part of retina outer plexiform layer BTO:0003174 BrendaTissueOBO The outer plexiform layer is a layer of neuronal synapses in the retina of the eye. It consists of a dense network of synapses between dendrites of horizontal cells from the inner nuclear layer, and photoreceptor cell inner segments from the outer nuclear layer. It is much thinner than the inner plexiform layer, where horizontal cells synapse with retinal ganglion cells. external plexiform layer molecular layer stratum plexiforme externum