10. Ear Slide Flashcards
What is our external ear made up of?
- auricle ear
- external acoustic meatus
- external layer. of. te. TM
What is the middle ear made up of?
- 3 ossicles
- Internal layer of tympanic membrane
- Tympanic cavity
What makes up our internal ear?
Vestibulocochlear organ
What pharyngeal arches is our auricle derived from?
1st and 2nd pharyngeal arches
How is our auricle formed?
Auricle is derived from six auricular hillocks from the first and second pharyngeal arches; swellings of mesenchyme (NCC) that is covered with surface ectoderm.
What innervates the external ear?
- CN V3: Auriculotemporal N.
- CN X: Auricular branch
- Great Auricular N (C2-C3)
- Facial N (CN VII)
If a patient as a auricular appendage (skin tag) how did this occur?
result from the development of accessory auricular hillocks; thus, there was a problem with the migration of surface ectoderm.
If a patient has microtia, what i s this a. result of?
Microtia has a small auricle that is formed d/t abnormal proliferation of NCC (mesenchyme) from the 1st. and 2nd pharyngeal arch.
What is anotia and how do we get it?
Anotia: no ear.
D/t NCC in the auricular hillox did not form or migrate.
External Auditory Meatus is derived from what pharyngeal arch?
1st
How do we form the External Auditory Meatus?
- External acoustic meatus develops from dorsal part of 1st pharyngeal groove
- It. will begin to invagine inward -> and ectodermal cells proliferate, creating a meatal plug.
- Around 6 months, meatal plug will undergo apoptosis and form our external auditory meatus.
What part of our ear develops first and when?
INNER EAR at week 4.
What. is. the inner ear derived from?
- Surface ectoderm
How do we form our inner ear?
- Week 4: Otic placode (surface ectoderm) will form
- Will invaginate into underlying mesenchyme, forming the otic pit
- Edges of the pit fuse→ otic vesicle
- Otic vesicle will create the primordium of the membranous labyrinth. It has parts (dorsal and ventral part)
- will then coil to make vestibules, semicircular canals and cochlea.
Once we have gone from:
Otic placode -> otic pit -> otic vesicle -> primordium of membranous labyrinth.
What do they form?
Dorsal part of the primordium of membranous labyrinth forms the utricle.
Ventral part of the primordium of membranous labyrinth forms the saccule
Dorsal part of the primordium of membranous labyrinth forms the utricle.
- This is dependent on:
Ventral part of theprimordium of membranous labyrinth forms the saccule
- This is dependent on:
Utricle: DlX5/6
Saccule: PAX6
What is our membranous labyrinth?
Sac that forms our utricle and saccule.
Dorsal part. of membranous labryrinth will form what?
forms the
- endolymphatic ducts,
- utricles
- 3 semicircular canals with dilations on each end called ampulae.
- lateral canal of the semicular duct
- Macula of the utricle
• Lateral canal of semicircular duct is dependent on ____.
Otx-1
Ventral part of membranous labyrinth forms what?
- Cochlear duct, which grows and coils to become the membranous cochlea.
- Ductus reunions
- saccule
- Macula of saccule and organ of corti