Figure 1.

Anatomy of olfactory sensory neurons (OSN) and photoreceptors (PR). (A) OSN are defined by the expression of a unique odorant receptor, OSN expressing the same receptor (red, green, blue, or orange) are dispersed throughout the olfactory epithelium (OE) but the axons of these OSN converge to synapse in the same glomeruli of the olfactory bulb (OB). The major compartments of OSN are the cilia for signal detection which extends from an apical dendritic knob, a bipolar cell body for housekeeping functions and housing the genome, and an axon that traverses the cribriform plate (CP) to synapse in the OB. The cell bodies and dendrites of OSN are surrounded by support cells (brown). Basal cells (gray) are stem cells that generate the immature OSN (pale red, green, blue, or orange). (B) PR consist of rods for dim light vision (gray) and cones for bright light and color vision (red, green and blue). The major compartments of PRs are organized into four layers—outer segments (OS) for signal detection, inner segments (IS) for housekeeping functions, the nucleus in the outer nuclear layer (ONL) for housing the genome, and the synaptic terminal in the outer plexiform layer (OPL). PR are supported by retinal pigment epithelial (RPE) cells (black) and by Muller Glia (brown).