THE MAXILLARY REGION 373 



Nerves. All of the muscles of this group are supplied by the facial nerve. 



Actions. The Pyramidalis nasi draws down the inner angle of the eyebrows and produces 

 transverse wrinkles over the bridge of the nose. The Levator labii superioris alaeque nasi draws 

 upward the upper lip and ala of the nose; its most important action is upon the nose, which it 

 dilates to a considerable extent. The action of this muscle produces a marked influence over 

 the countenance, and it is the principal agent in the expression of contempt and disdain. The 

 two Dilatatores nasi enlarge the aperture of the nose. Their action in ordinary breathing is 

 to resist the tendency of the nostrils to close from atmospheric pressure, but in difficult breath- 

 ing they may be noticed to be in violent action, as well as in some emotions, as anger. The 

 Depressor alae nasi is a direct antagonist of the other muscles of the nose, drawing the ala of the 

 nose downward, and thereby constricting the aperture of the nares. The Compressor naris 

 depresses the cartilaginous part of the nose and compresses the alee together. 



6. The Maxillary Region (Fig. 289). 



Levator labii superioris. Zygomaticus major. 



Levator anguli oris. Zygomaticus minor. 



In the BXA term musculus quadratus labii superioris three muscles are in- 

 cluded. The caput angulare is called in this book the Levator labii superioris 

 alaeque nasi. The caput infraorbitale is called the Levator labii superioris. The 

 caput zi/f/omaticum is called the Zygomaticus minor. 1 



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 infra- 

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

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

 upper lip. 



The Levator anguli oris (m. caniiius) arises from the canine fossa immediately 

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

 be inserted into the deep surface of the skin and into the subcutaneous tissue 

 near the angle of the mouth and intermingles with the fibres of the Zygomaticus 

 major, the Depressor anguli oris, and the Orbicularis oris. 



The Zygomaticus major (m. zyyomaticus) 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 deep surface of the skin and 

 subcutaneous tissue at the outer portion of the upper lip and into the angle of 

 the mouth, where it blends with the fibres of the Levator anguli oris, the Orbicu- 

 laris oris, and the Depressor anguli oris. 



The Zygomaticus minor, which is often absent, arises from the malar bone 

 immediately behind the maxillary suture, and, passing downward and inward, 

 is inserted internal to the angle of the mouth and is continuous with the Orbicularis 

 oris at the outer margin of the Levator labii superioris. It lies in front of the 

 Zygomaticus major. 



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 nasolabial 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 draws it inward, and assists the Levator labii su- 

 perioris in producing the nasolabial ridge. The Zygomaticus major draws the angle of the mouth 

 backward and upward, as in laughing; while 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 That this grouping is quite artificial and morphologically unwarranted has been shown by McMurrich 

 American Journal of Anatomy, vol. iii, Proceedings, p. iii. 



