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 Back To Module ListModule Main | Module Description | Instructional Outcomes | Instructional EventsLearners who are Deaf or Hard of Hearing Author Joan Houghton, Ed.D.What are the different sections and parts of the auditory system? The auditory system consists of many different sections and parts that enable a learner to hear. Primarily there are two major parts to the ear that play an important role in how sound is transmitted and how sound is interpreted by the brain. First, there is a peripheral auditory system. This system begins with the outer ear and ends at the auditory nerve. If there is a malformation in the peripheral nervous system, it usually means the learner has a hearing loss. The second system is the central auditory system. It begins from the auditory nerve to the brain. If there is an interruption of sound reaching the brain, the learner most likely will have difficulty interpreting what she heard.
The auditory system primarily consists of three sections: (1) the outer ear, (2) the middle ear, and (3) the inner ear. Within these sections are parts of the ear that are responsible for sending auditory input to the auditory nerve which, in turn, sends auditory input to the auditory cortex (i.e., part of the brain). The auditory cortex is responsible for interpreting what is being heard by the ear. Sometimes the auditory input is clear, sometimes it is distorted, and sometimes the information is not interpreted at all.
The following is an illustration of the ear that is accompanied by descriptions that are intended to (1) gain a better understanding of the ear, and (2) describe how each part of the ear reacts to sound, Although the three areas of the ear - outer, middle, and inner - are included in the below illustration, not all parts of the ear within each area are represented in this illustration. The parts of the ear included in the illustration are meant to give you a general understanding of their functions.
The major parts of the ear and their functions are:
The Outer Ear. The outer ear consists of the pina (i.e. ear flap), the ear canal, and the outer portions of the tympanic membrane (i.e. ear drum).
Pina. The pina is the first structure of the ear to capture sound waves either bilaterally (i.e. both ears) or unilaterally (i.e. one ear). Once the sound waves reach the pina, the pina passes the sound waves through the ear canal.
Ear canal. The length of the ear canal is reported to be no longer than the top part of your thumb. It is responsible for transmitting the sound waves to the tympanic membrane. If the ear canal is full of wax or other substances (e.g., cotton from Q-tips), it will not be able to smoothly transmit the waves and the sound will be distorted or occluded. If this should happen, the learner often either will complain that he or she can not hear the sound clearly, or request an increase in amplification (e.g., increase the volume on the TV or stereo).
Tympanic membrane. The outer portion of the tympanic membrane is included in the outer ear; however, most of its important functions occur in the middle ear. The eardrum is responsible for turning the sound waves that have traveled through the outer ear into mechanical waves that causes it to vibrate. These vibrations affect the structures of the middle ear. However, if there is an ear infection, the tympanic membrane may become swollen and tender. The swelling interrupts how the vibrations move through the middle ear. This swelling also reduces the learner¹s ability to hear sounds clearly.
The Middle Ear. The middle ear consists of part of the tympanic membrane, the round window, the oval window, part of the Eustachian tube and the three ossicles. The three ossicles are the (1) malleus (i.e. hammer), (2) incus (i.e. anvil), and (3) stapes (i.e., stirrup). The middle ear is where sound is conducted. If there is some type of obstruction in the middle ear that interferes with the mechanical waves preventing them from vibrating, this is referred to as a conductive hearing loss.
Round window. The round window is located near the cochlea (which is part of the inner ear). It is responsible for transmitting sound waves through the perilymph which is the fluid that passes through the inner and outer chambers of the ear.
Oval window. The oval window is located near the stapes. It is the opening to the inner ear. It is responsible for passing sound wave vibrations to the inner ear.
Eustachian tube. The Eustachian tube is partly connected in the middle ear with a portion of it extending into the outer ear. The Eustachian tube is responsible for ventilating the middle ear. It also ensures that the air pressure in the middle ear is equalized since oxygen is constantly changing from the outside forces (e.g., high altitudes, air travel etc.).
Malleus. The malleus (i.e. hammer) is the first of the ossicle bones that is attached to the tympanic membrane. It is responsible for transmitting vibrations to the incus.
Incus. The incus (i.e. anvil) is situated between the malleus and the stapes. It is responsible for transmitting vibrations from the malleus to the stapes.
Stapes. The stapes (i.e. stirrup) is situated at the end of the ossicle chain. It is the closest to the oval window which assists in transmitting vibrations to the inner ear.
The Inner Ear. The inner ear is not only responsible for ensuring that sound waves pass through the necessary channels to reach the auditory cortex, but is largely responsible for balance. The inner ear consists of four parts including; (1) cochlea, (2) the semicircular canals (also referred to as the vestibular apparatus), (3), Organ of Corti, and (4) the VIIIth Auditory Nerve. If there is some type of obstruction in the inner ear that interferes with the transformation of mechanical waves to electrical waves that prevent sounds to pass through the physical structures, this is referred to as a sensorineural hearing loss.
Cochlea. The cochlea is situated at the round window. It has three chambers; two of which contain fluid. The third chamber is the Organ of Corti.
Organ of Corti. The Organ of Corti is the third chamber that is housed inside the cochlea. It is primarily responsible for turning mechanical sound waves into electrical impulses that pass along to the VIIIth Auditory Nerve. It contains hair cells that connect to the VIIIth Auditory Nerve that transmits sound waves to the auditory cortex. It also contains some fluid. The hair cells that are closer to the oval window carry high frequency sounds while those hair cells that are further away from the oval window carry low frequency sounds.
Semicircular canals. The semicircular canals often are referred to as the vestibular apparatus of the inner ear. These canals are largely responsible for balance. The semicircular canals are situated in planes that are at right angles with two other parts including the utricle and the saccule. Working together, these parts of the semicircular canals helps maintain balance regardless where the head is positioned in space.
VIIIth Auditory Nerve. The VIIIth Auditory Nerve carries sound to the auditory cortex which is located in the temporal lobe of the brain. This is where sound is combined with other sensory information. Both interpretation and perception of sound is conducted in this section of the auditory cortex.
Task for Completion and Discussion #2:
Please pick one section of the ear that was described in this section of the module and further explore the intricacies of the hearing mechanisms. Write a one page, double spaced paper on the section of the ear (outer, middle, and inner) that you choose and the physical structure of that section of the ear. For example, you might choose the middle ear and the bones of the middle ear.
There are several websites that contain a virtual tour of the ear. These websites are listed at the end of this task. Pick one and take a virtual tour. After viewing the virtual tour of the ear, write a more complete description about the function of the section of the ear that you chose and the physical structure of the ear that is contained within the section that you chose.
The websites for virtual tours of the ear are:
Virtual Tour of the Ear: Welcome For More Information:
If you would like further information about the anatomy of the ear and how it works, some of the below listed resources may be useful to you.
AudiologyNet |
