Nerve supply of each segment of intestines
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Nerve Supply of Each Intestinal Segment
The intestines receive three types of innervation: sympathetic (extrinsic, inhibitory), parasympathetic (extrinsic, stimulatory), and enteric (intrinsic - the "brain of the gut"). These are organized by embryological origin: foregut, midgut, and hindgut.
Overview: Intrinsic (Enteric) Nervous System - Common to ALL Segments
Two plexuses run throughout the entire intestinal wall from esophagus to anus:
| Plexus | Location | Function |
|---|---|---|
| Myenteric plexus (Auerbach's) | Between circular and longitudinal muscle layers | Controls gut motility and peristalsis |
| Submucosal plexus (Meissner's) | In the submucosa (small & large intestine) | Controls secretion, absorption, blood flow |
The ENS can function independently of the CNS - peristalsis continues even after vagal or pelvic nerve severance. Extrinsic (sympathetic/parasympathetic) fibers connect with these intrinsic plexuses.
- Histology: A Text and Atlas, p. 991-992
1. Duodenum (Foregut - Midgut junction)
| Type | Supply |
|---|---|
| Parasympathetic | Vagus nerve (CN X) via celiac ganglion - stimulates secretion and motility |
| Sympathetic | Greater splanchnic nerve (T5-T9) → celiac ganglion → celiac plexus; also T6-T10 for proximal, SMA plexus for distal portion |
| Referred pain | Epigastrium (T5-T8) |
The proximal duodenum is supplied via the celiac axis (foregut), while the distal duodenum is supplied via the SMA (midgut). The nerve supply follows the same embryologic divide.
- Sabiston Textbook of Surgery, p. 1938
- S. Das Manual on Clinical Surgery, p. 456
2. Jejunum and Ileum (Midgut)
| Type | Supply |
|---|---|
| Parasympathetic | Vagus nerve (CN X) - traverses the celiac ganglion; stimulates motility, secretion, and all phases of bowel activity. Vagal afferents do NOT carry pain |
| Sympathetic | Three sets of splanchnic nerves (T5-T9, T10-T11) → ganglia in the plexus around the base of the superior mesenteric artery (SMA); motor impulses affect blood vessel motility, gut secretion, and motility |
| Pain afferents | General visceral afferent fibers of the sympathetic system |
| Referred pain | Jejunum: epigastrium (T5-T8) / Ileum & appendix: periumbilical (T9-T10) |
The nerve supply runs alongside the SMA branches into the mesentery, reaching the gut wall.
- Sabiston Textbook of Surgery, p. 1938
- S. Das Manual on Clinical Surgery, p. 456
3. Cecum and Appendix (Midgut)
| Type | Supply |
|---|---|
| Parasympathetic | Vagus nerve (CN X) |
| Sympathetic | SMA plexus (T10-T11) |
| Referred pain | Periumbilical (T9-T10) - classic early appendicitis pain location |
4. Ascending Colon and Right/Transverse Colon (Midgut)
| Type | Supply |
|---|---|
| Parasympathetic | Vagus nerve (CN X) - innervates up to approximately the splenic flexure (2/3 of transverse colon) |
| Sympathetic | Splanchnic nerves T6-T12, L1-L3 → SMA plexus; run parallel to the arteries |
| Referred pain | Periumbilical (same as small intestine - supplied by SMA) |
- Schwartz's Principles of Surgery, 11th Ed., p. 951
- Bailey & Love's Short Practice of Surgery, 28th Ed., p. 1375
5. Descending Colon, Sigmoid Colon (Hindgut)
| Type | Supply |
|---|---|
| Parasympathetic | Pelvic splanchnic nerves (nervi erigentes), S2-S4 |
| Sympathetic | Splanchnic nerves (L1-L3) → inferior mesenteric artery (IMA) plexus; run parallel to the arteries |
| Referred pain | Hypogastrium/suprapubic region (T11-T12, L1-L2) |
- Schwartz's Principles of Surgery, 11th Ed., p. 951
- Bailey & Love's Short Practice of Surgery, 28th Ed., p. 1375
6. Rectum (Hindgut)
| Type | Supply |
|---|---|
| Parasympathetic | Sacral parasympathetics (S2-S4) via pelvic splanchnic nerves - pass via the inferior hypogastric plexus |
| Sympathetic | Lumbar splanchnics (L1-L3) → superior hypogastric plexus → inferior hypogastric plexus |
| Somatic (anal sphincter) | Inferior rectal nerve (branch of pudendal nerve, S2-S4) - sensory to anal skin, motor to external sphincter |
The sympathetic supply is excitatory to the internal anal sphincter; parasympathetic supply is inhibitory (allows relaxation during defecation).
- Color Atlas of Human Anatomy Vol. 2, p. 351
- Goldman-Cecil Medicine
7. Anal Canal
| Region | Nerve Supply |
|---|---|
| Above dentate line (endoderm) | Autonomic (visceral) - insensitive to pain, touch; responds to stretch |
| Below dentate line (ectoderm) | Somatic - inferior rectal nerve (pudendal, S2-S4); sensitive to pain, temperature, touch |
| Internal sphincter | Sympathetic (excitatory) + Parasympathetic (inhibitory, involuntary) |
| External sphincter | Pudendal nerve (S2-S4) - voluntary control |
| Puborectalis | Sacral somatic nerves - maintains anorectal angle |
- Color Atlas of Human Anatomy Vol. 2, p. 351
- Sleisenger & Fordtran's GI and Liver Disease
Quick Reference Summary Table
| Segment | Sympathetic | Parasympathetic | Referred Pain |
|---|---|---|---|
| Duodenum (proximal) | Celiac plexus (T5-T9) | Vagus (CN X) | Epigastrium |
| Duodenum (distal) | SMA plexus (T10) | Vagus (CN X) | Epigastrium |
| Jejunum | SMA plexus (T5-T9) | Vagus (CN X) | Epigastrium (T5-T8) |
| Ileum / Appendix | SMA plexus (T10-T11) | Vagus (CN X) | Periumbilical (T9-T10) |
| Cecum / Ascending colon | SMA plexus (T10-T12) | Vagus (CN X) | Periumbilical |
| Transverse colon | SMA plexus (T10-T12) | Vagus (CN X) | Periumbilical |
| Descending / Sigmoid | IMA plexus (L1-L3) | Pelvic splanchnics (S2-S4) | Hypogastrium (T11-L2) |
| Rectum | Lumbar splanchnics (L1-L3) | Pelvic splanchnics (S2-S4) | Suprapubic / perineal |
| Anal canal (above dentate) | Autonomic | Autonomic | Visceral (stretch only) |
| Anal canal (below dentate) | Pudendal (somatic) | Pudendal (somatic) | Well-localized pain |
Key Clinical Points
- Midgut-hindgut watershed at the splenic flexure - the divide between vagal (proximal) and pelvic (distal) parasympathetic supply. Important in Hirschsprung's disease and during rectal surgery.
- Pain localization follows sympathetic (not vagal) afferents - vagal afferents do not carry pain.
- Nervi erigentes (pelvic splanchnics, S2-S4) supply all hindgut - damage during rectal surgery or APR can cause bladder dysfunction and sexual dysfunction.
- Enteric nervous system is autonomous - gut motility continues after extrinsic denervation. However, loss of intrinsic ganglia (as in Hirschsprung's disease, affecting the ENS) causes functional obstruction.
- Referred pain segmental levels: Stomach/duodenum/jejunum = T5-T8 (epigastric); Ileum/appendix = T9-T10 (umbilical); Colon = T11-T12/L1-L2 (hypogastric).
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