Eye Development Flashcards
What is the critical period?
week 4-7
but susceptible until birth
What are the three embryo sources of the eye?
- Neuroectoderm
- Surface ectoderm
- Mesoderm/NC (mainly NC)
The eye is an extension of what?
the brain (diencephalon)
The structure growing out from the brain is called what from the inside, and what form the outside?
- Optic sulcus
- Optic vesicle (forms optic cup)
- connected to brain via optic stalk
- optic fissure forms on the bottom (BV runs through)
*whole structure is hollow
What is the optic cup?
- comes from optic vesicle
- has an outer and inner layer due to invagination
- intraretinal space forms b/t layers
What gives rise to the Iris and Ciliary Body?
rims of optic cup
*Where the outer and inner layers of the optic cup are connected
What structures come neuroectoderm?
- Iris - epithelium, SMC
- Ciliary Body - epithelium
- Retina - neural, pigmented
What comes form the inner layer of the optic cup? outer layer?
- Neural
2. Pigmented
What are the only muscles to come form neuroectoderm?
dilator and constrictor pupallae M of the iris
Where does the stroma of the iris come from? ciliary muscle (SMC) of the ciliary body?
- NC
2. mesenchyme (NC/mesoderm)
How do we get separation of the pigmented and neural retina?
- they should fuse, but some pathologies they don’t (DS, marfains, trauma)
- get intraretinal space
What is/causes Aniridia?
- lack of iris tissue or complete absence of the iris
- Pax6 gene mutation
- Caused by: arrest development at rim of optic cup during 8th week
*associated with glaucoma, cataracts, eye abnormalities
What is the induction of the lens?
the optic cup touches the surface ectoderm —> lens placode –invaginates–> lens pit –migrates in and lose attachments with SE–>lens vesicle
*eventually lens will be surrounded by optic cup, and SE re-constitute to give you epi of cornea
Where do the lens and epithelium of the cornea come from?
surface ectoderm
What type of epithelium comprises anterior lens? primary? secondary?
- cuibodal cells
- columnar cells (elongate and become transparent)
- cuibodal cells
*all come from surface ectoderm
What causes congenital cataracts?
- Genetics
- Rubella Virus
- Radiation of mom
- Enzyme deficiency (congenital galactosemia; galactose from milk accumulates in blood and tissues)
*Lens is opaque; problem with only lens (only hazy in lens)
What is the sclera?
outer layer (whites of eyes) that is continuous with the dura and stroma of cornea -fibrous layer, and forms stroma of cornea
What does the stroma come from?
NC
What is the choroid?
- vascular layer b/t sclera and retina
- just like pia and arachnoid layers in brain
- itself is NC, but the BVs inside are mesoderm
What is the pupillary membrane?
- transient structure due to eye lids fusing shut; covers the lens
- part of sclera
Where is the anterior chamber between? posterior? vitreous?
- cornea and iris
- iris and lens
- lens and back of eye
What is congenital glaucoma?
- Elevated intraocular pressure
- Abnormal development of the drainage mans of aqueous humor (scleral venous sinus)
* NC problem - Causes: genetics (mutations in CYP1B1 gene), Rubella infection
*affects the whole eye (whole eye is hazy)
Where do extra-ocular muscles come from?
prechordal mesenchyme –> preotic metopes –> muscles
What does the Hyaloid A. due?
- branch of ophthalmic a.
- supplies inner layer of optic up, lens vesicle, mesenchyme in optic cup
- eventually becomes central retinal a. to supply retina
What do choroidal vessels do?
- develop in the choroid + keeps it vascular
- come from ciliary a.s
What occurs with persistence of a Hyaloid A?
- distal part persists
- in most cases eye is microphthalmic
- if you are born this way, you learn to ignore it
What are the two layers of neuroblasts and what do they do?
- Rods and cones - vision
2 Ganglion cells - form optic n.
Optic cup/vesicle/stalk becomes the optic nerve.
wrong you idiot
they only provide the template for it
How do we get formation of the optic n?
- the fibers of the ganglion cells grow through the inner part of the optic stalk
- they trap the hyaloid a inside nerve
- continuous with meningeal layers, and covered by them because it’s continuous with the brain
What is papilledema?
-increased intracranial pressure
slows venous return from retina, cuaseing fluid accumulation of the optic disc
Why does edema occur in papilledema?
the retinal vessels are covered by the meninges and lie in the extension of the subarachnoid space
What causes coloboma?
- Optic fissure fails to close completely, leaving a gap in eye structures
- Causes: environmental, genetic AD
*only problem is not being able to constrict your pupal as well
