscle, while inferiorly it rests upon the levator anguli oris. 



The depressor labii superioris alceque nasi (myrtiformis) is seen 

 by drawing upwards the upper lip, and raising the mucous mem- 

 brane. It is a small oval slip of muscle, situated at each side of the 

 fraenum, arising from the incisive fossa, and passing upwards to be 

 inserted into the upper lip and ala of the nose. This muscle is con- 

 tinuous by its outer border with the edge of the compressor nasi. 



Relations. By its superficial surface with the mucous membrane 

 of the mouth, the orbicularis oris and levator labii superioris aleeque 

 nasi muscle ; and by its deep surface with the superior maxillary 

 bone. 



Actions. The orbicularis oris produces the direct closure of the 

 lips by means of its continuity at the angles of the mouth, with the 

 fibres of the buccinator. When acting singly in the forcible closure 

 of the mouth, the integument is thrown into wrinkles in consequence 

 of its firm connexion with the surface of the muscle. The levator 

 labii superioris alaeque nasi lifts the upper lip with the ala of the nose, 

 and expands the opening of the nares. The depressor labii superioris 

 alaeque nasi is the antagonist to this muscle, drawing the upper lip 



