Thursday, March 30, 2023

Anatomy Of The Inner Ear

Clinical Relevance: Meniere’s Disease

Inner ear Anatomy Animation : Cochlear component, Vestibular component, Semi-circular component

Meniere’s disease is a disorder of the inner ear, characterised by episodes of vertigo, low-pitched tinnitus, and hearing loss.

The symptoms are thought to be caused by an excess accumulation of endolymph within the membranous labyrinth, causing progressive distension of the ducts. The resulting pressure fluctuations damage the thin membranes of the ear that detect balance and sound.

How Does Sound Normally Travel To The Inner Ear

Sound is captured and localized by the pinna or external ear. This sound is then concentrated and directed into the ear canal until it strikes the eardrum. The eardrum then vibrates, causing vibration of the three middle ear bones. The last bone, called the stapes, then moves in and out into the inner ear. This causes a wave of fluid within the inner ear to stimulate the inner ear hair cells. These hair cells communicate with the hearing nerve via electrical impulses. The impulses from the hearing nerve tell our brain that we are hearing sound.

Whats Happening When You Have Problems With Your Hearing

Hearing well depends on all parts of our auditory system working normally so that sound can pass through the different parts of the ear to the brain to be processed without any distortion. The type of hearing problem you have depends on which part of your auditory system is not responding well.

If you have a problem in the outer or middle ear, it means that there is inefficient transfer of sound to the cochlea in the inner ear. Generally, this affects the volume of sound so that it simply doesnt seem loud enough.

A typical example would be the effect of a blockage of wax in the ear canal or a perforated eardrum. This is called a conductive hearing loss because sound vibrations are not being conducted efficiently. The cochlea is still working normally but simply not receiving enough information via its connection with the middle ear.

If the problem is somewhere between the cochlea in the inner ear and the brain, this is called a sensorineural hearing loss. The pathway through the outer and middle ears is functioning normally but, after sound arrives at the cochlea, it isnt processed normally either because of damage to the delicate hair cells in the cochlea or to the auditory nerve or because of defects in the auditory pathway leading to the brain.

It is also possible to have both conductive and sensorineural hearing loss and this is generally called a mixed hearing loss.

For more detail about types of hearing loss, see our causes of hearing loss page.

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Cancer Of The Middle Ear


  • Discharge from ear for long period of time
  • Recent blood stained discharge
  • Sometimes facial paralysis

Cause: Unknownbut may be more common in adults with history of discharge from ears for long periods of time.

Treatment of people with cancer of the middle ear includes surgery and radiation, which targets rays of energy at small areas of cancer cells that might not have been removed during surgery.

Otosclerosis is the buildup of spongy or bone-like tissue in the middle ear that prevents the ossicles, namely the stapes in the middle ear, from working properly. The impaired movement and function reduces the sound that actually reaches the ear. Otosclerosis usually results in conductive hearing loss, a hearing loss caused by a problem in the outer or middle ear.

If the buildup of tissue spreads to the inner ear, it is called Cochlear Otosclerosis. This can cause permanent sensorineural hearing impairment due to interference with how the nerves in this part of the ear work.

Scientists aren’t sure about the exact cause but there is some research suggesting a relationship between otosclerosis and the hormonal changes associated with pregnancy and also with viruses.

If the hearing loss is mild, surgery may not be an option but a properly fitted hearing aid may help some people with otosclerosis. A hearing aid is designed to compensate for a hearing loss by amplifying sound.

Cancer Of The Outer Ear

How We Hear

Symptoms: A scabbed area of skin that is jagged and irregular with crusting and oozingusually on the upper edge of the outer part of the ear. This area may be present for many years and may or may not be associated with a swelling or lump in the neck.

Cause: Long periods of time in the sun.

Treatment for people with small cancers of the skin of the ear includes surgery to remove the affected area. Often no further treatment is required, especially if the cancer is confined to the outer edge of the ear.

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How Do We Hear

The brain and auditory system work together to control how we hear and how we balance ourselves. The human ear is a complex organ and many scientists consider hearing to be the most complex of the human senses.

Sound can be detected whether a person is on land, underwater or in the air. Hearing is our ability to perceive sound by detecting vibrations that travel through our ears. The main purpose of the ear is to turn sound waves from the air into electrical signals that are interpreted by the brain.

Sound travels through the auricle and the auditory canal, a short tube that ends at the eardrum. Sound entering the outer ear travels through the middle ear and causes the eardrum and ossicles in the middle ear to vibrate. As it travels, it amplifies and changes from air to liquid. When the stapes moves, it pushes the oval window, which then moves the cochlea. The cochlea takes the fluid vibration of sounds from the surrounding semicircular ducts, translates them into signals sent to the brain by nerves like the vestibular nerve and cochlear nerve. The brain translates the information into recognizable sound patterns. It is a complex process but it occurs in a split-second of time.

The human ear can detect different tones and loudness levels, which can help a person determine the direction of something , and helps to pick out specific sounds despite lots of background noise. Specifically, when someone is speaking, the sounds may be vocalized or non-vocalized.

Blood Supply And Lymphatics

The blood supply to the inner ear is via the labyrinthine artery , also known as the internal auditory artery. The LA usually arises from the anterior inferior cerebellar artery , but can also arise from the basilar artery . It enters the internal acoustic meatus alongside the vestibulocochlear nerve and supplies both the facial and the vestibulocochlear nerves. The LA then divides into three arteries while coursing through the internal acoustic canal: anterior vestibular artery , vestibulocochlear artery , and cochlear artery . The VCA separates into the cochlear and vestibular branches. The cochlear branch eventually forms an anastomosis with the CA, which makes up the main vascular supply to the cochlea. The vestibular branch and the AVA are responsible for vascular supply to the vestibular system.

Vestibular and cochlear aqueducts are responsible for venous drainage of the inner ear. The anterior and posterior spiral modiolar veins drain blood from the cochlea. The anterior and posterior vestibular veins drain blood from the vestibule, connects with the vein of the round window , and eventually empties into the inferior cochlear vein . The ICV then drains into the inferior petrosal sinus.

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Anatomy Of The Inner Ear

There are two parts of the inner ear. One part is for hearing. The other part is for balance.

The canals are filled with a fluid called endolymph. The level of this fluid is maintained by a small organ called the endolymphatic sac. In the hearing canal, sound waves cause vibrations in the endolymph. The inner ear detects these sound waves and sends nerve impulses to the brain. The sound we hear is a result of the brain’s interpretation of these nerve impulses.

In the balance canals, change in position causes movement of the fluid. This movement is detected in the balance portion of the inner ear, and nerve impulses are sent to the brain.

The endolymphatic sac keeps inner ear fluid at a constant level. The balance canals collect balance information. The hearing canal collects sound information. The hearing and balance nerves carry information to the brain from both parts of the inner ear.

Understanding The Hearing Process

Special Senses | Inner Ear Anatomy

Any disruption to the hearing process, no matter how small, can cause hearing and balance issues.

Knowing how the ear works and what parts make up your bodys auditory mechanism makes it easier to understand when something is affecting your hearing and balance.

With a system so delicate and precise, the best thing to do if you notice hearing loss or other issues is to reach out to professionals who can help you.

Happy Ears Hearing Center is here to help individuals dealing with hearing loss in the greater Phoenix area. We have locations in Mesa, Surprise, and Peoria. Contact us today to make an appointment.

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Anatomical Position And Structure

The inner ear is located within the petrous part of the temporalbone. It lies between the middle ear and the internal acoustic meatus, which lie laterally and medially respectively. The inner ear has two main components – the bony labyrinth and membranous labyrinth.

  • Bony labyrinth – consists of a series of bony cavities within the petrous part of the temporal bone. It is composed of the cochlea, vestibule and three semi-circular canals. All these structures are lined internally with periosteum and contain a fluid called perilymph.
  • Membranous labyrinth – lies within the bony labyrinth. It consists of the cochlear duct, semi-circular ducts, utricle and the saccule. The membranous labyrinth is filled with fluid called endolymph.

The inner ear has two openings into the middle ear, both covered by membranes. The oval window lies between the middle ear and the vestibule, whilst the round window separates the middle ear from the scala tympani .

How Does The Ear Work

Several parts in the ear work together to collect and transmit sound and movement to the brain. Sound waves enter the ear at the ear canal, or the coiled part of the ear you can see on the outside of the head. Waves are collected in this canal and hit the eardrum, which sends vibrations into the middle ear. Once the sound waves hit the eardrum, the force causes small bones called ossicles in the middle ear to vibrate. As the ossicles vibrate, a wave of fluid is sent to the neighboring inner ear. This is where fluid movement is measured and signals are sent through the cranial nerves to the brain. The inner ear is embedded in the temporal bone, or the sections of the skull located on the sides at each temple.

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Vasculature Of The Internal Ear

The bony labyrinth is vascularized by the anterior tympanic artery , stylomastoid artery , and the petrosal artery . On the other hand, the membranous labyrinth is supplied by the labyrinthine artery .

Venous blood is drained by the vestibular and cochlear veins. They merge and form the labyrinthine vein, which empties into the sigmoid or the inferior petrosal sinus. Lymphatic drainage is by the parotid, mastoid, and superficial cervical lymph nodes.

Bony And Membranous Labyrinths

Ears and hearing: How do they work?

The bony labyrinth, or osseous labyrinth, is the network of passages with bony walls lined with periosteum. The three major parts of the bony labyrinth are the vestibule of the ear, the semicircular canals, and the cochlea. The membranous labyrinth runs inside of the bony labyrinth, and creates three parallel fluid filled spaces. The two outer are filled with perilymph and the inner with endolymph.

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Vasculature Of The Middle Ear

The arteries that supply the tympanic cavity are the following:

  • Anterior tympanic artery
  • Posterior tympanic artery
  • Superior tympanic artery
  • Inferior tympanic artery
  • Anterior, superior, and inferior tympanic arteries
  • Mastoid branch of the occipital artery

The tympanic veins drain deoxygenated blood into the superior petrosal sinus and the pterygoid venous plexus. Lymph drains into the retroauricular cervical lymph nodes.

Usmle Step 1 Style Questions Usmle

A 36-year-old rockstar is being evaluated by their primary care doctor for progressive over the last two years. They state that they have not been wearing ear protection while rocking out during loud concerts. A physical examination and a series of tests would most likely reveal results consistent with damage to hair cells located in which part of the ?

Content Reviewers:

How is it you can listen to your favorite song, close your eyes, dance, and not fall on your face? Well, there is a little thing called the that contains the which gives you the ability to perceive sounds and maintain your balance.

The is found in the petrous part of the temporal bone between the laterally, and the internal acoustic meatus medially. It is a small and important area which houses the irregularly shaped , which kind of looks like a snail shell attached to a few bony rings.

Now, the contains the and the . The is connected to the by two windows. The oval window is found on the lateral wall of the and is covered by the base of the , while the round window is found at the base of the and is covered by the secondary .

The , within the otic capsule, is filled with perilymph and is made of a series of which are the , the , and the . Suspended within the , thereâs the , which is basically a series of sacs and ducts filled with endolymph.

The is organized into the within the , the three and their membranous ampullae, and the within the .

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Innervation Of The Middle Ear

When it comes to innervation, the mucosa that covers the walls of the middle ear is supplied with the tympanic nerve ), whereas the muscles of the auditory ossicles are innervated by the tensor tympani nerve and stapedius nerve .

The tympanic nerve and caroticotympanic nerves of the internal carotid plexus form the tympanic plexus in the mucous membrane that covers the promontory on the labyrinthine wall. This plexus supplies the mucosa of the middle ear, pharyngotympanic tube, and mastoid antrum. It also gives off the lesser petrosal nerve, which provides parasympathetic innervation for the otic ganglion.

How Does The System Work

Anatomy of Inner Ear

The outer ear captures sound waves. The sound travels down the ear canal and hits the ear drum. The ear drum vibrates which causes the ossicles to vibrate. A piston action of the ossicles creates a wave in the fluid in the inner ear. The fluid wave stimulates the hair cells in the cochlea and an electrical impulse is sent through the eighth cranial nerve to the brain.

The balance system works by sending continuous electrical impulses to the brain. Moving the head causes the fluid in the semi-circular canals to shift. This in turn changes the electrical impulses to the brain. The brain uses this information to make any adjustments the body needs for balance.

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Vestibular And Cochlear Systems

In the middle ear, the energy of pressure waves is translated into mechanical vibrations by the three auditory ossicles. Pressure waves move the tympanic membrane which in turns moves the malleus, the first bone of the middle ear. The malleus articulates to incus which connects to the stapes. The footplate of the stapes connects to the oval window, the beginning of the inner ear. When the stapes presses on the oval window, it causes the perilymph, the liquid of the inner ear to move. The middle ear thus serves to convert the energy from sound pressure waves to a force upon the perilymph of the inner ear. The oval window has only approximately 1/18 the area of the tympanic membrane and thus produces a higher pressure. The cochlea propagates these mechanical signals as waves in the fluid and membranes and then converts them to nerve impulses which are transmitted to the brain.

The vestibular system is the region of the inner ear where the semicircular canals converge, close to the cochlea. The vestibular system works with the visual system to keep objects in view when the head is moved. Joint and muscle receptors are also important in maintaining balance. The brain receives, interprets, and processes the information from all these systems to create the sensation of balance.

Anatomy And Physiology Of The Ear

Our help us hear and balance ourselves in space, and they have three parts.

The first part is the which is the part you see and hang earrings on, called the , as well as the .

The second part is the , which is a tiny chamber that houses even tinier ear bonesthe , , and .

The third part is the , which contains the , a special structure that converts sound waves into electrical impulses for the brain, as well as the which help with balance.

Lets start with the . The , also called the , is made up of that gives our their various shapes and sizes, and it also has a fleshy bit at the bottom- called the ear lobe, or lobule.

The directs sound waves towards the opening of the .

The , or the , is a short, curved that burrows through the temporal bone for about 1 inch – or 2 and a half centimeters – and ends at the .

On the inside, the is covered by skin, along with hair follicles and ceruminous glands – which secrete , or the sticky, yellow-ish, earwax.

helps prevents foreign objects or tiny insects from getting in and damaging the . Thats a creepy thought.

The is also called the , and its a thin, translucent membrane that separates the from the . Its shaped a bit like a cone, protruding slightly into the .

When sound waves reach the , it vibrates and transmits those vibrations to the tiny bones in the .

Now, the is an air-filled cavity inside the temporal bone, shaped like tiny chamber with 4 walls, a floor and a roof.

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