The liver is a large, dark, red organ that rests below the diaphragm.  Much of the liver is located on the right side of the body and is protected by the right side of the rib cage. However, the liver also extends across the body from right to left and tapers off behind the fifth rib on the left side of the rib cage. The liver is attached to the body in a number of places. A ligament called the falciform ligament attaches the liver to the diaphragm and the front of the abdominal wall. The top of the liver is also attached to the diaphragm at a place called the bare area. Unlike the rest of the liver, the bare area does not have a serosa. This helps to ensure that the liver stays in place. Directly below the falciform ligament is the round ligament. This ligament is what remains of the umbilical vein, which carried blood from our umbilical cord to our liver before we were born.

The liver has four lobes.  These are called the right lobe, the left lobe, the quadrate lobe, and the caudate lobe. The right lobe and the left lobe, which can be seen from the front, are separated by the falciform ligament. The other lobes are visible from the back.

Although the liver has many functions, such as removing toxins from the body and breaking down drugs into simpler compounds so that they can be excreted by the body, the chief role of the liver in digestion is to make and secrete bile. This bile helps the body to digest fats. The bile is secreted by cube-shaped cells called hepatocytes. These hepatocytes secrete bile into tiny channels called the bile canaliculi. These bile canaliculi converge into bile ductules. The bile ductules merge to become the right and the left hepatic ducts, which then merge to form the common hepatic duct. The hepatic duct meets the cystic duct, which comes from the gallbladder, and becomes the common bile duct. The bile duct then meets the pancreatic duct before it ends at the duodenum. The liver also secretes bilirubin, which is indirectly responsible for the brown color of feces.

At the place where the common bile duct meets the duodenum is a sphincter muscle called the sphincter of Oddi. This sphincter muscle helps to determine when bile and pancreatic juice are secreted into the duodenum. When there is no chyme in the duodenum, the sphincter is closed.  However, when chyme from the stomach arrives into the duodenum, the sphincter opens up.

Last Updated: Saturday, July 16, 2011