Splanchnic nerves !
The splanchnic nerves carry sympathetic (fight-or-flight) nerve fibres from the spinal cord to the abdominal organs and the adrenal glands.
Official name: Greater thoracic splanchnic nerve
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What it is
Nerves from the thoracic sympathetic chain that pass through the diaphragm to the celiac ganglia.
What it does
Carry pain signals from the abdominal organs; this is why organ pain is felt vaguely in the middle of the abdomen at first.
Key facts
- Roots
- Thoracic: greater T5–T9 (some texts: T5–T10 or T7–T9), lesser T10–T11, least T12; lumbar L1–L2; pelvic S2–S4 (parasympathetic)
- Moves
- Thoracic/lumbar: preganglionic sympathetic to celiac, aorticorenal and mesenteric ganglia and adrenal medulla; pelvic: parasympathetic to hindgut and pelvic organs
- Feeling from
- Visceral pain afferents run with them: foregut felt in epigastrium, midgut around umbilicus, hindgut in hypogastrium
Relations
- Course
- The greater splanchnic nerve forms from branches of the T5–T9 ganglia, runs down on the sides of the thoracic vertebral bodies, pierces the crus of the diaphragm and ends in the celiac ganglion; the lesser reaches the aorticorenal ganglion, the least the renal plexus; some texts: the lesser ends in the celiac ganglion and the least in the aorticorenal ganglion
- In front
- In the thorax, the parietal pleura: they are seen through it at thoracoscopy
- Medial
- Azygos vein on the right; hemiazygos vein and descending aorta on the left
- Lateral
- The thoracic sympathetic trunk from which they arise
How to find it
At thoracoscopy they show through the parietal pleura as white cords on the sides of the lower thoracic vertebral bodies, medial to the sympathetic trunk. In the abdomen they are found where they pierce the crura, behind the celiac ganglia.
On imaging
Not seen on routine imaging. The thoracic splanchnic nerves run along the sides of the lower thoracic vertebral bodies and pierce the diaphragmatic crura to reach the celiac ganglia, so the crura, the celiac trunk and the vertebral bodies are the landmarks. CT or endoscopic ultrasound guides celiac plexus or splanchnic nerve blocks for pain from pancreatic cancer.
Common problems
- Pain from pancreatic cancer can be eased by blocking it with an injection (celiac plexus block).
Clinical notes
- Thoracoscopic splanchnicectomy, or a block or radiofrequency treatment behind the crura, is an option for severe pancreatic cancer or chronic pancreatitis pain
- A retrocrural celiac block actually targets the splanchnic nerves before they reach the ganglia
- Referred pain explains why appendicitis begins around the umbilicus and gallbladder pain in the epigastrium
Anatomical variants
- Root levels vary widely, and recent dissections question the classic textbook levels
- The least splanchnic nerve is inconstant; a small splanchnic ganglion on the greater splanchnic nerve is present in some people
Memory aid
Pelvic splanchnics are Parasympathetic: P for P. Every other splanchnic nerve is sympathetic.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
What are the root levels of the thoracic splanchnic nerves?
Greater T5–T9, lesser T10–T11, least T12 (some texts give the greater as T5–T10).
Where do the preganglionic fibres of the thoracic and lumbar splanchnic nerves synapse?
They pass through the sympathetic trunk without synapsing and synapse in prevertebral ganglia: celiac, aorticorenal and mesenteric.
Which sympathetic preganglionic fibres synapse without a ganglion?
Those to the adrenal medulla, which synapse directly on its cells; the medullary cells act as the postganglionic neurons.
Which splanchnic nerves are parasympathetic?
Only the pelvic splanchnic nerves (S2–S4); sacral splanchnic nerves, like all other splanchnics, are sympathetic.
Where is visceral pain from the foregut, midgut and hindgut felt?
Foregut in the epigastrium, midgut around the umbilicus, hindgut above the pubis; the pain afferents run back with the splanchnic nerves.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- nervus splanchnicus thoracicus major; nervus splanchnicus thoracicus minor TA2 6631
- Official Spanish (DeCS)
- Nervios esplácnicos DeCS D013153
- English (TA2)
- Greater thoracic splanchnic nerve
- Also called
- greater splanchnic nerve · lesser splanchnic nerve
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Abdomen and Pelvis, Splanchnic Nerves; Anatomía humana (4.ª ed.), tomo 1, cap. 41: Porción simpática.
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Representative model, for educational purposes only.
