Organogenesis is an organ formation which is prepared by the embryo having three layered structure with separation of following layers.
Organ is formed by different groups of cells which interacts among themselves, and may consist of several component made up of different tissues after derived from different germinal layers.
Eye is an extremely complex organ, the cells that make up the various parts of the eye are contributed by
- The retina, lens, are made up of ectodermal
- The cornea, iris, ciliary body are formed from cellular contributions of both ectoderm and mesoderm.
- The extrinsic and intrinsic muscles are purely mesodermal and so are the choroid and sclera
- The eyelid, lacrimal gland are ectodermal
Development of eyeball can be considered to commence around 22 of pregnancy when the embryo has 8-pairs of somites and is around 2mm in length.
STAGE OF GROWTH AND DEVELOPMENT-EMBRYONIC AND FETAL PERIOD
Embryo size – 2.6mm (3rd week) – development of optics pit on either side of cephalic end of forebrain
Embryo size – 3.5mm (4th week) – primary optic vesicle invaginates
Embry size – 5.5-6mm – development of embryonic fissure
Embryo size – 10mm (6th week) – retinal layers, lens vesicle formed
Embryo size – 20mm (9week) – sclera, cornea, EOM differentiated
Embryo size – 25mm (10week) – lumen of optic nerve obliterated
Embryo size – 50mm (3rd month) – optic tracts completed
Embryo size – 60mm (4th month) – hyaloid vessels develop
Embryo size – 230-265mm (8th month) – foetal nucleus of lens is completed.
Embryo size – 265-300mm (9th month) – except macula, retina is fully developed