Development of the Eye Flashcards
What marks the beginning of eye development?
The optic grooves appearing at day 22.
Eyes are derived from which layers? (4)
Neuroectoderm
Surface ectoderm
Mesoderm
NCCs
The retina, posterior iris, and CN II are from:
Neuroectoderm
Lens and external corneal epithelium are from:
Surface ectoderm
The fibrous and vascular coats of the eye are from:
Mesoderm
The choroid, ciliary body, sclera and inner corneal epithelium is from:
NCCs
What is the optic vesicle?
A from the optic groove that protrudes into head mesenchyme to contact surface ectoderm.
How is the optic stalk formed?
The distal end of the optic vesicle contricts
How is the lens placode formed?
What does it eventually become as it invaginates? Then what does it become?
Surface ectoderm thickens.
The lens pit, then the lens vesicle once it loses contact with the surface ectoderm.
How is the optic cup formed?
The optic vesicles invagine and form the cup, a double layered structure of neuroectoderm.
What does the optic cup form?
What does the optic stalk form?
Retina
CN II
What structure is continuous with neural retina and optic stalk?
Optic disk
Which cells invaginate into the optic stalk to form CN II?
Ganglion cells
What are hyaloid BVs from?
What do they supply?
Mesenchyme of retinal fissures.
The fetal eye.
What causes closure of the optic stalk?
Retinal fissures
What happens to the hyaloid vessels distally and proximally?
Distally they degenrate.
Proximally they persist as central a. and v. of the retina.
Which layers of the optic cup become the pigmented layer and neural retina?
The pigmented layer is the outer, thin layer.
The neural retina is the inner, thick layer.
What space separates the retinal layers (pigmented and neural)?
Intraretinal space. It will degenerate.
What does the inner layer (neural retina) of the optic cup become?
Becomes neuroepithelium.
Differentiates in photoreceptors, bipolar cells, and ganglion cells.
Which cells of the neuroepithelium are closest to the outer pigmented layer of the retina?
Photoreceptor cells
Sheaths of CN II
Outer dural sheath: from dura, thick, blends in with sclera.
Intermediate sheath: from arachnoid.
Inner sheath: from pia mater. Vascular and closely contacts nerve and BVs.
Function of ciliary m.
Focus the lens
How does the iris form?
What is unique about it?
The rim of the optic cup grow inward and partially covers lens.
It has both layers of optic cup.
What are dilator pupillae m. and sphincter pupillae m. derived from?
Neuroectoderm of optic cup
What cells determine eye color?
Chromatophores in the loose CT
How does iris heterochromia occur?
Changes to sympathetic innervations of the eye
Which part of the lens forms the transparent epithelial cells, the primary lens fibers?
Posterior wall of lens vesicle
What does the tunica vasculosa lentis do?
They are BVs that invest the lens
What is primary vitreous humor from?
NCCs
How do the aqueous chambers communicate?
Through scleral venous sinus
Layers that make the cornea
Surface ectoderm (external corneal epithelium)
Mesenchyme
NCCs
How is the choroid and sclera made?
Both from mesenchyme (NCCs).
The inner layer is the choroid and the outer layer is sclera.
Coloboma is from:
Incomplete closure of retinal fissure
Congenital glaucoma
Abn increased introcular pressure in neonates.
Aqueous humor does not drain properly –> abn development of scleral venous sinuses.
What is aniridua?
How does it occur?
Absence of the iris.
Arrested development at rim of optic cup (wk 8)
Persistent hyaloid a. looks like what in the adult?
Worm-like squiggle projecting from optic disk.
Eye may be smaller.
