A lobed structure that sits immediately below the ribcage with many vital functions. It is the largest single internal organ in the mammalian body and has critical functions, mostly to do with BLOOD. Blood comes to and from the liver from the intestine, spleen, gall bladder, pancreas and stomach via the hepatic portal vein and the hepatic artery (HEPATIC is the adjective meaning pertaining to the liver). The liver has many functions relating to the synthesis of PROTEINS for PLASMA; detoxification of the blood (removal of DRUG metabolites for example); and storage. It is an important site for the storage of certain VITAMINS (the human liver contains sufficient vitamin B12 to last for 12–36 months) and GLYCOGEN, a POLYSACCHARIDE found in MUSCLES and the liver. It is important because it can be mobilized very rapidly to provide energy to fuel processes such as FIGHT-ORFLIGHT. (The ENERGY stored as FAT cannot be mobilized quickly.) The pancreatic enzyme GLUCAGON promotes the mobilization of glycogen.
The liver is under neural control of the VAGUS NERVE, as well as the SPLANCHNIC NERVE and PHRENIC NERVE. The vagus nerve also carries sensory information back to the central nervous system. OSMORECEPTORS, GLUCORECEPTORS and mechanisms for detecting the ION (e.g. SODIUM) balance in the blood are all present in the liver and all capable of relaying information to the central nervous system. Similarly, structures in the BRAINSTEM and HYPOTHALAMUS are involved in the regulation of liver function. The state of the liver appears to be a critical determinant of behaviour, especially of FEEDING. Glucose applied to the liver in experimental conditions promotes strong firing in the vagus, while infusion of glucose into the hepatic portal vein inhibits it. Several authors have speculated that the liver has a greater degree of control over feeding than does the brain.
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