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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.
Unlike structures of the inner and middle ear, which develop from pharyngeal pouches, the ear canal originates from the dorsal portion of the first pharyngeal cleft. [18] [20] It is fully expanded by the end of the 18th week of development. [21] The eardrum is made up of three layers (ectoderm, endoderm and connective tissue).
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.
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 cochlear duct (a.k.a. the scala media) is an endolymph filled cavity inside the cochlea, located between the tympanic duct and the vestibular duct, separated by the basilar membrane and the vestibular membrane (Reissner's membrane) respectively.
There are two different types of fluid that surround the hair cells of the inner ear. The endolymph is the fluid that surrounds the apical surfaces of hair cells. Potassium is the major cation in the endolymph and is thought to be responsible for carrying the receptor currents in the cochlea .
Section through the organ of Corti, showing inner and outer hair cells. The deflection of the hair-cell stereocilia opens mechanically gated ion channels that allow any small, positively charged ions (primarily potassium and calcium) to enter the cell. [10] Unlike many other electrically active cells, the hair cell itself does not fire an ...