Ganglioni

Ganglioni, or ganglia in English, are clusters of nerve cell bodies located outside the central nervous system. They function as processing and relay points for neural signals, notably sensory information and autonomic commands. A connective tissue capsule surrounds each ganglion, and it contains neuron cell bodies, glial satellite cells, blood vessels, and supporting stroma. Fibers connecting to the ganglion enter and exit via nerves or autonomic fibers.

Most ganglia are peripheral. Sensory ganglia, such as the dorsal root ganglia and cranial nerve ganglia, contain pseudounipolar sensory neurons whose peripheral and central processes connect to the peripheral tissue and the spinal cord or brainstem, respectively, with no synapses within the ganglion. Autonomic ganglia include sympathetic trunk ganglia and prevertebral (e.g., celiac, superior mesenteric, inferior mesenteric) ganglia, as well as parasympathetic terminal ganglia near or within target organs. In autonomic ganglia, preganglionic fibers synapse with postganglionic neurons; in sensory ganglia there are no synapses involved in signal transmission.

Developmentally and histologically, ganglionic neurons originate from neural crest cells. Neurons in the ganglia are typically surrounded by satellite glial cells; autonomic ganglia have a capsule and connective tissue framework that supports neuronal clusters and synaptic contacts between pre- and postganglionic neurons where appropriate.

In Italian usage, the term ganglioni can also refer to ganglion cysts, which are not true ganglia. Ganglion cysts are mucin-filled lesions near joints or tendon sheaths that arise from connective tissue and are generally clinically distinct from neural ganglia.