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Structure of the Ear
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Given below is a diagrammatic cross section of a single loop of human cochlea:
Which one of the following options correctly represents the names of three different parts?In a cross section, each loop of the cochlea shows three canals.
The upper canal is the scala vestibuli and the lower canal is the scala tympani; both are filled with perilymph. In the figure both of these outer chambers are labelled A, so A is perilymph.
The middle canal is the scala media (cochlear duct), which is filled with endolymph. It is separated from the scala vestibuli by Reissner's membrane and from the scala tympani by the basilar membrane. This is the part labelled C, so C is endolymph.
The organ of Corti is located on the basilar membrane and contains the sensory hair cells that act as auditory receptors.
Above the rows of hair cells is a thin elastic membrane called the tectorial membrane, labelled B.
The hair cells are sensory cells, not secretory cells, and the fluid in the outer canals is perilymph, not endolymph or serum.
So the correct labelling is A: Perilymph, B: Tectorial membrane, C: Endolymph.