400 THE MUSCLES AND FASCIA. 



6. Superior Maxillary Region (Fig. 269). 



\ Levator labii superioris. / Zygomaticus major. 



/ Levator anguli oris. y Zygomaticus minor. 



The Levator labii superioris (proprius) 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 above, with the lower segment of the 

 Orbicularis 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 nerve, as they escape from the infraorbital 

 foramen. 



The Levator anguli oris arises from the canine fossa immediately below the 

 infraorbital foramen ; its fibres incline downward and a little outward, to be 

 inserted into the angle of the mouth, intermingling with those of the Zygomaticus 

 major, 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 downward and 

 inward, is inserted into the angle of the mouth, where it blends with the fibres of 

 the Levator anguli oris, the Orbicularis oris, and the 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 downward and inward, is continuous with the 

 Orbicularis oris at 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 Masseter, Buccinator, and 

 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 forward. It assists in forming the naso-labial 

 ridge, which passes from the side of the nose to the upper lip and gives to the face 

 an expression of sadness. The Levator anguli oris raises the angle of the mouth, 

 and assists the Levator labii superioris in producing the naso-labial ridge. The 

 Zygomaticus major draws the angle of the mouth backward and upward, as in 

 laughing ; whilst the Zygomaticus minor, being inserted into the outer part of the 

 upper lip and not into the angle of the mouth, draws it backward, upward, and 

 outward, and thus gives to the face an expression of sadness. 



1 



7. Inferior Maxillary Region (Fig. 269). 



Levator labii inferioris (Levator menti). 

 j Depressor labii inferioris (Quadratus menti). 

 j 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. 268. 



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, 



