![]() The amplified vibration is picked up by the oval window causing pressure waves in the fluid of the scala vestibuli and scala tympani. This vibration is amplified as it moves across the malleus, incus, and stapes. ![]() The membrane covering the round window will bulge out or pucker in with the movement of the fluid within the scala tympani.įigure 8.6. Transmission of Sound Waves to Cochlea A sound wave causes the tympanic membrane to vibrate. The frequency of the fluid waves match the frequencies of the sound waves ( Figure 8.6). As vibrations of the ossicles travel through the oval window, the fluid of the scala vestibuli and scala tympani moves in a wave-like motion. The scala tympani ends at the round window, which is covered by a membrane that contains the fluid within the scala. The fluid-filled tube, now called the scala tympani, returns to the base of the cochlea, this time travelling under the cochlear duct. At the uppermost tip of the cochlea, the scala vestibuli curves over the top of the cochlear duct. The scala vestibuli extends from the oval window, travelling above the cochlear duct, which is the central cavity of the cochlea that contains the sound-transducing neurons. The oval window is located at the beginning of a fluid-filled tube within the cochlea called the scala vestibuli. The cochlea is attached to the stapes through the oval window. These ganglia are located within the spiral-shaped cochlea of the inner ear. Sound is transduced into neural signals within the cochlear region of the inner ear, which contains the sensory neurons of the spiral ganglia. However, these two distinct bundles travel together from the inner ear to the brain stem as the vestibulocochlear nerve. The neural signals from these two regions are relayed to the brain stem through separate fiber bundles. It has two separate regions, the cochlea and the vestibule, which are responsible for hearing and balance, respectively. The inner ear is often described as a bony labyrinth, as it is composed of a series of canals embedded within the temporal bone. The inner ear contains the cochlea and vestibule, which are responsible for audition and equilibrium, respectively. The middle ear contains the ossicles and is connected to the pharynx by the Eustachian tube. The tube is normally closed but will pop open when the muscles of the pharynx contract during swallowing or yawning.įigure 8.5. Structures of the Ear The external ear contains the auricle, ear canal, and tympanic membrane. The middle ear is connected to the pharynx through the Eustachian tube, which helps equilibrate air pressure across the tympanic membrane. The stapes is then attached to the inner ear, where the sound waves will be transduced into a neural signal. The incus, in turn, articulates with the stapes. The malleus is attached to the tympanic membrane and articulates with the incus. The three ossicles are the malleus, incus, and stapes, which are Latin names that roughly translate to hammer, anvil, and stirrup. The middle ear consists of a space spanned by three small bones called the ossicles. The auricle, ear canal, and tympanic membrane are often referred to as the external ear. At the end of the auditory canal is the tympanic membrane, or ear drum, which vibrates after it is struck by sound waves. The canal enters the skull through the external auditory meatus of the temporal bone. The C-shaped curves of the auricle direct sound waves toward the auditory canal. Some sources will also refer to this structure as the pinna, though that term is more appropriate for a structure that can be moved, such as the external ear of a cat. The large, fleshy structure on the lateral aspect of the head is known as the auricle. Hearing, or audition, is the transduction of sound waves into a neural signal that is made possible by the structures of the ear ( Figure 8.5).
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