Description
Traveling lateral to the right and left sides of the vertebral column are the right and left sympathetic trunks. The sympathetic trunk begins bilaterally on the base of the skull, anterolateral to the atlas. These trunks exist as a pair of long, ganglionated nerve chains that extend from the base of the skull superiorly, to the coccyx inferiorly. Inferiorly, at the level of coccyx, the sympathetic trunks meet at a single midline ganglion, known as the ganglion impar.
The sympathetic chain ganglia (paravertebral ganglia) are located along the sympathetic trunk. They are divided into four groups based on the region of the vertebral column that they lie adjacent to. These are the cervical, thoracic, lumbar, and sacral paravertebral ganglia.
There are many branches to the sympathetic trunks. Firstly, there are branches that connect the sympathetic trunk to the spinal nerves. The white rami communicans are found connecting all spinal nerves (from the first thoracic nerve to the second lumbar nerve) to the sympathetic trunk. The gray rami communicantes are found at all vertebral levels and connect the sympathetic trunk to the spinal nerves.
Splanchnic nerves are fasciculated axons that leave the sympathetic trunk ganglia and travel to visceral tissues. The thoracic splanchnic nerves include the greater splanchnic nerve (fifth to ninth thoracic nerve levels), lesser splanchnic nerve (tenth and eleventh thoracic), and least splanchnic nerve (twelfth thoracic). The lumbar splanchnic nerves arise from the first and second lumbar ganglia. The sacral splanchnic nerves arise from sacral levels of the sympathetic trunk, but their axons originate at the twelfth thoracic, first lumbar, or second lumbar nerve levels.
A number of plexuses form from axons emerging from the sympathetic chain. The carotid and aortic plexuses form from axons emerging from the superior cervical ganglion. The cardiac, esophageal, and pulmonary plexuses form from axons emerging at thoracic levels.
The sympathetic trunk passes all sympathetic innervation to the body. Targets include blood vessels, sweat glands, and arrector pili muscles. Sympathetic innervation also targets visceral organs such as the heart, lungs, digestive system, kidneys, ovaries, and related fascial layers.
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Sympathetic Trunk
The sympathetic trunk is comprised of a chain of these paravertebral ganglia that traverse bilaterally on the anterolateral aspect of the vertebral bodies from the base of the skull to the coccyx where they converge to form a single, midline coccygeal ganglion (Ganglion of Impar, Ganglion of Warthon).
