Ultimate Guide to Ear Anatomy: Parts, Structure, Functions & Diagram

Overview of Ear Anatomy

The human Ear does two main jobs: it helps us hear and keeps us balanced. It works by turning sound waves into signals our brains can understand. The ear anatomy consists of three parts: the outer Ear, middle Ear, and inner Ear. The outer Ear is the part you can see, including the flap of skin called the pinna and the tube-like ear canal. The middle Ear is inside your head, and there is a space called the middle Ear. It has three tiny bones called ossicles and a cavity called the tympanic cavity. The inner Ear is part deep inside your head and is filled with fluid. It has the cochlea, which helps with hearing, and the semicircular canals, which help with balance. Earwax keeps the Ear clean by trapping dirt and dust.

Our ears are usually placed on both sides of our head, which helps us figure out where sounds are coming from. Let’s see the detailed anatomy of the ear and its different parts and functions.

Ear Anatomy Diagram

Parts of Ear

External Ear Anatomy

Auricle (Pinna)

The visible piece of our outer ear is called the auricle or pinna. It is made of cartilage and skin and sits on the side of our heads. Its principal role is to collect and guide sound waves into the ear canal for amplification.

It is composed of two distinct curves: the helix on the outside and the antihelix on the inside, which is divided into front and upper-back sections. In the center, there is a hollow called the concha that directs sound into the ear canal.

Just before the canal begins, there is an elevated section called the tragus that aids in sound direction. The antitragus is located opposite the tragus.

These components work together to effectively catch and guide sound into our ears, allowing us to hear the world around us.

External Auditory Meatus (Ear Canal)

The outer ear has a canal called the external acoustic meatus. It is like a tube, about 2.5 centimeters long and 0.7 centimeters wide, running from the outside of your ear to your eardrum.

This canal curves inward and forward. If you looked at it from the side, it would be oval-shaped, with the long side pointing downward and slightly backward.

The walls of this canal are made partly of bone and partly of cartilage. The front and bottom parts are bony, while the top and back parts are made of a bony plate called the squama.

At the inner end of this canal is your eardrum. At the outer end, you have the opening of your ear, just below a part of your cheekbone called the posterior root of the zygomatic process.

Sometimes, you might see a tiny bump called the supramental spine just above and behind this opening. But mostly, it is the end of your ear canal.

Tragus

The tragus is a little pointy bump in your ear, right in front of the inner part. It sticks backward over the ear canal. This area also has some hair.

Because the tragus points backward, it helps gather sounds from behind you. Those sounds take a bit longer to reach your ears compared to sounds coming from the front. It helps your brain figure out where sounds are coming from.

In a positive fistula test, which checks for a passage between a cholesteatoma and the inner ear, pressing on the tragus can make you feel dizzy, or your eyes might move funny. It happens because it messes with the fluid in your inner ear.

Antitragus

The antitragus is a little bump on the outside of your ear, just above where your earlobe ends. It faces towards the front of your face.

You can feel it as a small raised area when you touch your ear. It is different from the tragus, which is the little bump in front of the ear opening.

In humans, it is not very big, but in some animals, like bats, it can be much larger. There’s a tiny muscle in the ear called the antitragicus muscle that connects to the outer part of the antitragus.

Helix

The outer part of the ear goes from where it attaches to your head at the top to where it ends at the earlobe. We can split the helix, which is the outer rim of the ear, into three parts:

1. The part that goes up from the base of the ear (ascending helix).
2. The part that goes across from the top of the ascending part and curves backward (superior helix).
3. The part that goes down from the curved part to the top of the earlobe (descending helix).
4. Sometimes, the lower part of the descending helix isn’t made of cartilage. The edge of the helix usually makes a rolled shape, but the helix itself can look different for different people.

Antihelix

The antihelix is like a Y-shaped ridge in your ear that starts from the part just above the earlobe (antitragus). It divides the inner part of the ear into three sections: the concha, triangular fossa, and scapha.

It is made of flexible cartilage. Normally, it is shaped like a “Y” with a gentle curve at the bottom. About two-thirds of the way up, it splits into two parts: one bends outward (superior), and the other turns inward (inferior). These parts can look different in size and how much they fold.

Concha

The concha is like the central hub of your ear, shaped like a conch sea shell. It sits in the middle of the outer part of your ear, which is a hollow area in the cartilage. Different parts like the tragus, incisura, antitragus, and more surround the concha.

Its job is to help direct sound into your ear canal. It is like a funnel for sound. This sound then travels into your ear and eventually to your brain so you can hear it.

The concha gets messages from different nerves in your body to do its job. These nerves help it to work properly so you can hear sounds clearly.

Lobule

The lobule is the soft bottom part of your ear that doesn’t have cartilage like the rest of your ear. It is made up of flexible tissues and fat. Because it lacks cartilage, it isn’t as firm or bouncy as the rest of your ear.

Nerves

The skin of your outer ear gets feelings from different nerves:

1. Greater auricular nerve: Feels things on your auricle from the neck area.
2. Lesser occipital nerve: Feels things on your auricle from the neck area, too.
3. Auriculotemporal nerve: Feels things on your auricle and ear canal from your jaw nerve.
4. Facial and vagus nerves: Feel deeper parts of your ear and ear canal.
5. When some people clean their ears, they might cough without meaning to. It happens because the nerve in your ear connected to your cough reflex can get stimulated.

Middle Ear Anatomy

Tympanic Membrane (Eardrum)

The eardrum, found at the end of your ear canal, is an important tissue structure. It is like a thin, transparent sheet covered outside by skin and inside by mucous membrane, and it is firmly attached to a ring of tough cartilage on the bone.

You can easily see the middle ear through it using a special tool called an otoscope. Inside, there’s a little handle called the malleus, which attaches to the eardrum at a point called the umbo.

On the handle, there’s a small bump called the lateral process. From there, two folds extend outwards, which help the eardrum move around the lateral process.

Ossicles

The smallest bones in your body are in your ears! They are called the auditory ossicles, and there are three of them: the hammer, the anvil, and the stirrup.

These bones are like a tiny chain that connects your eardrum to another part of your ear called the cochlea. When sound enters your ear, your eardrum starts vibrating. These little bones help carry that vibration to the cochlea.

Inside the cochlea, the vibration gets turned into electrical signals that your brain understands as sound. So, with these tiny bones, it is easier for you to hear properly!

Eustachian Tube (Auditory Tube)

The Eustachian tube (ET) is like a tunnel that connects your ear to the back of your nose. It is also called the pharyngotympanic tube or auditory tube.

It helps in

1. Equalizing Pressure: The ET helps balance the pressure inside your ear, which is important for hearing properly.
2. Draining Mucus: It also helps to clear out mucus from your ear, keeping it clean and healthy.
3. Protecting the Ear: The ET acts as a barrier, preventing loud sounds and nasal stuff from harming your ear.
4. Normally, the ET stays closed, but it opens up when you do things like swallowing, yawning, or chewing gum.

Middle Ear Cavity

The middle ear cavity, also called the tympanic cavity, is a space in the temporal bone between the outer and inner ear. It is filled with air and lined with a thin layer of tissue. Inside are three small bones: the hammer, anvil, and stirrup.

Its main job is to carry sound vibrations from the eardrum to the inner ear. Think of it like a small box with walls, a roof, and a floor. Because of its shape, it is narrower in the middle.

In simple terms, the middle ear cavity is about 2 mm wide in the middle, 6 mm wide at the top, and 4 mm wide at the bottom.

Overall, it is around 15 mm tall and wide. Its role is to help us hear by transmitting sound and also to balance air pressure in the ear.

Tensor Tympani Muscle

The tensor tympani is a muscle in your ear that helps reduce loud sounds, like chewing or shouting. It connects to a bone in your ear called the malleus.

But it can’t protect against sudden loud noises, like explosions or gunshots, because it reacts too slowly.

The muscle starts from the tube in your ear and a bone called the sphenoid. Then, it goes through a canal and ends in the ear cavity, connecting to the malleus bone.

Stapedius Muscle

The stapedius muscle is a tiny, hook-shaped muscle in your ear that helps protect it from loud noises. It is about the length of a grain of rice. Its job is to steady the smallest bone in your body, the stapes bone.

When you hear sounds, signals travel to your brain, which then tells the stapedius muscle to contract. This action helps stabilize the tiny bones in your ear and adjusts the pressure inside your inner ear. It is like a built-in defense mechanism against loud noises.

This muscle gets its orders from a branch of the facial nerve and gets its blood supply from a small artery branching from the main artery in your neck.

Promontory

The promontory, or cochlear promontory, is a rounded bump inside your ear. It is formed by the first part of the cochlea, like a little hill in your ear canal.

A network of nerves covers it called the tympanic plexus, which comes from the glossopharyngeal nerve and the internal carotid plexus.

On its surface, there are tiny grooves where these nerves sit. In a healthy ear, there’s a gap of at least 2.5 mm between the eardrum and the tissue near the promontory.

Chorda Tympani Nerve

The chorda tympani is a component of the facial nerve. It originates right above a hole known as the stylomastoid foramen.

Then, it travels into the ear and connects with the lingual nerve. Its name is derived from the fact that it crosses the eardrum. It passes near a few tiny bones in the ear.

Inner Ear Anatomy

Cochlea

The cochlea is like a tiny snail shell in your ear, filled with fluid. It helps you hear by turning sound vibrations into signals for your brain. Think of it as a map where different parts respond to various sounds, like high or low pitches.

Inside the cochlea, there’s a special part called the organ of Corti. It is made up of tiny hair cells that pick up vibrations. These hair cells send messages to your brain, letting you know what you are hearing.

As we get older or expose our ears to loud noises, these hair cells can get damaged. When that happens, it is harder for them to send signals, leading to hearing problems.

Vestibule

The ear’s vestibule is a small space in your inner ear, only about 4 millimeters in size. It is made of bone and holds important parts for balance. It sits between the cochlea and the semicircular canals.

The vestibule is connected to the cochlea in front and the semicircular canals behind. Inside, there are two important parts called the saccule and utricle, which help us keep our balance. It is separated from the middle ear by a window called the oval window.

Semicircular Canals

The semicircular canals are like three tubes filled with liquid in your inner ear that help you stay balanced and keep your head in the right position. They are part of the balance system in your ear.

They are tiny sensors that feel when your head turns. Inside each canal, there’s a bulge called the ampulla, where there are special cells with small hairs. These hairs move when the liquid in the canal moves, telling your brain which way your head is turning.

So, when you move your head, the liquid in these canals sloshes around and nudges those small hairs, which send messages to your brain to help you keep your balance. 

Each canal is positioned differently, so they are like detectors for different directions of movement. For instance, one canal is set at a 30-degree angle from straight, so it is called the “horizontal” canal because it senses side-to-side movements.

Vestibular Nerve

The vestibular nerve is part of the vestibulocochlear nerve, which helps us with balance and hearing. It has two main jobs: sending signals from special cells in our ears to our brain and helping us stay balanced.

There are two parts to this nerve: one that picks up on movements and gravity and another that senses rotation. Together, they tell our brain where our head is and how it is moving.

The nerve helps our body understand where our head is in relation to our body, which is important for keeping our balance and making sure our vision stays steady when we move.

Oval Window

The oval window is like a doorway between the middle and inner ear. When sound comes in, it makes the oval window vibrate, which starts the process of hearing.

Sometimes, there can be a problem with the oval window called oval window anomaly (OWA), where it is not shaped right and may be covered by a thin bony plate.

Things like diving, flying, or lifting heavy stuff can mess with the pressure in your ear and cause issues like perilymphatic fistula. It means there’s a weird hole near the oval window, messing up how you hear things.

Round Window

The round window acts as a gateway between the middle and inner ear. It is close to another entrance known as the oval window.

When sound enters, the circular window rotates in the opposite direction, allowing fluid in the inner ear to circulate freely. This movement helps microscopic hair cells inside the ear take up sound, allowing us to hear.

The spherical window also allows pressure to exit the inner ear, which helps the hearing system function correctly. If this venting does not function properly, it might result in hearing issues.

Bony Labyrinth

The bony labyrinth is like a protective shell inside your skull, holding the inner workings of your ear. It surrounds a soft, delicate part called the membranous labyrinth, which is filled with a fluid called endolymph.

Between the bony and membranous labyrinths, there’s another fluid called perilymph.

Inside the bony labyrinth, there are three important parts:

1. Cochlea: This is like the ear’s sound receiver. It helps you hear by converting sound vibrations into signals your brain can understand.
2. Vestibule: This part enables you to keep your balance and know which way is up. It helps with spatial orientation, like knowing if you are standing straight or tilting.
3. Semicircular Canals: These canals detect when your head moves in different directions, like when you turn your head sideways or tilt it up and down. They help your brain keep track of your head’s movements.

Membranous Labyrinth

The inner ear has a delicate system called the membranous labyrinth, nestled inside a bony structure. It is filled with fluid and has two main parts: one for balance (vestibular) and one for hearing (cochlear).

The vestibular part helps us stay balanced and has chambers and tubes, including the utricle, saccule, and semicircular canals. The cochlear part is essential for hearing and contains the cochlear duct.

These parts work together to help us keep a clear vision when we move our heads. If both parts don’t work properly, it can cause a condition called oscillopsia, where our vision gets jumpy during movement.

Perilymph

Perilymph is a transparent liquid that surrounds and protects the inner ear’s key components. It acts as a protection for the fragile structures inside.

The inner ear contains two types of fluid: perilymph and endolymph. They are not compatible due to their distinct nature.

Consider perilymph to be comparable to the fluid found outside our body’s cells but with more sodium and less potassium. Endolymph, on the other hand, is similar to the fluid within our cells but contains more potassium and less sodium.

Perilymph promotes inner ear health by supplying vital nutrients and ions. It is critical to our hearing and balance.

The perilymphatic duct is a small channel that links the perilymph to the fluid around our brain and spine, known as cerebrospinal fluid. It is like a small bridge that keeps everything in balance.

Endolymph

Endolymph is a special fluid in our inner ear that helps us hear and keep our balance. It is sometimes called Scarpa’s fluid. This fluid is made by something called the stria vascularis, which is like the “battery” for our inner ear.

One important thing about endolymph is that it is full of potassium, which helps our hair cells send electrical signals for hearing and balance. This electrical signal is like a message telling our brain what sounds we are hearing and how we are moving.

The endolymph also creates a special electrical current called the endolymphatic potential (EP), which is super important for our ears to be really good at hearing high-pitched sounds.

It helps our ears pick up on those higher frequencies, like bird chirps or high-pitched.

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External Sources-

• Wikipedia
• KenHub
• Optometrists
• Cleveland Clinic
• American Academy of Ophthalmology