Organ of Corti function and structure

ORGAN OF CORTI

Organ of Corti is the receptor organ for hearing. It is the neuroepithelial structure in cochlea.

Organ of Corti function and structure


Situation and Extent

Organ of corti rests upon the lip of osseous spiral lamina and basilar membrane. It extends throughout

the cochlear duct, except for a short distance on either end. Roof of the organ of Corti is formed by

gelatinous tectorial membrane.

Structure

Organ of Corti is made up of sensory elements called hair cells and various supporting cells. All the cells of organ of Corti are arranged in order from center towards the periphery of the cochlea.

Cells of organ of Corti:

1. Border cells

2. Inner hair cells

3. Inner phalangeal cells

4. Inner pillar cells

5. Outer pillar cells

6. Outer phalangeal cells

7. Outer hair cells

8. Cells of Hensen

9. Cells of Claudius

10. Tectorial membrane and lamina reticularis.

1. Border Cells

Border cells are the slender columnar cells, arranged in a single layer on the tympanic lip along the inner

side of inner hair cells. Surfaces of the border cells have cuticle.

2. Inner Hair Cells

Inner hair cells are flaskshaped cells and are broader than the outer hair cells. Inner hair cells are arranged in a single row and occupy only the upper part of epithelial layer. Rounded base of each cell rests on the adjacent supporting cells called the inner phalangeal cell. Surface of the inner hair cell bears a cuticular plate and a number of short stiff hairs, which are called stereocilia. Each hair cell has about 100 sterocilia. One of the sterocilia is larger and it is called kinocilium. Stereocilia are in contact with the tectorial membrane. Inner hair cells and outer hair cells together form the receptor cells. Sensory

nerve fibers are distributed around the hair cells. Both inner hair cells and outer hair cells have afferent and efferent nerve fibers .

3. Inner Phalangeal Cells

Inner phalangeal cells are the supporting cells of inner hair cells and are arranged in a row along the inner surface of inner pillar cells. Their bases rest on the basilar membrane. Cuticular plate of cells (formed by the lower portion of cells) look like the finger bones, phalanges.

4 and 5. Inner and Outer Pillar Cells – Rods of Corti

Inner and outer pillar cells are called rods of Corti.

Each pillar cell has a broader base, an elongated body or pillar and a head at the tip of pillar. Bases of inner pillar cells are close to the lip of osseous spiral lamina (tympanic lip), whereas the bases of outer pillar cells are close to basilar membrane. Pillars of inner and outer pillar cells slope towards each other and their heads articulate. Thus, the pillars of cells form series of arches, which enclose a triangular tunnel called inner tunnel or tunnel of Corti.

6. Outer Phalangeal Cells

Outer phalangeal cells or the cells of Deiters are the supporting cells of outer hair cells. Outer phalangeal

cell is the tall columnar cell. It sends stiff phalangeal processes upward between the hair cells, to form the

part of lamina reticularis. Rows of outer phalangeal cells vary in different regions of cochlear duct like the outer hair cells, i.e. from three to five rows. Between the inner most outer phalangeal cells and outer pillar cells, is a fluid space known as the space of Nuel.

7. Outer Hair Cells

Outer hair cells are the columnar cells occupying the superficial part of epithelium of organ of Corti.

Their bases are supported by outer phalangeal cells. Structure of outer hair cells is similar to that of inner

hair cells.

8. Cells of Hensen

Cells of Hensen are tall columnar cells forming the outer border cells of organ of Corti. These cells are

arranged in several rows on basilar membrane, lateral to outer phalangeal cells. The space between outer phalangeal cells and cells of Hensen is called outer tunnel.

9. Cells of Claudius

Cells of Claudius are cuboidal in nature and line the lower surface of external spiral sulcus. In certain

areas, some groups of cells are present between the cells of Claudius and basilar membrane. These cells

are called Boettcher cells.

10. Tectorial Membrane and Lamina Reticularis

Tectorial membrane extends from vestibular lip to the level of cells of Hensen. It forms the roof of organ of

Corti. It is in contact with the processes of hair cells. It is assumed that the processes of hair cells are

stimulated by the movements of tectorial membrane, in relation to vibrations in endolymph.

Cuticular plates of all the supporting cells collectively form a reticular membrane, which is known

as lamina reticularis. It covers the organ of Corti. It looks like a mosaic and has rows of holes, through

which the heads of hair cells are inserted.

 

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