The Middle Ear Flashcards
The tympanic bulla of the temporal bone is a bony shell situated caudal and medial to the (2)
zygomatic and temporomandibular joint (TMJ)
What is the middle ear lined with?
respiratory epithelium
What is the middle ear continuous with?
Nasopharynx
The tympanic bulla in the dog is divided into (2) and what by?
dorsal and ventral compartment
- an incomplete bony shelf.
Tympanic bulla in cats; what is the division and how do they communicate?
Almost completely separated by a bony septum, communicating only by a small slit like medial opening which become a foramen more caudally
The dorsal epitympanic recess contains the auditory ossicles and communicates with the inner ear through (2)
round and oval windows.
What connects the middle ear to the nasopharynx and opens in the middle of the medial wall of the bulla?
Eustachian tube
What nerve passes through the periosteum of the medial bulla?
sympathetic
What separates the external acoustic meatus of the ear canal from the middle ear?
Tympanic membrane
The majority of the tympanic membrane is the ?
pars tensa
pars tensa:
A) What does this look like?
B) What is embedded here?
A) grey-white, translucent, taut membrane
B) malleus
Which “fleshier” part of the TM sits dorsally?
pars flaccida
What allows repair of the TM?
There is a constant centrifugal movement of cells that clear debris from the surface of the membrane
If the TM isn’t present; how can we gauge where it should be?
There are a few hairs that sit at the ventral insertion of the tympanic membrane
The tympanic cavity in cats is almost completely divided into:
A) a large ventral cavity called?
B) and a smaller rostrolateral component (2) )
C) What is it separated by?
A) Hypotympanum
B) Epitympanum and mesotympanum
C) a bony septum.
What are the ossicles of the middle ear role?
concentrate sound waves striking the tympanic membrane, focussing them at the smaller vestibular (oval) window.
What are the ossicles of the middle ear connected by?
A series of ligaments and muscles.
A) Where is the malleus embedded?
B) What does the head articulate with?
A) TM
B) Incus
Incus:
A) What is it within?
B) What does it articulate with?
A) epitympanum
B) Stapes
What is attached to a cartilaginous ring around the vestibular window – the separation between the tympanic cavity and the perilymphatic space of the inner ear.
Stapes
The A) nerve enters the internal auditory meatus alongside the B) nerve.
It travels in the facial canal of the petrous temporal bone before exiting the bulla at the C) foramen. It is exposed within the dorsal D) cavity near the vestibular window.
A) facial
B) vestibulocochlear
C) Stylomastoid
D) Tympanic
The tympanic plexus is formed from the tympanic branches of what nerves (2)
glossopharyngeal nerve
caroticotympanic nerve.
The tympanic plexus spreads along the bony promontory and gives rise to parasympathetic fibres to the A) Which 2 salivary glands, and sensory fibres to B)
A) parotid and zygomatic
B) the middle ear cavity.
What supplies the middle ear, in conjunction with the meningeal and pharyngeal arteries?
The tympanic artery
What is The tympanic artery a branch of?
Maxillary a.
Physiology of hearing sound?
The middle ear conducts sound from the external auditory meatus across the tympanic membrane, through the air-filled tympanic cavity into the fluid-filled inner ear and receptor cells of the cochlear. The ossicles focus sound that strikes the tympanic membrane to the vestibular window.
Which of these arteries is not involved in the vascular supply to middle ear?
Tympanic
Maxillary
Meningeal
Pharyngeal
Maxillary
In dogs, the most common cause of otitis media is?
Infection spreading from the external ear canal across the tympanic membrane.
What are the most common organisms isolated from the canine ear canal (3)
Staphylococcus intermedius (pseudintermedius),
Pseudomonas
Malassezia
In cats, middle ear infections most commonly arise from?
ascending infection through the auditory tube, often associated with episodes of nasopharyngeal viral infection.
Middle ear infections are also implicated in the development of?
Middle ear polyps
Clinical findings with otitis media? (9)
Pain
Otorrhoea
Head shaking
Purulent discharges at the external meatus;
The head being carried lower on the affected side
pain on opening of the mouth (in cases with TMJ involvement);
Facial nerve palsy/paralysis (10% of the cases);
Loss of hearing
vestibular signs, if the otitis media spreads to the inner ear
What does the normal TM look like? (4)
is shiny
translucent
visible malleus and vascular structures.
What on otoscope suggests middle ear dx? (3)
loss of translucency,
a change in colour
rupture/perforation
If the tympanic membrane is intact but abnormal, what diagnostics should be performed? (4)
myringotomy is performed and samples for:
- cytology,
- histopathology
- bacteriology should be taken.
What is the most sensitive for detecting middle and inner ear disease?
MRI
Medical management is only effective with otitis media if?
Disease of the external ear canal is adequately controlled.
How to medically manage otitis media?
The middle ear is lavaged using warm saline to remove debris and topical and systemic antibiotics (based on culture and sensitivity results) are administered for 4-6 weeks.
With otitis media, when i TECA +/- LBO recommended? (3)
If infection is established
osseous changes to the tympanic bone
stenosis of the external ear canal,
Polyps of the middle ear are inflammatory in nature, arising from the epithelium of (2)
the tympanic chamber
auditory tube