A forebrain diverticulum forms from the developing neural tube and it induces the formation of a lens at the overlying ectoderm,  very good example of inductive influence in mechanistic embryology.

The lens placode transforms into a lens vesicle while the diverticulum from the brain becomes the optic cup. The diverticulum forms a stalk which is embedded in mesenchyme that ultimately forms the vascular capsule of the lens and the hyaloid artery. The vessel will supply the inner walls of the optic cup formed from the diveticulum.

The optic cup then extends and invaginates the developing lens while the lips of the choroid fissure formed from the optic diverticulum fuses to encircle the hyaloid artery. The hyaloid artery becomes the central artery of the retina and runs runs with the optic nerve. Its distal portion will soon degenerate  so that it supplies only the retina.

The inner wall of the optic cup now forms the retina with its many layers, which includes  layers of cones and rods, while its outer wall forms a pigmented retinal layer. The mesenchyme surrounding the optic cup condenses around the cup to form the choroid, iris and ciliary body (which includes the ciliary muscles and also the outermost coat of the eye ball called the sclera. The sphincter and dilator pupillae are from the ectoderm having being derived from the walls of the optic cup.

The distal part of the lens vesicle obliterates thereby loosing its attachment to the overlying eyelids.  The lacrimal gland develops from ectodermal cords which grow into mesenchyme.











Face development with audio - Interactive video text

1 sclera 2 choroid 3 central artery of retina 4 optic nerve 5 retina 6 lens 7 iris 8 anterior chamber 9  lower eyelid 10 conjunctiva 



Oluwole Ogunranti 

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