What is Hepatitis?
The word "hepatitis" means inflammation of the liver, which is the body’s normal response to infection and toxic stimuli. The liver defends itself by trying to destroy or seal off viruses, damaged liver tissue or dangerous substances such as chemicals, alcohol or other drugs. This inflammatory response can protect against an infection or substance but may also cause damage in itself. Hepatitis can be caused by a number of factors.
Viral hepatitis can be caused by any of the six hepatitis viruses which are identified as A, B, C, D, E and G. These are discussed in more detail in the following sections.
A virus is a micro-organism with a simple structure of genetic material (DNA or RNA) and a protective coat of protein. In order to reproduce a virus must be inside living cells. It can then reproduce using the machinery of the cell to make more virus particles, disrupting the normal role of the cell and sometimes destroying it in the process.
Alcoholic or other drug hepatitis occurs when alcohol is consumed in quantities large enough to cause poisoning (this varies between individuals). The liver is involved in a number of body functions, including detoxification, digestion and metabolism, making it a primary target for alcohol-related harm. Alcoholic drinks contain ample calories but little nutrition, which may result in under nourishment for people who consume excess alcohol. Researchers suspect both alcohol and poor nutrition are involved in the onset of alcoholic hepatitis (Polsdorfer, 2007). Prolonged exposure to some chemical agents can also produce a similar response. This includes some prescribed medications if taken at high dosages.
Autoimmune hepatitis is a disorder of immune regulation, resulting in a destructive response of T-cells on the liver. There is a genetic predisposition to this form of hepatitis, as well as associations with other autoimmune disorders such as thyroid disease, autoimmune diabetes and rheumatoid arthritis (Farrell, 2002, p.254).
Damaged liver tissue, gall bladder or pancreatic problems as well as other infections can also cause inflammation of the liver.
In order to discuss viral hepatitis, it is important to understand the vital roles of the liver. The liver is located in the top right hand corner of the abdominal cavity, lying just below the diaphragm (the large muscle that separates the lungs from the abdomen and helps to control breathing). The gallbladder is tucked underneath the liver, with the stomach just to the left. Weighing almost 1.5kg in an adult, the liver requires nearly one third of the blood flow through the body at rest to carry out its many important functions.
The liver has four important roles which include:
- producing proteins to help digestion,
- storing essential proteins, carbohydrates, vitamins and minerals,
- cleaning up toxic substances and dead cells (detoxification) and
- producing essential proteins and substances required for body functions.
Food is made up of carbohydrates (commonly called sugars and starches), proteins, fats, vitamins and minerals. Food enters the stomach for the first phase of digestion, then passes on to the small intestine for further digestion. The liver assists in the process by making bile salts and digestive enzymes – special proteins that help to break down food to give the body energy. Bile salts are made by the liver but stored in the gall bladder. Bile is a complex fluid containing bile salts and other substances that are secreted into the small intestine. Bile acts like a detergent, making the fat more easily broken down and absorbed. Many waste products are secreted into bile before leaving the body in faeces. Cholesterol and bilirubin (a waste product from old red blood cells) are also excreted with bile. When the liver does not function properly, fat digestion is particularly affected. Fat-soluble vitamins such as vitamin A, D, E and K may not be well absorbed under these circumstances.
The liver stores essential substances such as iron and some vitamins, including vitamin B12. It is also critical in the maintenance of brain function, as it takes up glucose absorbed after a meal and turns it into glycogen (a form of glucose or sugar suitable for storage). Glucose is the only form of energy that the brain can use, so this store is essential to ensure that there is always enough glucose for the brain. When liver glycogen reserves become depleted (after not eating for hours), the liver begins to make glucose from other forms of energy such as proteins in the body. Excess carbohydrates and proteins are also converted into fat for storage, and fats are also broken down for energy when needed.
When digestion has occurred, the broken down parts of carbohydrates, proteins and fats, vitamins and minerals are absorbed directly into the liver. The liver also acts as a filter against toxic substances (chemical and infectious) entering the main blood system. Toxic substances can also be changed into substances that can be removed by the kidneys. For example, ammonia is a toxic substance that comes from the breakdown of proteins. The liver changes ammonia into urea which is easily processed and removed by the kidneys.
Essential proteins and substances for body function
Proteins and other substances play major roles in the growth, reproduction and control of the body cells. The liver is crucial in the production of hormones (like oestrogen, progestogens, testosterone, cortisol and insulin). It also produces proteins needed for circulation (like plasma proteins to help keep the water balance in the body just right, and the blood pressure okay), proteins for blood clotting (like prothrombin and fibrinogen) and antibodies needed by the immune system. The liver makes lymph as well as kupffer cells, both of which help remove toxic substances from circulation.
The liver has a large blood supply that not only provides oxygen and nutrients to working liver cells, but also carries blood that is rich in food from the gut for processing. A large volume of blood flows through the liver every minute.
Hepatitis Council of Victoria (2005) Impact: Hepatitis C information (4th Ed.) Hepatitis Council of Victoria, Brunswick, Victoria
J. Ricker Polsdorfer MD www.healthatoz.com
Farrell, G (2002) Hepatitis C, other liver disorders and liver health: a practical guide.