The liver is the largest internal organs of the human body. The adult human liver normally weighs between 1.0 - 2.3 kilograms (2.2 - 5.0 pounds), and is a soft, pinkish-brown "boomerang shaped" organ.
Its anatomical position in the body is: immediately under the diaphragm on the right side of the upper abdomen. The liver lies on the right of the stomach.
It plays a major role in metabolism and has a number of functions in the body including drug detoxification, glycogen storage, and plasma protein synthesis.
It also produces bile, which is important for digestion. Medical terms related to the liver often start in hepato- or hepatic from the Greek word for liver, "hepar" (for example, hepatocytes - liver cells),
as well as terms related to the bile are from the Greek word for bile, "khole" (for example, cholecystitis, which means inflammation of cholecyst - gallbladder).
The liver is supplied by two major blood vessels: the hepatic artery and the portal vein. The portal vein brings venous blood from the spleen, pancreas, stomach, small and large intestines (except rectum),
so that the liver can process the nutrients and byproducts of food digestion; processing of absorbed nutrients and byproducts of food digestion is one of key liver functions for the body.
The bile produced in the liver is collected in bile ductules, which merge next to form bile ducts. These eventually drain into the right and left hepatic ducts, which in turn merge to form the common hepatic duct.
The branchings of the bile ducts resemble those of a tree, and indeed the term "biliary tree" is commonly used in this setting.
Bile can either drain directly into the duodenum (the first part of small intestine) via the common bile duct or be temporarily stored in the gallbladder via the cystic duct.
The intrahepatic biliary tree is regarded as an excretory duct of two secretory units: hepatocytes (which excrete bile) and intrahepatic peribiliary glands.
The liver is among the few internal human organs capable of natural regeneration of lost tissue; as little as 25% of remaining liver can regenerate into a whole liver again.
Traditional gross anatomy divided the liver into four lobes based on surface features. One of liver ligaments (the falciform ligament) is visible on the front of the liver. This divides the liver into a left anatomical lobe, and a right anatomical lobe.
If to look at the liver from behind (the visceral surface), there are two additional lobes between the right and left.
The specific functions of the liver are carried out by the liver cells which are termed hepatocytes and include:
- Processing of the nutrients absorbed by the intestines during digestion and converting those nutrients into forms that can be used by the body.
- Performing key roles in the body energy metabolism - it converts different nutrients in the body energetic fuels (glucose, for example) as far as
- The liver performs several key roles in controlling the amounts of sugar (carbohydrate metabolism):
- Gluconeogenesis - the formation of glucose (blood sugar) from certain amino acids, lactate or glycerol; that is necessary to support the stable concentration of glucose in the blood;
- Glycogenolysis - the formation of glucose from glycogen - to mobilize glucose for the body from intrahepatic resource;
- Glycogenesis - the formation of glycogen from glucose - to make resource of glucose for future requirement;
- The liver also controls fat and lipoproteins entering the bloodstream and performs several roles in lipid and cholesterol metabolism:
- Cholesterol synthesis;
- The production and turnover of lipoproteins;
- The production of triglycerides (fats);
- The production of a "ketone body" beta-hydroxybutyrate - an additional fuel (along with the main fuel glucose) for brain especially during starvation
- The liver produces and excretes bile required for food digestion.
- The liver performs plasma protein synthesis (proteins for blood circulation), such as albumin.
- The liver is an endocrine organ. It is the main source of somatomedin C (insulin-like growth factor I) in systemic circulation.
Insulin-like growth factor is a part of growth hormone axis. The liver performs also other functions for endocrine system such as hormone inactivation (including steroid hormones),
and synthesis of hormone binding proteins (for example sex hormone binding globulin, cortisol binding globulin) and growth factors binding proteins.
- The liver produces substances that help blood to clot.
- The liver breaks down hemoglobin from dead red blood cells, toxic substances and most medicinal products. Most of waste substances (bilirubin and processed metabolized toxins) are excreted with bile to be removed from the body;
the bilirubin results from the breakup of the hemoglobin of dead red blood cells; normally, the liver removes bilirubin from the blood and excretes it through bile.. Many diseases of the liver are accompanied by
jaundice caused by increased levels of bilirubin [a bile pigment] in the system, because of the liver in disease can not manage with excretion of bilirubin.
- The liver converts ammonia to urea. Ammonia is a byproduct of metabolism of aminoacids and is a toxic substance.
- The liver stores a multitude of substances, including glucose in the form of glycogen, vitamin A, vitamin B12, iron, and copper.