Large Blood Vessel of the Gastrointestinal Tract

Learning Objectives

To describe the origins, course and major branches of the abdominal aorta, celiac axis, superior and inferior mesenteric arteries, the renal and gonadal arteries.

To describe the origins, course and major tributaries of the inferior vena cava.

To understand the anatomy of the portal vein, the portal venous system and portal-systemic anastomosis and its significance.

Celiac artery area of distribution: Artery of the foregut.

Supplies the gastrointestinal tract from the lower one third of the esophagus to middle of the second part of the duodenum.

Superior mesenteric artery area of distribution: Artery of the midgut Supplies the gastrointestinal tract

from the middle of the second part of the duodenum to distal one third of the transverse colon.

Inferior mesenteric artery area of distribution: Artery of the hindgut. Supplies the large intestine from

the distal one third of the transverse colon to halfway down the anal canal.

Celiac Artery: The trunk is short

Arises from abdominal aorta at the level of the 12th thoracic vertebra.

Has three terminal branches:

• Left gastric• Splenic• Hepatic arteries.

Left Gastric Artery Runs to the cardiac end

of the stomach

Gives off a few esophageal branches,

Turns to the right along the lesser curvature of the stomach.

Anastomoses with the right gastric artery.

Splenic Artery Runs to the left in a wavy

course behind the stomach and along the upper border of the pancreas

On reaching the left kidney the artery enters the splenicorenal ligament and runs to the hilum of the spleen.

Branches: 1. Pancreatic2. Left gastroepiploic3. Short gastric, five or six

in number

Hepatic Artery: Runs forward and to the right and

then ascends between the layers of the lesser omentum .

In the lesser omentum the artery, placed to the left of the bile duct and in front of the portal vein.

At the porta hepatis divides into right and left branches to supply the corresponding lobes of the liver.

Branches1. Right gastric artery2. Gastroduodenal artery: divides

into the right gastroepiploic artery and the superior pancreaticoduodenal artery.

3. Right and left hepatic arteries enter the porta hepatis. The right hepatic artery usually gives off the cystic artery, which runs to the neck of the gallbladder.

Superior Mesenteric Artery (SMA) : Arises from the front of the

abdominal aorta just below the celiac artery

Runs downward and to the right behind the neck of the pancreas and in front of the third part of the duodenum.

Continues downward to the right between the layers of the mesentery of the small intestine.

Ends by anastomosing with the ileal branch of its own ileocolic branch.

supplies the distal part of duodenum, jejunum, ileum, caecum, appendix, ascending colon, and most of the transverse colon.

SMA Branches:Inferior pancreaticoduodenal artery: Passes to the right as a

single or double branch along the upper border of the third part of the duodenum and the head of the pancreas.

Supplies the pancreas and the adjoining part of the duodenum.

Superior mesenteric artery. Digital subtraction angiography of the superior mesenteric artery and its branches.

Middle colic artery: Supply: Transverse

colon and divides into right and left branches.

Right colic artery: Branch of the ileocolic

artery. Passes to the right to

supply the ascending colon and divides into ascending and descending branches.

Ileocolic artery: Superior branch:

anastomoses with the right colic artery.

Inferior branch: anastomoses with the end of the superior mesenteric artery.

• Inferior branch gives rise to the anterior and posterior cecal arteries.

• Appendicular artery is a branch of the posterior cecal artery.

Jejunal and ileal branches: 12 to 15 in number Arise from the left side of the

superior mesenteric artery which unite with adjacent branches to form a series of arcades.

Branches from the arcades divide and unite to form a second, third, and fourth series of arcades.

Fewer arcades supply the jejunum than supply the ileum.

From the terminal arcades, small straight vessels supply the intestine.

Inferior Mesenteric Artery(IMA): Arises from the abdominal

aorta about 1.5 in. (3.8 cm) above its bifurcation.

Runs downward and to the left and crosses the left common iliac artery and continue as superior rectal artery.

Supplies: • Distal third of the transverse

colon• Left colic flexure• Descending colon• Sigmoid colon• Rectum• Anal canal (upper half)

Left colic artery: Runs upward and to the

left. Divides into ascending and

descending branches.

Supplies:• Distal third of the

transverse colon• Left colic flexure• Upper part of the

descending colon.

Sigmoid arteries: Two or three in number Supply:• Descending colon• Sigmoid colon.

Superior rectal artery: Continuation of the inferior

mesenteric artery. Crosses the left common iliac

artery. Anastomoses with the middle

rectal and inferior rectal arteries.

Descends into the pelvis behind the rectum.

Supplies:• Rectum• Anal canal (upper half)

Marginal ArteryThe anastomosis of the colic arteries around the concave margin of the large intestine forms a single arterial trunk called the marginal artery.

Begins at the ileocecal junction

Anastomoses with the ileal branches of the superior mesenteric artery

Ends by anastomoses less freely with the superior rectal artery

Venous DrainageThe venous blood from the greater part of the gastrointestinal tract and its accessory organs drains to the liver by the Portal venous system.

Inferior Vena Cava Begins anterior to the L5

vertebra by the union of the common iliac veins.

Union occurs approximately 2.5 cm to the right of the median plane

Ascends on the right sides of the bodies of the L3-L5 vertebrae and on the right psoas major to the right of the aorta.

Leaves the abdomen by passing through the caval opening in the diaphragm to enter the thorax at the T8 vertebral level.

Inferior Vena Cava: Branches

Portal vein Enters the liver and breaks

up into sinusoids, from which blood passes into the hepatic veins that join the inferior vena cava.

Drains blood from the abdominal part of the gastrointestinal tract from the

• Lower third of the esophagus to halfway down the anal canal

• Spleen• Pancreas• Gallbladder.

Portal circulation:

Begins as a capillary plexus in the organs it drains

Ends by emptying its blood into sinusoids within the liver.

Portal vein enters the liver and breaks up into sinusoids, from which blood passes into the hepatic veins that join the inferior vena cava.

Portal vein: 5 cm long

Formed behind the neck of the pancreas by the union of the superior mesenteric and splenic veins .

Ascends to the right, behind the first part of the duodenum, and enters the lesser omentum.

Runs upward in front of the opening into the lesser sac to the porta hepatis

Divides into right and left terminal branches.

Tributaries of the Portal Vein:

Splenic vein:

Passes to the right in the splenicorenal ligament.

Unites with the superior mesenteric vein behind the neck of the pancreas to form the portal vein.

Receives:• Short gastric • Left gastroepiploic• Inferior mesenteric • Pancreatic

Tributaries of the Portal VeinInferior mesenteric vein: Ascends on the posterior

abdominal wall

Joins the splenic vein behind the body of the pancreas.

Receives:• Superior rectal veins• Sigmoid veins• Left colic vein.

Tributaries of the Portal VeinSuperior mesenteric vein: Ascends in the root of the

mesentery of the small intestine.

Passes in front of the third part of the duodenum and joins the splenic vein behind the neck of the pancreas.

Receives the following veins:• Jejunal (1)• Ileal (1)• Ileocolic (2)• Right colic (3)• Middle colic (4)• Inferior pancreaticoduodenal (5)• Right gastroepiploic veins (6)

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Tributaries of the Portal Vein

Left gastric vein: Terminates directly into the

portal vein .

Drains the left portion of the lesser curvature of the stomach and the distal part of the esophagus.

Right gastric vein: Terminates directly into the

portal vein

Drains the right portion of the lesser curvature of the stomach.

Cystic veins: Terminates directly into the liver or join the

portal vein.

Drain the gallbladder

Portal-Systemic Anastomoses Portal venous blood traverses the liver and drains into

the inferior vena cava of the systemic venous circulation by way of the hepatic veins. This is the direct route.

Other, smaller communications exist between the portal and systemic venous systems.

The communications are as follows: At the lower third of the esophagus: the esophageal

branches of the left gastric vein (portal tributary) anastomose azygos veins (systemic tributary).

Halfway down the anal canal: the superior rectal veins (portal tributary) draining the upper half of the anal canal anastomose with the middle and inferior rectal veins (systemic tributaries)

Paraumbilical veins connect the left branch of the portal vein with the superficial veins of the anterior abdominal wall (systemic tributaries). The paraumbilical veins travel in the falciform ligament and accompany the ligamentum teres.

Veins of the ascending colon, descending colon, duodenum, pancreas, and liver (portal tributary) anastomose with the renal, lumbar, and phrenic veins (systemic tributaries).

Portal Hypertension Portal hypertension: a common

clinical condition Enlargement of the portal-

systemic connections is frequently accompanied by congestive enlargement of the spleen.

Porta-caval shunts: Distal splenorenal shunt (DSRS): For the treatment of portal hypertension, the splenic vein may be anastomosed to the left renal vein after removing the spleen.

Portosystemic Shunts A common method for reducing portal hypertension is to divert blood

from the portal venous system to the systemic venous system by creating a communication between the portal vein and the IVC.

Portosystemic shunt may be done where these vessels lie close to each other posterior to the liver.

Another way of reducing portal pressure is to join the splenic vein to the left renal vein, after splenectomy (splenorenal anastomosis or shunt)

PORTAL HYPERTENSIONIn severe cases of portal obstruction, the veins of the anterior abdominal wall that anastomose with the paraumbilical veins (portal tributaries) may become varicose and look somewhat like small snakes radiating under the skin around the umbilicus.

This condition is referred to as caput medusae because of its resemblance to the serpents on the head of Medusa, a character in Greek mythology.

Arrows indicate the direction taken by venous blood when the portal vein is obstructed.

Blood Flow in the Portal Vein and Malignant Disease

The portal vein conveys about 70% of the blood to the liver. The remaining 30% is oxygenated blood, which passes to the liver via the hepatic artery.

The wide angle of union of the splenic vein with the superior mesenteric vein to form the portal vein leads to streaming of the blood flow in the portal vein.

The right lobe of the liver receives blood mainly from the intestine, whereas the left lobe plus the quadrate and caudate lobes receive blood from the stomach and the spleen. This distribution of blood may explain the distribution of secondary malignant deposits in the liver.

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