Three ganglia are usually described along the course of the sympathetic trunk in the cervical region, and in these ganglia ascending preganglionic sympathetic fibers from upper thoracic spinal cord levels synapse with postganglionic sympathetic fibers. The postganglionic sympathetic fibers are distributed in branches from these ganglia.
Superior cervical ganglion. A very large superior cervical ganglion in the area of cervical vertebrae CI and CII marks the superior extent of the sympathetic trunk (Figs. 8.193 and 8.194). Its branches pass to: the internal carotid and external carotid arteries, forming plexuses around these vessels, cervical spinal nerves C1 to C4 through gray rami communicantes, the pharynx, and the heart as superior cardiac nerves.
Middle cervical ganglion. A second ganglion inferior to the superior cervical ganglion along the course of the sympathetic trunk (the middle cervical ganglion) is encountered at about the level of cervical vertebra CVI (Figs. 8.193 and 8.194). Branches from this ganglion pass to: cervical spinal nerves C5 and C6 through gray rami communicantes, and the heart as middle cardiac nerves.
Inferior cervical ganglion. At the lower end of the cervical part of the sympathetic trunk is another ganglion (the inferior cervical ganglion), which becomes very large when it combines with the first thoracic ganglion and forms the cervicothoracic ganglion (stellate ganglion). The inferior cervical ganglion (Figs. 8.193 and 8.194) is anterior to the neck of rib I and the transverse process of cervical vertebra CVII, and posterior to the first part of the subclavian artery and the origin of the vertebral artery.
Branches from this ganglion pass to: spinal nerves C7 to T1 through gray rami communicantes, the vertebral artery, forming a plexus associated with this vessel, and the heart as inferior cardiac nerves.
This ganglion may also receive white rami communicantes from thoracic spinal nerve T1, and occasionally, from T2.
The thoracic duct is a major lymphatic channel that begins in the abdomen, passes superiorly through the thorax, and ends in the venous channels in the neck.
It passes through the lower thoracic cavity in the midline with: the thoracic aorta on the left, the azygos vein on the right, and the esophagus anteriorly.
At about the level of thoracic vertebra TV the thoracic duct passes to the left and continues to ascend just to the left of the esophagus. It passes through the superior mediastinum and enters the root of the neck to the left of the esophagus (Fig. 8.195). Arching laterally, it passes posterior to the carotid sheath and turns inferiorly in front of the thyrocervical trunk, the phrenic nerve, and the vertebral artery.
The thoracic duct terminates in the junction between the left internal jugular and the left subclavian veins (Fig. 8.195). Near its junction with the venous system it is joined by: the left jugular trunk, which drains lymph from the left side of the head and neck, the left subclavian trunk, which drains lymph from the left upper limb, and occasionally, the left bronchomediastinal trunk, which drains lymph from the left half of the thoracic structures (Fig. 8.196).
A similar confluence of three lymphatic trunks occurs on the right side of the body. Emptying into the junction between the right internal jugular and right subclavian veins are: the right jugular trunk from the head and neck, the right subclavian trunk from the right upper limb, and occasionally, the right bronchomediastinal trunk carrying lymph from the structures in the right half of the thoracic cavity and the right upper intercostal spaces (Fig. 8.196).