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Cross-section through the spiral organ of Corti at greater magnification, showing position of the hair cells on the basement membrane. The organ of Corti is located in the scala media of the cochlea of the inner ear between the vestibular duct and the tympanic duct and is composed of mechanosensory cells, known as hair cells. [2]
It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. [2] [3] A core component of the cochlea is the organ of Corti, the sensory organ of hearing, which is distributed along the partition separating the fluid chambers in the coiled tapered tube of the cochlea.
Cross-section through the spiral organ of Corti at greater magnification. Rosenthal's canal or the spiral canal of the cochlea is a section of the bony labyrinth of the inner ear that is approximately 30 mm long and makes 2¾ turns about the modiolus, the central axis of the cochlea that contains the spiral ganglion.
While the semicircular canals respond to rotations, the otolithic organs sense linear accelerations. Humans have two otolithic organs on each side, one called the utricle, the other called the saccule. The utricle contains a patch of hair cells and supporting cells called a macula. Similarly, the saccule contains a patch of hair cells and a macula.
The spiral (cochlear) ganglion is a group of neuron cell bodies in the modiolus, the conical central axis of the cochlea. These bipolar neurons innervate the hair cells of the organ of Corti . They project their axons to the ventral and dorsal cochlear nuclei as the cochlear nerve , a branch of the vestibulocochlear nerve (CN VIII).
It helps to transmit vibrations from fluid in the vestibular duct to the cochlear duct. Together with the basilar membrane, it creates a compartment in the cochlea filled with endolymph, which is important for the function of the spiral organ of Corti. It allows nutrients to travel from the perilymph to the endolymph of the membranous labyrinth.
Perilymph and endolymph have unique ionic compositions suited to their functions in regulating electrochemical impulses of hair cells necessary for hearing. The electric potential of endolymph is ~80-90 mV more positive than perilymph due to a higher concentration of potassium cations (K +) in endolymph and higher sodium (Na +) in perilymph. [4]
The basilar membrane stretches from the tympanic lip of the osseous spiral lamina to the basilar crest and consists of two parts, an inner and an outer. The inner is thin, and is named the inner tunnel (or zona arcuata): it supports the spiral organ of Corti.