Liver - Anotomy, Functions, Disorders and Interesting Facts
Know your Body

The Liver

Authored by DesiMD Doctor on 20 Mar 2013 - 18:55

The liver, the largest solid organ in the human body, is also considered to be the largest gland. Actually, the liver is two different types of glands. It is both a secretory gland and an endocrine gland. A specialized structure, located within it, lets the liver both produce bile and secrete it into the bile ducts. Bile is a bodily fluid containing acids that aid in the digestion and intestinal absorption of fats as well as the fat soluble Vitamins A, D, E, and K. Waste products are carried into the intestines by the bile. Since the liver makes and secretes chemicals directly into the bloodstream, the liver is referred to as an endocrine gland. These chemicals affect other organs in the body.

Anatomy of the Liver

Weighing about three and a half pounds (1.6 kilograms), the liver is a reddish brown, “meaty” looking organ. Measuring about 8 inches (20 cm) across by 6.5 inches (17 cm) down, it is approximately 4.5 inches (12 cm) thick.

The liver lies immediately under the diaphragm which is the muscular membrane that separates the chest from the abdomen. Primarily situated in the upper right part of the abdomen, the liver is located mostly under the ribs but also extends across the center of the upper abdomen and part way into the left upper abdomen. Irregularly shaped, the liver is divided into two main components, the larger right lobe and the smaller left lobe. These lobes are separated by the falciform ligament. The liver also has two minor lobes. The upper border of the right lobe is located at the top of the fifth rib which a little less than one half inch below the nipple. In turn, the upper border of the left lobe is just below the fifth rib, about three quarters of an inch below the nipple. When you breathe in, the liver gets pushed down by the diaphragm. At the same time, the lower edge of the liver descends below the margin of the lowest rib known as the costal margin.

In order for the liver to carry out the secretory functions mentioned above, there are ducts that connect it closely to the gallbladder and intestines. Hence, the bile produced by the liver travels through these tubes on its way to the gallbladder. At mealtime, the bile stored in the gallbladder between meals, is discharged into the intestines to aid in the digestion of food.

Another special feature of the liver is that it is conveniently situated so that it directly receives the blood that comes from the intestines known as portal blood. As a result of its location, the liver can readily metabolize the nutrients absorbed from food and other contents of this blood. The liver’s numerous biochemical functions makes it the “biochemical factory of the body”.

A unique, dual blood supply services the liver. One part of the supply comes from the portal vein and the other from the hepatic artery. The latter brings oxygenated blood to the liver coming from the lungs, heart, and branches of the aortic artery. Tiny branches of the portal vein and hepatic artery travel within the liver together with the tiny bile ducts in what is known as portal tracts or triads.

The hepatic artery supplies blood to feed the bile ducts and the liver cells. These liver cells are also called hepatocytes. This blood joins with the blood from the portal vein in very small blood vessels called sinusoids. These tiny vessels, located on each side of hepatocytes, have a particularly porous lining. Such a unique arrangement allows the passage of large molecules, such as lipoproteins, through the sinusoidal lining to and from the liver cells. Blood travels in the sinusoids through areas known as the three acinar zones. Finally, the blood drains from the liver by way of the hepatic veins and it then heads back to the lungs and heart.

Functions of the Liver

  • As one of the most vital organs of the body, the liver has many complex and important functions.
    • Manufacturing of proteins including albumin. This helps to maintain the volume of blood as well as blood clotting factors
    • ​​Synthesizing, storing and processing of fats including fatty acids, which are used for energy, and cholesterol
    • ​Metabolizing and storing of carbohydrates. These carbohydrates are used as the source for blood glucose used by the red blood cells and brain
    • ​As previously mentioned, forming and secreting of bile which contains bile acids used to aid in the intestinal absorption of fats and fat soluble vitamins such as Vitamins A, D, E, and K.
    • Elimination, by way of metabolizing and/or secreting, the potentially harmful biochemical products made by the body. These include bilirubin which is formed from the breakdown of old red blood cells and ammonia resulting from the breakdown of proteins
    • Detoxification of drugs, alcohol, and environmental toxins in the body. This is accomplished by metabolizing and/or secreting of these substances

Disorders or Diseases of the Liver

  • The most common liver diseases include:
    • Various types of acute hepatitis (inflammation of the liver)
    • Chronic hepatitis
    • Cirrhosis (scarring of the liver)
    • Forms of cancers that most commonly affect the liver are metastatic cancers which have spread from other primary sites in the body by way of the bloodstream. However, primary liver cancers can also occur. Hepatocellular carcinomas are the most common types of primary liver cancer
    • Viruses, drugs and alcohol as well as metabolic immune system and hereditary abnormalities are the main causes of many diseases of the liver. Contrary to the popular misconception, excessive consumption of alcohol is only one of the many reasons for the development of liver disease. Sometimes, the cause of  a certain liver disease is not even known

The above mentioned liver diseases can interfere with the proper functioning of the liver thereby causing symptoms. However, it usually takes considerable damage to the liver before a disease, interfering with normal liver function, causes symptoms.

Examples of these Symptoms are

  • Jaundice which is a yellowing of the skin.  This can occur when the liver is not able to sufficiently metabolize or secrete the yellow pigment, known as bilirubin, in bile
  • Bleeding or bruising that may happen when the liver is unable to make enough normal blood clotting proteins
  • Edema or swelling of the legs with fluid. This occurs when the liver cannot make enough albumin and levels of serum albumin get too low
  • Fatigue, of unknown cause, may be related to impaired metabolic function of the liver

Interesting Liver Facts

  • On average, the liver secretes about a pint (500 ml) of bile a day
  • As a result of its diverse functions, a single liver cell can be compared to a factory (production), a warehouse (storage), a waste disposal plant (detoxification) and a power plant (heat production)
  • The liver is 96% water. This is the water inside the liver cells and blood
  • Words associated with the liver often contain the word hepato or “hepatic” coming from the Greek word for liver
  • A human liver is capable of regenerating itself. If as little as 25% of the organ is still healthy, it can rebuild itself into a fully functioning liver again