Template:Frog Cornea Timeline table
From Embryology
Stage | Event |
---|---|
stage 25 | cornea starts from a simple embryonic epidermis overlying developing optic vesicle |
stage 30 | detachment of lens placode, cranial neural crest cells start to invade the space between the lens and the embryonic epidermis to construct the corneal endothelium. |
stage 41 | second wave of migratory cells containing presumptive keratocytes invades the matrix, leading to formation of inner cornea and outer cornea. A unique cell mass (stroma attracting center) connects the two layers like the center pole of a tent. |
stage 48 | secondary stromal keratocytes individually migrate to the center and form the stroma layer. |
stage 60 | stroma space is filled by collagen lamellae and keratocytes, and the stroma attracting center disappears. At early metamorphosis, embryonic epithelium gradually changes to adult corneal epithelium, covered by microvilli. |
stage 62 | embryonic epithelium thickens and cell death is observed in the epithelium, coinciding with eyelid opening. |
After metamorphosis | cornea has attained the adult structure of three cellular layers, epithelium, stroma, and endothelium, and between the cellular layers lie two acellular layers (Bowman's layer and Descemet's membrane) |
Table data from Xenopus laevis[1] | frog | vision |