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This chapter describes the structure of the ear and discusses its pertinent
physiology and innervation. I have limited the coverage to what is most
important to the practitioner, while making points of clinical interest along
the way. The anatomy and physiology of the ear are quite complex for such
a small structure of the body, but reading through these pages will provide
a good background for the clinical chapters. In this and the following chap-
ters on diagnosis and treatment, we progress anatomically from the out-side inward.
The External Ear
The Auricle
The external ear consists of the outer portion, the auricle (or pinna ), and
the external auditory canal, leading to, but not including, the tympanic
membrane (TM). Figure 3.1 shows an auricle with its landmarks labeled.
The auricle is composed of skin overlying an irregular framework of
fibroelastic cartilage; it “gathers” sound and directs it into the canal.
With the external canal, it actually acts as a resonator to slightly amplify
lower frequency sounds. It also helps to localize sounds, especially in
conjunction with the other ear. Innervation of the auricle occurs through
the greater and lesser auricular nerves (from cervical roots C3 and C2) posteriorly, and the auriculotemporal branch of cranial nerve V anteriorly. The
skin and vascular channels on the outer surface are somewhat adherent
and “brittle,” making the auricle susceptible to traumatic hematoma for-
mation that might lead to “cauliflower ear” if not treated. The innervation
is not particularly sensitive, especially in the lobule. To prove this, pinch
yourself anywhere on the auricle; then compare the pain with the same
insult to other body sites. This insensitivity facilitates ear piercing, but un-
fortunately masks frostbite pain.
Fig. 3.1 The auricle and its landmarks:
1. Helix; 2. Scapha; 3. Antihelix; 4. Concha;
5. Crus of helix; 6. External auditory meatus;
7. Tragus; 8. Antitragus; 9. Lobule.
(Source: Becker W, Naumann HH, Pfaltz CR. Ear,
Nose, and Throat Diseases. Stuttgart: Thieme; 1994) |
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