Spiral Organ of Corti: Structure, Function, and Its Role in Hearing

Organ Of Corti

Write a short note on the spiral organ of Corti.
Answer.

It is an end organ of hearing, located on the basilar membrane of the cochlear duct.

Spiral Organ of Corti Components Microscopically, the organ of Corti consists of five components:

• Basilar membrane: A fibrous membrane that extends from the osseous spiral lamina to the outer wall of the cochlear duct.
• Tunnel of Corti: Formed by inner and outer rod cells and contains corticolymph.
• Hair cells are receptor cells of hearing located on the basilar membrane. These cells bear stereocilia and form the most important component of the spiral organ of Corti. They are divided into inner and outer hair cells.
  The hair cells perform the following functions:
  • Detect movements of endolymph
  • Detect vibrations of the basilar membrane
  • Transfer vibrations into nerve impulses to the cochlear nerve
• Supporting cells: The inner hair cells are supported by phalangeal cells, while the outer supporting cells are called Henson’s cells.
• Membrana tectoria: It is a gelatinous membrane that overlies the hair cells. The shearing force between the hair cells and tectorial membrane stimulates the hair cells.

Innervation of the organ of Corti The hair cells are innervated by the peripheral processes of bipolar neurons of the spiral ganglion located within the modiolus near the base of the spiral lamina. There are two types of neurons:

Type 1 neurons: They are myelinated and afferent. They innervate inner hair cells and are responsible for auditory sensation.

Type 2 neurons: They are unmyelinated and efferent from the contralateral superior olivary nucleus. They innervate outer hair cells and are responsible for auditory discrimination.