13. Eye Development Flashcards
When does the eye begin to develop?
Day 22: When optic grooves appear
Describe the three embryonic sources of the tissue of the eye.
- Neuroectoderm
- Surface ectoderm
- Mesoderm (Neural crest)
Describe the three embryonic sources of the tissue of the eye.
- Neuroectoderm
- SE
- Mesoderm/NCC
- retina (neural retina and pigmented retina)
- epithelium of iris
- smooth muscle cells of the iris
- Epithelium of ciliary body
- optic nerve
Describe the three embryonic sources of the tissue of the eye.
- Neuroectoderm
2. Surface ectoderm
- Mesoderm/NCC
- lens of the eye
- corneal epithelium
Describe the three embryonic sources of the tissue of the eye.
- Neuroectoderm
- Surface ectoderm
3. Mesoderm/NCC
NCC
- Choroid
- Sclera
- Corneal endothelium
- Stroma of iris
Mesoderm:
- CT and vascularature of eye
- Ciliary muscle
Describe the development of optic cup and lens
- Optic grooves appear in neural folds
- As neural folds fuse, optic vesicles protude in head mesenchyme and contact surface ectoderm.
- Distal end of optic vesicle constricts to form optic stalk, which connects to brain.
- Optic vesicles sends signals to surface ectoderm adjacent to the vesicles to thickens → form lens placode, primordia of the lens.
- As placode invaginates into surface ectoderm, lens pit forms.
- Edges of lens pit fuses -> forms lens vesicle, which then loses contact with surface ectoderm.
- Anterior wall of vesicle: makes the lens epithelium (cuboidal cells)
- Cells in posterior wall lengthen -> forming transparent cells called primary lens fibers
- Secondary lens fibers are added to external sides of primary lens fibers
- Optic vesicles invaginate to form the optic cup (double layered) connected to brain by optic stalks
- Optic cup → retina;
- Optic stalk → optic nerve
Now that we have the optic cup, what. happens?
- Retinal fissures develop on ventral surface of optic cups & along optic stalks
- Axons of ganglion cells pass directly into optic stalk → form optic nerve.
- Myelination occurs late fetal period & first postnatal year
What are the parts of the retina and what are they made out of
Made from the wall of the optic cup from neuroectoderm
- Neural retina (inner layer of optic cup)- neuroectoderm
- Pigmented retina (outer layer of optic cup) - neuroectoderm
Components of iris and where are they made from?
Made from rim of the optic cup.
- Iris epithelium: neuroectoderm
- Stroma of iris: NCC
- Smooth muscle cells of iris (dilator pupillae and sphincter pupillae ms) are made of NEUROECTODERM.
What are. the only muscles that do NOT come from mesoderm?
Smooth muscle cells of iris (dilator pupillae and sphincter pupillae ms) are made of NEUROECTODERM.
Components of ciliary body and where are they madefrom?
- Epithelium of ciliary body: neuroectoderm
- Ciliary muscle is from mesoderm
Retina develops from walls of optic cup & forms two layers. How do we separate the two layers?
Intraretinal space separates retinal layers. As the retinal layers fuse, space disappears.
YOUR LAYERS OF RETEINA SHOULD NORMALLY FUSE.
What is aniridia?
- Aniridia: Mutation in PAX6 gene that causes lack of iris tissue or complete absence of the iris d/t arrested development at rim of optic cup at 8th week.
- Assx with: glaucoma, cataracts, other.
As lens is being made, it will be surounded by what?
optic cup
Lens is made from what cells?
Surface ectoderm
What is epithelium of cornea made from?
stroma of cornea?
Epithelium of cornea: Surface ectoderm
Stroma of cornea: Neural crest
What are congenital cataracts?
The lens is opaque & frequently appears grayish white. Can cause blindness.
Causes of Congenital Cataracts
- Genetics
- Rubella virus between 4-7 weeks
- Radiation.
- Deficient in galactose (congenital galactosemia) 2-3 weeks after birth.
What is the sclera and what is it made out of?
From: NCC
White, fibrous outer layer of eye that is continous with the dura and stroma of the cornea.
What is the choroid and what is it made out of?
Made from: NCC.
Choroid is the vascular layer in between the sclera and retina.
It is analogous to pia and arachnoid layer.
What is the pupillary membrane and what is it made out of?
Made from: NCC
- PM is a transient structure that is part of the sclera and covers the lens.
- Around 26 weeks, it degenerates.
Ciliary body is made from
mesenchyme/NCC
Aqeuous chambers of the eye: Differentiate between the anterior and posterior chambers.
- Anterior chamber of the eye: located in between cornea and iris.
- Posterior chamber of the eye: is in between iris and lens.
Vitrous humor and aqeous humor
- Aqeous humor is made by the ciliary body -> ciliary epithelium secretes into posterior chamber -> pupil -> anterior chamber, where it is reasorped by sclera venous sinus.
- Vitrous humor: made by choroid is located in between lens and back of eyeball (in vitrous body.
What is congenital glaucoma?
- Elevated intraocular pressure d/t abnormal drainage of aqeuous humor from the sclera venous sinus.
- Causes: Mutation in CYPB1, rubella
Where do our extraocular muscles come from?
- Prechordal mesenchyme
- makes preotic myotomes
- makes eye muscles
Explain the development of the blood supply to the eye.
Blood Supply is from: mesdoerm.
2 arteries supply the eye:
- Hyaloid A, branch of the opthalamic a. supplies the:
- inner layer of optic cup,
- lens vesicle,
- mesechyme in the cavity of optic cup.
Will become the central retinal A.
- Choroidal vessels are made in the choroid during 15th week.
Once the hyaloid a. degenerates and becomes the central retinal a., only. supplying the retina, how the fuck do we nourish the lens?!
Aqeous humor!
What happens if we have persistance of hyaloid a.?
- Distal part of the hyaloid artery normally degenerates as proximal part forms central artery of the retina. If it does not, it looks like a worm coming out of optic disk. Eye is typically micopthalmic.
What forms our optic N?
- Retina has two layers of neuroblasts: rods and cones and ganglion cells.
- Ganglion cells form our optic nerve and the fibrous layer forms the axons of the optic nerve -> grow through optic stalk,
- obliterating the cavity
- incorperating the hyaloid A.
optic n is continous with what?
meninges of brain, choroid, sclera
Papilledema
Why does the edema occur?
- Increased intracranial pressure slows venous return from the retina, causing fluid to build up in the optic disk
- Edema occurs because retinal vessels are covered by meninges & lie in the extension of the subarachnoid space that surrounds the optic nerve
Coloboma
D/t
Causes:
- Incomplete closure of the optic fissure, creating a gap in eye structure.
- Caused by: environment, autosomal dominant
Which of the following statements is not correct?
The inner layer of the optic cup forms the ganglion cell layer of the retina.
The sclera is formed by neuroectoderm.
The outer layer of the optic cup forms the pigmented retina.
The pupillary sphincter muscles are derived from neuroectoderm.
B. sclera is NC
Which of the following structures form the photoreceptors of the eyeball?
Inner layer of the optic cup
Outer layer of the optic cup
Optic stalk
Optic fissure
A. inner layer makes neural portion of the retina
Which of the following structures form the pigmented retina of the
eyeball?
Inner layer of the optic cup
Outer layer of the optic cup
Optic stalk
Optic fissure
B
Which of the following statements about the cornea is correct?
The anterior corneal epithelium is derived from surface ectoderm.
The posterior corneal endothelium is derived from surface ectoderm.
The cornea is derived from neural crest cells.
The cornea contains many blood vessels.
A. epithelium of cornea is surface ectoderm
what makes stroma of cornea
sclera
What is the origin of the pupillary muscles?
A. Lateral plate mesoderm
B. Neural crest cells
C. Surface ectoderm
D. Axial mesoderm
E. Neuroectoderm
E. neuroectoderm
Which of the flowing plays a primary role in the induction of
the lens?
Optic cup
Definitive endoderm
Opticstalk
Primary vitreous body
Mesenchymal capsule surrounding the optic cup
a. optic cup
