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Embryology > Ocular Embryology > Flashcards

Ocular Embryology Flashcards

1
Q

What is gastrulation

A

Change form bilayer to trilaminary disc on day 14

Ectoderm
esoderm
Andendoderm

Formerly epiblast and hypoblast

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2
Q

What is produced from neural ectoderm

A

Optic cup

Neural retina
RPE
Pupillary sphincter and dilator msucles
Posterior iris epithelium
Ciliary body epithelium
Optic nerve

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3
Q

What is produced from neural crest

A

(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

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4
Q

What is produced from surface ectoderm

A

(Epithelium)

Corneal and conjunctival epithelium
Lens
Lacrimal gland
Eyelid epidermis
Eyelid cilia
Epithelium of adnexa glands
Epithelium of nasolacrimal duct

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5
Q

What is derived from mesoderm

A

(muscle and vascular endothelium)

EOMs
Vascular endothelium
Schlemm’s canal endothelium
Blood

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6
Q

When does melanization of the outer neuroectodermal layer of hte optic cup being? When is the RPE layer formed?

A

Week 6
Week 8

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7
Q

When is the RPE fully fucntional

A

Month 4

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8
Q

Where does retinal cell diferentiation start

A

Adjacent to optic nerve and spreads erpiherally

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9
Q

What is the ora serrata

A

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

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10
Q

When are the layers of the retina established

A

By 4.5 months

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11
Q

When does macular development occur

A

Late in gestation until 4 years post partum

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12
Q

When does the optic nerve begin formation

A

Week 6

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13
Q

When does myelination of the optic nerve begin? Where? When does it complete?

A

Month 7 at the optic chiasm

Finishes after birth

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14
Q

What is the origin of the central retinal artery

A

Regression of the distal hyaloid artery within the vitreous in month 4 leaving the proximal segment

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15
Q

When does the lens vescicle separate from the surface ectoderm?

A

Day 33

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16
Q

What are the anterior and posterior lens sutures?

A

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

17
Q

When does the cornea start developing

A

Day 33
(Week 4)
When the lens vesicle detaches

18
Q

what is the corneal epithelium and endothelium formed form?

A

Epithelium - surface ectoderm

Endothelium - neural crest mesenchyme

stroma - neural crest cell differntiaitng into keratocytes which secrete type 1 collagen

19
Q

when does descemet’s form?
Bowman’s

A

Month 3

Bowman’s at month 5

20
Q

What is schlemm’s canal derived from

A

Starts as blood vessel derived from mesoderm

At end of month 3

Drainage canal at month 5 when aqueous humour production starts

21
Q

What are sphincter and dilator muscles derived from

A

Ectoderm

Marginal sinus of von Szily reaches future pupil in month 4 and differentiates into muscles - myofibrils laid in month 5

22
Q

When does pigmentation of the iris start and end?

A

Starts at the pupil margin at 8 months gestation and continues until 7 months post partum

23
Q

What is vitreous derived from?

A

Mesoderm mesenchyme

24
Q

When does primary vitreous development peak?

A

8 weeks

Forms the developing vascualr system

Regresses at 5 months

25
Q

What is secondary vitreous?

A

Avascular
ASsocaited with hyalocytes
Secrete type 2 collagen fibrils

26
Q

What is the choroid continuous with around the ON

A

Pia and arachnoid mater

27
Q

When do eyelids develop and split?

A

Aggregations of surface ectoderm 6-7 weeks
Proliferate across cornea and fuse at 10 weeks
Orbicularlis at week 12
Lid divides at 20 weeks

28
Q

How is the lacrimal gland split

A

Month 5
LPS bisects lacrimal galnd into oribtal and palpebral sections

29
Q

When does tear production being?

A

20 days to 3 months post partum
Full maturation of gland at 3 years

30
Q

What are orbital bones formed form?

A

Nerual crest mesenchyme

31
Q

When doe EOM form from what?

A

Week 5 mesoderms differntiates into the EOMs

LPS develops from the dorsomedial SR at week 7

32
Q

What is the membrane of Hasner

A

Nasolacrimal duct outlet - remains imperofrate within 70% of newborns but normally regresses within the first month post partum

33
Q
A

Embryology (5 decks)

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