Embryology of Eyes and Ears Flashcards
What do the Ossicles develop from?
Meckels Cartilage (PA 1) form Malleus and Incus Reicharts Cartilage (PA 2) for the stapes
What does the middle ear develop from?
From the 1st pharyngeal pouch
What does the Auricle develop from?
Pharyngeal arch 1 and 2
What does the Inner Ear develop from?
It is the sensory part so… the otic placode
What does the EAM develop from?
The dorsal part of the 1st pharyngeal cleft
Describe the development of the middle ear
Comes from the 1st pharyngeal pouch
The pouch elongates laterally and touches the floor of the 1st cleft (External ear) a
The distal part becomes the ttubotympanic recess, widens and becomes the tympanic cavity
The proximal part becomes the Eustachian Tube
Describe the development of the ossicles
Comes from the Cartilage bars of PA 1 and 2
They are surrounded by tissue at the start of their development which degenerates
Describe the development of the ossicles
Comes from the Cartilage bars of PA 1 and 2
They are surrounded by mesenchyme until month 8 which degenerates
Describe the development of the auricle
The mesenchymal proliferations of arch 1 and 2 form swellings.
These swellings become the auricular hillocks which then fuse to become the auricle
What is the optic cup
A double layer of the optic vesicle
It has an intraretinal space which dissappears so the layers touch
What will the Optic Cup become?
The Rim…
It will become the pupil
The surrounding edge will become the iris and ciliary body
What will the Optic Cup become?
The internal part…
The Inner layer - retina
Outer layer - Choroid
What lies in the choroid fissure?
The hyaloid artery
What is on the inferior edge of the optic cup?
The Choroid Fissure
What happends to the contents of the Choroid Fissure?
The hyaloid artery degenerates slightly, and becomes the central retinal artery
When does the eye begin development?
What happens first?
Week 4
Two grooves appear on the sides of the forebrain (after the neural tube has closed). This is the optic stalk.
What do the optic stalks do?
They grow out towards the overlying ectoderm.
WHen they touch, the ectoderm thickens (the Optic Placode)
What does the Optic Placode do?
It invaginates and becomes the optic vesicle The placode (thickened bit) will become the future retina
What will the optic vesicle become?
The optic cup
What happens to the optic cup?
The Choroid fissure fuses at week 7 and it becomes it’s new parts of the eye
Where do extraoccular muscles come from?
They come from preotic myotomes which develop near the developing eye
