Three Thoracic splanchnic nerves
Called ‘thoracic’ as they pass through the ganglia of the thoracic sympathetic trunk


Greater splanchnic nerve	Origin: Medial branches of thoracic sympathetic ganglia 5-9 Termination: Ganglia coeliaca, adrenal medulla Function: Sympathetic supply of foregut and adrenal medulla
Lesser splanchnic nerve	Origin: Medial branches of thoracic sympathetic ganglia 10-11 Termination: Aorticorenal/superior mesenteric ganglia Function: Sympathetic supply of the midgut
Least splanchnic nerve	Origin: Medial branches of thoracic sympathetic ganglia 11 and/or 12 Termination: Renal ganglia Function: Sympathetic supply of the kidneys

Greater splanchnic nerve

Formed by the medial branches of the 5th to 9th thoracic sympathetic ganglia.
Courses along the anterior surface of the spine and gives off branches to the descending aorta.
Then traverses the fibers of the ipsilateral crus of the diaphragm to enter the abdomen.
The majority of its fibers terminate by synapsing with the celiac ganglia, contributing to the celiac plexus. These fibers are involved in the control of the enteric nervous system of the foregut.
A small amount of fibers of the greater splanchnic nerve travels towards the ipsilateral suprarenal gland to innervate the adrenal medulla and stimulate the release of catecholamines (epinephrine and norepinephrine).

Lesser splanchnic nerve

The lesser splanchnic nerve originates from the medial branches of the 10th and 11th thoracic sympathetic ganglia.
Courses lateral and in parallel to the greater splanchnic nerves, over the anterior surface of the spine and enters the abdomen in the same manner - by traversing the ipsilateral diaphragmatic crus.
The lesser splanchnic nerves terminate by synapsing within the aorticorenal or superior mesenteric ganglia. The corresponding postsynaptic fibers then modulate the activity of the midgut.

The least splanchnic nerves originate from the medial branches of the 11th and/or the 12th thoracic sympathetic ganglia.
They travel lateral and parallel to the lesser splanchnic nerves, over the anterior surface of the spine, close to its lateral margin. It enters the abdomen by passing beneath the medial arcuate ligament and then joins the renal ganglia, contributing to the sympathetic innervation for the renal plexus.
The fibers of this nerve are sometimes joined by the lesser splanchnic nerve. In this case, the lesser splanchnic nerve gives off small branches to the renal ganglia.