Ocular Embryology Flashcards
What is gastrulation
Change form bilayer to trilaminary disc on day 14
Ectoderm
esoderm
Andendoderm
Formerly epiblast and hypoblast
What is produced from neural ectoderm
Optic cup
Neural retina
RPE
Pupillary sphincter and dilator msucles
Posterior iris epithelium
Ciliary body epithelium
Optic nerve
What is produced from neural crest
(Connective tissue)
Corneal endothelium
Corneal stroma
Iris stroma
Ciliary body stroma
Trabecular meshwork
Ciliary muscles
Choroid
Sclera
Perivascular CT and SMCs
Meninges of ON
Orbital cartilage
Bones
CT of EOMs
Secondary vitreous
Zonules
What is produced from surface ectoderm
(Epithelium)
Corneal and conjunctival epithelium
Lens
Lacrimal gland
Eyelid epidermis
Eyelid cilia
Epithelium of adnexa glands
Epithelium of nasolacrimal duct
What is derived from mesoderm
(muscle and vascular endothelium)
EOMs
Vascular endothelium
Schlemm’s canal endothelium
Blood
When does melanization of the outer neuroectodermal layer of hte optic cup being? When is the RPE layer formed?
Week 6
Week 8
When is the RPE fully fucntional
Month 4
Where does retinal cell diferentiation start
Adjacent to optic nerve and spreads erpiherally
What is the ora serrata
Line posterior to ciliary body demarcating the neruosensory retina anteiror border
Inner and outer neuroectodermal layers of the optic cup anterior to the ora serrata extend forward on tot he ciliary body and posterior iris
When are the layers of the retina established
By 4.5 months
When does macular development occur
Late in gestation until 4 years post partum
When does the optic nerve begin formation
Week 6
When does myelination of the optic nerve begin? Where? When does it complete?
Month 7 at the optic chiasm
Finishes after birth
What is the origin of the central retinal artery
Regression of the distal hyaloid artery within the vitreous in month 4 leaving the proximal segment
When does the lens vescicle separate from the surface ectoderm?
Day 33
What are the anterior and posterior lens sutures?
Base of secondary fibres remainattached to basal lamina at equator
Apex extends anteriorly or posteriorly
Anterior suture - UPRIGHT Y SHAPE
Posterior lens suture INVERTED Y SHAPE
When does the cornea start developing
Day 33
(Week 4)
When the lens vesicle detaches
what is the corneal epithelium and endothelium formed form?
Epithelium - surface ectoderm
Endothelium - neural crest mesenchyme
stroma - neural crest cell differntiaitng into keratocytes which secrete type 1 collagen
when does descemet’s form?
Bowman’s
Month 3
Bowman’s at month 5
What is schlemm’s canal derived from
Starts as blood vessel derived from mesoderm
At end of month 3
Drainage canal at month 5 when aqueous humour production starts
What are sphincter and dilator muscles derived from
Ectoderm
Marginal sinus of von Szily reaches future pupil in month 4 and differentiates into muscles - myofibrils laid in month 5
When does pigmentation of the iris start and end?
Starts at the pupil margin at 8 months gestation and continues until 7 months post partum
What is vitreous derived from?
Mesoderm mesenchyme
When does primary vitreous development peak?
8 weeks
Forms the developing vascualr system
Regresses at 5 months
What is secondary vitreous?
Avascular
ASsocaited with hyalocytes
Secrete type 2 collagen fibrils
What is the choroid continuous with around the ON
Pia and arachnoid mater
When do eyelids develop and split?
Aggregations of surface ectoderm 6-7 weeks
Proliferate across cornea and fuse at 10 weeks
Orbicularlis at week 12
Lid divides at 20 weeks
How is the lacrimal gland split
Month 5
LPS bisects lacrimal galnd into oribtal and palpebral sections
When does tear production being?
20 days to 3 months post partum
Full maturation of gland at 3 years
What are orbital bones formed form?
Nerual crest mesenchyme
When doe EOM form from what?
Week 5 mesoderms differntiates into the EOMs
LPS develops from the dorsomedial SR at week 7
What is the membrane of Hasner
Nasolacrimal duct outlet - remains imperofrate within 70% of newborns but normally regresses within the first month post partum
