1084 SPECIAL SENSE ORGANS 



and the sulcus of the crus of the helix. The attachment of approximately one- 

 third of the medial surface covers up the two latter depressions. The cephalo-au- 

 ricular angle, between the dorsal free part of the auricle and the side of the 

 head, averages 20 to 30 degrees. 



Structure of the Auricle 



The features of the auricle just described are mainly produced by a plate of yellow elastic 

 cartilage, the auricular cartilage. In addition to the elevations and depressions already 

 noted, it presents the following additional features. Projecting anteriorly from the helix, 

 near the crus is a small tubercle, spine of the helix (fig 828) ; while the posterior margin of the 

 helix terminates in a pointed tail-like process, the cauda helicis which is separated inf eriorly 

 from the antitragus by the deep antitrago-helicine fissure. Another deep fissure, the terminal 

 notch [incisura terminaUs auris], separates the cartilage of the auricle from that of the meatus, 

 leaving only a narrow strip, the isthmus, connecting the two. The cartilage of the tragus, 

 the lamina tragi, is separated from that of the auricle and is attached to the lateral margin of 

 the cartilage of the meatus. 



The auricle is covered on both its medial and lateral aspects by skin which 

 closely follows the irregularities of the cartilage. Thus it is tightly bound to the 

 perichondrium of the lateral surface by the subcutaneous areolar tissue, but much 

 more loosely attached to the medial surface, and in the subcutaneous tissue there 

 is little fat except in the lobule, which is made up almost entirely of fat and tough 

 fibrous tissue. Hairs are abundant but rudimentary, except in the region of the 

 tragus and antitragus, where they may be large and long, particularly in males and 

 in the aged. Sebaceous glands are found on both surfaces, and are especially well 

 developed in the concha and triangular fossa, but sudoriferous glands are few and 

 scattered. 



Ligaments and muscles. — The auricle is attached to the side of the head by the skin, by 

 the continuity of its cartilage with that of the acoustic meatus, and by certain extrinsic ligamente 

 and muscles. Three ligaments may be distinguished in the connective tissue: — The anterior 

 ligament, stretching from the zygoma to the helix and tragus; the superior ligament, from the 

 superior margin of the bony external acoustic meatus to the spine of the helix; and the posterior 

 ligament, from the mastoid process to the eminence of the concha. There are also three ex- 

 trinsic muscles, the anterior, superior, and posterior auricular (see p. 337, fig. 341). Six intrinsic 

 muscles are distinguished. These are poorly marked in man and vary much in development. 

 Upon the lateral surface (fig. 828) the helicis major stretches from the spine of the helix to 

 the ventral superior margin of the heHx; the helicis minor overlies the crus helicis; the tragicus 

 runs vertically upon the tragus; and the antitragicus stretches from the antitragus to the cauda 

 helicis. Upon the medial surface (fig. 828) the transversus auriculae stretches between the 

 eminences of concha and scapha, and the obliquus between the eminences of the concha and the 

 triangular fossa. Two small muscles occasionally present are the m. pyramidalis auriculae 

 (Jungi) and the m. incisurse helicis (Santorini). 



Vessels and Nerves of the Auricle 



The arteries are the auricular branch of the posterior auricular and the anterior auricular 

 branches of the superficial temporal arteries. The veins are the anterior auricular vein 

 of the posterior facial (temporal) and the auricular branches of the posterior auricular veins. 

 The latter vessels sometimes join the transverse (lateral) sinus through the mastoid emissary 

 vein. The lymphatics empty into the anterior, posterior and inferior auricular lymph-nodes. 

 The sensory nerves of the auricle are the branches of the great auricular, small occipital (p. 977, 

 fig. 753), and auriculo-temporal (p. 941, fig. 740). The muscles are supplied by the posterior 

 auricular branch of the facial (p. 944, fig. 740). 



Variations 



There are many variations in the size, shape, and conformation of the auricle and in the 

 cephalo-auricular angle. These arc associated not only with difi"erence8 in sex, age, and race, 

 but are also found in individuals of the same family. 



THE EXTERNAL AUDITORY MEATUS 



The external auditory (acoustic) meatus [meatus acusticus externus] extends 

 medially and somewhat anteriorly and infcriorly from the concha to the tympanic 

 membrane (fig. 829). It is about twenty-five mm. (1 in.) long, and, owing to the 

 obliquity of the tympanic membrane, its anterior and inferior wall is 5-6 mm. 



