Anatomy and physiology of hearing Flashcards
describe the Lateral 1/3rd of the external ear canal
made of skin and cartilage
Skin containing ceruminous and sebaceous glands. Producing wax
Thick hairs on the outside, becoming finer inside
Protective barrier and disinfectant
describe the Medial 2/3rds of the external ear canal
made of skin and bone
No hairs or cilia
Doesn’t produce wax
what is infection of the external ear called ?
otitis externa- swimmers most at risk
describe the 3 layers of the Tympanic membrane
Outer layer is continuous with skin of EAC.
Middle fibrous layer
Inner layer of respiratory epithelium (ciliated columnar epithelium with goblet cells)
what are the Ossicles?
bones of the middle ear- Conduct sound waves from tympanic membrane to inner ear
what can cause disruption of the ossicles?
trauma or bony sclerosis (otosclerosis)
the middle ear is capable of producing mucus, what can this lead to?
glue ear
how is the middle ear connected to:
mastoid system
nasopharynx
mastoid system via aditus and nasopharynx via Eustachian tube
what is the facial nerve inside the middle ear called?
Chorda tympani (CN VII)
what is infection of the middle ear called ?
otitis media
what is cholesteatoma?
abnormal collection of skin cells in the middle ear
Cause problems because they grow and are destructive
what does the inner ear contain?
Bony and membranous labyrinth contains fluid – perilymph and endolymph Cochlear-hearing organ Peripheral vestibular apparatus Vestibulocochlear nerve (CN VIII)
what make up the Peripheral vestibular apparatus?
Utricle
Saccule
Semicircular canals
how do you hear?
Function of middle ear is transduce vibration into nervous impulses
Foot of stapes vibrates in oval window
Causes pressure wave through fluid in cochlear
This is detected by hair cells in organ of corti
Transmitted to brainstem by Vestibulocochlear nerve
which part of the inner ear is responsible for detecting head rotation?
semicircular canals
