Blood Supply

Abdominal Aorta

Major Branches Include:

  1. Celiac Trunk - this is located at the T12 vertebral level and supplies viscera that are embryologically derived from the foregut. It further branches into:

    • Left Gastric Artery

      • Supplies stomach

      • Gives off esophageal branches

      • Anastomoses with right gastric artery

    • Splenic Artery

      • Pancreatic branches

      • Left gastroepiploic artery branch that anastomoses with right gastroepiploic artery

      • Short gastric artery branch that supplies the fundus of the stomach

    • Common Hepatic Artery

      • Right gastric artery branch that anastomoses with left gastric artery

      • Gastroduodenal artery branch which itself branches into the right and left gastroepiploic arteries that anastomose with each other

      • Superior pancreaticoduodenal artery branch

      • The common hepatic artery then continues in the free edge of the lesser omentum as the hepatic artery proper before branching into the right and left hepatic arteries, and cystic artery which supplies the gallbladder

  2. Superior Mesenteric Artery - this is located at the L1 vertebral level and supplies viscera that derive embryologically from the midgut. It further branches into:

    • Inferior pancreaticoduodenal artery which anastomoses with the superior pancreaticoduodenal artery

    • Middle colic artery to supply the transverse colon

    • Right colic artery to supply the ascending colon

    • Ileocolic artery which has:

      • Superior branch that anastomoses with the right colic artery

      • Inferior branch that branches into the colic, cecal, appendicular, ileal arteries

    • Jejunal and ileal branches that come together to from the arterial arcades and vasa recta

  3. Renal Arteries - supply kidneys

  4. Gonadal Arteries - supply testes or ovary

  5. Inferior Mesenteric Artery - this is located at the L3 vertebral level and supplies viscera that derive embryologically from the hindgut. It further branches into:

    • Left colic artery to supply the distal third of the transverse colon, left colic flexure, and descending colon

    • Sigmoid arteries to supply the descending and sigmoid colons

  6. Common Iliac Arteries - terminal branches of the abdominal aorta.

Venous Drainage

Azygos Venous System

  1. Azygos Vein - the unpaired azygos vein is formed by the union of the right ascending lumbar vein and the right subcostal vein. The lower end of the azygos vein communicates with the inferior vena cava. The azygos vein ascends on the right side of the vertebral column and forms a collateral pathway from the IVC to the SVC. The azygos vein communicates with the posterior intercostal veins and the external and internal venous plexuse.

  2. Hemiazygos Vein - the unpaired hemiazygos vein is formed by the union of the left ascending lumbar vein and the left subcostal vein. The lower end of the hemiazygos vein communicates with the renal vein. The hemiazygos vein ascends on the left side of the vertebral column and crosses to the left side at vertebral level T9 to join the azygos vein.

Inferior Vena Cava

  • It is formed by the union of the right and left common iliac veins at vertebral level L5.

  • The IVC drains all the blood from below the diaphragm (even portal blood from the GIT after it percolates through the liver) to the right atrium

  • The IVC is in jeopardy during surgical repair of a herniated intervertebral disc

  • The IVC above the kidneys (infrarenal) may be ligated (there is 50% mortality rate)

  • The right gonadal vein drains directly into the IVC, whereas the left gonasal vein drains into the left renal vein.

    • this is important in females, where the appearance of a right-side hydronephrosis may indicate thrombosis of the right ovarian vein that constricts the ureter, since the right ovarian vein crosses the ureter to drain into the IVS.

    • this is also important in males, where the appearance of left-side testicular varicocele may indicate occlusion of the left testicular vein and/or left renal vein due to a malignant tumour of the kidney

  • Routes of collateral venous return exist in case the IVC is blocked by either a malignant retroperitoneal tumour or a large blood clot (thrombus). These include:

    • azygos vein -> SVC -> right atrium

    • lumbar veins -> external and internal vertebral venous plexus -> cranial dural sinuses -> internal jugular vein -> right atrium

Hepatic Portal System

In general, the term portal refers to a vein interposed between two capillary beds (ie capillary bed -> vein -> capillary bed). The hepatic portal system consists specifically of the following vascular structures: capillaries of GI tract -> portal vein -> hepatic sinusoids.

The portal vein is formed posterior to the neck of the pancreas by the union of the splenic vein and superior mesenteric vein. The portal vein drains all the blood from the gastrointestinal tract, the blood it carries has high levels of nutrients from the GI tract and products of red blood cell destruction from the spleen. Its tributaries include:

  • Splenic vein

    • Which receives blood from the following:

      • Inferior mesenteric vein

      • Short gastric veins

      • Left gastroomental vein

      • Pancreatic veins

  • Superior mesenteric vein

    • Which receives blood from the following:

      • Right gastroomental vein

      • Inferior pancreaticoduodenal vein

Clinical Notes:

  1. Portal hypertension may arise as a result of liver cirrhosis.

  2. Esophageal varies are dilated veins that communicate between the esophageal branches of the left gastric vein and the esophageal veins. These varices may rupture and cause a hemorrhage.

  3. Caput medusae is a condition where varicose veins radiate from the umbilicus.

  4. Hemorrhoids occur where there is an anastomosis between superior and inferior rectal veins.