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Sympathetic Trunk

Q: What specific branches arise from the superior cervical ganglion of the sympathetic trunk?

The superior cervical ganglion gives rise to: Superior cervical cardiac nerve (n. cardiacus cervicalis superior) — descends along the carotid sheath.Internal carotid nerve (n. caroticus internus) — enters the cranial cavity. Additionally, the superior cervical ganglion communicates with the vagus nerve, glossopharyngeal nerve, and the cervical plexus of spinal nerves.

Q: Which nerves comprise the group of thoracic splanchnic nerves?

The thoracic splanchnic nerves (nn. splanchnici thoracici) include the greater and lesser splanchnic nerves. Greater splanchnic nerve (n. splanchnicus major) — formed from the V–IX thoracic sympathetic trunk ganglia.Lesser splanchnic nerve (n. splanchnicus minor) — arises from the X–XI thoracic ganglia. These nerves travel along the lateral surface of the thoracic vertebral bodies through the crura of the diaphragm to reach the celiac plexus ganglia.

Q: Where is the stellate (cervicothoracic) ganglion located topographically?

The stellate, or cervicothoracic, ganglion (ganglion cervicothoracicum s. stellatum) is located in the deep region of the neck, specifically within the scalenovertebral triangle (trigonum scalenovertebrale). The ganglion lies deep to the prevertebral (fifth) fascia of the neck. The boundaries of this space are: medially — longus colli muscle (m. longus colli);laterally — anterior scalene muscle (m. scalenus anterior);base — suprapleural membrane (dome of the pleura);apex — transverse process of the sixth cervical vertebra.

Q: From which segments do white communicating rami arise?

White communicating rami (rr. communicantes albi) arise from spinal nerves at the Th1 to L2 levels.

Truncus sympathicus

For medical students2 min readUpdated 2026-10-10

The sympathetic trunk (truncus sympathicus) is a chain of nerve ganglia connected sequentially by interganglion branches (rr. interganglionares). It is a crucial component of the autonomic nervous system, responsible for distributing sympathetic fibers to spinal nerves, visceral organs, and vascular plexuses.

Trunk BasisGanglia consist of clusters of postsynaptic (postganglionic) neurons

VariabilityThe number of ganglia is variable, especially in the cervical and lumbar regions

ConnectionsGray communicating rami arise from absolutely all trunk ganglia

Cervical RegionCompletely devoid of white communicating rami

Classification of Sympathetic Trunk Ganglia

Topographically, the sympathetic trunk is divided into several parts. The ganglia themselves represent clusters of postsynaptic (postganglionic) neuron cell bodies. The number of these ganglia exhibits individual variability (particularly in the cervical and lumbar regions).

Main groups of trunk ganglia:

Cervical ganglia — ganglia cervicalia
Thoracic ganglia — ganglia thoracica
Lumbar ganglia — ganglia lumbalia
Sacral ganglia — ganglia sacralia
Ganglion impar — an unpaired coccygeal ganglion that caudally unites the sympathetic chains of both sides.

Connecting Branches (Rami communicantes)

To exchange fibers with spinal nerves, the sympathetic trunk utilizes specialized communicating branches. They are divided into two types based on their structure and fiber direction.

White communicating rami (rr. communicantes albi) These serve as "input" pathways to the sympathetic trunk.

Arise only from a limited number of spinal nerves: specifically from Th1 to L2 levels.
Contain presynaptic (preganglionic) myelinated fibers (myelin gives them their white appearance).
Project directly to the ganglia of the sympathetic trunk.

Gray communicating rami (rr. communicantes grisei) These serve as "output" pathways.

Arise from all trunk ganglia without exception.
Contain postsynaptic (postganglionic) unmyelinated fibers.
Return to the spinal nerves, subsequently distributing via their branches to innervate skin structures, blood vessels, and sweat glands.

Fiber Course and Visceral Branches

Upon entering a sympathetic trunk ganglion, presynaptic fibers may follow one of three pathways:

Synapse — synapse on neurons within that specific ganglion.
Truncal transit — ascend or descend via interganglionic branches to reach other sympathetic trunk ganglia.
Peripheral transit — pass through the ganglion without synapsing, continuing toward visceral ganglia and plexuses.

From the ganglia and the trunk itself, visceral branches extend to internal organs as well as vascular and organ plexuses (plexus). Major splanchnic nerves play a special role by carrying predominantly presynaptic fibers to prevertebral ganglia:

Thoracic splanchnic nerves (nn. splanchnici thoracici)
Lumbar splanchnic nerves (nn. splanchnici lumbales)
Sacral splanchnic nerves (nn. splanchnici sacrales)

Characteristics of the Cervical Region

The cervical portion of the sympathetic trunk possesses several unique features. It typically features three ganglia:

Superior cervical ganglion (ganglion cervicale superius)
Middle cervical ganglion (ganglion cervicale medium)
Cervicothoracic, or stellate ganglion (ganglion cervicothoracicum / stellatum)

The primary topographical feature of the cervical region is the absence of white communicating rami (as they terminate at the Th1 level). Branches arising from the cervical ganglia project primarily to the vessels of the head and neck, and descend to thoracic cavity organs, playing an active role in forming the carotid and cardiac autonomic plexuses.

Mnemonic

White rami are the "INPUT" to the trunk (found only where spinal cord lateral horns exist: Th1–L2). Gray rami are the "OUTPUT" from the trunk (present at all ganglia to return fibers back to the spinal nerves).

Frequently asked questions

What specific branches arise from the superior cervical ganglion of the sympathetic trunk?

The superior cervical ganglion gives rise to:

Superior cervical cardiac nerve (n. cardiacus cervicalis superior) — descends along the carotid sheath.
Internal carotid nerve (n. caroticus internus) — enters the cranial cavity.

Additionally, the superior cervical ganglion communicates with the vagus nerve, glossopharyngeal nerve, and the cervical plexus of spinal nerves.

Which nerves comprise the group of thoracic splanchnic nerves?

The thoracic splanchnic nerves (nn. splanchnici thoracici) include the greater and lesser splanchnic nerves.

Greater splanchnic nerve (n. splanchnicus major) — formed from the V–IX thoracic sympathetic trunk ganglia.
Lesser splanchnic nerve (n. splanchnicus minor) — arises from the X–XI thoracic ganglia.

These nerves travel along the lateral surface of the thoracic vertebral bodies through the crura of the diaphragm to reach the celiac plexus ganglia.

Where is the stellate (cervicothoracic) ganglion located topographically?

The stellate, or cervicothoracic, ganglion (ganglion cervicothoracicum s. stellatum) is located in the deep region of the neck, specifically within the scalenovertebral triangle (trigonum scalenovertebrale).

The ganglion lies deep to the prevertebral (fifth) fascia of the neck. The boundaries of this space are:

medially — longus colli muscle (m. longus colli);
laterally — anterior scalene muscle (m. scalenus anterior);
base — suprapleural membrane (dome of the pleura);
apex — transverse process of the sixth cervical vertebra.

Which prevertebral ganglia receive presynaptic fibers from the splanchnic nerves?

Presynaptic fibers from the splanchnic nerves project to prevertebral ganglia and plexuses, notably:

to the celiac plexus ganglia — fibers of the greater and lesser splanchnic nerves;
to the aortorenal ganglion — branches of the lesser splanchnic nerve.

What do the sympathetic trunk ganglia consist of?

The ganglia of the sympathetic trunk contain the cell bodies of postsynaptic (postganglionic) neurons, where presynaptic fibers can synapse.

From which segments do white communicating rami arise?

White communicating rami (rr. communicantes albi) arise from spinal nerves at the Th1 to L2 levels.

What is the main difference between gray and white communicating rami?

Gray rami contain postsynaptic unmyelinated fibers and arise from all trunk ganglia. White rami contain presynaptic myelinated fibers and are present only at the Th1–L2 levels.

What is the function of gray communicating rami?

They return postsynaptic fibers to the spinal nerves for subsequent sympathetic innervation of the skin, blood vessels, and sweat glands.

Go deeper

Topography and structure of the cervicothoracic (stellate) ganglion
Formation of carotid plexuses by cervical trunk branches
Participation of sympathetic trunk branches in cardiac plexuses
Course and distribution of thoracic splanchnic nerves (nn. splanchnici thoracici)