Lecture 28: Ear Flashcards
What is the order of structures in the middle ear from most external to internal
Tympanic membrane—> auditory ossicles (malleus, incus, stapes)—> oval window
What are some functions of the ear
Balance, orientation and hearing
Balance and orientation
Detection of movement of the body relative to the outside world
Hearing
Detection of movement of the outside world
What are the three parts of the hearing and balance apparatus
Inner ear, middle ear, and external ear
What is the inner ear composed of and what is the function
Fluid filled space within the petrous portion of the temporal bone
Fx: hearing and balance
What is the middle ear composed of and what is the function
Air filled space within the petrous and tympanic portions of the temporal bone
Fx: hearing
Where does the external ear emerge from and what is it continued by
What is the function
Emerges from the tympanic part of the temporal bone and is continued by additional cartilaginous pieces
Fx: hearing
Sound waves that pass through water (ex: body of fish) don’t ___ when transferred to fluids of inner ear and therefore only require ____
Lose energy and therefore only require internal ear structures
Sound waves traveling through the air reflex off a surface much denser and the waves ____ in transfer from air to ear fluids and therefore require ___
Lose energy and therefore require hearing structures to amplify the weak waves
What structure amplifies the weak waves
Tympanic ear
What is the tympanic ear
Ear drum, air filled middle ear and bony connection to inner ear
What is the primary function of the middle ear or tympanic cavity
Transmit sound vibration from the lateral external ear to the more medial inner ear
What bone transmits vibrations from outside the head to the inner ear
Stapes
What bone has an oval-shaped footplate that fits into the oval window and causes the vibrations in the perilymph of the inner ear
Stapes
What is the incus
Intermediate bone between the two other bones of the ossicular chain
What type of joint connects the incus to stapes and incus to malleus
Synovial joint
What is the malleus
Body of the malleus is fixed to the tympanic membrane so that the vibrations of the membrane are passed along the ossicular chain
What are the two skeletal muscles within the middle ear that are associated with the ossicles
Tensor tympani and stapedius
Where does the tensor tympani originate and insert
Comes from the anterior wall of the middle ear and inserts onto the body of the malleus
What nerve innervates the tensor tympani
Mandibular nerve CN V3
Where does the stapedius originate and insert
Comes from the posterior wall of the middle ear and inserts onto the head of the stapes
What nerve innervates the stapedius
Facial nerve- CN VII
What is the function of the tensor tympani and the stapedius
Act to clarify hearing and protect from excessively loud noises
What nerve does the mucosa lining in the middle ear, including the inner surface of the tympanic membrane send its sensory input on
Glossopharyngeal nerve
What nerve carries preganglionic parasympathetics from the glossopharyngeal nerve through the middle ear cavity to the otic ganglion
Minor petrosal nerve
What nerve travels through the internal acoustic meatus to the sytlomastoid foramen and runs through the posterior wall of the tympanic cavity
Facial nerve CN VII
What are the two branches off the facial nerve that run through or in the wall of the cavity
Major petrosal nerve and chorda tympani
What nerve carries preganglionic parasympathetic axons from CN VII to the pterygopalatine ganglion
Major petrosal nerve
What branch of CN VII carries both preganglionic sympathetic input to the Mandibular and sublingual ganglia and taste from the rostral portion of the tongue
Chorda tympani
What nerve crosses the tympanic membrane to get on the lingual nerve in the infratemporal fosssa and then its axons hitchhike to the oral cavity on the lingual
Chorda tympani
For most efficient function of tympanic membrane what must the air pressure in the middle ear be in relation to the outside pressure
The air pressure in the middle ear cavity must match the outside pressure
What connects the middle ear to the nasopharynx
Auditory tube
How does the auditory tube maintain pressure
Tube is typically pressed closed and must be activity opened to equalize air pressure
What two muscles are involved in opening the auditory tube
Tensor veli palatine and levator veli palatine
Otitis media
Infection of the middle ear cavity/build up of infectious fluid in the tympanic cavity
How can otitis media damage hearing
Negatively impact the sensitivity of hearing by dampening the vibrations of the tympanic membrane as well as possibly lesion it any nerves that pass through
What structure might be sensitive upon palpation in animals with otitis media
Tympanic bulla
How can infections of the tympanic bulla/otitis media be drained
Surgically open the tympanic bulla rostromedially into the nasopharynx
What is the function of the auricle (pinna)
Serves to funnel and focus sound into the external auditory canal
Highly mobile auricles help with detection of directionality of sound
Describe the anatomical position of erect, alert auricles
Concave, lightly haired surface is rostral
Convex, furred surface is caudal
What are some additional functions of the ear beyond hearing, balance, and orientation
Thermoregulation, communication and improved olfactory efficiency
What two canals lead from the auricle to the tympanic membrane
Vertical canal—> horizontal canal
What is the ceruminous gland
Earwax gland that helps keep the casual clean and free of particles that might interfere with the sensitivity of the tympanic membrane
What is the suctiform cartilage
Smaller isolated cartilage, associated with the musculature of the external ear
What is the function of the extensive auricle musculature
Provide fine control of the position and attitude of the auricle, important in facial expression
What artery branches off the superficial temporal artery and supplies some of the rostral concave surface of the external ear
Rostral auricular
What artery branches off the external carotid artery and has four large branches-medial, lateral, intermediate, and deep that supply the auricle cartilage and rostral surface of external ear
Caudal articular artery
What happens to the skin and cartilage of the ear when an aural hematoma forms
Blood pools and separates the skin from the underlying cartilage
What carries sensory innervation from the caudal surface of the auricle
Ventral and dorsal rami of C2
What nerve comes off the ventral rami of C2 to provide sensory innervation to the lateral side of the caudal external ear
Great auricular nerve
What nerve comes off of the dorsal rami of C2 to supply the medial side of the caudal external ear
Great (major) occipital nerve
What nerve carries sensory innervation on the rostral, medial part of the external ear
Auriculotemporal nerve- division of CN V3
What nerve provides sensory innervation to the petrous portion of the temporal bone
Vagus CN X
