540 ANATOMY IN A NUTSHELL. 



Action. To contract the nostrils. 



Nerve Supply. — Facial. 



Blood Supply.— Branches of the facial. 



7 Dilator nares posterior. — 



Origin.— It arises from the margin of the nasal notch and sesamoid car- 

 tilages. 



Insertion. — Into the skin at the margin of the nostril. 



Action. — To dilate the nostril. 



\ki;\ e Supply. — Facial. 



Blood Supply. — Branches from the facial artery. 



(8) Massetef muscle which has been described on page 520. 



(0) Buccinator. — Description. The upper and lower fibers of the Bucci- 

 nator muscle meet at the angle of the month where they decussate to he con- 

 tinuous with the fibers of the Orbicularis oris, however, the highest and the 

 lowest of these fibers do not decussate. This muscle, which is united with the 

 Superior constrictor of the pharynx by the pterygo-maxillary ligament, forma 

 a muscular wall for the mouth, while the Superior constrictor forms a mus- 

 cular wall for the pharynx. 



Origin. — From the posterior areolar processes of both the maxillary bonea 

 and the pterygo-maxillary ligament. 



Insertion.— Into the Orbicularis oris in a manner which has been del 

 scribed in the description of the muscle. 



Action.- To compress the cheeks. 



Xia;\ e Supply. — Facial, and buccal branch of the inferior maxillary 

 division of the fifth nerve. 



Blood Supply. — Facial artery. 



(10) Internal pterygoid which has been described on page 529. 



(11) Orbicularis oris. — Description. — The fibers of this muscle are de- 

 rived from the other facial muscles which are inserted into the lips, and it has 

 fibers which belong to the lip itself. The fibers which belong to the lips pass in 

 an oblique direction from the under surface of the skin through the thickness 

 of the lip to the mucous membrane. Besides these two sets of fibers just men- 

 tioned, it has a third set of fibers wheh connect it with the superior maxillary 

 bone :tnd the septum of the nose. 



Origin. By accessory fibers of nasal septum and the facial muscles sur- 

 rounding the mouth. 



Insertion. Into the Buccinator and other muscles surrounding the 

 mouth. This muscle is not a sphincter muscle. 



ACTION.-— To pucker and close 1 the mouth. 



Nerve Supply.— Buccal and supramaxillary divisions of the cervico- 

 facial division of the seventh nerve. 



Blood Supply. — Superior and inferior coronary, and inferior labial. 



(12) Levator labil superioris proprius. — DESCRIPTION. — This muscle covers 

 the origin of the Compressor nasi and Levator anguli oris muscles, and the in- 

 fraorbital vessels and nerve as they pass from the infraorbital foramen. 



( )i;i<;i\. from the superior maxillary bone above the infraorbital foramen. 



