The liver and digestion
The liver and digestion
The liver is both the largest gland and the largest solid organ in the body. It is also one of the body’s most important organs, performing over 500 functions, of which digestion is one.
A dark reddish-brown colour, the liver holds approximately 13 per cent of the body’s total blood supply at any one time. It is split into two lobes, which are further divided into around 100,000 lobules. Approximately 60 per cent of the liver is made up of hepatocytes, which are cells that absorb nutrients and detoxify and remove harmful substances from the blood.
One of the liver’s most important functions is breaking down food and converting it into energy, or glucose, which is stored in the liver and muscles as glycogen. When energy is required, the liver quickly converts this back into glucose for use (see Body Talk: the endocrine system for more). People with liver damage may sometimes lose the ability to control their blood glucose and may need a regular supply of sugar as a result.
The liver also helps to remove waste that is not excreted by the kidneys and has a role in blood clotting, hormone balance and storing iron, vitamins and other chemicals. In addition, it plays a vital role in fighting infections, particularly bowel infections. If the liver is damaged in any way, its ability to fight infections is impaired.
Bile
Bile is an important substance when it comes to digestion. It is produced from cholesterol by liver cells, and mainly serves to break down fats so they are easier to absorb. Bile is secreted into the bile ducts, which join to form the hepatic duct. This then divides, with one branch going to the duodenum and the other to the gall bladder.
Entry to the duodenum is controlled by a sphincter muscle. If this is closed, bile can back up and may be stored in the gall bladder until needed. If the bile contains too much cholesterol or too little water, deposits may form within the gall bladder. Known as gallstones, these can cause abdominal discomfort – particularly if they accumulate and become sizeable – and may need to be surgically removed.