The liver plays a wide array of function when talking about regulatory and metabolic roles. When it comes to its digestive function, the liver is responsible in producing bile. Bile breaks up the fat, making it easier for the digestive enzyme to break it down further and then be available for absorption. The bile produced by the liver is then stored in the gallbladder.
Gross Anatomy of the Liver
The liver, being the largest gland in the body, occupies almost the entire epigastric and right hypochondriac region. The largest gland of the body is being protected by the rib cage and lies directly under the diaphragm.
Generally, the liver is studied using its four primary lobes. A deep fissure separates the largest lobe, the right lobe, to that of the much smaller left lobe. The caudate lobe is found in the posteriormost region of the liver and the quadrate lobe can be found inferior to the left lobe. The falciform ligament is the one responsible for anchoring the liver from the anterior abdominal wall and the diaphragm. It also separates the left and right lobes anteriorly.
The ligamentum teres or round ligament can be found running along the edge, the inferior edge to be exact, of the falciform ligament. This ligamentum teres is a remnant of the fetal umbilical vein. Almost the entire surface of the liver is covered by visceral peritoneum except for the part which is in contact with the diaphragm.
Another anchoring mechanism of the liver, the lesser omentum, is responsible for anchoring the liver to the lesser curvature of the stomach. The hepatic portal vein and hepatic artery all enter the liver by way of the porta hepatis. Together with the common bile duct that runs inferior from the liver, must traverse through the lesser omentum in order to reach their destinations.
The gallbladder is a muscular organ with thin walls. It is positioned in the shallow fossa found on the ventral surface of the liver. The main function of the gallbladder is to store the produced bile from the liver that is not yet needed. When the bile is being stored in the gallbladder, it becomes more and more concentrated to a point where it is almost ten times as concentrated compared to the time it enters the gallbladder. The concentration is increased by absorbing trace ions and water on the entering bile.
Regulation of Bile Release
The hepatopancreatic sphincter is responsible for regulating the flow of bile to the small intestines. When no digestion is occurring, the sphincter is close which causes the bile to flow back to the gallbladder. Even though the liver continuously creates bile, it is not at all times releasing it to the intestines. The presence of cholecystokinin, a hormone released when fatty, acidic chyme enters the duodenum, stimulates the gallbladder to release bile. The presence of cholecystokinin also causes the hepatopancreatic sphincter to relax, allowing the bile and pancreatic juice to enter the duodenum.