an anatomically isolated cluster of nerve cells (neurons), nerve fibers, and tissues, found in many invertebrates, all vertebrates, and man. In vertebrates, ganglia are located along the nerve stems.
Intervertebral ganglia, ganglia near the vertebrae, prevertebral ganglia, and ganglia enclosed in the thickness of the walls of the internal organs are topographically distinguished from each other. The intervertebral ganglia and similar ganglia are made up of sensory pseudo-unipolar neurons. Other ganglia are part of the peripheral sector of the autonomous nervous system and are mainly clusters of effector multipolar autonomous neurons, including sensory and association neurons. The clusters of neurons in each ganglion are surrounded by a layer of satellite cells, outside of which there is a thin capsule of connective tissue. Between the groups of neurons there are thicker connective tissue layers forming the connective tissue base, or stroma, of the ganglion. On the outside the ganglion is covered by a fibrous capsule, from which blood vessels reach the ganglion by way of the connective tissue layers. The synapses (nerve fibers that form the end, or terminal, contacts) lead to the bodies and branches of the autonomic neurons. In invertebrates, the ganglia arecoordinating centers carrying out the functions of a central nervous system. By means of reciprocal connections the ganglia in invertebrates form a single system that corresponds in its arrangement to the overall structure of their bodies.
IU. I. DENISOV-NIKOL’SKII