6. Examine the liver, gallbladder and biliary system, defining their peritoneal relations and parts.
The Liver
Next turn your attention to the liver. Recall that this liver develops in the ventral mesogastrium between the lesser omentum and falciform ligament. The falciform ligament separates the left lobe from the right. The falciform ligament continues up to the diaphragm and then its two layers of peritoneum split and go to the right and to the left. These layers form the coronary ligament. Following along the left side of the falciform ligament, the coronary ligament heads towards the tip of the left lobe of the liver. It ends in a thin membranous attachment, which is called the left triangular ligament. From this point, the coronary ligament passes behind the liver and down towards the esophagus. It continues as the lesser omentum, the hepatogastric, and hepatoduodenal between the liver and the stomach and the liver and duodenum. Return to the falciform ligament and follow the right side of the ligament up towards the liver. The falciform ligament is like a mesentery and has two layers of peritoneum. They split as they approach the liver. The right side of the peritoneum forms the coronary ligament on the right. It runs along the top of the liver, attaching the liver to the diaphragm. Next, sever the falciform ligament from the diaphragm itself and follow that, incising the coronary ligament as it attaches the liver to the diaphragm. As you continue the incision towards the diaphragm you will see the right and left sides of the coronary ligament. As you pass posteriorly, you will have to cut the inferior vena cava as it passes from the liver to the diaphragm. The incision is shown here. Having severed the liver from the diaphragm, review its attachments: The falciform ligament splitting into the coronary ligament on either side, to the right and to the left. The left side of the coronary ligament ends in the left triangular ligament, the left lobe of the liver. The coronary ligament then proceeds posteriorly and to the right around the inferior vena cava and then to the posterior side of the right lobe of the liver. As it comes around it ends in the right triangular ligament. The coronary ligament then continues back to the left and ends in the falciform ligament. The area subscribed is the bare area of the liver. Next turn your attention the liver itself, its inferior border and its costal surface. The falciform ligament separates a left anatomical lobe from a right anatomic lobe. This is also the gallbladder, here collapsed. On its visceral surface, four lobes are identified, anatomically: a quadrate lobe, a left anatomical lobe, and a caudate lobe. Reviewing once again: the left lobe, the caudate, the quadrate, and the right lobe. Physiologically, the liver is separated into a right and a left lobe by the inferior vena cava and bed of the gallbladder, into a right lobe and a left lobe. The left includes the caudate and quadrate, as well as anatomical left lobe. Next turn your attention to the porta hepatis, where all the large structures enter the liver. First of all, the arterial system, the proper hepatic artery, the common bile duct, and behind it, between the portal vein. The hepatic artery arises from the celiac, gives rise to the gastroduodenal and the proper hepatic. The proper hepatic usually splits into a right and a left. The right gives rise to the cystic artery. In this particular individual, the right hepatic artery is a separate branch off the common hepatic artery and passes behind the portal vein and the common bile duct, but then enters the right lobe of the liver, and the cystic artery is actually arising from the left hepatic branches. Next turn your attention to the extra hepatic biliary system. It begins as a right and a left hepatic duct coming out of the respective lobes of the liver. These join to form a common hepatic duct. The common hepatic duct joins the cystic duct coming from the gall bladder to form the common bile duct. This passes behind the head of the pancreas and enters the second portion of the duodenum with the main pancreatic duct. The third element of the porta hepatis is the portal vein. The portal vein passes behind the biliary system and the arterial system. It splits into a right and left portal vein into the respective lobes of the liver.
The Gallbladder
The gallbladder is attached to the visceral surface of the liver and overhands the first portion of the duodenum. Its parts include the fundus, here collapsed, its main portion, body, a neck, and finally the cystic duct, which joins the common hepatic duct. It is supplied by the cystic artery, which is usually a branch of the right hepatic artery. In this case, it arises from the left. The veins of the gallbladder drain directly into the bed of the gallbladder and into the liver itself. Next open the gallbladder. Many specimens will display gallstones. These may be palpated through the surface if they are present. The interior of the gallbladder itself is relatively smooth and velvety and has no prominent folds. Here three gallstones were found. Return to the falciform ligament. Within the falciform ligament, you may notice small veins. These are paraumbilical veins which drain from the porta hepatis along the falciform ligament to the anterior abdominal wall around the umbilicus. They may be prominent and important in collateral circulation of the liver during portal hypertension. In the free margin of the falciform ligament, the ligamentum teres heads towards the left branch of the portal vein. This is the remnant of the umbilical vein, which closes off shortly after birth. During life in utero, the liver does not need to be able to process foodstuff, so much of the blood returning from the umbilical vein, bypasses the liver and goes directly to the inferior vena cava. The connection between the left branch of the portal vein and inferior vena cava, in utero, is a vessel called the ductus venosus. After birth, this becomes a cord-like structure, the ligamentum venosum, and can be seen in the connection of the hepatic gastric ligament to the liver.
The Hepatic Veins
Next turn your attention to the venous drainage of the liver. Recall that the inferior vena cava is embedded into the posterior surface of the liver, the visceral surface. As it passes upwards towards the diaphragm it receives veins draining the liver, the hepatic veins, which are usually three large veins: the left hepatic vein, a middle hepatic vein, and a right hepatic vein.
If you have difficulty receiving this movie, try the smaller version.