DEPRESSOR ALjE NASI— DILATATOR ^ARIS POSTERIOR 433 



Origin. — The sides of the nasal aponeurosis. 



Insertion. — (1) The lower and front part of the canine fossa of the maxilla; 



(2) part of its fibres are continued into those of adjacent muscles, especially the 

 levator lahii superioris alseque nasi, and the levator anguli oris. 



Structure. — Arising from the side of the aponeurosis in a vertical line ahout 

 half an inch (1-2 cm.) from the ridge of the nose, the fibres of the muscular sheet 

 converge as they pass ]»ackwards, outwards and downAvards to a narrow band just 

 aljove and behind the ala nasi. Here they are partly attached to the maxilla, and 

 partly they ])ass into the adjacent muscles. 



Nerve-supply, — The infraorbital l)ranch of the upper division of the facial 

 nerve, which sends filaments to the deep surface of the muscle near its upper border. 



Action. — (1) To depress slightly the cartilaginous ridge of the nose; (2) to 

 throw' into vertical wrinkles the side of the nose, as when a bad smell is perceived; 



(3) to assist the adjacent muscles in dilating the nostril and drawing up parts of 

 the ui»))er lip. 



Relations. — Superficially, the skin and levator labii superioris alaque nasi; 

 deeply, the cartilages of the nose. 



3. DEPRESSOR AL.E NASI 



The depressor alae nasi (fig. 311) — named from its action uiwn the cartilage 

 of the nostril — is a small triangular sheet. 



Origin. — The incisive fossa of the maxilla. 



Insertion. — (1) The lower and back part of the cartilage of the ala nasi; (2) 

 the adjacent part of the lower border of the cartilaginous septum nasi. 



Structure. — Its muscular fibres diverge upwards and outwards from their origin. 



Nerve-supply. — Small filaments from the buccal branch of the lower division 

 of the facial nerve, which enter the muscle near its outer border. 



Action. — To draw downwards and inwards the alar cartilage. 



Relations. — Superficially, the orbicularis oris; deeply, the maxilla. It is also 

 closely connected with the fibres of the previous muscle and the elevators of the 

 upper lip. 



4. LEVATOR LABII SUPERIORIS AL^QUE NASI 

 This muscle will be described with the Muscles of the Mouth. 



5. DILATATOR NARIS ANTERIOR 



The dilatator naris anterior (fig. 309) — named from its action and position — 

 is a small quadrilateral sheet. 



Origin. — The lower edge of the lateral cartilage of the nose. 



Insertion. — The deep surface of the skin covering the ala nasi. 



Structure. — A thin stratum of muscle, which may occasionally be found pass- 

 ing downwards upon the U]:)])er part of the alar cartilage. 



Nerve-supply. — The infraorbital ])ranch of the upper division of the facial 

 nerve. 



Action. — To dilate the nostril, e.g. in the expression of anger, or in hard 

 breathing. 



Relations. — Superficially, the skin below and the compressor narium above; 

 deeply, the cartilages of the ala. 



6. DILATATOR XARIS POSTERIOR 



The dilatator naris posterior (fig. 309) — named from its action and position 

 — is a similar sliect of soniewliat quadrilateral sha]»e. 



Origin, — (1) The edge of the nasal aperture of the maxilla; and (2) the outer 

 surface of the sesamoid cartilages of the nose. 

 •28 



