276 Introduction to Anatomy & Physiology Eustachian tube, and middle ear to the same level as pressure outside the ear. This is a good strategy to use when air (barometric) pressure changes rapidly, such as during an airplane descent or while driving down a mountain road. Internal Ear The oval window connects the middle ear with the inner ear. The inner ear structures reside in a hollow tunnel that winds and twists like a bowl of interconnected spaghetti noodles. Figure 7.13 shows a representation of these winding tunnels, known as the bony labyrinth. The three components of the inner ear are the cochlea (KAHK-lee-uh), vestibule (VEHS-ti-byool), and semicircular (sehm-ee-SIR-kyoo-lar) canals. or anvil and the stapes, or stirrup. Together, these bones connect the tympanic membrane to the membrane of the oval window. The hammer attaches to the tympanic membrane, the anvil attaches to the hammer, and the stirrup attaches to the anvil on one side and to the oval window on the other. Because of their mechanical arrangement, the ossicles not only transmit, but also amplify, sound waves. The Eustachian (yoo-STAY-shuhn) tube connects the middle ear to the pharynx. The pharynx is the part of the throat that connects the mouth and nasal cavity to the esophagus (the digestive tube between the throat and stomach). The Eustachian tube equalizes the pressure on either side of the tympanic membrane. Yawning widely is a way to help bring pressure in the pharynx, © Body Scientific International Figure 7.12 Anatomy of the ear. Which structure separates the outer ear from the middle ear? Semicircular canals Vestibulocochlear nerve Oval window Cochlea Ossicles External (outer) ear Middle ear (tympanic cavity) Internal (inner) ear Vestibule Round window Eustachian tube Tympanic membrane (eardrum) Hammer (malleus) Anvil (incus) Stirrup (stapes) Auricle (pinna) Auditory canal (external acoustic meatus) Copyright Goodheart-Willcox Co., Inc.