Development of the eye Flashcards
eyes are derived from what
- surface ectoderm
- lateral neuroectodermal walls of the embryonic diencephalon
- mesenchyme
- neural crest cells
what do you see at the beginning of the 4th week (D22)
-a pair of optic grooves/sulcus appear on the sides of the forebrain
-as the neural tube fuses :
1. the optic grooves evaginate to form optic vesicles
2. and the optic vesicles become continuous with the cavity of the forebrain
what induces the optic grooves to evaginate to form the optic vesicles
mesenchyme adjacent to the brain
during the mid of the 4th week what happens to the optic vesicles as they expand
their connections constrict to form optic stalks
as the optic vesicles contact the surface ectoderm what happens (mid of 4th week)
-it induces the surface ectoderm to thicken and form lens placodes
what happens to the lens placodes
-they evaginate and sink into the surface ectoderm forming lens pits
-the edge of the lens pits then later fuse to form the lens vesicle
-the lens vesicle then later pinches off the surface ectoderm
what are the layers of the optic cup
inner layer- neuroepithelium (neural retina)
outer layer- retinal pigment epithelium
intraretinal space
what happens as the lens develops
-the optic vesicles invaginate to form the double layered optic cup due to the lens vesicles invaginating into the optic vesicle/pinching off the surface ectoderm
-retinal fissures/optic fissures develop on the ventral surface of the optic cup due to incomplete folds in the inferior portion of the optic cup and stalk
retinal/optic fissures form a passage way for what
hyaloid artery and vein (branch of the ophthalmic artery)
what happens when the optic fissures fuse
the hyaloid artery and vein are enclosed within the primordial optic nerve (hyaloid system is incorporated within the eye)
what does the hyaloid artery and vein later become
the central artery and vein of the retina
when does the hyaloid artery enter the optic fissure
5th week
whats a coloboma
its when there is failure of closure of the optic/choroidal fissure
what does a coloboma look like
it gives a key hole appearance in the iris
whats the position of the coloboma
the infero-nasal quadrant (which is reflective of the location of the optic fissure during development)
where does the retina develop from
walls of the optic cup
what forms the retina pigment epithelium
the outer thin layer of the optic cup
what forms the neural layer of the retina
the inner thick layer of the optic cup
during embryonic/fetal period what separates the 2 layers of the retina
the intraretinal space
what eventually happens to the 2 layers of the retinal that are separated by the intraretinal space
they loosely fuse
what causes the inner layer of the optic cup to form the thick neuroepithelium- which later then forms the neural retina (photoreceptor cells) , bipolar and ganglion cell bodies
the induction by the lens
what is incomplete at birth with the axons given off by the ganglion cells to form the optic nerve
myelination
what is the cavity of the optic stalk filled with
axons of the optic nerve
what happens when the outer and inner layers of the optic cup fail to fuse
congenital detachment of the retina
what is the ciliary body
its a wedge shaped extension of the choroid
what does the medial surface of the ciliary body do
it projects towards the lens and forms ciliary processes
where is the pigmented portion of the ciliary epithelium derived from
the outer layer of the optic cup
the pigmented portion of the ciliary epithelium is continuous with what
the retinas pigmented epithelium
the non pigmented portion of the ciliary epithelium is an anterior prolongation of what
the neural retina epithelium
where does the ciliary muscle develop from
mesenchyme located at the edge of the optic cup
what structure of the eye develops from the inward growth at the rim of the optic cup
iris
what are the 2 layers of the optic cup like at the iris
they remain thin in that area
the iris epithelium represents what
both layers of the optic cup
the iris epithelium is continuous with the double layered epithelium of what
-ciliary body
-retina pigment epithelium and neural retina
where do the dilator and sphincter pupillae muscles arise from
the neuroectoderm
where does the lens develop from
the lens vesicle
the lens vesicle is a derivative of what
the surface ectoderm
what is the anterior wall of the lens composed of
cuboidal epithelium
what does the anterior wall of the lens form
the subcapsular lens epithelium
what does the posterior wall of the lens form
primary lens fibers which are tall columnal cells that eventually lose their nuclei
what is the rim of the lens called
the equatorial zone
what do the cuboidal cells of the equatorial one do
they continuously elongate lose nuclei and become secondary lens fibers
the developing lens is invested by what
a vascular mesenchymal layer/ dense capillary network called the tunic vasculosa lentis
what does the anterior part of the tunica vasculosa lentis form
the pupillary membrane
what supplies the tunica vasculosa lentis
hyaloid artery
what happens when the hyaloid artery degenerates in the fetal periods
the tunica vasculosa lentis also degenerates leaving behind a hyaloid canal
what forms the posterior part of the tunica vasculosa lentis
the posterior pupillary membrane ( which covers the lens capsule)
the tunica vasculosa grows towards what
the equator of the lens
where does the anterior chamber develop from
the cleft like space that forms in the mesenchyme between the developing lens and cornea
where does the posterior chamber develop from
the space that forms in the mesenchyme posterior to the developing iris and anterior to the developing lens
the external corneal epithelium is derived from what
the surface ectoderm
CT of mesenchyme of the cornea is derived from what and is continuous with what
-derived from mesoderm
-is continuous with developing sclera
where does the corneal endothelium develop from
neural crest cells migrating into the cornea
where do the choroid (inner vascular) and sclera (outer fibrous) develop from
condensation of the neural crest mesenchyme surrounding the optic cup
what happens to the choroid at the rim of the optic cup
its becomes modified to form the ciliary processes consisting of capillary blood vessels with CT
when do the eyelids develop
6th week
the eyelids develop from what
-neural crest cell mesenchyme
-two folds of skin that grow over the cornea
what do the eyelids do when developing
they adhere to each other in the 10 week and reopen in the 26-28th week
what lies anterior to the cornea
the conjunctiva sac
what does the surface ectoderm differentiate into
-lens of eye
-cornea epithelium
what does the neuroectoderm differentiate into
-retina
-posterior layers of the iris
-optic nerve
what does the mesenchyme differentiate into
-fibrous coat of the eye
-vascular coat of the eye
what develops from neural crest cells in the mesenchyme
-choroid
-sclera
-corneal endothelium
what is derived from the surface ectoderm
-lens
-epithelium of the cornea, conjunctiva and lacrimal gland and its drainage system
what is derived from the neural ectoderm
-vitreous body (from neural ectoderm of the optic cup and from mesenchyme)
-epithelium of the retina, iris, and ciliary body
-sphincter pupillae and dilator pupillae muscles
-optic nerve
what is derived from the mesoderm
-sclera
-stroma of the cornea, ciliary body, iris and choroid
-extra ocular muscles
-eyelids (except epithelium and conjunctiva)
-hyaloid system
-coverings of the optic nerve
-connective tissue and blood vessels of the eye, bony orbit and vitreous body
