What is the internal ear and what are its main functions?

The internal ear, also known as the labyrinth, is located in the petrous part of the temporal bone. It consists of a bony labyrinth filled with perilymph and a membranous labyrinth filled with endolymph, containing sensory organs for hearing and balance.

What are the components of the membranous labyrinth and their roles?

The membranous labyrinth includes the cochlear duct for hearing, saccule and utricle for static balance, and semicircular ducts for kinetic balance. These structures are interconnected and contain sensory receptors like maculae and cristae ampullaris.

How is the cochlear duct structured and what is the Organ of Corti?

The cochlear duct is triangular, located between the scala vestibuli and scala tympani. The Organ of Corti is its sensory receptor for hearing, containing hair cells, a tectorial membrane, and supporting cells, innervated by the spiral ganglion.

What are the main parts of the bony labyrinth?

The bony labyrinth, housed in the petrous temporal bone, includes the cochlea anteriorly, vestibule centrally, and semicircular canals posteriorly. It is filled with perilymph and encloses the membranous labyrinth.

How do the semicircular canals contribute to balance?

The three semicircular canals (anterior, posterior, lateral) are arranged in orthogonal planes and detect angular acceleration. They contain ampullae with cristae ampullaris receptors, which send signals via the vestibular nerve to help maintain kinetic balance.

What is the role of the saccule and utricle in the internal ear?

The saccule and utricle are located in the vestibule and contain maculae receptors. They detect gravity and linear acceleration, playing a key role in static balance, and are innervated by the vestibular nerve.

How are the cochlear duct and vestibular structures connected?

The cochlear duct connects to the saccule via the ductus reuniens. The utricle connects to the saccule through the utriculo-saccular duct and to all semicircular ducts via five openings, forming a continuous system for fluid and signal transmission.

Internal Ear – Cochlea & Vestibular System

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