Rajvin Samuel Ponraj

Embryogenesis :

Organisation and development of the primary layers of the developing embryo

After fertilization - sequential formation of three cell masses

Organogenesis: process in which segregatory cells

become rudimentary organs

Derivatives of embryonic tissues

Neural Crest

Neural crest

Corneal keratocytes, Cornea endotheliumTrabecular meshwork, Stroma of the iris and choroid,Ciliary muscle, Fibroblasts of the sclera, the vitreous, and

the optic nerve meninges., Extraocular muscles, Subepidermal layers of the eyelids.

Surface ectoderm

lensthe lacrimal glandthe epithelium of the cornea conjunctivaepidermis of the eyelids

Neuro ectoderm

optic vesicle and optic cup

Retinal pigment epithelium Ciliary epithelium Iris muscles optic nerve fibers and glia.

Mesoderm

Vitreous Extra ocular & lid musclesOrbital and ocular vascular

endothelium

3 to 4 week stage of embryo

2 nd month stage of embryo

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3 rd month stage of embryo

4 th month stage of embryo

5 th month to birth

At birth :Anterior – posterior diameter : 16.5 mmAnterior chamber – shallowLens - sphericalCornea diameter = 10 mmOrbit is divergent to 50 degreesMyelination occurs till lamina cribrosa Retina except macula is fully differentiated and formed

Post natal period :

Fixation completed by 6 monthsMacula formed by 6 monthsSteropsis and accomadation by 6 monthsCornea reaches adult size by 2 yearsLens develops throughout life

RETINAIt develops from the optic cup.

The outer layer of the optic cup is the pigment layer.

The neural layer is formed from the inner layer of the optic cup.

MACULA

It develops as a result of localized increase of superimposed nuclei in the ganglion cell layer, lateral to the optic disc.

Optic nerve

Develops from glial cells of neuro ectodermal cells and axons fron ganglion cells with meningeal coverings forming the optic nerve sheets

Lens

The posterior wall begin to elongate anteriorly and form long fibers that gradually fill the lumen of the vesicle.

The secondary lens fibres start from equator region elongate towards anteriorly and soon detach to form the next lens fibre layer

Migration of neural crest cells

1 st wave – corneal and trabecular endothelium

• 2 nd wave - corneal stroma

• 3 rd wave - Iris stroma

Vitreous

Primary vitreous

Secondary vitreous

Tertiary vitreous

SCLERA : This tough outer fibrous coat is

formed from the condensation of the mesenchyme around the optic cup

CHOROID: This inner vascular layer is

formed from the mesenchyme surrounding the optic vesicle.

Ciliary glands and eyelashes develop as outgrowths of epithelial buds

Eyelid develop from surface ectoderm

Lacrimal glands develop as ectodermal buds

superolaterally into mesenchyme

Lacrimal sac and nasolacrimal duct develop from ectoderm - nasolacrimal furrow which gets burried into a cord

Part Derived from

Lens Surface ectoderm

Retina Neuroectoderm (optic cup)

Vitreous Mesoderm

Choroid Mesoderm (infiltrated by neural crest cells?)

Ciliary body Mesoderm

Ciliary muscles Mesenchymal cells covering the developing ciliary body (neural crest)

Iris Mesoderm

Muscles of the iris Neuroectoderm (from optic cup)

Sclera Mesoderm (infiltrated by neural crest cells?)

Cornea Surface epithelium by ectoderm, substantia propria and inner epithelium by neural crest

Conjunctiva Surface ectoderm

Blood vessels mesoderm

Optic nerve Neuroectoderm. Its covering (pia, arachnoid and dura) are derived from mesoderm

Summary of various part of the eye ball.

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