Ear and Audition - Case Study Example

of Ear and Audition Introduction Hearing is one of the basic senses of the human body whichis essential for proper functioning and performance of daily activities. Hearing means perceiving sound and interpreting it into a reasonable or logic meaning. The ear is the sense organ that facilitates sound perception. General biological sciences show that the ear is a common feature of all vertebrates ranging from fish to human beings with major variation depending on genus and species. The ear is not only involved in sound perception but also helps the body to maintain balance as well as giving the body a suitable posture and orientation in space. Audition is defined as the scientific term for that is used to describe the sound perception process by the ear. The ear is part of the auditory system and hence helps communication since sound is a way of passing information. Sound is an energy form that travels through matter. Parts of the Ear The main functions of the ear are to perceive sound and to maintain body equilibrium. In order to understand the parts of the ear well and to correctly describe its functions, the ear has bee divided into three major components basing on their position and their specific functions they perform. The components are the outer ear, the middle ear and the inner ear the. Each of the three components carries out unique function that contributes tot thee overall outcome in response to a stimulus. A stimulus is the specific items or an incentive that motivates the sensing function of the ear or other sense organs. The external ear is basically comprised of two parts; the pinna (it’s a cartilage that is covered by skin, practically the visible part on the head) and the Meatus or the auditory canal, this is the tunnel like feature leading to the inner ear. Since the outer ear protects the inner, there are sweat glands that secrets ear wax (Buser et al 1992, 130). The eardrum separates the outer ear from the middle ear. The middle ear is the hollow part of the ear, filled with air and the parts are basically bony. It comprises the tympanic cavity that is the air filled cavity, three bones also referred to as auditory ossicles. The three bones are called; Malleus – also termed as the hammer, Incus – also called the anvil and Stapes which is commonly known as the stirrup. These bones connect to the oval window of the inner ear in order to execute their functions (Buser et al 1992, 134). The middle ear is also connected to the nose and the throat through the Eustachian tube, this tube helps to maintain pressure where one can yawn and swallow. The inner ear appears to be the most complex component of the three, and is located in the tiny space of the temporal bone and it’s not accessible by direct clinical examinations. The inner ear consist of three closely related structures namely the cochlea which is a spiral tube, the three semicircular canals and the vestibule also known as the labyrinth. The cochlea is highly innervated because of its hearing functions. Functions of the Ear There are two basic functions of the ear namely hearing and maintaining body balance. The other minor function of the ear is to maintain pressure balance. Hearing involves the detection of sound and interpretation in to a logic meaning. Sound is usually the way by which auditory communication is effected for many of the vertebrate animals including frogs, bats, birds and human beings who use spoken language. The ear is connected to the brain by the vestibular and cochlea nerves (Buser et al 1992, 130). These nerves transmit the sound waves to the brain where interpretation takes place, the ear only detects sound but it’s the brain which ‘hears’. Hearing This is the basic function of the ear as recognized by everybody. All the three components play a unique role to bring about the overall hearing result. The first step is the collection of sound waves. The outer ear has a funnel shaped pinna which functions to collects sound and directs it in to the meatus or the auditory ear canal. The sound waves hit the ear drum and cause it to vibrate. The ear drum also known as the tympanic membrane is connected to the outer ear via the round window and the inner ear through the oval window; the three ossicles (Malleus, Incus and Stapes) link the eardrum to the oval window. The size ratio of the eardrum and the oval window is about 20: 1 making it adequate for energy transfer of sound waves between the air filled cavity and the liquid filled inner ear (Buser et al 1992, 136). Sound waves from the eardrum hit the Malleus first then the Incus and finally hits the stapes. Sound waves enter the inner ear via the oval window. The inner ear is hollow and filled with liquid and contains a sensory membrane covered by hair cells that are structural protein filaments projecting in to the fluid. When sound waves moves through the fluid, the hair cells are stimulated to release a chemical neurotransmitter because they respond to mechanical stimulation. Through this process the sound waves are converted in to nerve impulses in the cochlea. The nerve impulse travel from the left and the right ear then through the vestibulocochlea nerve which is the eighth cranial nerve into the brain where it is interpreted into logic by the brain (Buser et al 1992, 139). The eighth nerve has two branches, vestibular which is concerned with balance and cochlea nerve which is concerned with hearing. Balance and Equilibrium The other crucial role of the ear is the maintaining of balance. The inner ear has three semicircular canals oriented at 90ºC from each other plus macula and succule of the Utricle which play a key role in balancing. The organs of the utricle are responsible for the gravity sensation. The structures of the utricle (maculae and saccule) are made of nerve endings connected to a structure of calcium carbonate. These structures are denser than the fluids in which they are contained and due to these, they fall in response to gravity (Buser et al 1992, 138). Macula and saccule are at right angle to each other, but usually make slight structural changes in response to the head movements. By these means, the inner ear is able to convey a message to the brain about the position of the head in relation to gravity. Information about the angular position or rotation of the body is conveyed by the semicircular canals. They are three of them in each ear namely; superior, lateral and posterior. They are filled with endolymph fluid which rotates in response to turning of the head. The nerve endings are stimulated by mechanical movement of the fluid and they send information to the brain via firing neurotransmitter, indicating the direction and speed of the movement of the head (Buser et al 1992, 139). The sensory nerves merge into the vestibular portion of the eighth cranial nerve which is concerned with balance. The nerve conveys the information to the central nervous system. The ear is an essential part of the sensory system of the body since it’s connected to the brain directly by the vestibulocochlea nerve and on the other hand it performs functions that are consistent with life. Ear and Audition Defects A defect in any of the three components of the ear would result in loss of function since they all work in concert. Microtia is a malfunction of the external ear; Anotia is the total absence of the external ear. The defects of the ear are usually congenital though some are acquired and are attributed to failure during embryonic development. Basically defect in the part of ear would translate to lack of function for that part and consequently impaired or total loss of the main functions of the ear (Ackley & Limb 2007, 120). These are hearing impairment, deafness and balance disorder. Hearing impairment is caused by damage to one or several parts of the ear. Conductive hearing loss results from damage to the outer and middle ear parts. Senso-neural hearing loss is as a result of damage to the inner ear or specifically the auditory nerve. A person has problems with hearing clearly and difficulties in understanding and interpretation of speech, this is usually permanent. Mixed hearing loss is situation where the patient has both senso-neural and conductive. Balance disorder is a malfunction of the vestibular system. The individual feels unsteady, frivolous, light-headed and may feel a sensation of head movement especially spinning or a feeling of floating (Ackley & Limb 2007, 123). Conclusion Hearing and body balance are major functions of the ear and are critical to the general functioning of the body. Diagnosis of any defect is very important since the problem can be rectified medically depending on the cause of the defect. References Ackley R.S & Limb C J (2007) An Essential Guide to Hearing and Balance Disorder Routledge pp 120 - 131 Buser P A Imbert M & Kay R H (1992) Audition MIT Press pp 130 - 143 Read More