Development of eye.
-
Upload
dr-laxman-khanal -
Category
Health & Medicine
-
view
51 -
download
0
Transcript of Development of eye.
Development of eyeTo MBBS 2nd year
Dr. Laxman Khanal
Assistant professor, department of anatomy
BPKIHS, Dharan
02-04-2017
Eye development : start at Day 22.
Before NT closure- Day 25 to Day 28
Diencephalon of forebrain
PAX 6Key regulatory gene for eye development.
Optic vesicleOptic groove
Lens placode Optic stalk Optic cup
1. Fibrous covering2. Vascular covering (#ICC)3. Nervous covering
Limbus Equator
• Key steps - Formation of optic vesicle and optic stalk.
• Optic vesicle/ stalk – neuro-ectodermal in origin.
• Lumen of the optic vesicle is connected with the 3rd ventricle through thelumen of optic stalk.
• As the optic vesicle comes in contact with the surface ectoderm, itinduces it to thicken and forms lens placode (primordium of lens), so lensis ectodermal (surface ectoderm) in origin.
• As the lens vesicle is being formed, optic vesicle invaginates to formdouble-layered optic cup.
Choroidal fissure• Vascular mesoderm invade the fissure.• This mesoderm later form hyaloid vessels &
vitrous humor.• Only the proximal part of these vessels persists
as a central artery/vein of retina
Up to now…..• Optic vesicle• Optic cup• Optic stalk• lens placode• Choroidal fissure
Development of Retina- two layers of optic cupDevelopment of optic nerve- optic stalk (axons of ganglion cells)
Retinal detachment:
Separation of pigment epithelium from the neural layer.
Ora serrata
• Ora serrata is the junction betweenphotosensitive and non-photosensitiveretina.
• Lies between limbus and equator of eyeball.
Coloboma• Failure to close choroidal fissure• Key hole appearance in iris• Follow AD inheritance
Retinal detachment • Medical emergency• Occurs between 2 layers of retina
Development of optic nerve
• Second cranial nerve• Optic nerve encloses retinal vessels• Formed by axons of ganglionic cells• Covered by meningeal layers• Myelinated by Oligodendrocytes
@ 7th week
Development of-• Iris• Ciliary body
Development of IrisEpithelium: both layers of retina (ant part)Stroma: mesenchymeMuscles: outer layer of retina
Development of ciliary bodyEpithelium: both layers of retina (ant part)Stroma: mesenchymeMuscles: mesenchyme
Aqueous humor
Derivatives of optic cup • Retina• Dilator pupillae• Sphincter pupillae• Epithelium of the iris• Epithelium of ciliary body
Derivatives of optic stalk
Optic nerve
MesodermPosteriorlydivide into two layersAnteriorlyVacuolization occurs
Surface Ectoderm Double folding occurs
Development of-• Sclera• Choroid• Cornea• Conjunctiva• Eyelids
Double folding of surfaceectoderm give rise to theconjunctiva and eye lids.
Surface Ectoderm • Outer epithelium of cornea• Conjunctiva• Lining of eye lids• Tarsal gland• Eye lashes
Persistent iridopupillary membrane Congenital cataractTORCH infection
Aniridia
Synophthalmiaor
CyclopiaLoss of midline structure• Alcohol• Maternal DM• Mutation of SHH (sonic hedgehog)• Abnormal cholesterol metabolism
Conclusion
• The eyes begin to develop as a pair of outpocketings on each side ofthe forebrain at day 22.
• The optic vesicles contact the surface ectoderm and induce lens formation.
• Through a groove (the choroid Fissure), the hyaloid artery (later thecentral artery of the retina) enters the eye
• PAX6, the master gene for eye development.
• Cornea develops from both ectoderm and mesoderm.