MUSCLES OF THE NOSTRILS 



259 



Origin. — The maxilla, close to the anterior extremity of the facial crest. 



Insertion. — The lateral wing of the nostril. 



Action. — To dilate the nostril. 



Structure. — The muscle has a flat tendon of origin, passes between the two 

 branches of the levator nasolabialis, and spreads out in the lateral wing of the 

 nostril. The lower fibers blend with the orbicularis oris. 



Relations. — Superficially, the skin, fascia, and the labial branch of the levator 

 nasolabialis; deeply, the maxilla and the nasal branch of the levator nasolabialis. 



Blood-supply. — Facial artery. 



Nerve-supply. — Facial nerve. 



3. Transversus nasi.^ — This is an unpaired, quadrilateral muscle, which lies 

 between the nostrils. It consists of two layers. 



Fig. 263. — Nasal and Supehior Labial Muscles of Horse. 

 a, a', Transversus nasi; b, levator labii superioris proprius; 6', tendon of b; b", common tendon of two 

 levatores labii superioris proprii; c, c', c", d, ventral part of lateralis nasi; e, dorsal part of lateralis nasi; /, or- 

 bicularis oris; g, levator nasolabialis, a portion of which is removed; h. dilatator nans lateralis {the terminal part of 

 which is removed); i, cornu of alar cartilage; k, nostril; k', upper commissure of nostril; /, nasal diverticulum: m, 

 nasal bone. (After EUenberger-Baum, Top. Anat. d. Pferdes.) 



Attachments. — Superficial layer, the superficial faces of the laminae of the alar 

 cartilages; deep layer, the convex edges of the cornua of the same. 



Action. — To dilate the nostrils. 



Structure.- — It is composed of transverse fleshy fibers, which blend below with 

 the orbicularis. 



Relations. — Superficially, the skin, fascia, and tendinous expansion of the 

 levator labii superioris proprius; deeply, the alar cartilages, the extremity of the 

 septum nasi, and the palato-labial artery. 



Blood-supply. — Palato-labial artery. 



Nerve-supply. — Facial nerve. 



Lateralis nasi. — This is situated along the margins of the naso-maxillary notch, 

 and may be regarded as consisting of dorsal and ventral parts. 



The dorsal part (Pars dorsalis m. lateralis nasi)^ is a thin layer which lies along 



' Also called the dilatator naris transversus. ^ ^gQ known as the dilatator naris superior. 



