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Describe the structure of the spiral organ.
The Correct Answer and Explanation is:
Correct Answer:
The spiral organ, also known as the organ of Corti, is located in the cochlea of the inner ear and is responsible for detecting sound. It lies on the basilar membrane inside the cochlear duct (scala media) and contains hair cells, supporting cells, and is covered by the tectorial membrane.
Explanation
The spiral organ, or organ of Corti, is the sensory organ of hearing found within the cochlea of the inner ear. It is a highly specialized structure situated on the basilar membrane inside the scala media, the central compartment of the cochlea. The spiral organ extends along the entire length of the cochlear spiral and is crucial for converting sound wave vibrations into electrical nerve impulses that the brain interprets as sound.
The organ of Corti comprises three main types of cells: inner hair cells, outer hair cells, and supporting cells. The inner hair cells are the primary sensory receptors that send auditory information to the brain via the cochlear nerve (a branch of the vestibulocochlear nerve, cranial nerve VIII). These are arranged in a single row and are fewer in number. In contrast, the outer hair cells are arranged in three to four rows and function primarily to amplify and fine-tune sound vibrations, improving the sensitivity and selectivity of hearing.
Above the hair cells lies the tectorial membrane, a gelatinous structure that comes into contact with the stereocilia (hair-like projections) of the hair cells. When sound waves cause the basilar membrane to vibrate, the movement causes a shearing motion between the basilar and tectorial membranes. This mechanical stimulation bends the stereocilia, leading to changes in ion flow into the hair cells and initiating electrical signals sent to the brain.
Supporting cells such as Deiters’ cells, Hensen’s cells, and pillar cells provide structural stability to the organ. Overall, the spiral organ is a delicate yet highly efficient structure that plays a vital role in the process of hearing.
