Diagram Of Ear- Structure, Functions of the Ear

One of the five sense organs in the human body, the ear is primarily responsible for hearing and balancing the body. The term "statoacoustic organ" refers to the human ear's dual role in maintaining body balance and detecting sound waves.

A sound wave entering the ear canal causes the eardrum to vibrate. Vibrations are transmitted to the oval window, a membrane at the entrance to the inner ear, via three minuscule bones called ossicles, including the tiniest bone in the body, the stapes.

A combination of the inner ear's sensory system, visual information, and data from the body's receptors, particularly those near joints, creates balance. The brain's cerebral cortex and cerebellum process information that enables the body to adapt to changes in head speed and direction.

In this article, we will discuss the diagram of ear and various structures that compose the ear and their placement to understand the complete diagram of the ear.

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Parts of the Ear

The sides of the skull where the ears are placed are called the laminae. The pinna is a tissue flap that is the external ear in most animals. In contrast to animals like elephants, which have increased movement, humans have decreased mobility in their ear pinna.

Anatomically, three main sections comprise the human ear:

• The external ear,
• The Internal ear, and
• The Middle ear.

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The External or Outer Ear

• The pinna and auditory canal, which comprise the external ear, collect sound waves and direct them towards the tympanic membrane (or eardrum).
• The biological membrane, the eardrum, separates the inner ear from the outer ear.
• The eardrum is made up of connective tissues that are coated with mucous membranes on its interior and skin on its exterior.
• The epidermis of the pinna and auditory canal contains wax-secreting sebaceous glands and very fine hair, both of which are components of innate immunity.

Middle Ear

• The malleus (hammer), incus (anvil), and stapes (stirrup) are three ear ossicles that are located in the middle ear and are connected in a chain-like manner.
• The stapes and malleus are joined at the cochlea's oval window and the tympanic membrane.
• By boosting the intensity of the sound waves, the ear ossicles improve the transmission effectiveness to the inner ear.
• The throat and middle ear are connected via the eustachian tube.
• Both sides of the eardrum are kept under pressure by the Eustachian tube.
• The stapes is the smallest bone in the skeletal system.

Malleus

The malleus, an average of eight millimetres in length in the adult, is the outermost and biggest of the three tiny bones in the middle ear.

Because it is an ossicle or small bone attached to the ear and has the shape of a hammer, it is commonly referred to as a hammer. It is made up of the head, neck, manubrium, anterior process, and lateral process.

The malleus, related to the stapes and the oval window, transports the sound waves from the eardrum to the incus when sound reaches the tympanic membrane (eardrum). The malleus is unlikely to result in hearing loss because it is directly attached to the eardrum.

Incus

The incus, which connects the malleus and stapes, is in the middle of the ossicles. The bone is sometimes called "the anvil" because of its anvil-like form.

There are a few fundamental areas of the bone. Its head-shaped surface joins the malleus ossicle at this junction. The long and short crus are two further expansions of the incus. The incus meets with the head of the stapes at the lenticular process, a hooked-shaped area of the incus situated close to the end of the long crus.

The short crus connects to the middle ear cavity, which contains the ossicles; the body is another name for the incus's central region.

Stapes

Due to their horseshoe-like form, the stapes are comparable to a tuning fork.

The inferior and superior crus, two branches of the stapes, transmit sound vibrations to the flat bottom of the bone.

The vibrations then go to the inner ear, which is converted into neuronal information and sent to the brain through the cochlea and auditory nerve.

Ear Canal

• The ear canal connects the eardrum to the outer ear and is a tiny, tube-like passageway. The ear canal shields the sensitive inner ear from germs and debris, which also serves various purposes, including warming air before it enters the inner ear.
• The ear canal is open primarily to the outside world. It defends itself by producing earwax, or cerumen, through various specialised glands.
• The sticky earwax prevents insects, dust, and other material from entering the sensitive middle ear through the ear canal.
• Additionally, it deflects water, preventing injury to the eardrum and ear canal.
• The ear cleans itself by gently removing debris and wax as it exits the ear canal. After that, the wax dries and exits the ear, usually in small flakes.

Inner Ear

• The skull's temporal bone creates a cavity in which the inner ear is contained. This cavity is made up of a labyrinth of fluid-filled chambers.
• The inner ear, commonly known as the labyrinth, comprises two different kinds of labyrinths, the bony labyrinth and the membranous labyrinth, which are made up of canals and sacs.
• A membrane labyrinth can be found inside the channels that make up a bony labyrinth.
• A membranous labyrinth is encircled by a liquid called perilymph, contained within a bony labyrinth.
• The fluid called endolymph occupies the membranous labyrinth.

• The inner ear's three primary components are the cochlea, semicircular canals, and vestibule.
• The auditory portion of the inner ear, or cochlea, converts sound waves into nerve impulses.
• Semicircular canals: They aid in preserving balance and posture.
• Vestibule: This space between the cochlea and semicircular canals helps keep the body balanced.

Organ of Corti

• Scala tympani and scala media are separated by the basilar membrane, which contains the auditory organ of the cochlear duct known as the organ of Corti.
• The ear's mechanoreceptors are found in the Organ of Corti as hair cells.
• On the inside of the organ of Corti, there are rows of hair cells that serve as auditory sensors.
• There are two different types of hair cells: inner hair cells and outside hair cells.
• The number of outside hair cells is about 20,000, whereas the number of inner hair cells is approximately 3500, occurring in one layer.
• The inner hair cells react when the basilar membrane moves quickly.
• The basilar membrane movement caused by sound waves is the primary function of outer hair cells.
• Each hair cell's apical region projects a significant number of stereocilia.
• The tectorial membrane, a thin elastic membrane found above the rows of hair cells, controls how sound waves vibrate.
• The afferent nerve fibres and the basal end of the hair cell are nearby.

Cochlea

• The cochlea is the coil-like part of the labyrinth or inner ear.
• The stapes, which are the middle ear's ossicles, send sound waves to it.
• Scala vestibuli and Scala tympani are two significant canals separated from the bone labyrinth by the membranes that comprise the cochlea (the Reissner's and Basilar).
• Scala media, a small cochlear channel filled with endolymph, separates the scala vestibuli from the scala tympani.
• Perilymph is the fluid that fills the scala vestibuli and scala tympani.
• The scala vestibuli terminates at the oval window. In contrast, the scala tympani finishes at the round window leading to the ear's interior at the bottom of the cochlea.
• Scala vestibuli and scala tympani converge in the cochlea area known as the helicotrema.
• Low-frequency vibration detection is the major function of helicotrema.

Vestibular Apparatus

• The inner ear houses the intricate vestibular apparatus, which is situated above the cochlea.
• It is made up of the otolith organ, the saccule and utricle, and three semicircular canals.
• Each semicircular canal is located in a separate plane At right angles to one another,
• The perilymph of the bone canals holds the membrane-filled canals in suspension.
• The enlarged base of the canals, known as the ampulla, has a protruding ridge called the crista ampullar.
• The crista ampullaris has sensory hair cells linked to the perception of angular rotation.
• The macula, a protruding ridge, is seen in the saccule and utricle.
• The vestibular apparatus's crista and macula are the particular receptors in charge of preserving posture and bodily balance.
• As stereocilia are pressed against gravity, otoliths aid in perceiving spatial orientation.

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Hearing Mechanism

The external ear collects sound waves from vibrating objects and transmits them internally to the tympanum.

The ear ossicles transmit the tympanum's vibrations to the cochlea's oval window.

Pressure waves are created in the vestibular canal's perilymph by the movement of the oval window.

Later, the pressure waves are conveyed to the tympanic canal's perilymph.

Finally, by the vibration of the circular window, sound waves are dispersed into the air of the middle ear canal.

The vestibular and basilar membranes vibrate due to the passage of pressure waves from the vestibular canal to the tympanic canal.

The basilar membrane's vibrations push the sensory hair cells against the tectorial membrane.

The movement of the hair causes receptor potentials, which then trigger nerve impulses in the cochlear nerve fibres.

These impulses go to the temporal lobe of the brain's auditory cortex.

Human hearing is perceived between, 20 and 20000 Hz.

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Body Balance Mechanism

The communication between the inner ear, eyes, muscles, joints, and the brain allows the body's balancing system to constantly monitor our posture, provide feedback, and correct it.

The cochlea, which is in charge of the hearing process, and the vestibular system, which is in charge of maintaining posture and balance, comprise most of the inner ear.

Three semicircular canals and two pockets known as otolith organs (utriculus and sacculus) comprise the vestibular system, continuously conveying information about the cerebellum's head movement.

Each semicircular canal has a different orientation to recognise head motions, such as nodding and spinning.

Due to head motions, the vestibular nerve stimulates tiny hair to convey signals to the cerebellum via the semicircular canal's fluid flow.

The brain receives signals from the two otolith organs about head motions, gravity and straight-line body movements.

Tiny crystals in the otolith organs are dislodged during these motions, stimulating the microscopic hair cells to send signals to the brain through the vestibular nerve.

The vestibular system collaborates with the visual system to prevent items from blurring as the head moves. It also helps keep positional awareness when engaging in activities like walking, jogging, cycling, etc.