Ear Development Flashcards
What is the critical development period of the ear?
Weeks 4-8
What are the components of the external ear?
Auricle (Pinna)
External Acoustic Meatus
External layer of Tympanic Membrane
What are the components of the middle ear?
Three Ossicles (Incus, Malleus, Stapes)
Internal layer of Tympanic Membrane
Middle ear cavity
What are the components of the inner ear?
Vestibulocochlear organ
The component of the outer ear is developed from the 1st and 2nd pharyngeal arches.
Auricle
The Auricle is developed from ________ _______ which are from NCC and are swellings covered with Surface Ectoderm.
Auricular Hillocks
What innervates the external ear?
Great Auricular N.
Auriculotemporal N. (CN V3) – from 1st arch
CN VII – from 2nd arch
Auricular branches (CN X)
When skin tags or formed by the ear, this could be the result of what?
– The Auricular Hillocks did not migrate properly IF there is NCC (cartilage) within the skin tags.
– The Surface Ectoderm did not migrate properly
How is Anotia (no ear) caused?
Abnormal migration of NCC, no Auricular Hillocks were formed.
How is Microtia (small ear) caused?
Abnormal migration of NCC (abnormal migration of Auricular Hillocks).
The External Auditory Meatus is formed by what pharyngeal component?
1st Pharyngeal Cleft (Groove)
The 1st Pharyngeal Cleft (Groove) will meet up with the 1st Pharyngeal Pouch, and this will induce the formation of the…
Meatal plug – This closes off the opening until later stages when the cells undergo apoptosis and create the actual External Auditory Meatus.
The Tubotympanic Recess, which meets up with the 1st Pharyngeal Cleft to make the meatus, is derived from what pharyngeal component?
1st Pharyngeal Pouch
***Becomes Tympanic Cavity
The inner ear is developed from what embryological layer?
Surface ectoderm
In the formation of the inner ear, a new genetic program starts that initiates the thickening of the Surface Ectoderm which forms the _______ _______. This will invaginate and form the _______ _______, which will eventually round up and form the ________ ________.
Otic Placode
Otic Pit
Otic Vesicle
The inner ear is developed during what week?
4th week
The Otic Placode, Otic Pit, and Otic Vesicle (all inner ear) form the primordium of…
Membranous Labyrinth
T/F. As the mandibular prominence grows together medially, the ears will rise up to their appropriate spot on the head.
True
The Membranous Labyrinth (from Surface Ectoderm) is divided into a ventral and dorsal side. What develops from the dorsal side?
Utricle
Endolymphatic Duct and Sac
Semicircular Ducts and Ampullae
Macula of Utricle
The Membranous Labyrinth (from Surface Ectoderm) is divided into a ventral and dorsal side. What develops from the ventral side?
Saccule Cochlear Duct Ductus reunions Macula of Saccule Organ of Corti
Where are hair cells located in the inner ear?
Ampullae
Macula of Utricle and Saccule
Organ of Corti
Hair cells are derived from what embryological layer?
Surface Ectoderm
***Remember, they’re in the inner ear and it is surface ectoderm!
What do the hair cells in the Ampullae detect?
Rotational acceleration