9.3 Ear and auditory tube Flashcards
Describe the structures of the outer ear?
Auricle, External acoustic meatus, Cerumen glands, Tympanic membrane
Desribe the Auricle
Collects sound, supported by cartilage
Describe the External acoustic meatus
Supported by cartilage for lateral 1/3, bone medial 2/3. Innervated by Vagus posteroinferiorly and Auriculotemporal nerve anterosuperior
What are the structures of the middle ear?
Epitympanic recess, Tympanic cavity proper, Auditory tube, Mastoid air cells
Describe Epitympanic recess
Above the tympanic membrane and communicates with mastoid hair cells
Describe the Auditory tube
Protects anterinferiorly to nasopharynx
Describe the location of the Tympanic cavity proper
It is medial to the tympanic membrane
What are the ossicles?
Malleus, Incus and Stapes
What is different between adult and infant eustachian tubes?
In infants, the eustachian tube is more horizontal making it easier for bacteria to move into the middle ear leading to increased infections
What is the Stapedius?
Posterior, Innervated by CN 12, muscle that attaches to Stapes
What is the Tensor Tympani?
Anterior, Inervated by CN 5, muscle that attaches to malleus
What is a reflex mechanism between Stapedius and Tensor Tympani
When there is a loud noise they can contract, pulling on the ossicles making them not vibrate as much, thus dampening the sound
What is the Chorda tympani?
Nerve branch from the facial nerve that goes down into the tongue
Name the structures of the Inner ear
Oval window, Petrous part of temporal bone, Bony labyrinth, Membranous labyrinth, Round window
Describe the bony labyrinth
Space in bone filled with perilymph, consists of the Semicircular canals, Vestibule, Cochlea, Oval window, Round window
Describe the membranous labyrinth
Closed sac frilled with endolymph, Cochlear duct (sensory receptors for hearing), Cochlear nerve, vestibular nerve, saccule, utricle, ampulla and semicircular ducts
What are the 3 semicircular ducts?
Anterior, Horizontal and Posterior
What is the Ampulla?
Swelling that gives info about the head movement
High frequency sound is registered where in the Cochlea?
At the base
Low frequency sound is registered where in the Cochlea?
At the apex
What is a brief physiological understanding of hearing?
That the vibration of the basilar membrane results in movement of hair cells against the tectorial membrane sending signals to the nerve and then to the brain
What is dynamic equilibrium?
Movement of endolymph through semicircular ducts in Ampulla deflecting cupula and activating hair cells
What is static equilibrium?
Movement of otolithic membrane due to gravity activates hair cells in utricle and saccule
