Where Is Your Liver and What Does It Do?
The liver is the largest organ in the abdomen, and it sits just under the diaphragm in the right upper quadrant. It’s a busy organ because just about every substance you eat goes to the liver to be metabolized before going anywhere else in the body. (Fats are the exception — they enter the lymphatic system.) The liver also makes bile, which helps break down fat in the small intestine, and also stores various substances. The following sections cover the parts, nerves, and vessels of the liver.
Liver surfaces and lobes
The liver has two surfaces: The diaphragmatic surface includes the anterior, superior, and part of the posterior surface, and the visceral surface is located on the posteroinferior surface.
Most of the liver is covered with peritoneum except for a posterior section that contacts the diaphragm, the bed of the gallbladder, and the porta hepatis, which is an opening that allows the passage of the hepatic portal vein, hepatic artery, nerves, ducts, and lymphatic vessels. The visceral surface contacts the following: esophagus, stomach, duodenum, gallbladder, right colic flexure of the colon, right kidney, and suprarenal gland.
The liver is divided into two lobes by the falciform ligament: the larger right lobe and the smaller left lobe. The falciform ligament is a fold of peritoneum that extends from the umbilicus to the liver. The falciform ligament contains the round ligament of the liver.
The presence of fissures, or grooves, further divides the liver.
Right sagittal fissure: This groove is formed by the fossa (depression) for the gallbladder and a groove that makes room for the inferior vena cava.
Left sagittal fissure: This groove is formed by the fissure for the round ligament of the liver on the front and the fissure for the ligamentum venosum on the back.
The left and right sagittal fissures divide the right lobe to include the caudate lobe and quadrate lobe.
Liver nerves, blood vessels, and lymphatics
Nerve supply is brought to the liver by the hepatic plexus, which has sympathetic fibers from the celiac plexus and parasympathetic fibers from the vagal trunks.
The liver receives blood from the following two sources:
Hepatic artery: Systemic circulation comes from the hepatic artery, which brings oxygenated blood to the liver.
Hepatic portal vein: This vein carries venous blood from the abdominal part of the digestive tract.
The hepatic portal system is made up of the hepatic portal vein and its tributaries: the superior mesenteric vein, the splenic vein, the gastric veins, and the cystic veins.
Additional veins of the portal system include:
Gastro-omental veins: Drain blood from the stomach and greater omentum into the splenic vein (left gastro-omental vein) and superior mesenteric vein (right gastro-omental vein)
Short gastric veins: Drain blood from the stomach to the splenic vein
Ileocolic vein: Drains blood from the cecum and appendix into the superior mesenteric vein
Inferior mesenteric vein: Drains blood from the rectum, sigmoid, and descending colon into the splenic vein
Left colic vein: Drains blood from the descending colon to the inferior mesenteric vein
Middle colic vein: Drains blood from the transverse colon into the superior mesenteric vein
Right colic vein: Drains blood from the ascending colon into the superior mesenteric vein
In the liver, the hepatic portal vein branches out and ends in capillaries called the venous sinusoids of the liver.
Lymph is drained from the liver by lymphatic vessels of the liver, which include superficial and deep lymphatic vessels. Hepatic lymph nodes are found along the hepatic vessels and the lesser omentum. Lymph from these lymphatic vessels drains into the celiac lymph nodes and then into the cisterna chyli. Lymph nodes on the posterior and anterior surfaces of the liver drain into the phrenic lymph nodes (near the diaphragm) and then into the posterior mediastinal lymph nodes before draining into the right lymphatic and thoracic ducts.
The bile duct
The liver produces bile and secretes it into bile canaliculi, which drain the bile into interlobular bile ducts. Those ducts then lead to larger ducts that eventually merge to form the right and left hepatic ducts (one for each lobe). The two hepatic ducts merge to form the common hepatic duct. This duct, along with the cystic duct, forms the bile duct.
The bile duct runs down to the duodenum to form the hepatopancreatic ampulla with the pancreatic duct. The ampulla opens into the duodenum through the major duodenal papilla. The terminal portion of the bile duct is surrounded by the sphincter of the bile duct. The hepatopancreatic ampulla has its own sphincter called the sphincter of Oddi.