Parts of ear and their functions pdf
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- Anatomy and physiology of the ear
- Anatomy and Physiology of the Ear
- How Do We Hear?
- Anatomy and physiology of the ear
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Anatomy and physiology of the ear
The ear is the sense organ that enables us to hear. Hearing can be defined as the perception of sound energy via the brain and central nervous system. Hearing consists of two components: identification of sounds what the sound is and localisation of those sounds where the sounds are coming from.
The ear is divided into three main parts — the outer ear , the middle ear , and the inner ear. The inner ear is filled with fluid. The inner ear also contains the receptors for sound which convert fluid motion into electrical signals known as action potentials that are sent to the brain to enable sound perception. The airborne sound waves must therefore be channelled toward and transferred into the inner ear for hearing to occur.
The role of the outer and middle ear is to transmit sound to the inner ear. They also help compensate for the loss in sound energy that naturally occurs when the sound waves pass from air into water by amplifying the sound energy during the process of sound transmission. In addition to converting sound waves into nerve action potentials, the inner ear is also responsible for the sense of equilibrium, which relates to our general abilities for balance and coordination.
The outer ear acts as a funnel to conduct air vibrations through to the eardrum. It also has the function of sound localisation. Sound localisation for sounds approaching from the left or the right is determined in two ways.
Firstly, the sound wave reaches the ear closer to the sound slightly earlier than it reaches the other ear. Secondly, the sound is less intense when it reaches the second ear, because the head acts as a sound barrier, partially disrupting the spreading of the sound waves. All these cues are integrated by the brain to determine the location of the source of the sound.
It is therefore difficult to localise sound with only one ear. The outer ear consists of the pinna and the ear canal. The pinna is a prominent skin-covered flap located on the side of the head, and is the visible part of the ear externally. It is shaped and supported by cartilage except for the earlobe. It collects sound waves and channels them down the external ear canal through patterns formed on the pinna known as whorls and recesses.
Its shape also partially shields sound waves that approach the ear from the rear, therefore enabling a person to tell whether a sound is coming directly from the front or the back. The ear canal is roughly 3cm long in adults and slightly S-shaped. It is supported by cartilage at its opening, and by bone for the rest of its length. Skin lines the canal, and contains glands that produce secretions that mix with dead skin cells to produce cerumen earwax.
Cerumen, along with the fine hairs that guard the entrance to the ear canal, helps prevent airborne particles from reaching the inner portions of the ear canal, where they could accumulate or injure the eardrum and interfere with hearing. Cerumen usually dries up and falls out of the canal.
However, it can sometimes become impact and disrupt hearing. Information on re-publishing of our images. The middle ear is located between the external and inner ear. It is separated from the ear canal of the outer ear by the tympanic membrane the eardrum.
The middle ear functions to transfer the vibrations of the eardrum to the inner ear fluid. This transfer of sound vibrations is possible through a chain of movable small bones, called ossicles, which extend across the middle ear, and their corresponding small muscles.
The tympanic membrane is commonly known as the eardrum, and separates the ear canal from the middle ear. It is about 1cm in diameter and slightly concave curving inward on its outer surface.
It vibrates freely in response to sound. The membrane is highly innervated, making it highly sensitive to pain. For the membrane to move freely when air strikes it, the resting air pressure on both sides of the tympanic membrane must be equal. The outside of the membrane is exposed to atmospheric pressure pressure of the environment in which we find ourselves through the auditory tube, so that the cavity in which it is located, called the tympanic cavity, is continuous with the cells in the jaw and thorat area.
Normally, the auditory tube is flattered and closed, but swallowing, yawning and chewing pull the tube open, allowing air to enter or leave the tympanic cavity. This opening of the auditory tube allows air pressure in the middle ear to equilibrate with atmospheric pressure, so that the pressures on both sides of the tympanic membrane become equal to each other.
Excessive pressure on either side of the tympanic membrane dampens the sense of the hearing because the tympanic membrane cannot vibrate freely.
When external pressure changes rapidly, for example during air flight, the eardrum can bulge painfully because as the pressure outside the ear changes, the pressure in the middle ear remains unchanged.
Middle ear infection is common in children because their auditory tubes are relatively short, compared to adults. This leads to fluid accumulation in the middle ear, which is not only painful but also disrupts the transference of sound across the middle ear. If the infection is left untreated, it can spread from the cells near the jaw, causing meningitis inflammation of the brain lining. Middle ear infection can also cause the fusion of the ear ossicles, resulting in hearing loss.
The bones are also referred to as auditory ossicles, and connect the eardrum to the inner ear. From the outermost to innermost, the bones are called the malleus , incus and stapes.
As the eardrum vibrates in response to air waves, the chain of inner ear bones are set into motion at the same frequency. The frequency of movement is transmitted across from the eardrum to the oval window another structure in the ear , resulting in a pressure being exerted on the oval window with each vibration. This produces wavelike movements of the inner ear fluid at the same frequency as the original sound wave. However, in order to set the fluid into motion, greater pressure is required, so that the pressure must be amplified.
This amplification of the pressure of the airborne sound wave to set up fluid vibrations in the cochlea is related to two mechanisms. Firstly, the surface area of the tympanic membrane is much large than that of the oval window. In addition, the lever action of the ossicles greatly increases the force exerted on the oval window. The extra pressure generated through these mechanisms is sufficient to set the cochlea fluid in motion.
The inner ear is the deepest part of the whole ear, and is located in a place known as the bony labyrinth, which is a maze of bone passageways lined by a network of fleshy tubes known as the membranous labyrinth. A cushion of fluid, called perilymph , lies between the bony and membranous labyrinth, while a fluid called endolymph is found within the membranous labyrinth itself. Within the inner ear is a chamber called the vestibule, which plays a major role in the sense of balance.
Balance is further discussed later in this article. Equilibrium — Coordination and Balance. Arising from the vestibule is the cochlea, which is sometimes referred to as the organ of hearing, as it is the part of the whole ear that actually converts sound vibrations to the perception of hearing.
The cochlea is in the form of a snail-like spiral, so that a longer cochlea is able to fit inside an enclosed space. It is about 9mm wide at the base and 5mm high, and winds around a section of spongy bone called the modiolus. The modiolus is shaped like a screw whose threads form a spiral platform that support the cochlea, which is fleshy and unable to support itself.
The cochlea contains three fluid-filled chambers separated by membranes. The upper chamber, scala vestibule , and the bottom chamber, scala tympani, are filled with perilymph. The scala tympani is covered by a secondary tympanic membrane. The middle chamber is the scala media, or the cochlea duct. It is filled with endolymph, instead of perilymph. The organ of corti is supported by a membrane called the basilar membrane. It about the size of a pea, and acts as a transducer, converting vibration into nerve impulses.
It has hair cells and supporting cells. Hair cells have long stiff microvilli called stereocilia on their apical surfaces. Microvilli are fine hair-like structures on cells that help to increase cell surface area.
On top of these stereocilia is a jelly-like membrane called the tectorial membrane. Four rows of hair cells spiral along the length of the organ of Corti. Of these, there are about inner hair cells IHCs , each with a cluster of stereocilia graded from short to tall.
Each OHC has about stereocilia with their tips embedded in the tectorial membrane above them. These outer hair cells adjust the response of the cochlea to different sound frequencies so as to enable the inner hair cells to function more accurately. The physiological mechanisms, by which hair cells within the cochlea act to produce hearing, are discussed in more detail below. Physiology of the inner ear Book your health appointments online Find and instantly book your next health appointment with HealthEngine.
Find health practitioners. The function of the auditory ossicles in the middle ear is to concentrate the energy of the vibrating eardrum so as to create a greater force per unit area at the oval window, as previously described. In addition to this, the ossicles and their adjacent muscles also serve a protective function. In response to a loud noise, the tensor tympani pulls the eardrum inward and tenses it.
At the same time, the stapedius reduces movement of the stapes. These actions of the muscles are known collectively as the tympanic reflex.
This reflex muffles the transfer of vibrations from the eardrum to the oval window. It is thought that the tympanic reflex is an evolutionary adaptation for protection against loud but slowly building noises such as thunder. However, because it has a time delay of about 40 ms, it is not quick enough to protect the inner ear from sudden loud noises such as gunshots.
It also does not adequately protect the ears from sustained loud noises such as factory noises or loud music. These noises can irreversibly damage the stereocilia of the hair cells in the inner ear, leading to hearing loss. The muscles of the middle ear also assist in coordinating speech with hearing, so that the sound of our own speech is not so loud as to damage our inner ear and drown out soft or high-pitched sounds from other sources. Just as we are about to speak, the brain signals the middle ear muscles to contract, dampening the sense of hearing in coordination with the sound of our own voice.
This makes it possible to hear other people while we are speaking ourselves. As previously mentioned, the cochlea is the organ that enables sound perception. The physiology of the cochlea revolves around the functioning of the inner and outer cochlea hair cells.
Anatomy and Physiology of the Ear
The ears are organs that provide two main functions — hearing and balance — that depend on specialized receptors called hair cells. Sound waves enter through the outer ear, move into the middle ear, and finally reach the inner ear and its intricate network of nerves, bones, canals, and cells. There are three bones located in the middle ear: the incus, the malleus and the stapes. Collectively, all three bones comprise the ossicles. The malleus is the outermost and largest of the three small bones in the middle ear, and reaches an average length of about eight millimeters in the…. The human ear consists of three regions called the outer ear, middle ear, and inner ear. The oval window, also known as the fenestra ovalis, is a….
The ear is the sense organ that enables us to hear. Hearing can be defined as the perception of sound energy via the brain and central nervous system. Hearing consists of two components: identification of sounds what the sound is and localisation of those sounds where the sounds are coming from. The ear is divided into three main parts — the outer ear , the middle ear , and the inner ear. The inner ear is filled with fluid.
Anyone can learn for free on OpenLearn, but signing-up will give you access to your personal learning profile and record of achievements that you earn while you study. Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available. Figure 1 is a diagram of the human ear. The outer ear consists of the visible part of the ear or pinna , the external auditory canal meatus , and the tympanic membrane tympanum or eardrum.
Four major divisions of auditory system - Anatomy. 1. The outer ear. - pinna. - ear canal. - eardrum. 2. The middle ear. - three ossicle bones;. (malleus, incus.
How Do We Hear?
The middle ear is the portion of the ear internal to the eardrum , and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles , which transfer the vibrations of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear is also known as the tympanic cavity and is surrounded by the tympanic part of the temporal bone. The auditory tube also known as the Eustachian tube or the pharyngotympanic tube joins the tympanic cavity with the nasal cavity nasopharynx , allowing pressure to equalize between the middle ear and throat.
The inner ear internal ear , auris interna is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. The inner ear is found in all vertebrates, with substantial variations in form and function. The inner ear is innervated by the eighth cranial nerve in all vertebrates. The bony labyrinth , or osseous labyrinth, is the network of passages with bony walls lined with periosteum.
The ear can be divided into three parts: the outer ear , middle ear and inner ear. The inner ear is the innermost part of the ear, and houses the vestibulocochlear organs. It has two main functions:. In this article, we shall look at the anatomy of the inner ear — its position, structure, and neurovascular supply.
Human ear , organ of hearing and equilibrium that detects and analyzes sound by transduction or the conversion of sound waves into electrochemical impulses and maintains the sense of balance equilibrium. The human ear, like that of other mammals , contains sense organs that serve two quite different functions: that of hearing and that of postural equilibrium and coordination of head and eye movements. Anatomically, the ear has three distinguishable parts: the outer, middle, and inner ear.
Anatomy and physiology of the ear
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The outer ear consists of two primary components: the pinna and the ear canal. The pinna is the most visible portion of the ear, which extends laterally from the.
What is the ear?
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