Eye Development Flashcards
What is the critical period of eye development?
Weeks 4-8
The eye is an extension of the brain, so it is composed mainly of what embryologic layer?
Neuroectoderm
The eye consists of three embryonic sources, which are…
Neuroectoderm
Surface Ectoderm
Mesoderm/Neural Crest Cells (Mesenchyme)
The portion of the brain the eye develops from is called the Prosencephalon, which is further divided into the _________ and __________. The eye is specifically from the __________.
Telencephalon
Diencephalon
Diencephalon
This is the invagination that begins the development of the eye.
Optic Sulcus (Groove)
This is made of neuroectoderm and it is what will form the Optic Cup.
Optic Vesicle
***Think of Optic Vesicle as a ping pong ball, and when you push down on it then it will indent and make a “cup” shape.
This is what connects the eye (during development) to the brain.
Optic Stalk
As the inner and outer layers of the Optic Cup form, it creates an _______ _______ that is a groove going along the Optic Stalk.
Optic Fissure
The development of the Optic Cup begins at ______ weeks.
4
When the Optic Vesicle starts to form the Optic Cup, there will be an ________ layer and an ________ layer that have a distinct space between them.
Inner
Outer
***These will give rise to retina!
What vasculature runs in the Optic Fissure?
Hyaloid A.
Hyaloid V.
What components of the eye develop from neuroectoderm?
Retina
Iris
Ciliary body
The retina has an outer layer called the ________ ________ and an inner layer called the ________ ________.
Pigmented retina
Neural retina
Iris and Ciliary body come from the tips of the…
Optic Cup
What are the parts of the Iris, and what embryological layer are they derived from?
Epithelium – Neuroectoderm
Stroma – Mesenchyme (both mesoderm and NCC)
SMC – Neuroectoderm
The muscles involved with the iris are the ONLY muscles in the entire body derived from neuroectoderm (the rest is mesoderm). What are these muscles?
Sphincter Pupillae
Dilator Pupillae
What are the parts of the Ciliary body, and what embryological layer are they derived from?
Epithelium – Neuroectoderm
SMC – Mesenchyme (both mesoderm and NCC)
What muscles are involved with the Ciliary body?
Ciliary muscle
***Remember, these are mesenchyme
During development, there is a small space between the Pigmented retina (outer layer) and the Neural retina (inner layer) called the __________ space. The layers will normally fuse, and this space will go away.
Intraretinal
Normally, the Pigmented retina (outer layer) and the Neural retina (inner layer) should fuse, but some diseases can cause them not to resulting in a detached retina. What are these diseases?
Down’s Syndrome
Marfan’s Syndrome
***Can also occur from a car accident, fall, etc.
This presents as a lack of iris tissue or complete absence of the iris. It’s caused by the arrest of development at the rim of the Optic Cup during the 8th week. From a Pax6 gene mutation and often associated with glaucoma, cataracts, and other eye abnormalities.
Aniridia
Surface ectoderm is going to form the ______ and epithelium of the ________.
Lens
Cornea
How is the formation of the lens induced by the Optic Cup (from neuroectoderm)?
Optic Cup will go out and touch the surface ectoderm. The cell-cell interaction induces the lens to begin to form.
The interaction from the Optic Cup makes the surface ectoderm form a _______ _______, which is a thickening of the surface ectoderm. This will begin to invaginate to form the _______ _______, and finally it will round up and close off to form the _______ _______.
Lens Placode
Lens Pit
Lens Vesicle
The epithelium of the cornea is from surface ectoderm, but the stroma is from…
Mesenchyme (both mesoderm and NCC)
This occurs when the lens is opaque and frequently appears grayish white.
Congenital Cataracts
What are the causes of congenital cataracts that will cause it to show up right away?
Genetics
Rubella virus
Radiation
What are the causes of congenital cataracts that will cause it show up after a period of time?
Enzyme deficiency – Congenital galactosemia
- appears 2-3 weeks after birth
- Galactose from milk accumulate in blood and tissues
If a mother contracts this during weeks 4-7 of pregnancy, the fetus is at great risk for developing congenital cataracts along with a bunch of other problems.
Rubella virus
What components of the eye are developed from mesenchyme/NCC?
Sclera
Choroid
Pupillary membrane
Ciliary body
These are the components of the lens, and they function to keep it clear.
Anterior lens epithelium
Primary lens fibers
Secondary lens fibers
What are the parts of the Sclera, and what embryological layer are they derived from?
Outer layer – mesenchyme
Fibrous layer – mesenchyme
Stroma of Cornea – mesenchyme
***Remember, the epithelium of the cornea is from surface ectoderm!
The outer layer of the Sclera is continuous with what layer of meninges?
Dura mater
***Mesenchyme
This component of the eye is heavily NCC and is vascular and its inner layer is continuous with the Pia Mater and Arachnoid Mater.
Choroid
This is a transient structure that is part of the sclera and covers the lens. In 6-8 months in utero it should degenerate, but if it doesn’t it can be removed via laser surgery.
Pupillary Membrane
This chamber is between the cornea and the lens.
Anterior Chamber
This chamber is between the lens and iris.
Posterior Chamber
In the Posterior Chamber, the _______ _______ is secreted into it by the ________ ________.
Aqueous humor
Ciliary epithelium
***Remember, the Ciliary epithelium is neuroectoderm and it has ciliary muscles derived from mesenchyme!
The aqueous humor will secrete into the Posterior Chamber, leave via the _______ and go into the Anterior Chamber. From here, the aqueous humor is resorbed by the _______ _______ _______.
Pupil
Scleral Venous Sinus (Schlemm’s Canal)
This is the jelly-like substance that is from the Choroid. It’s in the back of the eye for protection and lubrication.
Vitreous humor
This is from elevated intra-ocular pressure that results from the abnormal development of the drainage mechanism of aqueous humor (Scleral Venous Sinus). Causes can be from genetics, specifically mutations in CYP1B1, or the Rubella infection.
Congenital Glaucoma
***You can see it’s different from cataracts because the cloudiness covers everything! Not just the lens!
The extra-ocular muscles (SR, IR, MR, LR, IO, SO) are developed from what embryological layer?
Prechordal Mesenchyme
***From prechordal plate, not pharyngeal arches!
This is a branch of the Ophthalmic A. that supplies the inner layer of the Optic Cup (neural retina), the lens vesicle, and the mesenchyme in the Optic Cup.
Hyaloid A.
The distal end of the Hyaloid A. should degenerate, and eventually only supply the retina. At this point, it is called the…
Central Retinal A.
T/F. The Choroidal vessels develop in the Choroid during the 4th week of development, and they will come from the Anterior and Posterior Ciliary As. in the orbit.
False. They develop during the 15th week.
When there is persistence of the Hyaloid A., that means the distal part of the artery never degenerated. You would see a little squiggly line in an eye exam within the Vitreous chamber. This most often occurs when the eye is…
Microphthalmic
The Optic N. is derived from what embryological layer?
Neuroectoderm
In the retina, the inner layer has two layers of neuroblasts which are…
Rods and cones
Retinal Ganglion cells
The fibrous layer beneath the retina has axons forming the Optic N. These axons are from what?
Retinal Ganglion Cells
The Retinal Ganglion Cell fibers will grow through the inner part of the _______ _______. This is NOT the Optic N., it just provides the pathway for the Retinal Ganglion Cells to grow.
Optic Stalk
Eventually, the lumen of the Optic Stalk will close and there will be bunches of axons from Retinal Ganglion Cells passing through. The Optic Stalk will also invaginate and incorporate the _______ _______.
Hyaloid A. and V.
***By birth the Optic Stalk will be gone and just the Optic N. with the Central Retinal A. and V. will remain!
This is caused by increased intracranial pressure that slows venous return from the retina, causing fluid accumulation of the optic disc.
Papilledema
Why does edema occur in Papilledema?
Because the retinal vessels are covered by the meninges and lie in the extension of the Subarachnoid Space.
This results when the Optic fissure fails to close completely, leaving a gap in the eye structures. Looks like a “key-hole”. Causes are environmental factors, and autosomal dominant characteristics.
Coloboma
Why can light damage someone’s eye with Coloboma?
Because they can’t constrict their pupil, which is what happens with bright light. Too much light can eventually cause damage to their retina.
This is an intracellular parasite that you can get by eating undercooked meat with parasites in it, as well as cleaning out the litter box. Can cause microphthalmia to your baby.
Toxoplasma gondii
