The ear Flashcards
Name the areas that you would pass through if you were to stick something in your ear.
External acoustic meatus
Tympanic membrane
Middle ear
Inner ear
Which cranial nerve leaves the inner ear?
CN VIII – vestibulocochlear nerve
What does CN VIII pass through to enter the intracranial cavity from the inner ear?
Internal acoustic meatus
The nasopharynx is connected to which part of the ear and via what?
The middle ear via the eustachian tube
Which part of the skull are the middle and inner ear located within?
The petrous portion of the temporal bone
Describe the innervation to the auricle, external acoustic meatus, and tympanic membrane.
Multiple nerves – both cranial & somatic
C2 + C3
CN Vc + CN VII + CN X
Name 2 areas involving CN Vc that referred pain to the ear can be from.
Mandible & mandibular teeth
Temporomandibular joint
Name 3 areas involving CN X that referred pain to the ear can be from.
Laryngopharynx
Larynx
Cardiac
How should an adult’s auricle be positioned for examination of the tympanic membrane?
Pulled posterior and superior
How should a child’s auricle be positioned for examination of the tympanic membrane?
Pulled posterior and inferior
Upon examination of the tympanic membrane, what is the position of the cone of light?
Pointing anterior and inferior
Upon examination of the tympanic membrane, what is the position of the malleus?
Pointing posterior and inferior
Which nerve branch may be seen on examination of the tympanic membrane?
Which CN does this branch off from?
Chorda Tympani, which branches off from CN VII
What is the function of the chorda tympani?
Carries taste sensation from the anterior 2/3rds of the tongue
Starting superficially, what are the 3 layers of the tympanic membrane?
Skin
Mesoderm
Respiratory mucosa
Describe the innervation of the skin layer of the tympanic membrane.
CN Vc + CN X
Describe the innervation of the respiratory mucosa layer of the tympanic membrane.
CN IX
Which bones comprise the ossicles?
Malleus
Incus
Stapes
The stapes sits in which structure which forms the boundary between the middle and inner ear?
Oval window
Which 2 muscles of the middle ear control the oscillatory range of the ossicles?
Tensor tympani
Stapedius
Where is the insertion of the tensor tympani?
The neck of the malleus
What is the function of the tensor tympani?
Pulls the tympanic membrane medially (taut) & thus reduces the force / amplitude of vibrations
What is the innervation of the tensor tympani?
CN Vc
What is the function of the stapedius?
Pulls stapes & limits its range of movement in response to large vibrations (loud noises)
What is the innervation of the stapedius?
CN VII
Describe the pathophysiology of hyperacusis in relation to the stapedius.
The stapedius muscle, which pulls the stapes & limits its range of movement in response to large vibrations (loud noises), is innervated by CN VII (facial nerve). If there is damage to CN VII, for example in Bell’s palsy, individuals may experience hyperacusis which is where ordinary sounds are perceived as abnormally loud or painful. This is because the stapes is no longer stabilized, allowing more sound energy to enter the cochlea
The posterior wall of the middle ear cavity leads to where?
The mastoid air cells via the mastoid aditus
How might a ruptured tympanic membrane cause loss of taste?
It could damage the chorda tympani, which carries taste sensation from the anterior 2/3rds of the tongue
Name the 6 boundaries (walls) of the middle ear.
Superior wall – tegmental
Inferior wall – jugular
Anterior wall – carotid
Posterior wall – mastoid
Medial wall – labyrinthine
Lateral wall – membranous
A middle ear infection which spreads through the posterior wall would cause what pathology?
Mastoiditis
Which 3 muscles open the eustachian tube during swallowing, yawning etc?
Tensor veli palatini
Levator veli palatini
Salpingopharyngeus
Describe the embryological development of the malleus and incus.
1st pharyngeal arch
Describe the embryological development of the stapes.
2nd pharyngeal arch
Describe the embryological development of the external acoustic meatus.
1st pharyngeal cleft
Describe the embryological development of the middle ear and eustachian tube.
1st pharyngeal pouch
Defects in the 1st pharyngeal arch can lead to the development of an extra what?
External acoustic meatus
In which rare genetic disorder can a defect in the 1st pharyngeal arch be seen, along with other associated tissue defects?
Treacher Collins syndrome
Vesicles on the external ear could be a sign of what condition?
What causes this?
Ramsay-Hunt syndrome, which is caused by chickenpox virus
Which clinical tests can be used to test the cochlear portion of CN VIII (vestibulocochlear)?
Rinne + Weber tests
Which part of the ear does CN VIII leave to enter the brain?
Inner ear
The eustachian tube connects which 2 structures?
Middle ear + nasopharynx
The external ear drains into which lymph nodes?
Pericraniocervical line
Which part of the external acoustic meatus contains sweat glands?
Outer part (cartilaginous)
What is inflammation of the external acoustic meatus called?
Otitis externa
What is the innervation to the nasopharynx?
CN Vb + CN IX
What is the innervation to the oropharynx?
CN IX
What is the innervation to the laryngopharynx?
CN IX + CN X
