570 ANATOMY IN A NUTSHELL. 



5. The concha is the deep hollow in the center of the pinna which leads 

 into the auditory canal. 



6. The tragus is a conical eminence in front of the concha projecting back- 

 ward over the orifice of the external auditory meatus. It is usually covered 

 with hair along its inferior border. 



7. The antitragus is a small projection posterior to the tragus from which 

 it is separated by a deep fissure called the incisura intertragica. 



The muscles of the external ear are divided into two sets, the extkixsk 

 ami the entrinsh . The extrinsic aie. the Attrahens aurem, Retrahens aurem, 

 and Attollens aurem. These muscles have been described on page 522 and in 

 the table of muscles in the back of the book. 



The [ntrinsic muscles are: 



1. Tragicus, which lies vertically on the outer surface of the tragus. 



L'. Antitragicus lies on the posterior wall of the auditory canal. It arise- 

 from the outer part of the antitragus and passes upward to be inserted into 

 the posterior extremity of the helix. 



3. Helicis minor is often absent, but when present is attached to the com- 

 mencemenl of the helix and extends into the concha. 



4. Helicis major is situated on the anterior margin of the helix. 



">. Transversus aurem is situated on the posterior surface of the auricle 

 in the depression between the helix and the convexity of the concha. 



6. Obllquus aurem is on the posterior surface of the auricle passing upward 

 from the convexity of the concha. 



Nerve Supply. — From the auriculo-temporai, auricularis magnus, occipi- 

 lalis minor, and Arnold's nerve from the tenth. The intrinsic muscles receive 

 the seventh nerve. 



Action of the Intrinsic muscles is to retard the passage of sound to the 

 meatus. These muscles are rudimentary and unimportant. 



Blood Supply. — The pinna receives the posterior auricular, the occipital. 

 and superficial temporal arteries. 



Lymphatics of the pinna empty into the preauricular nodes, and into the 

 nodes upon the insertion of the Sterno-cleido-mastoid muscle. 



Tin' external auditory canal is a little over an inch long, extending from 

 the concha to the membrana tympani. This canal is curved with its convexity 

 upward. This canal is lined with integument which contains sebaceous and 

 ceruminous glands and also numerous hair follicles. 



The outer one-third of this canal is cartilaginous, and the inner portion 

 osseous. 



The Annulus tympanicus isthe osseous portions of this canal at birth, at 

 which time it is an incomplete bony ring. 



Blood Supply.- From branches of the internal maxillary, posterior auri- 

 cular, and superficial temporal. 



Nerve Supply. Auriculo-temporai, auricularis magnus. and Arnold's 

 nerve. 



Tin LYMPHATICS of the external auditory meatus end in the parotid and 

 the posterior auricular nodes. 



