In the first of a four-part fortnightly series about the liver, CHIA HUI JUN looks at the myriad of jobs performed by the largest organ inside the body
The liver is the workhorse among the organs, responsible for a myriad of functions that keep every system going. If it were to stop working, everything would soon grind to a halt. So it is fortunate that the liver is the only internal organ capable of regenerating itself when damaged.
The liver is a reddish-brown mass under the diaphragm. Located in the right upper quadrant of the abdominal cavity, it is the largest internal organ in the human body, weighing 1.36kg. Because of this organ’s ability to keep growing, a healthy person can donate half of his liver to someone who needs it.
Even with half or a third of it removed, the liver can grow to its full size again with time, said Dr Kieron Lim, an associate consultant in the department of gastroenterology and hepatology at the National University Hospital. But, there are limits to how much the liver can regenerate. Viral infections and poor dietary and lifestyle habits can cause liver damage and possibly lead to hardening, known as cirrhosis.
Breaking things down
The liver is like the main factory of a country, producing important products and by-products, processing inputs and getting rid of unwanted toxins, said Dr Tan Hui Hui, a consultant at the Singapore General Hospital’s department of gastroenterology and hepatology.Doctors say the organ produces proteins such as albumin (in blood plasma), clotting factors, enzymes, antibodies and bile, a digestive juice required to break down fats and eliminate waste. On top of that, the liver metabolises, or breaks down, lipids, carbohydrates and proteins. As proteins are broken down, a toxin called ammonia is released and converted to urea, which is then excreted by the kidneys in urine.
The liver also breaks down medicines, herbal supplements, alcohol, industrial and food processing chemicals and hormones, such as insulin, estrogen and adrenalin, after they have served their function as messengers to other cells, said Dr Lim.
The liver also converts lactic acid from a toxin to storage fuels like pyruvate or glucose for energy generation. Lactic acid is produced when glucose is broken down and too much of it may irritate nerves and muscles. The liver serves as a storeroom for certain vitamins such as vitamins A, B12 and D, and trace elements like copper and iron. Infections from viruses, fat deposits in the liver and alcohol can cause the liver to malfunction, resulting in liver diseases.
Doctors say viral illnesses such as hepatitis B and C are spread by blood and body fluids, while hepatitis A can be contracted when one eats contaminated shellfish or cockles. The viruses cause the liver to become inflamed, damaging liver cells, which leak higher than normal amounts of liver enzymes into the bloodstream. Chronic liver inflammation may lead to liver fibrosis (scarring), followed by cirrhosis (hardening from scar tissue) and liver failure or liver cancer.
Usually, people with hepatitis A can recover fully and it rarely causes liver failure. But hepatitis B or C increases one’s risk of liver cirrhosis and liver cancer. Anti-viral medications can control the disease by reducing liver inflammation and viral replication. Poor diet and excessive alcoholic consumption can lead to fatty liver disease. Symptoms include lethargy, jaundice (a yellowing of the eyes and skin), dark brown urine, mental confusion, easy bruising and coma, said Dr Tan. In many cases, the liver can recover with the help of anti-viral medication and changes made to one’s diet and lifestyle.