Final answer:
The tectorial membrane is the structure in the spiral organ of the cochlea, extending above the hair cells and playing a key role in hearing by transducing sound waves into neural signals.
Step-by-step explanation:
The structure located in the spiral organ (Organ of Corti) of the cochlea, which extends like an overhang above the hair cells, is known as the tectorial membrane. This membrane is critical for the process of hearing, as it participates in the transduction of sound waves into electrochemical signals. The hair cells within the Organ of Corti have hair-like projections called stereocilia which are embedded in or make contact with the tectorial membrane. When sound waves cause the basilar membrane to move, this also causes the tectorial membrane to displace, resulting in the bending of the stereocilia. This bending motion is essential for the conversion of mechanical movements into neural signals, as it leads to depolarization of hair cell membranes and the initiation of nerve impulses sent to the brain.