Eye Development Flashcards
What is the critical perior of eye development?
When is the eye complete?
weeks 4-8
done week 38
What is the origin of eye?
prosencephalon (forebrain) –> invaginates = optic sulcus
inner layer = neuroecto
middle = NC
outer layer = surface ecto
At the 5th week, what are the recognizable structures of the eye?
optic cup = outer, ecto
optic fissure = middle fold, neuroecto
optic stalk = surface ecto extending from prosencephalon
What do the rims of the optic cup form?
iris and ciliary bodies
What structures of the eye form from neuroectoderm?
retina - neural and pigmented
iris = epithelium, smooth muscle cells
ciliary body = epithelium
What is the only smooth muscle in the body formed from neuroectoderm?
smooth muscle of the iris
What does the stroma of th iris form from?
NC
What does the ciliary muscle form from?
mesoderm
How can the retina be detached?
from trauma
pigmented and neural layers are initially separated and then fuse before birth –> possible they don’t fuse right
What is aniridia?
lack of iris tissue or complete absence of the iris
from arrested development at rim of optic cup
Pax6 gene mutation (would then have cochlea problems too)
may be assoc w/ glaucoma, cataracts, other eye probs
How is the lens formed?
neuroectoderm of optic cup touches surface ectoderm –> cell-cell interactions –> lens placode –> lens pit –> lens vesicle
What are the orgin and characteristics anterior lens epi, primary lens fibers, and secondary fibers?
all from surface ecto
anterior lens epi: cuboidal
primary lens fibers: tall columnar –> elongate –> nuclei dissociate = clear
secondary lens fibers: cuboidal
What does the epithelium of the cornea form from?
surface ectos
What is congenital cataracts?
lens opaque and grayish white
causes: genetics, rubella virus, radiation, enzyme deficiency
When is the lens vulnerable to rubella infection?
4-7 weeks –> can cause congenital cataracts
What enzyme deficiency can cause congenital cataracts?
congenital galactosemia
gal accumulates in blood and tissues
cataracts occur in infancy
What do neural crest cells contribute to the eye?
sclera = outer layer of eye, continuous w/ stroma of cornea
choroid = deep to sclera, vascular
pupillary membrane (transient structure, part of sclera)
ciliary body
What secretes aqueous humor?
What secretes vitreous humor?
aqueous = ciliary epi
vitreous = choroid
What is congenital glaucoma?
elevated intraocular pressure
results from failure of NC to migrate –> abn dev of drainage mechanism of aqueous humor
mutations in CYP1B1 assoc w/ 85% of cases
rubella infection
What do extra-ocular muscles form from?
prechordal mesenchyme (NC??)
What does the central retinal A form from?
mesoderm –> hyaloid A –> supplies inner layer of optic cup, lens vesicle, mesencyme –> becomes central artery
What are the choroidal vessels?
from mesoderm –> dev in 15th week –> nourish outer pars of eye
What occurs in persistence of hyaloid artery?
distal part should degenerate, but persists
see “worm” in vision
in most cases the eye is microphthalmic
What does the optic n form from?
What are the layers?
from neuroecto
2 layers of neuroblasts = rods and cones, ganglion cells
fibrous layer = axons forming optic n
How does the optic n form?
fibers grow through inner part of optic stalk (optic stalk doesn’t become n - just a template) –> back to brain
cavity becomes obliterated
hyaloid A incorporated 7th week
What is papilledema?
increased intracranial pressure –> slows venous return from retina –> fluid accumulates in optic disc
retinal vessels are covered by meninges and lie in extension of the subarachnoid space
What is coloboma?
iris not fused
optic fissure hasn’t fused
autosomal dominant characteristic
