Abdominal Slices

This is an abdominal CT scan showing anatomy and an aneurism.

The Hepatic Portal System

The circulatory system of the liver is unlike that seen in any other organ. Of great importance is the fact that a majority of the liver's blood supply is venous blood. Seventy five percent of the blood supply to the liver is from the portal vein. Venous blood returning from the small intestine and stomach drains into the superior and inferior mesenteric veins; these two vessels are then joined by the splenic vein just posterior to the neck of the pancreas to form the portal vein. This then splits to form the right and left branches, each supplying about half of the liver. The remaining twenty five pecent of the blood supply to the liver is arterial blood from the right and left hepatic arteries.

Terminal branches of the hepatic portal vein and hepatic arteries empty together and mix as they enter the sinusoids in the liver. Sinusoids are distensible vascular channels lined with highly "holey" endothelial cells and bounded circumferentially by hepatocytes. Here, the blood is screened by specialised macrophages (Kupffer cells) to remove any pathogens that manage to get past the GI defences. The plasma is filtered through the endothelial lining of the sinusoids and bathes the hepatocytes; these cells contain vast numbers of enzymes capable of braking down and metabolising most of what has been absorbed. Some of the blood is stored in the liver for later use, or emptied into the central vein of each lobe. Central veins join into hepatic veins, which leave the liver and empty into the inferior vena cava.

Branches of the Abdominal Aorta

The abdominal portion of the aorta begins at the level of the diaphragm, crossing it via the aortic hiatus at the vertebral level of T12. The aortic branches supply blood to the abdominal cavity. From superior to inferior, they are listed below, with the level and the main area that they supply:

Inferior phrenic: diaphragm (T12)

Suprarenal: adrenal glands

Celiac Trunk: (Anterior) Divides into:

• Lt. Gastric: stomach
• Common Hepatic: liver
• Splenic: Spleen

Superior Mesenteric: intestines (L1)

Renal: Kidneys (L2)

Gonadal: Ovarian or Testicular

Lumbar: Abdominal wall & Spinal Cord (L1-L4)

Inferior Mesenteric: Distal Colon (L3)