Thoracic Cardiac Nerves
Thoracic Greater Splanchnic Nerve
Thoracic Lesser Splanchnic Nerve
Thoracic Least Splanchnic Nerve
Upper Lumbar Splanchnic Nerve
Lower Lumbar Splanchnic Nerve
Preganglionic nerve fibers arise from intermediolateral horn cells (T1-T12, L1-L2) and synapse with postganglionic cell bodies in chain (paravertebral) ganglia or prevertebral ganglia of the mesenteric plexuses. The Splanchnic nerves are named for their level of departure from the medial aspect of the sympathetic chain. Although the splanchnic nerves appear to be branches of thoracic ganglia, they represent fibers of preganglionic horn cells that merely pass through paravertebral ganglia and the sympathetic trunk en route to the celiac and mesenteric ganglia. Thus the splanchnic nerves correspond to white rami comminicantes. Direct branches from the upper four or five thoracic ganglia go to the cardiac plexuses as the Thoracic Cardiac nerves T1-T4. The first thoracic ganglion, and frequently the second, contributes to the brachial plexus through the first thoracic nerve. The Thoracic Greater Splanchic nerve T5-T9 sends fibers to the celiac-superior mesenteric ganglia. The Thoracic Lesser Splanchnic nerve T10-T11 sends fibers to the aorticorenal ganglion. The Thoracic Least Splanchnic nerve T12 sends fibers to the renal plexus. The two Upper Lumbar Splanchnic nerves end primarily in the Intermesenteric Plexus. The lumbar splanchnic nerves of the right side pass behind the inferior vena cava to reach the intermesenteric plexus. The two Lower Lumbar Splanchnic nerves pass either anterior or posterior to the common iliac vessels and contribute to the superior hypogastric plexus. The lumbar splanchic nerves provide the Sympathetic Innervation for the pelvic viscera and the distal part of the large intestine.
The preganglionic fibers supplying the lower limb are derived from the lower three thoracic and upper two lumbar cord segments. They reach the lower thoracic and upper lumbar ganglia via white rami communicantes, while some fibers pass down the sympathetic trunk to synapse in the lumbar ganglia. Lumbar postganglionic fibers pass to the femoral nerve and distribute with the branches of the femoral artery. Other preganglionic fibers descend in the sympathetic trunk to synapse in the upper two or three sacral ganglia. Lumbar and sacral postganglionic fibers pass to the tibial nerve and distribute with the branches of the popliteal artery.
Removing the upper three lumbar ganglia and the intervening parts of the sympathetic
trunk produces sympathetic denervation of the vessels of the lower limb. Thoracosympathectomy
has been replaced by administration of central or peripheral acting sympathetic