Human Ear

Introduction

The human ear is a complex organ with the ability to hear sounds of different frequencies. The human ear can detect sounds between 20 Hz and 20,000 Hz (20 kHz), which corresponds to the range of sounds audible to the human ear. This frequency range is divided into smaller ranges called tones. The human ear can also detect differences in the loudness of sound, known as its amplitude.

Structure of Ear

Three sections make up the human ear−

• External ear

• Middle ear

• Internal ear

External Ear

Auricle (Pinna)

When we look at our ears, we can see and feel the fleshy component of the auricle. The tympanic membrane receives sound waves collected by the auricle (eardrum). The auricle sends a branch of the external auditory meatus to the mastoid air cells.

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External Auditory Meatus

The external auditory meatus is a passageway for sound waves, a path for infection, and an entrance for foreign objects. Through this opening, bacteria and viruses enter the middle ear, where they are trapped between the bones of the skull behind it. If unchecked, they may cause severe damage to the inner ear. Sound waves travel through this channel as well. They bring all the noises of our world into our heads− music, conversation, traffic noise, etc.

Tympanic Membrane

The tympanic membrane is also an external part of the ear and can be found just inside the opening of the ear canal. It's a thin layer of skin that separates outside air from the moist inner parts of our ears. Dryness is one of its many roles; the sound waves generated by the vibrating eardrum are transmitted to our cochlea, where they are translated into audible sounds.

Middle Ear

The middle ear has two parts− the tympanic cavity and the eustachian tube. The tympanic cavity, also known as the tympanic membrane, is a thin skinlike structure that cups the entrance of the outer ear canal. The eardrum is a thin, vibrating membrane that separates this cavity and the inner ear from each other. This skin-like membrane will stretch and vibrate when sound hits it, which causes our brains to interpret this as sound.

Following the middle ear is the eustachian tube. It's a passage that connects the back of your nose to your middle ear. This tube helps equalize pressure between your ears and nose when flying, diving, or climbing high altitudes. Doing this helps keep your ears from feeling clogged or popping during changes in air pressure.

The inner ear contains three ossicles− the malleus (hammer), the incus (anvil), and the stapes (stirrup). These bones work together to transform sound vibrations into electrical activity so that our brains can recognize them as noises.

Inner Ear

Both the bone and the membranous labyrinths make up our inner ear.

Inner ear canals form the bony labyrinth of the skull (temporal, sphenoid, and occipital bones).

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The bony labyrinth holds the endolymph, a fluid similar to blood plasma responsible for transmitting vibrations to the vestibular system. The bony labyrinth also contains the semicircular canals, which contain the endolymph and are responsible for sensing motion and maintaining balance.

The membranous labyrinth, in contrast, is a series of interconnected cavities that contain perilymph, a fluid similar to the spinal fluid. The membranous labyrinth houses the vestibular system, which detects linear acceleration−a movement that causes an object to move forward or backward−as well as angular acceleration−rotation about an axis. Both types of acceleration are detected by hair cells located on cilia that extend from the nerve endings into both the perilymph and endolymph.

Function of Ear

Hearing

Hearing is a complex process involving the action of three sensory cells− the outer, middle, and inner hair cells. These hair cells are part of a larger structure called the organ of Corti, which sits on top of an area called the basilar membrane. This membrane is like a taut piece of rubber with ridges (called "scutellar ridges"), which is very important for helping us discern high-pitched sounds.

The outer and middle hair cells are connected to one another by a bridge, which allows them both to receive sound waves from the eardrum. The resulting vibration causes these two types of sensory cells to send signals to the auditory nerve in the brain via this bridge.

The inner hair cells (different from the outer and middle ones) also respond to vibrations from the eardrum, but they transmit their signals separately through their own nerve connections. Once these signals reach their destination in the brain, they are able to be interpreted as sounds because of a type of brain cell called a "neuron." Neurons are able to transmit electrochemical messages from one place in your body to another through synapses. In other words, neurons act as communicators that allow your ears to talk.

Balance

Both the eustachian tube and the vestibular complex play significant roles in the ear's ability to maintain equilibrium.

There is a tube-like canal in the ear known as the eustachian tube. The passage leads from the middle ear to the nasopharynx, which is located behind the nose and the mouth. The Eustachian tube's job is to maintain a pressure balance in the middle ear, which is different from that of the surrounding environment.

When you travel by plane, it's important that your ears adjust to the change in air pressure, or else you could get a nasty earache. Without your eustachian tube, that wouldn't be possible!

The vestibular complex tells us where and how we're positioned in space to keep our balance, move around safely, and react to situations. The components of the vestibular complex include the semicircular canals (which detect rotational motion), the utricle and saccule (which detect linear acceleration), the otoliths (which detect linear speed), and gravity receptors in our inner ear. It's all tied together by neurons in our brainstem.

The semicircular canals are three tubes located within your inner ear that look like little doughnuts. Tiny hairs on their walls bend as you turn your head with corresponding movements.

Conclusion

The human ear is a complex and fascinating organ. It is responsible for our sense of hearing, balance, and body awareness. The ear is also susceptible to damage from loud noises, infections, and other health problems. By understanding how the ear works, we can better protect our hearing and maintain our overall health.

FAQs

1. What Is the Human Ear?

The human ear is made up of three parts− the outer ear, the middle ear, and the inner ear. They work together to hear sounds and send them to the brain.

2. How Does Sound Reach the Ear?

The pinna, or outer ear, receives sound waves that have travelled through the air. The sound waves then vibrate against the eardrum or tympanic membrane, which causes it to vibrate back and forth in sync with the waves. This causes vibrations in three tiny bones inside your middle ear − called ossicles − which then transmit these vibrations to fluid travelling through a tiny canal in your inner ear (cochlea). This fluid moves tiny hair cells inside the cochlea, which triggers electrical signals sent from your brain stem to your auditory cortex for interpretation as sound.

3. What Is Cochlear Implantation?

A cochlear implant replaces damaged parts of the inner ear with electrodes that pick up sound signals from an external device and send them directly to your auditory nerve, bypassing any damaged portions of your ears that may have prevented hearing before surgery.

4. How many bones are in a human ear?

The human ear is made up of three tiny bones called ossicles. These bones carry vibrations from our eardrums to our inner ears.

5. What is the function of the ear?

The ear has three main functions. It collects sound waves from our environment, converts them into neural signals, and sends them to our brains.