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Inner ear
 
 
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The inner ear
Ear

The ear is the sense organ that detects sounds. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species....
 is the bony labyrinth
Labyrinth (inner ear)

The labyrinth is a system of fluid passages in the inner ear, including both the cochlea which is part of the auditory system, and the vestibular system which provides the sense of balance....
, a system of passages comprising two main functional parts: Inner ears are found in all vertebrates, with substantial variations in the form and function of their sensory organs. Each animal has two inner ears, one on each side of its head.

Ear overview, in context
In mammals, the outer ear
Outer ear

The outer ear is the external portion of the ear, which consists of the pinna , concha, and auditory meatus. It gathers sound energy and focuses it on the eardrum ....
 focuses and directs sound waves into the middle ear.






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Gray920
The inner ear
Ear

The ear is the sense organ that detects sounds. The vertebrate ear shows a common biology from fish to humans, with variations in structure according to order and species....
 is the bony labyrinth
Labyrinth (inner ear)

The labyrinth is a system of fluid passages in the inner ear, including both the cochlea which is part of the auditory system, and the vestibular system which provides the sense of balance....
, a system of passages comprising two main functional parts:
  • the organ of hearing, or cochlea
    Cochlea

    The cochlea is the auditory portion of the inner ear. Its core component is the Organ of Corti, the sensory organ of hearing , which is distributed along the partition separating fluid chambers in the coiled tapered tube of the cochlea....
  • and the vestibular apparatus, the organ of balance that consists of three semicircular canal
    Semicircular canal

    The semicircular canals are three half-circular, interconnected tubes located inside each ear. The three canals are the horizontal semicircular canal, superior semicircular canal , and the posterior semicircular canal....
    s and the vestibule
    Vestibule of the ear

    DefinitionThe vestibule is the central part of the Labyrinth , and is situated medial to the tympanic cavity, behind the cochlea, and in front of the semicircular canals....
    .
Inner ears are found in all vertebrates, with substantial variations in the form and function of their sensory organs. Each animal has two inner ears, one on each side of its head.

Ear overview, in context


In mammals, the outer ear
Outer ear

The outer ear is the external portion of the ear, which consists of the pinna , concha, and auditory meatus. It gathers sound energy and focuses it on the eardrum ....
 focuses and directs sound waves into the middle ear. In the middle ear
Middle ear

The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear....
, the energy of these pressure waves
P-wave

P-waves are type of elastic wave, also called seismic waves, that can travel through gases , elastic solids and liquids, including the Earth....
 is translated into mechanical vibrations of the middle ear’s bone structure. The cochlea of the inner ear propagates these mechanical signals as waves in fluid and membranes, and finally transduces them to nerve impulses which are transmitted to the brain.

The vestibular system
Vestibular system

The vestibular system, which contributes to our balance and our sense of spatial orientation, is the sensory system that provides the dominant input about movement and equilibrioception....
 of the inner ear is responsible for the sensations of balance and motion. It uses the same kinds of fluids and detection cells (hair cells) as the cochlea uses, and sends information to the brain about the attitude, rotation, and linear motion of the head. The type of motion or attitude detected by a hair cell depends on its associated mechanical structures, such as the curved tube of a semicircular canal or the calcium carbonate crystals (otolith
Otolith

An otolith, , also called statoconium or otoconium is a structure in the saccule or Utricle of the inner ear, specifically in the Labyrinth ....
) of the saccule
Saccule

The saccule is a bed of sensory cells situated in the inner ear. The saccule translates head movements into neural impulses which the brain can interpret....
 and utricle.

The inner ear is innervated by the eighth cranial nerve in all vertebrates.

Non-humans

Birds have an auditory system similar to that of mammals, including an outer ear, middle ear, and cochlea, though their middle ear has only one bone whereas the evolution of mammalian auditory ossicles
Evolution of mammalian auditory ossicles

The evolution of mammalian auditory ossicles is one of the most well-documented and important evolutionary events, demonstrating both numerous transitional fossil as well as an excellent example of exaptation, the re-purposing of existing structures during evolution....
 resulted in three bones. Reptiles, amphibians, and fish do not have cochleas but hear with simpler auditory organs or vestibular organs, which generally detect lower-frequency sounds than the cochlea.

See also

  • Labyrinth (inner ear)
    Labyrinth (inner ear)

    The labyrinth is a system of fluid passages in the inner ear, including both the cochlea which is part of the auditory system, and the vestibular system which provides the sense of balance....
  • Vestibular system
    Vestibular system

    The vestibular system, which contributes to our balance and our sense of spatial orientation, is the sensory system that provides the dominant input about movement and equilibrioception....
  • Cochlea
    Cochlea

    The cochlea is the auditory portion of the inner ear. Its core component is the Organ of Corti, the sensory organ of hearing , which is distributed along the partition separating fluid chambers in the coiled tapered tube of the cochlea....


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