Retina

The internal layer of the optic cup is called the neural retina (stratum nervosum retinae). At S14, it is already subdivided into a ventricular and a marginal zone. As in the brain, the ventricular zone initially is in the direct vicinity of the ventricle (optic ventricle). The optic ventricle becomes obliterated and the ventricular zone will come into close contact with the external layer. Hence, mitoses do no longer take place in the vicinity of a ventricle, but instead occur close to the choroid which contains numerous capillaries. The pigmented epithelium, which develops from the external layer, lies between the choroid and the ventricular zone. Post-mitotic cells from the ventricular zone migrate towards the vitreous body, enter the marginal zone and form the intermediate zone. Ganglion cells, amacrine and Müller cells develop from the intermediate zone.