12. Ear Development (Dennis) Flashcards
What does the spiral organ differentiate from?
Cells of the cochlear duct itself.
Describe the formation of the ossicles of the middle ear.
The malleus and incus are all coming from cartilages that are neural crest derived - specifically from pharyngeal arch 1.
The stapes is a little different. The crus, base of the foot plate, and head come from neural crest derived cartilage from pharyngeal arch 2. The outer rim the foot plate is mesodermally derived.
They are stuck in the pharyngeal arches until the 8th month, where the mesenchyme is resorbed, leaving behind the supporting ligaments.
What transcription factor is responsible for the formation of the dorsal utricular part of the inner ear?
DLX 5/6
What differentiates in the ampullae of the semicircular ducts to help us detect rotational movement?
What differentiates in the utricle and saccule to help us detect linear movements?
Semicircular ducts: cristae ampullares
Saccule / Utricle: Maculae
What transcription factors regulate formation of the saccule and the cochlea?
TBX1 and PAX6
What is the fate of the prosensory region of the otic vesicle in the utricle and saccule?
What is its fate in the cochlea?
What about the semicircular canals?
Utricle and Saccule: Macula
Cochlea: Organ of Corti (aka spiral organ).
Semicircular canals: Cristae ampullares
How is the tympanic cavity formed?
The first pharyngeal pouch foms the tubotympanic recess, which forms the pharyngotympanic tube (proximally) and the tympanic cavity (distally).
From what structures is the external ear derived?
The auricular hillocks surrounding the first pharyngeal groove.
What structure connects the cochlea to the saccule?
The ductus reuniens.
What embryological tissue is the otic placode made of?
Surface ectoderm.
What is the external auditory meatus derived from?
The 1st pharyngeal groove.
What is the tympanic membrane derived from?
Three parts:
Ectoderm from the 1st pharyngeal groove.
Mesenchyme from pharyngeal arches 1 and 2.
Endoderm from the tubotympanic recess (1st pharyngeal pouch)
Where does the stapedius insert?
Where does the tensor tympani insert?
Tensor tympani inserts onto the handle of the malleus.
Stapedius inserts on the neck of the stapes.
What forms the endolymphatic duct and sac?
What trascription factor regulates this differentiation?
A diverticulum from the dorsal utricular part of the otic vesicle.
SOHOL
What are the tensor tympani and stapedius muscles derived from respectively?
Tensor tympani: 1st pharyngeal arch mesoderm.
Stapedius: 2nd pharyngeal arch mesoderm.
