Eye Development Flashcards
What are the three embryonic sources for the eye?
Neuroecteoderm, surface ectoderm, mesoderm/NCC
Where does the eye originate from in the brain?
Prosencephalon
What are the parts of the eye in the beginning?
Optic vesicle attached via optic stalk, turns into optic cup (with outer and inner layers) attached by optic stalk, makes a horseshoe shape called optic fissure where hyaloid a/v run
What is the prosencephalon divided into?
Telencephalon (gyri, sulci) and diencephalon (thalamus, hypothalamus, epithalamus, eyes)
What is the retina divided into?
Inner neural retina (rods and cones) and outer pigmented retina
What layer does the retina come from?
Both neural retina and pigmented retina come from neuroectoderm
What layer does the iris come from?
Epithelium and smooth muscle cells come from neuroectoderm, the stroma comes from mesenchyme
What layer does the ciliary body come from?
The epithelium comes from neuroectoderm, the smooth muscles/ciliary muscle comes from mesenchyme
What causes a detached retina?
When the pigmented and neural retinas do not fuse and come together (makes intra-retinal space). Seen in down syndrome or marfan’s syndrome, also in trauma
What is aniridia?
Lack of iris tissue/complete absence of iris due to arrest of development at the rim of the optic cup during week 8, caused by Pax6 gene mutation
What layer does the lens come from?
Surface ectoderm
How does the lens develop
Thickening of surface ectoderm = lens placode which is induced by the optic cup. Placode invaginates to form lens pit which rounds up and forms a lens vesicle that migrates down to space around optic cup
What layer does the epithelium of the cornea develop from? What about the stroma of the cornea?
Epithelium comes from surface ectoderm, stroma (deeper layer) comes from mesenchyme
What is congenital cataracts?
Opaque lens caused by genetics, rubella virus during pregnancy, radiation during pregnancy, enzyme deficiency (congenital galactosemia)
What layer does the sclera come from?
Mesenchyme (is continuous with dura of brain), forms stroma of cornea
What layer does the choroid come from?
NCC, is continuous with arachnoid/pia layers of brain
What layer does the ciliary body/smooth muscles come from?
Mesenchyme
What layer does the pupillary membrane come from?
Mesenchyme
What is the pupillary membrane?
Transient extension of the sclera, covers the lens as it is developing, degenerates in 6-8th month in utero
What is aqueous humor?
Produced by ciliary epithelium, delivers nutrients to lens, gets rid of waste products, is protective. Is absorbed into Schlemm’s canal (scleral venous sinus)
What is vitreous humor?
Primarily from choroid, thick & jelly-like, nourishes posterior aspect of eye
What is congenital glaucoma?
Caused by elevated intraocular pressure due to abnormal development of the drainage mechanism of the aqueous humor through the scleral venous sinus. Caused by mutations in CYP1B1 gene or rubella during pregnancy
Where do extraocular muscles of the eyes come from? (SR, IR, MR, LR, SO, IO)
Prechordal mesenchyme
What is the hyaloid artery?
Blood supply to retina and lens (inner layer of optic cup) during early development, runs through the optic fissure. Degenerates to become the central retinal artery and should only supply retina
When does the choroid develop?
Week 15, comes from ciliary arteries
What can you see with microphthalmic eyes?
Persistence of the hyaloid artery
What layer does the optic nerve come from?
Neuroectoderm
What are the two layers of neuroblasts within the inner neural layer of the retina?
Rods and cones
Ganglion cells
What cells form the optic nerve from the eye?
Retinal ganglion cells
What does the optic stalk do?
Provides a pathway for retinal ganglion cells to get back to the brain, is completely replaced by optic nerve
What is papilledema?
Due to increased intracranial pressure, causes optic disc to bulge.
What is coloboma?
Optic fissure fails to close completely leaving gap in eye, autosomal dominant. No pupillary constriction in bright light, can damage retina
