Enhance your knowledge with our comprehensive guide and curated study materials.
Three major ventral branches of the abdominal aorta supply the gut:
Coeliac trunk → foregut
Superior mesenteric artery (SMA) → midgut
Inferior mesenteric artery (IMA) → hindgut
There are rich anastomoses among their terminal branches, ensuring collateral flow.
Arises from the front of the abdominal aorta just below the aortic opening of the diaphragm (disc between T12 and L1).
About 1.25 cm long, divides into three branches:
Left gastric artery
Common hepatic artery
Splenic artery
Supplies all foregut derivatives in the abdomen:
Lower end of oesophagus
Stomach
Proximal duodenum (up to bile-duct opening)
Liver
Spleen
Greater part of pancreas
Surrounded by the coeliac plexus.
Anteriorly: lesser sac, lesser omentum
Right side: right crus, right coeliac ganglion, caudate process of liver
Left side: left crus, left coeliac ganglion, cardiac end of stomach
Inferiorly: body of pancreas and splenic vein
Arises from abdominal aorta at L1, 1 cm below the coeliac trunk.
Runs downward and forward between pancreas and third part of duodenum, then between two layers of mesentery to reach the right iliac fossa, where it ends by anastomosing with the ileocolic artery.
(A) Left side → jejunal and ileal branches forming arterial arcades within the mesentery.
(B) Right side →
Inferior pancreaticoduodenal artery – anastomoses with superior counterpart.
Middle colic artery – to transverse colon.
Right colic artery – to ascending colon.
Ileocolic artery – to terminal ileum, caecum, appendix (via appendicular branch).
Anteriorly: pancreas, splenic vein, root of mesentery.
Posteriorly: left renal vein, third part of duodenum, aorta.
On right: superior mesenteric vein.
Lies to the right of the artery; ascends behind pancreas.
Tributaries: veins corresponding to SMA branches + right gastroepiploic + inferior pancreaticoduodenal veins.
Unites with splenic vein behind the neck of pancreas → forms portal vein
Volume 2, BD Chaurasia’s Human …
.Identify the short coeliac trunk at the T12–L1 level.
Trace its three branches and their divisions.
Clean the SMA and its branches on both sides; trace up to organs supplied.
Identify the inferior mesenteric artery (at L3) and follow its left colic, sigmoid, and superior rectal branches.
Demonstrate the portal vein formation posterior to the pancreas.
Superior Mesenteric Artery Syndrome (Wilkie’s syndrome):
The third part of the duodenum may be compressed between aorta and SMA, producing duodenal obstruction — “nut-cracker” effect
Volume 2, BD Chaurasia’s Human …
.Mesenteric Ischaemia:
Sudden occlusion (embolus/thrombosis) of SMA or SMV → haemorrhagic infarction and rapidly spreading obstruction.
Jejunal Diverticulosis:
Acquired diverticula occur along mesenteric border where vasa recta penetrate, due to weak longitudinal muscle coat.
Aneurysm of Coeliac Trunk:
May compress coeliac plexus, producing epigastric pain radiating to the back.
Portal Venous Thrombosis:
Thrombosis of splenic + SMV + portal veins → portal hypertension, splenomegaly, varices.
| Artery | Level | Supplies | Key Branches |
|---|---|---|---|
| Coeliac trunk | T12 | Foregut | Left gastric, common hepatic, splenic |
| SMA | L1 | Midgut | Inferior pancreaticoduodenal, middle/right colic, ileocolic, jejunal & ileal |
| IMA | L3 | Hindgut | Left colic, sigmoid, superior rectal |
Arises from the front of the abdominal aorta at the level of the third lumbar vertebra (L3), 3–4 cm above the aortic bifurcation.
It originates behind the third part of the duodenum.
Descends downward and to the left, behind the peritoneum.
Crosses the left common iliac artery medial to the left ureter.
Continues in the sigmoid mesocolon as the superior rectal artery.
Supplies all hindgut derivatives, including:
Left one-third of transverse colon
Descending colon
Sigmoid colon
Rectum
Upper part of the anal canal (above anal valves)
Left Colic Artery
Ascending branch anastomoses with the middle colic artery (from SMA).
Descending branch joins sigmoid arteries.
Supplies the descending colon and the distal transverse colon.
Sigmoid Arteries
2–4 branches descending obliquely to the sigmoid colon.
Anastomose among themselves to form the lower part of the marginal artery.
The lowest sigmoid branch connects with the superior rectal artery
Volume 2, BD Chaurasia’s Human …
.Superior Rectal Artery
Continuation of the IMA beyond the root of the sigmoid mesocolon.
Descends in the mesocolon, crosses the left common iliac vessels, and divides opposite S3 vertebra into right and left branches.
These branches supply the rectum and anastomose with middle and inferior rectal arteries forming a rectal arterial plexus
Volume 2, BD Chaurasia’s Human …
.Begins as the superior rectal vein from the upper internal rectal venous plexus.
Receives blood from rectum, anal canal, sigmoid colon, and descending colon.
Longer than the artery; ascends behind the peritoneum.
Crosses the left common iliac vessels, lies lateral to IMA, and ascends behind the pancreas.
Passes lateral to the duodenojejunal flexure within the paraduodenal fold.
Opens into the splenic vein, which then joins the superior mesenteric vein to form the portal vein
Volume 2, BD Chaurasia’s Human …
.Veins corresponding to the branches of IMA:
Left colic vein
Sigmoid veins
Superior rectal vein
Volume 2, BD Chaurasia’s Human …
.Inferior Mesenteric Vein in Surgery
Lies in the free margin of the paraduodenal fold; during surgery for internal hernia at the duodenojejunal recess, this fold may need to be incised.
Important to note: the vein, not the artery, lies in the fold — it must be ligated carefully to avoid hemorrhage
Volume 2, BD Chaurasia’s Human …
.Marginal Artery of Drummond
Formed by anastomoses between ileocolic, right colic, middle colic, left colic, and sigmoid arteries.
Lies 2.5–3.8 cm from the colon and provides collateral circulation if one of the main arteries is blocked
Volume 2, BD Chaurasia’s Human …
.Sudeck’s Critical Point
The weak anastomotic zone between last sigmoid artery and superior rectal artery.
Prone to ischemia after surgical ligation of IMA or in low-flow states.
Ischaemic Colitis
Often affects the splenic flexure (watershed area between SMA and IMA) and Sudeck’s point due to poor collateral circulation.
| Feature | Inferior Mesenteric Artery | Inferior Mesenteric Vein |
|---|---|---|
| Origin | Aorta at L3 | Superior rectal venous plexus |
| Termination | Superior rectal artery | Splenic vein |
| Main Branches | Left colic, sigmoid, superior rectal | Left colic, sigmoid, superior rectal veins |
| Supplies/Drains | Hindgut derivatives | Corresponding regions |
| Surgical Note | Lies retroperitoneally | Lies in paraduodenal fold |
Definition:
A continuous arterial arcade running along the inner concavity of the colon, connecting the colic branches of the superior and inferior mesenteric arteries.
Formation:
Formed by the anastomosis of:
Ileocolic artery
Right colic artery
Middle colic artery
Left colic artery
Sigmoid arteries
Course:
Lies 2.5–3.8 cm from the colon wall; closest to the bowel in the descending and sigmoid colon.
Branches:
Gives rise to vasa recta, straight arteries entering the colon wall alternately on both sides.
Functional Importance:
Maintains collateral circulation between SMA and IMA territories. Even if one main trunk is obstructed, the marginal artery maintains perfusion to the colon.
Surgical Note:
At the junctions of its component vessels (especially between middle and left colic, and between sigmoid and superior rectal arteries), anastomoses may be weak.
These weak points are called Sudeck’s critical points, prone to ischemia after IMA ligation.
Definition:
A large vein that collects blood from the gastrointestinal tract and associated organs (from lower oesophagus to upper anal canal, pancreas, spleen, and gallbladder) and carries it to the liver.
Formed by the union of the superior mesenteric vein (SMV) and splenic vein
Occurs behind the neck of the pancreas at the level of L2 vertebra.
The inferior mesenteric vein (IMV) drains into the splenic vein before this junction.
Infra-duodenal part: behind the neck of pancreas.
Retroduodenal part: behind the first part of the duodenum.
Supraduodenal part: within the right free margin of the lesser omentum, anterior to the epiploic foramen (of Winslow).
Ends by dividing into right and left branches at the porta hepatis of the liver.
Splenic vein
Superior mesenteric vein
Left and right gastric veins
Cystic vein (from gallbladder)
Paraumbilical veins
Superior pancreaticoduodenal veins
Note:
Portal blood flow shows “streamline flow” —
SMV blood → right hepatic lobe
Splenic + IMV blood → left hepatic lobe
Sites where portal and systemic venous channels communicate — clinically vital because they become enlarged in portal hypertension.
| Site | Portal Vein Tributary | Systemic Vein Communication | Clinical Feature |
|---|---|---|---|
| Lower end of oesophagus | Left gastric vein | Azygos vein | Oesophageal varices |
| Anal canal (upper part) | Superior rectal vein | Middle & inferior rectal veins | Haemorrhoids |
| Umbilicus | Paraumbilical veins | Superficial epigastric veins | Caput medusae |
| Bare area of liver | Hepatic veins | Diaphragmatic veins | Silent anastomosis |
| Retroperitoneal colon | Colic veins | Lumbar veins | Retroperitoneal varices |
1. Portal Hypertension
Caused by obstruction to portal flow (e.g., cirrhosis, thrombosis, or compression).
Leads to raised portal pressure and dilatation of the portosystemic channels.
Manifestations:
Oesophageal varices → haematemesis
Caput medusae around umbilicus
Haemorrhoids
Splenomegaly and ascites
2. Caput Medusae
Radiating tortuous veins around the umbilicus due to engorged paraumbilical and superficial epigastric veins.
Named after Medusa’s head in Greek myth.
3. Surgical Importance
Portocaval shunts (e.g., splenorenal or mesocaval anastomoses) are created to divert portal blood into systemic circulation and reduce portal pressure.
4. Portal Vein Thrombosis
May follow inflammation, pancreatitis, or infection; results in portal hypertension without cirrhosis.
5. Varices Rupture
Bleeding from oesophageal varices is a medical emergency.
Treated by endoscopic band ligation, sclerotherapy, or TIPS (Transjugular Intrahepatic Portosystemic Shunt).
| Structure | Key Features |
|---|---|
| Marginal artery | Continuous arterial arcade along colon, connects SMA and IMA |
| Portal vein | Formed behind pancreas (SMV + Splenic vein) |
| Portosystemic sites | Oesophagus, rectum, umbilicus, bare area of liver |
| Critical point | Sudeck’s point at junction of sigmoid and superior rectal arteries |
| Clinical link | Portal hypertension → varices, haemorrhoids, caput medusae |
The abdominal aorta gives three unpaired anterior branches to supply the gut:
Coeliac trunk → Foregut
Superior mesenteric artery (SMA) → Midgut
Inferior mesenteric artery (IMA) → Hindgut
The coeliac trunk arises at T12–L1, just below the aortic opening of the diaphragm.
The SMA arises at the level of L1, about 1 cm below the coeliac trunk, and runs in the root of the mesentery.
The IMA arises at L3, about 3–4 cm above the aortic bifurcation.
Coeliac trunk branches: left gastric, splenic, and common hepatic arteries.
SMA branches: inferior pancreaticoduodenal, middle colic, right colic, ileocolic, and multiple jejunal and ileal arteries.
IMA branches: left colic, sigmoid, and superior rectal arteries.
The marginal artery of Drummond forms a continuous arcade along the inner border of the colon, linking the SMA and IMA systems.
The Sudeck’s point marks the weak anastomosis between the last sigmoid artery and superior rectal artery.
Portal vein is formed behind the neck of pancreas by union of SMV and splenic vein.
Inferior mesenteric vein joins the splenic vein, not the SMV.
The portal vein carries about 1,200 mL of blood per minute to the liver—about 75% of hepatic inflow.
Hepatic veins drain into the inferior vena cava (IVC) just below the diaphragm.
The portosystemic anastomoses form communications between portal and systemic veins, providing alternate channels in portal hypertension.
The most important anastomotic sites:
Lower oesophagus
Umbilicus
Anal canal
Bare area of liver
Posterior abdominal wall (retroperitoneal colon)
Portal hypertension results from cirrhosis, thrombosis, or obstruction of the portal vein.
Oesophageal varices, haemorrhoids, and caput medusae are classical manifestations of portal hypertension.
Collateral shunts (splenorenal, mesocaval, portocaval) are used surgically to relieve portal pressure.
Superior mesenteric artery syndrome compresses the third part of the duodenum between SMA and aorta, causing obstruction.
The portal venous system has no valves, permitting free communication and spread of infection or metastasis between abdominal viscera and systemic circulation.
Cause: Compression of the third part of duodenum between SMA and aorta due to loss of retroperitoneal fat (cachexia, trauma, prolonged bed rest).
Symptoms: Nausea, bilious vomiting, epigastric distension after meals.
Investigation: Barium meal shows duodenal obstruction.
Treatment: Postural correction or surgical duodenojejunostomy.
Effect: Compresses the coeliac plexus → causes severe epigastric pain radiating to the back.
May mimic peptic ulcer pain.
Diagnosed by angiography.
Cause: Thromboembolism of SMA.
Clinical Picture: Sudden severe abdominal pain, bloody diarrhoea, and peritonitis.
Complication: Infarction of midgut, high mortality without emergency resection.
Site: Junction between the last sigmoid branch and superior rectal artery.
Clinical Relevance: During ligation of IMA (in colorectal surgeries), inadequate collateral flow here may lead to rectosigmoid necrosis.
Causes: Cirrhosis (most common), portal vein thrombosis, hepatic fibrosis.
Effects: Splenomegaly, oesophageal varices, haemorrhoids, ascites, caput medusae.
Mechanism: Blood diverted via portosystemic channels.
Anatomy: Between left gastric (portal) and azygos (systemic) veins.
Clinical Significance: Common cause of fatal upper GI bleeding in cirrhotic patients.
Cause: Engorged paraumbilical and superficial epigastric veins due to portal obstruction.
Appearance: Radiating veins around umbilicus — “head of Medusa” sign.
Cause: Portal hypertension → dilatation of superior rectal veins (portal) communicating with middle and inferior rectal veins (systemic).
Feature: Painless bleeding per rectum.
Example: Splenorenal shunt — connects splenic vein (portal) to left renal vein (systemic).
Purpose: Bypasses liver to reduce portal pressure.
Causes: Pancreatitis, infection, trauma.
Result: Portal hypertension with preserved liver function.
Radiological Finding: Cavernous transformation (multiple small collateral veins replacing the obstructed portal vein).
Rare Occurrence: Internal hernia at paraduodenal recess.
Risk: Iatrogenic bleeding if the vein is incised accidentally during surgery.
Occurs at: Splenic flexure and rectosigmoid junction.
Reason: Poor collateral flow in marginal artery and Sudeck’s point.
Symptoms: Abdominal pain, bloody stools, mucosal necrosis.
Effect: May compress the splenic vein behind pancreas → segmental portal hypertension, splenomegaly, and gastric varices.
Cause: Thrombosis of hepatic veins or IVC.
Symptoms: Painful hepatomegaly, ascites, elevated hepatic venous pressure.
Example: Colonic carcinoma → spreads to liver via portal vein → secondary hepatic metastases.
Mechanism: Increased portal pressure and decreased albumin synthesis → transudation of fluid into peritoneal cavity.
Finding: Shifting dullness, fluid thrill on examination.
Must be performed proximal to the left colic branch to preserve the marginal artery circulation and avoid sigmoid ischaemia.
Cause: Shunting of ammonia-rich portal blood into systemic circulation bypassing the liver.
Manifestation: Confusion, altered consciousness, flapping tremor (asterixis).
Clinically measured via hepatic venous pressure gradient (HVPG);
Normal: <5 mmHg
Portal hypertension: >12 mmHg → risk of variceal bleed.
In portal hypertension, the obliterated umbilical vein (ligamentum teres) may reopen, forming part of caput medusae.
| Structure | Clinical Relevance |
|---|---|
| Coeliac trunk | Foregut supply, aneurysm pain |
| SMA | Midgut supply, SMA syndrome |
| IMA | Hindgut supply, Sudeck’s point |
| Portal vein | Liver inflow, site of hypertension |
| Marginal artery | Collateral supply along colon |
| Portocaval anastomoses | Sites of varices in portal obstruction |
What is the artery of the midgut?
→ The Superior Mesenteric Artery (SMA).
Describe its origin, course, and branches.
Arises from the front of the abdominal aorta at L1 level, behind the pancreas.
Runs between the layers of the mesentery to the right iliac fossa.
Branches: Inferior pancreaticoduodenal, middle colic, right colic, ileocolic, jejunal, and ileal branches.
Clinical anatomy: Thrombosis can cause mesenteric ischaemia; compression between SMA and aorta leads to SMA syndrome.
Describe the portal vein under following headings:
a. Formation: Behind the neck of pancreas by union of SMV and splenic vein.
b. Tributaries: Left and right gastric, cystic, paraumbilical, and superior pancreaticoduodenal veins.
c. Clinical anatomy: In portal hypertension, the pressure increases, leading to varices, haemorrhoids, and caput medusae.
d. Sites and veins taking part in portosystemic anastomoses:
Lower end of oesophagus → Left gastric ↔ Azygos
Umbilicus → Paraumbilical ↔ Superficial epigastric
Anal canal → Superior rectal ↔ Middle and inferior rectal
Bare area of liver ↔ Phrenic veins.
Write short notes on:
a. Coeliac trunk — Artery of foregut, arises at T12, branches: left gastric, splenic, common hepatic.
b. Inferior mesenteric artery — Artery of hindgut; branches: left colic, sigmoid, superior rectal.
c. Blood supply of colon — From SMA (up to proximal 2/3 transverse colon) and IMA (distal 1/3 transverse colon onwards).
d. Caput medusae — Dilated veins around umbilicus due to recanalised paraumbilical veins in portal hypertension.
e. Marginal artery of Drummond — Continuous anastomosis along colon between SMA and IMA branches; maintains collateral supply.
Inferior mesenteric vein opens into:
a. Portal vein
b. Inferior vena cava
✅ c. Splenic vein
d. Superior mesenteric vein
Which of the following is not a direct branch of the coeliac trunk?
✅ d. Inferior pancreaticoduodenal artery
Cystic artery arises from:
✅ a. Right hepatic artery
Jejunal and ileal branches arise from:
✅ b. Superior mesenteric artery
Appendicular artery arises from:
✅ c. Ileocolic artery
Portal vein is formed by:
✅ b. Union of superior mesenteric and splenic veins
Ligamentum venosum is attached to:
✅ b. Left branch of portal vein
Portocaval anastomoses occur at all the following except:
✅ c. Stomach
Hepatic flexure of colon is supplied by:
✅ b. Middle colic artery
Superior rectal artery is continuation of:
✅ c. Inferior mesenteric artery
Inferior mesenteric vein opens into:
a. Portal vein
b. Inferior vena cava
✅ c. Splenic vein
d. Superior mesenteric vein
Which of the following arteries is not a direct branch of the coeliac trunk?
a. Left gastric
b. Common hepatic
c. Splenic
✅ d. Inferior pancreaticoduodenal
Cystic artery is a branch of:
✅ a. Right hepatic
b. Left hepatic
c. Coeliac trunk
d. Common hepatic
Jejunal and ileal branches for small intestine arise from:
a. Coeliac trunk
✅ b. Superior mesenteric artery
c. Inferior mesenteric artery
d. Abdominal aorta
Appendicular artery is a branch of:
a. Middle colic
b. Right colic
✅ c. Ileocolic
d. Left colic
Portal vein is formed by union of which veins?
a. Inferior mesenteric and splenic
✅ b. Superior mesenteric and splenic
c. Superior mesenteric and inferior mesenteric
d. Splenic, superior mesenteric, and inferior mesenteric
Ligamentum venosum is attached to which vein?
a. Right branch of portal vein
✅ b. Left branch of portal vein
c. Both branches of portal vein
d. None of the above
Portocaval anastomoses occur at the following sites, except:
a. Umbilicus
b. Lower end of oesophagus
✅ c. Stomach
d. Bare area of liver
Hepatic flexure is supplied by which artery?
a. Ileocolic
✅ b. Middle colic
c. Right colic
d. Jejunal branches
Superior rectal artery is the continuation of:
a. Superior mesenteric artery
b. Coeliac trunk
✅ c. Inferior mesenteric artery
d. Abdominal aorta
Branches of coeliac trunk: Left gastric, splenic, and common hepatic.
Branches of SMA (right side): Inferior pancreaticoduodenal, middle colic, right colic, ileocolic.
Number of arterial arcades:
Jejunum → 1–2 arcades (long vasa recta)
Ileum → 3–5 arcades (short vasa recta).
Answer: Coeliac trunk, superior mesenteric artery, and inferior mesenteric artery.
Mnemonic: “CSI – Coeliac, Superior, Inferior.”
Answer: At the level of T12–L1 intervertebral disc.
Answer:
Left gastric artery
Common hepatic artery
Splenic artery.
Answer: Superior mesenteric artery.
Answer: L1 (just below the coeliac trunk).
Answer:
Left side: Jejunal and ileal branches
Right side: Inferior pancreaticoduodenal, middle colic, right colic, ileocolic arteries.
Answer: Inferior mesenteric artery.
Answer: L3, about 3–4 cm above the aortic bifurcation.
Answer:
Left colic artery
Sigmoid arteries
Superior rectal artery.
Answer: Superior rectal artery.
Answer: It forms a continuous arterial arcade along the inner border of the colon, providing collateral circulation between SMA and IMA.
Answer: It’s the weak anastomosis between the last sigmoid artery and the superior rectal artery, prone to ischaemia after IMA ligation.
Answer:
Splenic vein
Superior mesenteric vein
Left and right gastric veins
Cystic vein
Paraumbilical veins.
Answer: By the union of superior mesenteric vein and splenic vein behind the neck of the pancreas.
Answer: Sites where portal and systemic venous channels communicate — they provide alternate pathways in portal hypertension.
Answer:
Lower end of oesophagus
Umbilicus
Anal canal
Bare area of liver.
Answer: Dilated tortuous veins radiating from the umbilicus due to recanalization of paraumbilical veins in portal hypertension.
Answer: Lies in the paraduodenal fold; it must be identified carefully during surgery to prevent massive bleeding.
Answer:
Portal vein brings blood to the liver (from gut).
Hepatic veins drain blood from liver to inferior vena cava.
Answer: Because hepatic sinusoids are not congested; liver architecture is intact — pressure rise is prehepatic.
Answer: It lies in the watershed area between SMA and IMA territories with poor collateral supply.
Answer:
Supplies major portion of small intestine and colon.
Its occlusion causes mesenteric ischaemia.
It may compress the third part of the duodenum (SMA syndrome).
Answer: Compression of the left renal vein between SMA and aorta, causing left-sided renal venous hypertension.
Answer: Approximately 75–80%.
Answer: Haematemesis (vomiting of blood) — life-threatening emergency in portal hypertension.
Get the full PDF version of this chapter.
Continue with Google