Fig. 1. Location and morphology of SGCs.

a | Position of the dorsal root ganglia (DRG) in the sensory pathways leading from the skin to the brain. A paravertebral sympathetic ganglion (SG) is also indicated. These ganglia innervate most organs, including blood vessels. b | Location of the trigeminal ganglion (asterisk) which innervates the face and teeth. The three divisions of the trigeminal ganglion are indicated as V1–V3. c | Low-power electron micrograph showing the neuron–satellite glial cell (SGC) units in a DRG. Neurons are labelled N1–N6, SGCs are coloured blue. The widened area in the SGC surrounding N3 contains the cell’s nucleus. ct, connective tissue space; v, blood vessels. Scale bar, 10 µm. d | Schematic of three patterns of grouping of sensory neurons. Top: neurons are separated by a connective tissue space (indicated by arrow), and each has its own SGC sheath. Middle: a cluster of two neurons that share a common SGC sheath and are separated by a SGC process. Bottom: a cluster where the neurons share a common SGC sheath, but without an intervening SGC process. e | Schematic of a sympathetic neuron covered with an SGC envelope. The SGCs (arrows) cover the synapses. SGC processes extend beyond the neuronal soma and ensheath an axon and a dendrite. Part c adapted with permission from ref.⁸⁶, Elsevier. Part e adapted with permission from ref.¹²⁷, Elsevier.