The organ of Corti is composed of a lower basilar membrane against the scala tympani and an upper tectorial membrane within the cochlear duct (Fig. The organ for hearing, which contains the sensory receptors is known as the spiral organ of Corti and is located throughout the cochlear duct.

As the oval window is pushed in by sound waves vibrating from the ossicles, fluid within this tube is pushed along its length and the round window at its other end bulges out as a result of that movement. The cochlear duct is the third, middle chamber positioned between the scala vestibuli and scala tympani. The scala vestibuli (upper chamber) and the scala tympani (lower chamber) extend the length of the cochlea and are continuous with a connection at the helicotrema (Fig. The cochlea is composed of 3 chambers separated from one other by membranes. The vibrations transmitted through the ossicles pass into the cochlea by way of the oval window. The connection between the middle ear and inner ear is at the oval window, a membranous area at the entrance of the snail-shaped cochlea. The neural signals from the regions of the inner ear are relayed to the brainstem through separate fiber bundles, but which run together as the vestibulocochlear nerve, cranial nerve VIII. It has three separate regions: the cochlea, which is responsible for hearing and the vestibule and semicircular canals, which are responsible for balance and equilibrium. The inner ear is entirely enclosed within the temporal bone. Unfortunately, it is also the auditory tubes that play a role in causing otitis media, as microorganisms can use this path to move from the pharynx into the middle ear. The auditory tube also provides a pathway of drainage for fluids that accumulate during middle ear infections ( otitis media). For this reason, chewing gum or drinking as the plane climbs will often relieve these symptoms. The auditory tube is normally closed, but will typically open when muscles of the pharynx contract during swallowing or yawning. If there is not a corresponding decrease in pressure in the middle ear, the pressure difference will cause the eardrum to push outward, causing pain and muffled hearing. As the plane climbs, pressure on the outside of the membrane decreases. When flying, you may have experienced what happens when the pressures across the tympanic membrane are not equal. The middle ear is also connected to the pharynx through the auditory tube (Eustachian tube) that helps equilize air pressure across the tympanic membrane. The stapes is then attached to the inner ear at the oval window where the sound waves will be transferred to the inner ear. The malleus is attached to the tympanic membrane and articulates with the incus, which articulates with the stapes. These small bones are the malleus, incus, and stapes, which are Latin names that roughly translate to hammer, anvil, and stirrup (Fig. The middle ear consists of a space spanned by three small bones, the ossicles, which amplify the movements of the tympanic membrane. Cerumen also helps prevent bacterial growth, waterproofs the auditory canal and tympanic membrane, and may be a deterrent to small insects. Because cerumen is sticky it can help prevent small particles from finding their way to the tympanic membrane. At the end of the auditory canal (sometimes caused external acoustic meatus) is the tympanic membrane, or ear drum, which vibrates with the movement of air in sound waves.Īlong the length of the auditory canal are ceruminous glands that contribute to the production of cerumen (earwax).

The C-shaped curves of the auricle direct sound waves towards the ear canal, which enters into the skull through the external auditory meatus of the temporal bone. The outwardly visible structure that is often referred to as the ear is more correctly referred to as the outer ear (external ear), or the auricle.

The ear is subdivided into 3 major parts: the external ear, middle ear, and internal ear. Hearing is the transduction of sound waves into a neural signal that relies on the structures of the ear. The ear is the organ of both hearing and equilibrium.

Auditory ossicles function