Structure of the ear Flashcards
Explain the process of hearing
Hearing is the process by which the ear transforms sound vibrations in the external environment into nerve impulses that are conveyed to the brain, where they are interpreted as sounds
What are the 3 main structures of the ear
The outer ear
The middle ear
The inner ear
What are the structures are in the outer ear
The Pinna and the Ear Drum
What does the Pinna do
It is the part of your ear that you can see, it collects sound waves and channels them into the auditory canal this passes through the canal to meet the ear drum
What does the Ear Drum do
It is a transparent membrane which is sensitive to the vibrations of the ear - as the air vibrates so does the ear drum
It also separates the outer ear from the middle ear
What are the structures of the Middle ear
The ossicles - which consists of the mallus, incus and stapes
Explain how sound transfers in the middle ear
As the ear drum vibrates so does the ossicles which transfers vibrations from the ear drum into the inner ear
What are the main functions of the ossicles
To increase or amplify pressure of sound waves when it reaches the inner ear
What are the structures of the inner ear
The Cochlea
The organ of Corti
The Basilar Membrane
What are the main functions of the Cochlea
Nothing gets heard until the vibrations are converted into electricity and send to the brain - this is what the cochlea does
The Cochlea contains a liquid that vibrates. The cells in the cochlea convert these vibrations into electrical signals. The electrical signals go through the auditory nerves to the brain. The electrical signals are sensitive to loudness and frequency
What is the Organ of Corti
This is in the inner ear within the Cochlea. It includes 3 rows of outer hair cells and one row of inner hair cells.
The Outer hair cells: 3 rows - contact with the tectorial membrane (stereocillia move when tectorial membrane moves) - amplify low level sounds - respond to certain frequencies
The inner hair cells: 1 row
-convert the sound from vibrations of the
fluid to electrical signal
-Signal then transmitted to the brain via the
auditory nerve (cochlear nerve)
Explain the process of hearing:
1) The Pinna catches sound
2) Sound is funnelled into the auditory canal
3) Sound is amplified in the auditory canal
4) Sound is funnelled towards the tympanic membrane
5) Tympanic membrane vibrates as air hits it
6) Tympanic membrane vibrates ossicles
7) Ossicles then amplify the sound and vibrate the oval window
8) Fluid then vibrates in the inner ear and the basilar membrane vibrates
9) Hair cells in the organ of corti vibrate
10) Hair cells then convert vibrations to electrical signals
11) Electrical signals are then transmitted to the brain via the auditory nerve and vestibulococlear nerve
12) Information is processed via the primary auditory cortex in the temporal lobe
What do the inner and outer hair cells do
The Outer hair cells: 3 rows - contact with the tectorial membrane (stereocillia move when tectorial membrane moves) - amplify low level sounds - respond to certain frequencies
The inner hair cells: 1 row
-convert the sound from vibrations of the
fluid to electrical signal
-Signal then transmitted to the brain via the
auditory nerve (cochlear nerve)
What are the types of hearing loss
Conductive and Sensorineural and also Mixed hearing loss
Which parts of the ear does conductive hearing loss affect
The outer and middle ear
Which parts of the ear does sensorineural hearing loss affect
The inner ear
Explain Conductive Hearing Loss
Conductive hearing loss happens when there is an issue transferring the sound waves
What are some of the outer ear causes of conductive hearing loss
Blockage of ear e.g. wax or bug
Infection e.g. swimmers ear or infection due to use of cotton bud
Auditory canal tumour
Abnormal bone growth in ear canal - linked to cold water swimming
What are some of the middle ear causes of conductive hearing loss
Perforated or scarring of the ear drum
or
Otitis Media (Glue Ear) - Eustachian tube blocked then allows fluid from the nasal cavity to enter the middle ear and does not allow the fluid to drain - can contribute to the delay in development of speech and language skills
What is sensorinural hearing loss
The ear works but the messages to the brain do not get processed
What are some of the causes of sensorinural hearing loss
Congenital - stroke- damage to the cochlea
and/or auditory cortex in brain (head injury –
acquired)
Viral infections e.g Congenital rubella
syndrome (CRS) – maternal transmission of
rubella virus, Cytomegalovirus (CMV) infection
Disease – Inflammation Suppurative labyrinthitis
or otitis interna (inflammation of the inner ear)
Noise induced - cause of approximately half of
all cases of hearing loss, causing some degree
of problems in 5% of the population globally
Explain how hearing can be damaged by bacterial meningitis
Bacteria that our bodies produce to fight infection may get into the inner ear where they can cause damage to the hair cells of the cochlea or nerve fibres. This is a sensorineural hearing loss and permanent
What type of hearing loss is bacterial meningitis
sensorineural hearing loss
How can Otitis Media affect hearing
Otitis Media (Glue Ear) - Eustachian tube blocked then allows fluid from the nasal cavity to enter the middle ear and does not allow the fluid to drain - can contribute to the delay in development of speech and language skills
