Inner Ear - Diagram and Description

The human ear comprises three parts, namely the external, middle and inner ear. The inner ear or labyrinth is the innermost part that consists of the bony and membranous labyrinth. The vestibular apparatus is a part of the inner ear that plays a vital role in maintaining equilibrium and posture. The inner ear also has the cochlea, which is responsible for the sensation of hearing.

Let’s learn more about the description of the inner ear with a labelled diagram.

Table of Contents:

• Labelled Diagram of the Inner Ear
• Inner Ear – Description
• Significance
• Frequently Asked Questions

Labelled Diagram of Inner Ear

Inner Ear – Description

• The inner ear or labyrinth of the human ear comprises 2 structures – the bony labyrinth and the membranous labyrinth.
• Bony labyrinth is a series of cavities or channels present in the petrous part of the temporal bone. The membranous labyrinth is present within the bony labyrinth.
• The space between the bony and membranous labyrinth is filled with periodic fluid or perilymph. This fluid has large amounts of sodium ions.
• The bony labyrinth consists of 3 parts – cochlea, vestibule and semicircular canals.
• The cochlea is spirally coiled and resembles a snail shell. It forms the anterior part of the inner ear and is concerned with the sensation of hearing.
• The organ of Corti is the neuroepithelial structure in the cochlea and is the end organ of hearing. It is made up of sensory elements called hair cells and various other supporting cells. These hair cells detect pressure waves and send signals to the brain.
• The vestibule is the central part of the inner ear. It is mainly concerned with equilibrium and posture.
• The three semicircular canals are tubular structures placed at right angles to each other.
• The anterior or superior semicircular canal and the posterior canal lie in the vertical plane. The former is at right angles to the long axis of the petrous temporal bone, and the latter lies parallel. The lateral semicircular canal lies in the horizontal plane.
• The membranous labyrinth is a continuous closed cavity filled with endolymph. The endolymph has a large quantity of potassium ions.
• The membranous labyrinth consists of the spiral ducts of the cochlea or organ of Corti anteriorly. Within the vestibule, they also have a saccule and utricle with maculae as organs of static balance. Posteriorly, they comprise the semicircular ducts with cristae to form organs of kinetic balance.

Significance

Thus, the sound waves from the external ear are passed to the structures of the internal ear. The internal ear consists of organs for hearing as well as equilibrium. The cochlea has hair cells that detect sound pressure waves and transmits signals to the human brain. The vestibular apparatus is dedicated to balance or equilibrium.

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