Eye Development Flashcards
What 3 embryonic sources contribute to the development of the eye?
Neuroectoderm, surface ectoderm, and mesoderm/neural crest
What is the origin of the eye?
Prosencephalon
When does development of the optic cup begin?
4 weeks
What are the parts of the developing eye?
Optic groove (sulcus), optic vesicle, optic stalk, optic cup, and optic fissure
What parts of the eye come from neuroectoderm?
Retina, iris, and ciliary body
What are the parts of the retina?
Neural retina and pigmented retina
What makes up the iris?
Epithelium, stroma, and smooth muscle cells
What makes up the ciliary body?
Epithelium, smooth muscle cells (from mesoderm), and ciliary muscle
What occurs during detachment of the retina?
The pigmented and neural retinas become separated
What is aniridia? What causes this?
Lack of iris tissue or complete absence of the iris; may be associated with glaucoma, cataracts, other eye abnormalities, or a Pax6 gene mutation
What parts of the eye come from surface ectoderm?
Lens placode, lens pit, lens vesicle, anterior lens epithelium, primary/secondary lens fibers, and epithelium of cornea
What is induction in terms of the lens?
Lens development is induced by the optic cup through cell-cell interactions
What is congenital cataracts? What causes this?
Lens is opaque and frequently appears grayish-white; caused by genetics, rubella virus, radiation, or an enzyme deficiency
When is the lens most vulnerable to the rubella virus, leading to cataracts?
Weeks 4-7
What is congenital galactosemia?
Occurs when galactose from milk accumulates in blood and tissues; appears 2-3 weeks after birth; form of cataracts
What parts of the eye come from mesenchyme/neural crest cells?
Sclera, choroid, pupillary membrane, and ciliary body
What is the sclera?
It is the outer layer; it is fibrous and forms stoma of cornea
What is the choroid?
It is the inner layer (pia and arachnoid); it is vascular and this is the neural crest cell contribution
What is the papillary membrane?
It is a transient structure and forms part of the sclera
What occurs in the anterior chamber of the eye?
Aqueous humor is resorbed by scleral venous sinus
What occurs in the posterior chamber of the eye?
Aqueous humor is secreted by ciliary epithelium
Where does vitreous humor come from? Who primarily makes aqueous humor?
Vitreous: primarily from choroid
Aqueous: made by ciliary body
What is congenital glaucoma? What causes it?
Elevated intraocular pressure resulting from abnormal development of the drainage mechanism of aqueous humor (scleral venous sinus); caused by mutations in CYP1B1 gene in 85% of cases; can be caused by rubella infection
Where do extra-ocular eye muscles come from?
Prechordal mesenchyme
Where does the eye get its blood supply? What does this artery supply? What does this artery become?
Hyaloid artery (branch of opthalmic); supplies inner layer of optic cup, lens vesicle, and mesenchyme in optic cup; becomes central artery
When do the choroid vessels develop?
During the 15th week
What is persistence of the hyaloid artery?
Occurs when distal part of hyaloid artery persists when it should degenerate; in most cases the eye is microphthalmic
What makes up the optic nerve?
2 layers of neuroblasts (rods and cones and ganglion cells) and a fibrous layer (axons forming the optic nerve)
Where do the fibers of the optic nerve grow? What happens during this process?
Fibers grow through inner part of the optic stalk; the cavity becomes obliterated and the hyaloid artery becomes incorporated
What is papilledema? Why does edema occur with this?
Occurs when increased intracranial pressure slows venous return from retina, causing fluid accumulation in the optic disc; edema occurs because the retinal vessels are covered by the meninges and lie in the extension of the subarachnoid space
What is coloboma? What causes it?
Results from failure of optic fissure to close, leaving a gap in eye structures
What eye defects can a rubella virus cause?
Cataracts, microphthalmos, glaucoma, pigmented retinopathy
What eye defects can toxoplasma gondii cause?
Microphthalmia
What eye defects can venezuelan equine encephalitis virus cause?
Microphthalmia
What eye defects can varicella virus cause?
Cataracts, microphthalmia, and optic atrophy
