Abdominopelvic periarterial and hypogastric plexuses
Postganglionic · α1 sphincters α2 / β2 gut wall β1 renin
Postganglionic fibres leave the prevertebral ganglia as plexuses on the coeliac, mesenteric and renal arteries to reach the gut and kidney, and as the superior hypogastric plexus (in front of L5) whose hypogastric nerves descend to the pelvic viscera.
Traced from the start
- Sympathetic (thoracolumbar) outflow
- Intermediolateral cell column T1–L2 via white rami communicantes
- Prevertebral ganglia (coeliac, aorticorenal, superior and inferior mesenteric)
- Abdominopelvic periarterial and hypogastric plexuses
Detail
- Gut
- α2 on enteric cholinergic neurones inhibits acetylcholine release; β2 relaxes wall smooth muscle; α1 contracts pyloric, ileocaecal and internal anal sphincters; α1 constricts splanchnic vessels
- Kidney
- β1 on juxtaglomerular cells → renin release; α1 constricts afferent arterioles and increases proximal sodium reabsorption
- Pelvis
- Hypogastric nerves (T11–L2 origin) → α1 contraction of bladder neck, vas deferens, seminal vesicles and prostate; β3 relaxation of detrusor
When it goes wrong
Retroperitoneal lymph node dissection, aortoiliac surgery or anterior resection injuring the superior hypogastric plexus
Loss of emission and retrograde ejaculation from failure of α1-mediated bladder neck closure — erection is preserved because it is parasympathetic
Haemorrhagic shock or sepsis triggers massive splanchnic sympathetic discharge
Splanchnic vasoconstriction diverts blood to brain and heart; prolonged, it causes gut mucosal ischaemia and ileus
Practise this structure
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