Anatomy and physiology of hearing Flashcards
What is the pinna?
The visible part of the ear
What is the epithelium of the pinna?
Stratified keratinised squamous
What is the pinna not good at?
Sound localisation
What is the lateral 2/3 of the external ear made of?
Skin, containing ceruminous and sebaceous glands and hairs, and cartilage
What is the medial 1/3 of the external ear made of?
Skin and bone
No hairs of cilia
What happens to the skin on the external ear?
IS constantly being shed in the lateral 1/3 of the canal and trapped in wax as part of the cleaning mechanism
How many layers does the tympanic membrane have?
3
What is the outer layer of the tympanic membrane?
Skin continuous with the external auditory canal
What is the middle ayer of the tympanic membrane?
Fibrous layer
What is the inner layer of the tympanic membrane?
Resp epithelium- ciliated columnar with goblet cells
What is the size of the tympanic membrane?
1cm diameter and 1/10th mm thick
What is the tympanic membrane the division between?
External and middle ear
What is the function of the ossicles?
Conduct sound waves from tympanic membrane to inner ear
Play a very important role in sound conduction
What can cause disruption of the ossicles?
Trauma
Bony sclerosis- otosclerosis
What is the middle ear lines with
Respiratory epithelium
What does the middle ear connect with?
Mastoid system
Nasopharynx
How does the middle ear connect with the mastoid system?
Via audits
How does the middle ear connect with the nasopharynx?
Via Eustachian tube
What does the middle ear contain?
Facial nerve CN VII
What are the 6 segments of the facial nerve?
Intracranial Meatal Labyrinthine Tympanic Mastoid Extratemporal
Where is the metal segment of the facial nerve?
Internal auditory meatus
Where is the tympanic segment of the facial nerve?
Runs through fallopian tube
What does the facial nerve supply?
Muscles of facial expression
Taste to the anterior 2/3 of the tongue via chord tympani
What are the most important relations of the middle ear?
Middle cranial fossa
Internal carotid
Sigmoid sinus and internal jugular
What is the internal ear?
Bony and membranous laryrinth
What does the membranous labyrinth contain?
Fluid- perilymph and endolymph
What is the cochlea?
Spiral shaped cavity in the bony labyrinth
What is contained in the peripheral vestibular apparatus?
Itricle
Saccule
Semicircular canals
What is the function of the middle ear?
Transduce vibration into nervous impulses
How is hearing transduced?
Foot of stapes vibrates in oval window, causing pressure wave through fluid in cochlea detected by hair cells in the organ of corti
This is transmitted to brainstem via CN VIII
What parts of the ear are involve in balance?
Semicircular canal
What is the vestibule-ocular reflex?
What makes ou able to fix your eyes on an object even when your head is moving
What does the saccule do?
Detects linear acceleration in the vertical plane
What does the utricle do?
Detects linear acceleration in the horizontal plane
What provides sensation to the middle ear?
Tympanic branch of the glossopharyngeal nerve
What provides sensation to the posterior half of the external auditory canal?
Auricular branch of the vagus nerve
What provides sensation to the anterior half of the external auditory canal?
Facial nerve
What gives sensation to the pinna?
Mandibular branch of trigeminal nerve
