Auditory and vestibular apparatus Flashcards
How does sound travel through the ear?
External ear collects sound, middle conducts from external to internal, and internal ear converts sound waves to impulses
Sensory supply of the auricle
Great auricular nerve, auriculotemporal nerve of CN5c, vagus, facial nerve
Blood supply of auricle
Superficial and posterior auricular arteries - from ex. carotid
LFeatures of middle ear
Malleus, incus stapes
Tensor tympani
Eustachian tube
Air filled
What does the Eustachian tube do?
Connects middle ear to nasopharynx - equalises pressure within tympani cavity
Features of inner ear
Vestibulocochlear organ - hearing and balance
Body labyrinth and membranous labyrinth
Perilmyph - lots of K+
Oval window - closed by stapes
Which nerve innervates utricle and saccule
Vestibulocochlear
Cochlear duct
- Cochlear duct found in cochlear labyrinth - secured by spiral ligament
- Divides the perilymph-filled spiral canal into scala vestibuli and scala tympani
- Receptor of auditory stimuli is in basilar membrane and called organ of corti
- Organ of corti contains hair cells that are stimulated by the deformation of cochlear duct due to sound waves
Embryology of the ear
- Separates from external/middle/internal ear
- Internal ear develops from ectoderm on each side of the rhomboencephalon on day 22
- By week 6, otocyst forms saccule and cochlear duct, and dorsal part forms utricle, semicircular canals and endolymph duct
- By week 10, the scala vestibuli and tympani are formed from mesenchyme
- Epithelial lining forms hair cells
- Endoderm of first pharyngeal pouch forms tympanic cavity (middle ear)
Which pharyngeal pouch forms Eustachian tube?
endoderm of pouch 1
Which pharyngeal pouch forms ossicles?
MI = 1 S = 2
Otosclerosis
Fuses stapes at oval window, preventing movement
Autosomal dominant condition
Pharyngeal pouch 1 forms
Tensor tympani and malleus - trigeminal
Pharyngeal pouch 2 forms
Stapes and stapedius - facial
