Otic placode

Otic Placode

The otic placode is a thickened area of ectoderm that gives rise to the inner ear in vertebrates. It is one of the placodes, which are transient thickened regions of the embryonic ectoderm layer that give rise to various structures in the head and neck.

Development

The otic placode first appears as a thickening of the ectoderm adjacent to the hindbrain during the third week of embryonic development. This thickening, known as the otic pit, invaginates to form the otic vesicle or otocyst. The otocyst then detaches from the surface ectoderm and migrates into the underlying mesenchyme, where it differentiates into the structures of the inner ear.

Structure

The otic placode gives rise to all the sensory neurons of the inner ear, including those responsible for hearing and balance. It also gives rise to the non-sensory structures of the inner ear, including the cochlea, vestibule, and semicircular canals.

Clinical Significance

Defects in otic placode development can lead to congenital hearing loss and balance disorders. Several genes have been identified that are critical for otic placode development, including Pax2, Pax8, and Fgf3.

See Also

• Placodes
• Inner ear
• Cochlea
• Vestibule
• Semicircular canals