inner plexiform layer inner plexiform layer the inner plexiform layer is an area of the retina that is made up of a dense reticulum of fibrils formed by interlaced dendrites of retinal ganglion cells and cells of the inner nuclear layer. within this reticulum a few branched spongioblasts are sometimes embedded. inner plexiform layersection of retina. (inner plexiform layer labeled at right, fourth from the top.)plan of retinal neurons. (inner plexiform layer labeled at left, fifth from the top.)detailsidentifierslatinstratum plexiforme internum retinaeta98a15.2.04.015fma58704anatomical terminology