Human Ear

In earth, most of the mammals have an external ear. The ear is the part of our Auditory system. The part of the ear that is visible from outside is called Pinna. Being mammals, humans also have ears. Ears are located on both sides of the brain within the temporal bones of the skull. Pinna is made up of elastic yellow cartilages and it is covered with integument and tendons and muscles attach it with surrounding parts. In the fetus, the ear derives from the first pharyngeal pouch. Each layer of ear derives from different germinal layers, inner ear from Ectoderm, middle ear from Endoderm, and outer ear from Mesenchyme. 


Structure of the Human Ear

The human ear is divided into three sections, those are the outer ear, the middle ear, and the inner ear.

The Outer Ear – 

  • The outer ear is consisting of the pinna and the ear lobe. Pinna is cartilaginous and it directs the sound wave towards the external auditory canal. 

  • The external auditory canal channels the sound to the tympanic membrane. In general, the tympanic membrane is called the eardrum.

  • The tympanic membrane is thin and semi-transparent. 


The Middle Ear – 

  • The middle ear consists of three tiny bones and it is filled with air. The bones are known as ossicles.

  • The three bones of the middle ear are named malleus, incus, and stapes. Sound vibration on the tympanic membrane is transmitted further by these three bones.


The Inner Ear – 

  • The inner ear or, the labyrinth consists of two main structures. The structures are the cochlea and the vestibular system.

  • The main function of the cochlea is to help in hearing.

  • The vestibular system consists of 3 semi-circular canals, saccule, and utricle.

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The Smallest Bone in The Body

The bones in the ear are the 3 smallest bones of the human body. The bones are malleus, incus, and stapes. Among these 3 bones, stapes is the smallest bone. 


The Function of The Human Ear

  • The main function of the ear is to help in hearing. In our brain, the temporal lobe senses the sound. Pinna directs the sound wave toward the eardrum through the auditory canal and the eardrum amplifies it. Vestibulocochlear nerve sends the sound wave stimulus to the temporal lobe and then we are able to hear the sound.

  • The ear also helps in balancing the body. The human ear allows us to feel the effect of gravity that is known as stationary balance and it also helps to feel the acceleration that is known as dynamic balance. 

  • The utricle and saccule provide a static balance.

  • Dynamic balance is provided by semi-circular canals. 

  • While moving eye tracking is maintained by vestibule-ocular reflex.


Human Ear Diagram

In the human ear diagram, we can distinguish between the inner ear, middle ear, and the outer ear.

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Human Ear Structure and Function

Different structures of the human ear help in different functions. 

  • The pinna of the outer ear protects the eardrum from intense sound and channels the sound to the eardrum through the auditory canal.

  • The eardrum vibrates and transmits the sound to the inner ear.

  • The ossicles of the middle ear amplify the sound and pass the vibration to the oval window. The oval window is the membrane between the inner and middle ear.

  • There is a narrow tube that connects our nose to ear, named Eustachian tube. This tube helps to pass air into the middle air and drains the mucus to the nasopharynx.

  • In the inner ear, a structure named cochlea is observed. It is filled with fluid and contains the organ of Corti. The organ of Corti has several hairs like a sensory cell, named cilia. The waves from the middle year cause vibration in inner ear fluid and it makes cilia vibrate. This vibration of cilia sends nerve impulses to the brain.

  • The semicircular canals in the inner ear are situated vertically to each other. It also contains fluid and helps in movement.


The Basic Foundation of The Outer Ear

The outer ear consists of the fleshy pinna, the outer and inner rim curving of the pinna is called helix and antihelix respectively. Antihelix opens into the ear canal. The first part of the bone is surrounded by cartilage and the area near eardrum is surrounded by bone. The bony part near the eardrum is called auditory bulla, it is formed by temporal bone. 


Fun-fact

Egg-laying mammals are called monotremes, as they are primitive mammals they don’t have pinna in their body.

FAQ (Frequently Asked Questions)

1. Does the Oval Window Affect Amplification?

The oval window is involved in amplification. The surface area ratio of the tympanic membrane and oval window is 20:1. So it can allow adequate energy supply between the air-filled middle ear and the fluids of inner air. Without the presence of the middle ear, 98% of energy will be reflected back and will not enter the fluid-filled inner ear.  

The middle ear acts as the pressure amplifier. It collects the acoustic energy and augments the amplitude of the mechanic-acoustic stimuli in the inner ear. So, we can call the middle ear as the impedance matcher.

2. How Many Types of Hearing Loss can be Observed in Humans?

There are three types of hearing loss.

  • Conductive hearing loss: In this type of hearing loss sound cannot be transferred from the outer ear to the inner ear. This can happen due to ear infection, trauma to the ear, or, accumulation of ear wax.

  • Sensorineural hearing loss: In this type of hearing loss either cochlea is damaged or the hearing nerves are damaged. This can happen due to aging, noise exposure, or cancer treatment.

  • Mixed hearing loss: This type of hearing loss is the mixture of conductive hearing loss and sensorineural hearing loss. This can happen due to the cause of both the hearing losses.