The liver is one of the body’s largest and most important internal organs. Located in the upper right part of the abdomen, just beneath the diaphragm, it performs hundreds of chemical and metabolic tasks that keep the body’s internal environment stable.
The liver helps process nutrients from food, makes proteins that the body needs, stores energy and certain vitamins and minerals, produces bile for digestion, modifies medications and other chemicals, and removes waste products from the blood. It also plays an important role in immunity and blood clotting.
Unlike many organs that have one dominant job, the liver acts as a central processing and distribution center for substances moving between the digestive system and the rest of the body.
Where is the liver, and what does it look like?
The liver sits mainly in the upper right abdomen, behind the lower ribs. A smaller portion extends toward the upper left side. It is reddish-brown, wedge-shaped, and divided into major anatomical lobes. The liver receives a particularly large blood supply because it constantly processes substances arriving from the digestive tract.
Two major blood vessels are especially important. The hepatic artery supplies oxygen-rich blood, while the portal vein carries blood from the stomach and intestines to the liver. Blood arriving through the portal vein contains nutrients and other substances absorbed from food, as well as compounds that may need to be processed before they circulate throughout the body.
Inside the liver, microscopic functional units contain specialized cells called hepatocytes. These cells carry out much of the liver’s metabolic and chemical work.
The liver processes nutrients from food
After digestion, carbohydrates, fats, proteins, vitamins, minerals, and other substances are absorbed through the intestines. Much of the absorbed material travels first to the liver through the portal vein.
The liver then changes, stores, releases, or distributes these substances according to the body’s needs.
Carbohydrates
The liver helps keep blood glucose within a useful range. When blood glucose is plentiful, the liver can convert glucose into glycogen, a storage form of carbohydrate. When the body needs more glucose, the liver can break down glycogen and release glucose into the bloodstream.
The liver can also make glucose from certain non-carbohydrate materials, including components derived from proteins and other metabolic pathways. This process, called gluconeogenesis, becomes particularly important between meals and during fasting.
Fats
The liver plays a central role in fat metabolism. It helps process fatty acids, makes cholesterol and other lipids, and packages fats for transport through the bloodstream.
Cholesterol is often described simply as harmful, but the body needs it for cell membranes, certain hormones, and other biological functions. The liver helps regulate how much cholesterol is produced, used, transported, and removed.
The liver also converts some fatty acids into ketone bodies, which can serve as an energy source when carbohydrate availability is low.
Proteins
The liver processes amino acids, the building blocks of proteins. It also produces many proteins that circulate in the blood, including albumin and several proteins involved in blood clotting.
Albumin helps maintain the proper distribution of fluid between the bloodstream and surrounding tissues and also transports various substances through the blood.
It produces bile for digestion
The liver produces bile, a fluid that helps the body digest and absorb fats. Bile contains substances called bile acids or bile salts that help break large fat droplets into smaller ones, making fats easier for digestive enzymes to act on.
Bile also provides a route for eliminating certain substances from the body, including bilirubin, a yellow pigment produced when old red blood cells are broken down.
The gallbladder stores and concentrates bile between meals. When food containing fat enters the small intestine, the gallbladder can release bile into the intestine. The liver makes the bile; the gallbladder mainly stores and releases it.
The liver helps remove waste and process chemicals
The liver chemically modifies many substances so they can be used, transported, or eliminated more safely. This includes naturally produced compounds as well as medications and other chemicals that enter the body.
This work is often described as “detoxification,” but that word can be misleading if it suggests that the liver simply filters toxins out of the blood. Much of the liver’s work involves chemical transformation rather than simple filtration.
For example, liver enzymes can modify drugs and other compounds through reactions that make them easier for the body to eliminate. The resulting substances may leave the body through urine or bile.
The liver also converts ammonia, a potentially toxic waste product generated during protein metabolism, into urea. Urea enters the bloodstream and is eventually removed from the body by the kidneys in urine.
It helps regulate bilirubin
Bilirubin is produced as the body breaks down hemoglobin from aging red blood cells. The liver takes up bilirubin, chemically processes it, and excretes it into bile.
If bilirubin accumulates in the blood, it can cause jaundice, in which the skin and whites of the eyes become yellow.
Jaundice can occur for several reasons. The liver may be unable to process bilirubin effectively, bile may be unable to flow normally, or bilirubin production may exceed the body’s ability to handle it. Thus, jaundice is a sign of an underlying problem rather than a disease by itself.
The liver stores energy and essential nutrients
The liver serves as a storage site for glycogen, helping provide a readily available reserve of glucose between meals.
It also stores certain vitamins and minerals, including vitamins A, D, E, and K and vitamin B12, along with iron and copper. These reserves can help maintain normal body functions when immediate dietary intake is insufficient.
Storage is only one part of the liver’s role. It also helps regulate the movement of nutrients between storage sites, the bloodstream, and other tissues.
It makes proteins needed throughout the body
The liver manufactures many proteins that are essential for normal physiology. Among them are albumin and numerous proteins involved in coagulation, the process that stops bleeding after a blood vessel is damaged.
This is why significant liver dysfunction can affect blood clotting as well as fluid balance. A damaged liver may produce fewer of certain clotting proteins, increasing the tendency to bleed.
The liver also produces proteins involved in transporting substances through the bloodstream and contributes to the production of molecules involved in hormone and nutrient metabolism.
The liver contributes to immune defense
The liver is closely connected with the immune system. Specialized immune cells called Kupffer cells are located within the liver’s blood channels and can capture and destroy certain bacteria, damaged cells, and other particles arriving from the digestive tract.
Because blood from the intestines passes through the liver before reaching the rest of the circulation, the liver occupies an important position between the digestive system and the wider immune system.
The liver also produces proteins involved in innate immunity, the body’s rapid, nonspecific defense against potentially harmful organisms.
It helps regulate hormones and other signaling molecules
The liver participates in the body’s hormone system by chemically modifying and clearing various hormones from the bloodstream. This helps control how long certain hormones remain active.
It also produces and processes molecules involved in communication between organs. For example, the liver produces insulin-like growth factor 1 (IGF-1), an important mediator of growth hormone activity.
The liver therefore influences processes far beyond digestion, including metabolism, growth, and the regulation of circulating chemicals.
What happens when the liver is damaged?
The liver has a notable ability to repair itself after some types of injury. However, repeated or severe damage can overwhelm its ability to recover.
Liver disease can result from many causes, including certain viral infections, excessive alcohol exposure, metabolic dysfunction, inherited disorders, and some medications or toxins. Different diseases affect the liver in different ways, but persistent injury can lead to inflammation and scarring.
Fibrosis is the buildup of scar tissue in response to ongoing liver injury. When extensive scarring disrupts the liver’s normal structure and function, the condition is called cirrhosis.
As liver disease becomes advanced, problems can arise in several of the liver’s functions at once. A person may develop impaired production of blood proteins, abnormal handling of bilirubin, accumulation of substances the liver normally processes, or changes in blood flow through the liver.
Because the liver performs so many interconnected jobs, advanced liver disease can affect multiple organ systems rather than producing only digestive symptoms.
Why the liver matters so much
The liver is not simply a digestive organ or a filter for the bloodstream. It is a metabolic organ that continually receives materials from the digestive tract, chemically processes them, stores some, sends others into circulation, and prepares waste products for elimination.
Its major responsibilities include:
- regulating blood glucose and other aspects of energy metabolism
- processing carbohydrates, fats, and proteins
- producing bile for fat digestion and absorption
- making albumin and many blood-clotting proteins
- converting ammonia into urea
- processing medications and other chemicals
- handling bilirubin produced from the breakdown of red blood cells
- storing glycogen, vitamins, and minerals
- contributing to immune defense
- modifying hormones and other circulating molecules
Together, these functions make the liver essential for maintaining the body’s internal chemical balance. Its importance becomes especially clear when liver function is seriously impaired: problems with metabolism, blood chemistry, digestion, immunity, and waste handling can emerge simultaneously because so many physiological systems depend on its work.
