Liver

What is the Liver?

The liver is the largest glandular organ of the body. It weighs about 3 lb (1.36 kg). It is reddish brown in color and is divided into four lobes of unequal size and shape. The liver lies on the right side of the abdominal cavity beneath the diaphragm. Blood is carried to the liver via two large vessels called the hepatic artery and the portal vein. The heptic artery carries oxygen-rich blood from the aorta (a major vessel in the heart). The portal vein carries blood containing digested food from the small intestine. These blood vessels subdivide in the liver repeatedly, terminating in very small capillaries. Each capillary leads to a lobule. Liver tissue is composed of thousands of lobules, and each lobule is made up of hepatic cells, the basic metabolic cells of the liver.  

Structure of the Liver

The liver consists of four sections, or lobes. There are two main lobes--the right lobe, which is by far the larger, and the left lobe. Two small lobes lie behind the right lobe.

Each lobe is made up of multisided units called lobules. Most livers have between 50,000 and 100,000 lobules. Each lobule consists of a central vein surrounded by tiny liver cells grouped in sheets or bundles. These cells perform the work of the liver. Cavities known as sinusoids separate the groups of cells within a lobule. The sinusoids give the liver a spongy texture and enable it to hold large amounts of blood.

The liver has an unusual blood supply system. Like other organs, the liver receives blood containing oxygen from the heart. This blood enters the liver through the hepatic artery. The liver also receives blood filled with nutrients, or digested food particles, from the small intestine. This blood enters the liver through the portal vein. In the liver, the hepatic artery and the portal vein branch into a network of tiny blood vessels that empty into the sinusoids.

The liver cells absorb nutrients and oxygen from the blood as it flows through the sinusoids. They also filter out wastes and poisons. At the same time, they secrete sugar, vitamins, minerals, and other substances into the blood. The sinusoids drain into the central veins, which join to form the hepatic vein. Blood leaves the liver through the hepatic vein.

Each lobule also contains bile capillaries, tiny tubes that carry the bile secreted by the liver cells. The bile capillaries join to form bile ducts, which carry bile out of the liver. Soon after leaving the liver, the bile ducts join together, forming the hepatic duct. The liver manufactures bile continuously, even if the small intestine is not digesting food. Excess bile flows into the gall bladder, where it is stored for later use. Bile from the liver and gall bladder flows into the small intestine through the common bile duct. 

What the Liver Does

The liver is the largest organ in the body. It is located on the right side of the abdomen (to the right of the stomach) behind the lower ribs and below the lungs. The liver performs more than 400 functions each day to keep the body healthy. Some of its major jobs include:

  • converting food into nutrients the body can use (for example, the liver produces bile to help break down fats)

  • storing fats, sugars, iron, and vitamins for later use by the body

  • making the proteins needed for normal blood clotting

  • removing or chemically changing drugs, alcohol, and other substances that may be harmful or toxic to the body

Basic Functions of the Liver

The liver is the largest and one of the most complex organs in the body. It is located on the right side of the abdomen. The liver performs four basic functions:

  • It aids in digestion by helping in the absorption of fat and certain vitamins, including vitamins A, D, E, and K

  • It helps distribute the nutrients found in food

  • It helps "clean" the blood by removing medications and toxins

It produces important proteins that affect the blood, such as factors that are essential in making the blood clot after an injury.                                                                                                                    

Yet the liver is the link between the digestive and the circulatory systems. Some of the most important functions of the liver follow.

• The liver secretes bile that aids in the digestion of our food; for without it digestion could not take place.

• The liver detoxifies the blood and stores glucose, (i.e., sugar) the chief source of energy for the body.

• The liver acts as storage for numerous vitamins and minerals.

• The liver makes various substances that aid in the clotting of blood.

• The liver regulates the body’s metabolism.

• Finally, the liver regenerates itself.

These are just a few of the more than 500 functions of the liver.

The liver produces bile, which aids in the digestion and absorption of fats. Bile also aids in the absorption of substances such as vitamins A, D, E, and K and medication that patients take as an immunosuppressive agent following liver transplantation. The bile is stored in the gallbladder (which is located just below the liver) and then released into the intestines as needed. Together, these organs process the nutrients found in the foods we eat.

The liver also helps filter many chemical substances and waste products from the blood. Most medicines are cleaned from the bloodstream by the liver. The liver also removes any alcohol that's consumed.

Symptoms of Liver Disease

The symptoms of liver disease include:

  • jaundice (yellowing of eyes and skin)
  • severe itching
  • dark urine
  • mental confusion or coma
  • vomiting of blood
  • easy bruising and tendency to bleed
  • gray or clay-colored stools
  • abnormal buildup of fluid in the abdomen

Prevention

Prevention of liver diseases consists mainly of avoiding risk factors for liver disease or of prophylaxis by immunization.

Risk factor modification

  • Abstinence or reduced alcohol intake (Alcoholic liver disease, deterioration of other liver diseases).

  • Caution regarding intimate contact and use condoms when sexually active (HBV, HCV, HDV) - the hepatitis B virus is also present in saliva and, unlike HIV, can be transmitted through this fluid!

  • Careful hygiene when traveling (HAV).

  • Avoid accidental exposure to blood or needle stick (HBV, HCV) - the chance of HBV infection by needle stick is approx. 500 times greater than that of HIV infection.

  • Avoid syringe sharing if IV drug abuse (HBV, HCV).

  • Avoid potentially hepatotoxic drugs for the prevention of liver disease progression.
     

Potentially hepatotoxic medications

Analgesics

  • NSAIDs (Avoid in patients with chronic liver disease)

  • Acetaminophen = paracetamol (> 4 grams in 24 hours in adults; limit to < 2 grams in chronic liver disease)

Medications for diabetes

  • Acarbose

  • Pioglitazone

  • Sulfonylureas

Lipid-lowering medications

  • Statins

  • Nicotinic Acid

Antibiotics

  • Amoxicillin / Clavulanate

  • Erythromycin

  • Isoniazid

  • Nitrofurantoin

  • Tetracycline

Antifungal medications

  • Fluconazole

  • Itraconazole

  • Ketoconazole

Anticonvulsant medications

  • Phenytoin

  • Valproic acid

Psychotropic medications

  • Bupropion

  • Tricyclic antidepressants

  • Chlorpromazine

Hormonal medications

  • Tamoxifen

  • Testosterone

Miscellaneous medications

  • Halothane

  • Methotrexate

  • Etretinate

Avoid potentially hepatotoxic supplements for the prevention of liver disease progression, e.g. some mushrooms (amanita species), Echinacea, gentian, iron, mistletoe, sienna fruit extract, valerian root, vitamin A.

  • Institute low-fat diet.

  • Avoid potentially hepatotoxic chemical agents, e.g. aerosol cleaners, insecticides.

Causes Of Liver Diseases

Liver disease may be caused by one or more different factors. Most common causes for liver disease are alcohol abuse, viral hepatitis, genetic disorders, obesity, cancer, autoimmune disorders and drugs and other toxins.

Alcohol abuse is the major cause of liver disease in the US and most western countries. Like viral hepatitis and fatty deposits present in morbid obesity, it can lead to scarring and inflammation of the liver, which is known as cirrhosis.

Long exposure to harmful factors like certain drugs and copper may cause liver malfunction as well, and anomalies in the immune system can cause the body to attack its own liver as if it were a foreign element. Cancer is also an extended cause of liver disease, and most of the times presents itself as a manifestation of metastasis of a tumor present in another place in the body.

Liver Diseases

Several diseases can injure the liver and stop it from working correctly.  

These include:

  • Hepatitis

             viral hepatitis

  • Hepatitis A

  • Hepatitis B

  • Hepatitis C

  • Hepatitis D

  • Hepatitis E

  • Hepatitis G

Non viral hepatitis

  • Alcoholic hepatitis

  • Toxic/drug-induced hepatitis

  • Autoimmune Hepatitis

  • Granulomatous hepatitis

     

  • Budd Chiari

  • Cirrhosis

  • Cystic disease

  • Fatty liver and Non-Alcoholic Steatohepatitis (NASH)

  • Gallstones

  • Gilbert's syndrome

  • Haemochromatosis     

  • Obstetric cholestasis

  • Primary biliary cirrhosis

  • Primary sclerosing cholangitis

  • Portal hypertension

  • Wilson's disease

  • Liver cancer

  • Jaundice