Ganglia
Tharaka Dunuwila MD, PhD
• Ovoid structures containing
neuronal cell bodies and their
surrounding glial satellite cells
supported by delicate
connective tissue and
surrounded by a denser
capsule.
• They serve as relay stations to
transmit nerve impulses - at
least one nerve enters and
another exits from each
ganglion.
Ganglia
• The direction of the nerve
impulse determines whether
the ganglion will be a sensory
or an autonomic ganglion.
Sensory
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Receiving afferent impulses
Associated with cranial and spinal nerves
Associated with small glial satellite cells
Supported by connective tissue capsule
Pseudounipolar neurons
Sensory Ganglia
• A sensory ganglion (G) has a distinct connective tissue capsule (C) and internal framework continuous with the
epineurium and other components of peripheral nerves, except that no perineurium is present and that there is no
blood-nerve barrier function. Fascicles of nerve fibers (F) enter and leave these ganglia. (X56; Kluver-Barrera stain)
Autonomic
Two-neuron circuit of autonomic nerves
• Preganglionic
• Sympathetic - in thoracic and lumbar regions of spinal cord
• Parasympathetic - in medulla, midbrain and in sacral region of spinal cord
• Postganglionic
• Sympathetic - in small ganglia near vertebral column
• Parasympathetic - near effector organ
This small parasympathetic
ganglion was found within
the body of the tongue, in
association with the
minor salivary glands which it
innervates.
Each nerve cell body is quite
conspicuous, with relatively
basophilic cytoplasm, with a
large round euchromatic
nucleus, and with a single
prominent nucleolus.
The many smaller nuclei
associated with this ganglion
belong to satellite cells and
Schwann cells, as well as
fibroblasts of the surrounding
connective tissue.
• The muscularis externa consists
of smooth muscle fibers
arranged into two layers. The
layer of circular muscle fibers
(cut in longitudinal section)
appears at the upper left, while
the layer of longitudinal muscle
fibers (cut in cross section)
appears at lower right.
• In between the two layers of
muscle lies the myenteric nerve
plexus, an interconnected
network of parasympathetic
ganglia which is also called
"Auerbach's plexus"
• In routine histological
specimens, the ganglia (small
clusters of nerve cell bodies) are
the only noticeable feature of
Auerbach's plexus.