The Liver – An Amazing Organ
Where is your liver, and what does it look like?
A large, complex, triangular-shaped solid organ, the liver is located in the upper right abdomen, just below the diaphragm and behind the ribs, extending across the midline to the left side. It is the largest and heaviest internal organ, weighing about 1.5 kilograms. The liver is the only organ with two blood supplies: the hepatic artery, which brings blood from the heart, and the hepatic portal vein, which brings all the blood from the intestines. Blood leaves the liver through the hepatic veins. At a microscopic level, the liver is composed of individually functioning units called lobules, containing areas with blood vessels, ducts, and intervening cords of liver cells (hepatocytes).
How does your liver affect digestion and absorption?
The hepatocytes manufacture bile, a yellow or green alkaline fluid, containing bile salts. This synthesizing and secreting function of the hepatocytes means that the liver is also a gland. Bile travels from the liver cells through a network of ducts to the gallbladder for storage and concentration – to as much as five times its original potency. During a meal, the gallbladder releases bile into the small intestine to assist with digestion and absorption of dietary fats. Bile also contains bicarbonate ions, which help neutralize acid carried from the stomach to the small intestine. Bile salts originating from the liver aid in converting vitamin D into its active form, which is necessary for calcium utilization. This organ is also pivotal in absorption of other fat-soluble vitamins.
What are the metabolic functions of your liver?
Metabolism refers to the complex biochemical processes and reactions that take place in the human body. Carbohydrate, fat, and protein metabolism all require inputs from the liver, which stores glucose (derived from carbohydrates) when it is abundant, and releases it when needed, thereby ensuring a steady energy supply for the body. The liver also converts fats into an energy source for the body. This organ is the site for breakdown of protein into amino acids, as well as conversion of amino acids to glucose, fats, and proteins. Finally, the liver is responsible for the synthesis of cholesterol and regulation of cholesterol levels.
How does your liver affect blood clotting?
Bleeding within the body activates a complex system of plasma proteins, called coagulation factors, which promote blood clot formation. The liver is responsible for producing most of these coagulation factors. Some of these factors require vitamin K for synthesis, and the liver produces the bile salts essential for intestinal absorption of this fat-soluble vitamin. Uncontrolled bleeding may occur if the clotting factors are not produced or if vitamin K is not absorbed
What other proteins does your liver make?
The liver produces most of the proteins found in blood. Albumin is a major protein made by the liver that plays an important role in regulating blood volume and distribution of fluids in the body. One possible result of liver dysfunction is low albumin levels, which can lead to abnormal fluid retention causing swollen legs and abdominal distension. The liver also produces ferritin (a protein used to store iron in the body) as well as proteins that bind to hormones, lipoproteins involved in cholesterol transport, and acute phase proteins involved in inflammation and infection.
What are the hormonal functions of your liver?
The liver has many key functions associated with hormones in the body. For example, the liver is involved in the chemical conversion of thyroid hormone into its most active form. Thyroid hormone is responsible for modulating the body’s metabolic rate, the speed at which complex biochemical processes and reactions take place. In addition, the liver secretes IGF-1, a hormone that promotes cell growth. Angiotensinogen is another hormone produced by the liver. This hormone is part of a complex system that regulates sodium and potassium levels in the kidneys and is involved in blood pressure control. In addition, the liver regulates hormone levels by breaking down and removing these chemical messengers from the body when they are no longer needed.
What is your liver's role in breaking down unwanted substances?
Together with the spleen, the liver helps to degrade old red blood cells into breakdown products, such as bilirubin and other bile pigments. The liver extracts these products from the blood for elimination via urine and stool. When the liver fails to function properly, bilirubin may accumulate in the body and result in a yellow appearance of the skin and eyes, known as jaundice. The liver also plays a large role in detoxifying and breaking down toxic poisons, drugs, alcohol, and waste products. In patients with liver failure, these unwanted substances tend to accumulate in the body and potentially lead to toxicities.
The liver, truly an amazing organ!
A strong, working liver is vital for human health. This remarkable, hard-working organ and gland is responsible for a host of essential bodily functions, comprising critical roles in digestion and nutrient absorption, complex metabolic functions, protein production, and hormonal production and regulation. Moreover, it is the primary organ involved in the breakdown of every toxic substance your body encounters, whether you ingest, inject, touch, breathe, or otherwise come into contact with it, preventing accumulation of waste products.
- The liver can regenerate itself! As long as at least 25% of the healthy liver remains, it can become whole again.
- The ancient Greeks may have somehow known this fact, as in Greek mythology, the gods punished Prometheus for giving humans fire by chaining him to a rock, where a vulture would peck out his liver. Each night his liver would regenerate and the agony would repeat the next day.
- Not only is it the largest gland in the body, the liver is the most complex in function.
- We all know that alcohol consumption takes its toll on the liver, but did you know that cigarette smoking is bad for your liver too?
- A healthy liver filters about 1.7 litres of blood per minute.
- It contains 300 billion specialized cells.
- As far back as 400 BC, the importance of bile was recognized.
- Hippocrates believed that an imbalance of any of the four bodily humors, blood, phlegm, yellow bile, and black bile, would cause illness.
- It can produce as much as one litre of bile per day. The body reabsorbs most of the bile salts at the terminal ileum and regularly sends them directly back to the liver for reuse.
- During pregnancy, the liver increases in size and weight to accommodate the changing metabolic demands and hormonal balance of the mother.
- At any given moment, the liver holds about 13% of the body’s blood supply.
- More than 500 vital functions take place in the liver.
- A healthy human liver holds about a two-year store of Vitamin A.
- The Inuit will not eat polar bear liver or feed it to their dogs due to its toxic amount of Vitamin A.
- Although attempted in 1963, the first successful whole human liver transplant occurred in 1967.
- In 1989, surgeons transplanted a portion of a living adult’s liver into a child, resulting in both donor and recipient having normal liver function. Since that time, adult-to-adult living donations occur with a portion of the donor’s liver replacing the entire liver of the recipient. Over time, both livers grow into complete organs. Although amazing, this procedure still carries some risks.
Wilson W. Li, BSc(Pharm), MD
Faculty of Medicine, University of British Columbia
First published in The Inside Tract® Newsletter Issue 166 March/April 2008
Editor’s Note: A core aspect of your gastrointestinal health, the liver, is at the roots of our Society’s original mission in patient education. This organ was the focus of one of the very first resource pamphlets we published in 1976. GIS is pleased to present you with this article now, and plans to provide ongoing regular information about your liver. Look forward to more on this topic in upcoming issues of The Inside Tract®.