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The liver is supplied with blood from from the hepatic artery, which delivers oxygenated blood.
It is also supplied with blood from the hepatic portal vein, which delivers blood from the small intestine containing digestive substances.
The hepatic vein takes deoxygenated blood from the liver back to the heart.
The liver is made up of numerous lobules, packed with hepatocytes (liver cells)
In every lobule, the hepatocytes radiate outwards from the central vein. All central veins connect to the hepatic vein.
The hepatic artery and hepatic portal vein are also connected to the central vein by capillaries called sinusoids which pass blood through the hepatocytes. As blood flows through the sinusoids, the hepatocytes take in oxygen and remove any harmful substances from the blood.
This is further aided by macrophytic cells, called Kupffer cells, which line the sinusoids and ingest foreign particles to help protect against disease.
The hepatocytes secrete bile from the breakdown of blood into spaces called canaliculi and from there, the bile drains into the bile duct which takes it to the gall bladder, where it is stored. Bile is a substance that emulsifies fats.
The liver has many functions, they include:
Deamination of Amino Acids: a highly important function of the liver is the deamination of excess amino acids. Nitrogen-containing amino groups are removed by the hepatocytes and results in the formation of ammonia and organic acids. The organic acids are used in either respiration to make ATP, or are converted into carbohydrates to be stored as glycogen. The ammonia, however, is highly toxic and so combines with carbon dioxide to form urea. This reaction is controlled by enzymes and is known as the Ornithine cycle. Urea is then released into the blood and travels to the kidneys where it is excreted in the urine.
Carbohydrate Metabolism: as studied in homeostasis, the liver plays a crucial role in controlling blood glucose levels. When blood glucose levels are high, the hormone insulin is secreted from the beta cells of the Islets of Langerhans in the Pancreas and causes the liver to convert glucose into glycogen to store it. On the other hand, when blood glucose levels are low the alpha cells of the Islets of Langerhans in the Pancreas break down stores of glycogen to release more glucose into the blood.
Detoxification: hepatocytes break down and chemically change many harmful substances such as alcohol and drugs, which is why abuse of either can result in liver damage. In fact, excess alcohol could result in the death of hepatocytes which could lead to cirrhosis - scarring of the tissue caused by long-term liver damage. Scar tissue eventually replaces healthy tissue in the liver and so, as a result, it disrupts flow and prevents the liver from functioning correctly.