Splanchnic and portal circulation !
- Regulation
- Exam priority: medium
Blood from the gut, spleen and pancreas passes through the liver first via the portal vein; it is a large reservoir the body can mobilize.
Updated 2026-11-01
Also called: Mesenteric circulation, Hepatic portal system
See it in 3D: Celiac trunk · Superior mesenteric artery · Inferior mesenteric artery · Portal vein · Splenic vein · Mesenteric veins · Hepatic veins · Proper hepatic artery · Liver
What it is
The splanchnic circulation supplies the stomach, intestines, spleen, pancreas and liver, and receives ≈25% of resting cardiac output. All venous blood from the abdominal gut and spleen converges on the portal vein and crosses the hepatic sinusoids before returning to the heart, so the liver filters and processes what was absorbed. In shock, sympathetic nerves constrict this bed and shift blood toward the heart and brain.
Key facts
- In the villi, arteriole and venule run in opposite directions: countercurrent O₂ exchange leaves the villus tip relatively hypoxic, and it is the first part damaged in shock.
- Three trunks: celiac trunk (foregut), superior mesenteric artery (midgut) and inferior mesenteric artery (hindgut).
- The portal vein forms where the superior mesenteric and splenic veins join, behind the neck of the pancreas.
Regulation
- +Metabolites and absorbed nutrients (adenosine, CO₂, fatty acids, glucose): Local vasodilation after a meal
- +Gut hormones (CCK, VIP, gastrin, secretin) and bradykinin: Raise flow to the active mucosa
- −Sympathetic (α1 receptors): Strong vasoconstriction: mobilizes ≈200–400 mL or more of splanchnic blood into the central circulation
- −Angiotensin II and vasopressin: Constrict the splanchnic bed in hypovolemia
Clinical notes
- Acute mesenteric ischemia: severe abdominal pain out of proportion to a near-normal examination; cardiac embolism (atrial fibrillation) is a classic cause.
- Cirrhosis: fibrosis raises intrahepatic resistance, and splanchnic vasodilation raises portal inflow: both raise portal pressure.
- Non-selective beta-blockers reduce portal inflow (lower cardiac output and splanchnic vasoconstriction from β2 blockade).
- In shock, mucosal ischemia breaks the barrier and favours bacterial translocation.
Test yourself
Think of the answer, then tap the question to see it.
Why is the splenic flexure of the colon vulnerable to ischemia?
It is a watershed between the superior and inferior mesenteric territories with poor anastomoses; when perfusion falls it is the first to lose enough flow.
How does the liver compensate for a fall in portal flow?
Through the hepatic arterial buffer response: adenosine is no longer washed out, builds up around hepatic arterioles, the hepatic artery dilates and its supply rises.
What hepatic venous pressure gradient marks clinically significant portal hypertension, and what complication does it herald?
A gradient ≥ 10 mmHg (normal 1–5). It heralds varices and decompensation; from ≈12 mmHg the risk of variceal bleeding rises.
Why does the splanchnic bed matter in the response to hemorrhage?
It holds a large volume of venous blood; sympathetic constriction, angiotensin II and vasopressin squeeze it and shift that blood toward the heart, supporting venous return.
See it in 3D
The structures of Durgical's 3D anatomy where it happens.
- Celiac trunk
- Superior mesenteric artery
- Inferior mesenteric artery
- Portal vein
- Splenic vein
- Mesenteric veins
- Hepatic veins
- Proper hepatic artery
- Liver
Related topics
- Functions of the liver
- Shock physiology
- Local and humoral control of blood flow
- Nervous control of the circulation and the CNS ischemic response
- How edema forms
- The enteric nervous system, slow waves and GI control
Related conditions
- Acute mesenteric ischaemia
- Portal hypertension
- Cirrhosis
- Upper gastrointestinal bleeding
- Haemorrhoids
- Hypovolaemic shock
In Pharmacology
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: Anatomy, Abdomen and Pelvis, Portal Venous System (Hepatic Portal System) (StatPearls (NCBI Bookshelf), 2024); Portal Hypertension (StatPearls (NCBI Bookshelf), 2024); Acute Mesenteric Ischemia (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 63). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).
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Representative model, for educational purposes only.