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Correct Answer: basilar and tectorial.
the correct answer to the question is "basilar and tectorial." this is because within the organ of corti, which is essential for hearing, the tiny hairlike nerve endings known as hair cells are anchored in the basilar membrane (bm). these hair cells feature extensions called stereocilia that are crucial for the process of converting mechanical sound vibrations into electrical signals, which are then transmitted to the brain.
the basilar membrane extends throughout the length of the cochlea in the inner ear. it serves as the foundation upon which the hair cells sit. the flexibility and properties of the basilar membrane vary along its length, affecting the sound frequencies best detected at different points along the cochlea. high frequency sounds are best detected near the base of the cochlea where the basilar membrane is stiffer and narrower, while low frequency sounds are detected near the apex where it is wider and more flexible.
the unattached tips of the hair cells' stereocilia come into contact with the tectorial membrane (tm), which is an overhanging roof-like structure in the organ of corti. the tectorial membrane is gel-like and is composed mainly of water and collagen. this membrane plays a crucial role in the hearing process by interacting with the stereocilia of hair cells during sound vibrations. when sound waves travel through the cochlea, they cause the basilar membrane to move, which in turn causes the tectorial membrane to move relative to the stereocilia. this movement bends the stereocilia, opening ion channels that lead to the generation of electrical signals in the auditory nerve fibers.
reissner's membrane is another structure within the cochlea, but it separates the cochlear duct from the vestibular duct and mainly functions as a diffusion barrier. it does not play a direct role in the interaction with the hair cells' stereocilia. similarly, the otolithic membrane is found in the vestibular system, specifically in the utricle and saccule, where it functions in the detection of linear accelerations and head tilts, not in the hearing process.
therefore, the appropriate and correct answer is "basilar and tectorial," as these are the two membranes within the cochlea directly involved in the mechanics of hearing through their relationship with the hair cells of the organ of corti.
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