Horizontal Section through Left Ear
Horizontal section through left ear; upper half of section.
The External Acoustic Meatus
(meatus acusticus externus; external auditory canal or meatus) extends from the bottom of the concha to the tympanic membrane (Fig. 907, Fig. 908). It is about 4 cm. in length if measured from the tragus; from the bottom of the concha its length is about 2.5 cm. It forms an S-shaped curve, and is directed at first inward, forward, and slightly upward (pars externa); it then passes inward and backward (pars media), and lastly is carried inward, forward, and slightly downward (pars interna). It is an oval cylindrical canal, the greatest diameter being directed downward and backward at the external orifice, but nearly horizontally at the inner end. It presents two constrictions, one near the inner end of the cartilaginous portion, and another, the isthmus, in the osseous portion, about 2 cm. from the bottom of the concha. The tympanic membrane, which closes the inner end of the meatus, is obliquely directed; in consequence of this the floor and anterior wall of the meatus are longer than the roof and posterior wall.
(Text modified from Gray's 1918 Anatomy)
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Gray H. Anatomy of the human body. (1918) Philadelphia: Lea & Febiger.
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