2 - Hatcher - Ear Histology Flashcards
External Ear
Auricle, Pinna = Funnel to collect sound waves
External Auditory Meatus (auditory canal): S-shaped tube that leads to tympanic membrane
Lined with stratified squamous epithelium
Where does the auditory canal end?
Tympanic Membrane (eardrum)
Middle Ear
Contains tympanic cavity
Contains Ossicles: Malleus, Incus, Stapes
Communicates with auditory tube (Eustacian tube)
Tympanic Cavity
Air filled space in temporal bone
Where does the stapes vibrate?
Over the oval window to transfer vibrations to the inner ear
Auditory Tube
Connects middle ear cavity to pharynx (throat)
Below temporal bone the tube is typically collapsed–opening it during swallowing equalizes pressure in middle ear
Infection can travel form throat to middle ear through auditory tube
Ear Infection
Most common in children, 1/3 of all peds visits
Chronic infections can be treated by myringotomy “ear tubes”
Semicircular Canals vs Cochlea
Semicircular Canals = Balance/Acceleration
Cochlea = Hearing
Location of Semicircular Canals / Cochlea?
Located in petrous portion of temporal bone
Osseus
Bony canal in temporal bone
Auditory System of Inner Ear
Cochlear Duct (Organ of Corti)
Vestibular System of Inner Ear
Vestibule:
Ultricle (Macula)
Saccle (Macula)
Semicircular Ducts (crista ampullaris):
Horizontal (location of sens organ)
Perilymph
Endolymph
Fluid between the osseous and membranous labryinth
Fluid within the membranous labyrinth
Scala Vestibuli
Filled with perilymph
Anterior to Cochlear duct and Scale Tympani
Cohlear Duct
Filled with endolymph
In between Scala Vestibuli and Scale Tympani
Scale Tympani
Filled with perilymph
Posterior to Scala Vestibuli and Cohlear Duct
Organ of Corti
Consists of hair cells supported on basilar membrane
Stereocilia on hair cells project into overlying gel-like TECTORIAL membrane
Steps to Firing of Organ of Corti
- Pressure waves (generated by stapes at oval window) vibrate the perilymph in scala vestibuli
- Movement vibrates vestibular membrane and endolymph within cochlear duct
- Movement vibrates basilar membrane and distorts stereocilia of hair cells w/in tectorial membrane
- Displacement of hair cells initiates nerve signal in cochlear division of Cranial Nerve 8
What separates Scala Vestibuli and Cochlear Duct?
Vestibular Membrane
How is perception of sound terminated?
Fluid wave is dissipated at round window
Sense / Sense Organ
Hearing?
Static Equilibrium?
Dynamic Equilibrium?
Hearing - Organ of Corti (in Cochlear Duct)
Static Equilibrium - Macula (in Utricle/Saccule)
Dynamic Equilibrium - Crista Ampullaris (in Semicircular Ducts)
What detects static position and linear acceleration of the head?
Utricle / Saccule
What detects rotational movement of head relative to body?
Semicircular Canals
Located in expanded proximal region (ampulla) of each semicircular canal
