Development of the Eye

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Development of the Eye
Jittipan Chavadej, Ph.D.
Anatomy Department,Fac. of Science Mahidol
University
yr.2000
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Mature structures of the eye

• Eyeball - cornea sclera
• - lens , eye chamber
• - retina , optic nerve
• Surrounding muscular structure
• - ciliary body
• - iris muscles
• - extraocular musclesconjunctiva

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Structure of the eye
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Formation of the eye

• Are formed by 3 different germ layers.

1. Neuroectoderm 2. Surface ectoderm 3. Mesoderm
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• Neuroectoderm - forebrain(dien.) --gt - retina
  optic nerve - iris
  ciliary body

• Surface ectoderm - above optic vesicle --gt lens
  cornea

• Mesoderm -all CNT vascular structures --gt
  choroid layer sclera

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Retina Optic nerve form from optic vesicle
Diagram showing the formation of optic vesicle
the lens placode
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Ventrolateral view off the optic cup optic
stalk showing the hyaloid artery in the choroid
fissure
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Retina formation

• Changes of inner layer of optic cup (lens
  cornea) neural retina

Thickening
differentiation
Epith. cells neurons light photoreceptor
cells (rodscones)

• Outer layer of optic cup (thin) pigment layer
  of the retina

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• Neural retina (multilayers)
• consists of- rods cones
• - bipolar neurons in inner
  nuclear layer
• - ganglion cells in
  ganglion cell layer

• Differentiation

• 1st-ganglion cell--gt optic nerve
• 2nd-bipolar neurons rods - cones

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Optic nerve/stalk
Diagram showing the differentiation of layers of
the neural retina.
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Diagram showing the development of the layers of
the neural retina
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Formation of lens
Surface ectoderm lens placodes lens
vesicles lens

• Differentiation of the lens
• elongation of lens fiber
• contain large amount of crystallin proteins -
  alpha,beta gamma(mol.level)

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Crystallin(no)
Invagination
Lens cup
Alpha(/-)
Alpha() Beta(/-) Gamma(/-)
Lens vesicle
Alpha() Beta() Gamma()
Elongation of 10 fiber
Alpha() Beta() Gamma()
Embryonic lens
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Anteroposterior section of the eye showing optic
cup, optic stalk and lens vesicle
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Formation of cornea

• 2 sources-surface ectoderm

• Inductive influence of the lens
• -surface ectoderm- primary stroma
• collagen type I, II, IX
• -neural crest cells-corneal endothelium
  secondary stroma (hyaluronic acid-hyaluronidase)

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Anteroposterior section through the eye.
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• Final developmental changes of cornea Formation
  of transparency

-by removing water from secondary stroma
(40) -degradation of hyaluronic
acid -thyroxine--gt corneal endothelium - by
pumping sodium into antr chamber of the eye
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Iris Ciliary body formation
-at the lip of optic cup
Ciliary body -muscle containing structure
suspensory ligament of the lens(radial set of
muscle) --gtmodulate shape of the lens
Iris -2 sets of muscle(sphincter dilator
pupillae) --gtcontrol the amt of light passing
through the lens
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Development of the iris and the ciliary body.The
rim of the optic cup is covered by the
mesenchyme, in which the sphinter and dilator
pupillae develop from the underlying ectoderm.
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Choroid coat and sclera
Origin a layer of mesenchymal cells neural
crest cells outside the optic cup- under
influence of the pigmented epith. of the retina
Choroid coat-a highly vascular tunic
Sclera-dense collageneous covering -tough
outer coat of the eye
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Diagram showing the development of the choroid
the sclera
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Vitreous body Hyaloid artery
Vitreous body-loose mesenchyme forming a loose
fibrillar mesh along with a gelatinous substance
in optic cup
Hyaloid artery-enter the eyeball through the
choroid fissure of the optic stalk--gtretina,vitreo
us body --gtpostr wall of the lens
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Note antr chamber,vitreous cavity-vitreous body
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Changes of Hyaloid artery

• Regression of hyaloid artery
  (in the vitreous body)
• Persistance of prox. part of hyaloid artery as
  central artery of the retina

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B
A
Stages in development and regression of the
hyaloid artery in the embryonic eye
C
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Eyelid and Lacrimal gland

• 7thwk. - fold of skin
• 9thwk. - meet temporary fusion
• 6thmo. -loosening of epith. union
• 7thmo. - reopening of the eyelid

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Conjunctival sac - space betw. the front of
eyeball eyelid
Lacrimal gl.-multiple epithelial bud from lateral
surface ectoderm -nasolacrimal
duct -begin to function6 wk.
after birth
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Note eyelid,iridopupillary membrane
conjunctival sac
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Congenital malformations of the eye

• Anophthalmos -absence of an eye
• Microphthalmos -smaller than normal
• Coloboma iridis -nonclosure of choroid fissure
  of the iris

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THE END