Ear Development Flashcards
What structures are a part of the external ear?
Auricle (pinna), external acoustic meatus, external layer of tympanic membrane
What structures are a part of the middle ear?
The three ossicles, the internal layer of the tympanic membrane, middle ear cavity
What structures are a part of the inner ear?
Vestibulocochlear organ
What is the auricle derived from?
1st and 2nd pharyngeal arches. Auricular hillocks (NCC) covered in surface ectoderm. Migrate and proliferate to make shape of outer ear
What are auricular appendages/skin tags?
Hillocks did not migrate properly, may or may not contain cartilage (NCC)
What is anotia?
No external ear due to abnormal migration/proliferation of NCC
What is microtia?
Small external ear, due to abnormal migration/proliferation of NCC
What is the meatal plug?
Comes from the 1st pharyngeal cleft/groove. Migrates in to meet up with the pouch, proliferation of surface ectoderm. Supposed to undergo apoptosis to create external auditory meatus
When does the inner ear form? What is it derived from?
Week 4, surface ectoderm
How does the inner ear form?
Thickening of surface ectoderm makes the otic placode which invaginates to make the otic pit. The pit rounds up to make the otic vesicle which migrates deeper into the head.
Gives rise to the primordium of the membranous labyrinth
What layer does the membranous labyrinth come from?
Surface ectoderm
What is the membranous labyrinth divided into?
The utricle (dorsal) and saccule (ventral)
What does the utricle give rise to?
Endolymphatic duct/sac, semicircular ducts and ampullae, and macula of utricle
What does the saccule give rise to?
Cochlear duct, ductus reunions, macula of saccule, organ of corti
What parts of the membranous labyrinth contain hair cells?
ampullae of semicircular ducts, macula of utricle, macula of saccule, organ of corti