Page 631 - Fundamentals of anatomy physiology

618 Unit 3 Control and Regulation
Figure 17–22 The Middle Ear.

Auditory Ossicles
Malleus Incus Stapes

Temporal bone
(petrous part)

Stabilizing Oval window
ligaments
Muscles of
Branch of facial the Middle Ear
nerve VII (cut) Tensor tympani
muscle
External Stapedius muscle
acoustic meatus Round window
Tympanic cavity Auditory tube

(middle ear) Incus
Tympanic Malleus

membrane Points of
attachment
17 Malleus attached to Tendon of tensor to tympanic
membrane
tympanic membrane Malleus tympani muscle Stapes
Base of stapes
a The structures of the middle ear

Incus

Base of stapes
at oval window

Stapes
Stapedius muscle

Inner surface of
tympanic membrane

b The tympanic membrane and auditory ossicles c The isolated auditory ossicles

are shown in Figure 17–23a. (See the Appendix for a chemical within the vestibule are continuous with those of the semicir-
analysis of perilymph, endolymph, and other body fluids.) cular canals.

We can subdivide the bony labyrinth into the vestibule, The cochlea (KOK-le. -uh; cochlea, a snail shell) is a spiral-
three semicircular canals, and the cochlea (Figure 17–23b). The shaped, bony chamber that contains the cochlear duct of the
vestibule (VES-ti-bu. l) consists of a pair of membranous sacs: membranous labyrinth. Receptors within the cochlear duct
the saccule (SAK-u. l) and the utricle (U. -tri-kul). Receptors in provide the sense of hearing. The duct is sandwiched between
these sacs provide sensations of gravity and linear acceleration. a pair of perilymph-filled chambers. The entire complex spirals
around a central bony hub, much like a snail shell.
The semicircular canals enclose slender semicircular ducts.
Receptors in the semicircular ducts are stimulated by rotation of The walls of the bony labyrinth consist of dense bone
the head. The combination of vestibule and semicircular canals everywhere except at two small areas near the base of the
is called the vestibular complex. The fluid-filled chambers cochlear spiral (Figure 17–21). The round window is a thin,