- 1 HOW DOES MY LIVER WORK?
How does my liver work?
What happens when my liver is injured?
Prevention is key
BY JOHN LAUERMAN
HOW DOES MY LIVER WORK?
An organ is a complex part of the body that performs specific jobs. Your liver is the second largest organ in your body; only your skin takes up more room than your liver. The liver weighs about 3 pounds and is divided into 4 sections, called lobes. You might feel the lower edge just under the right side of your rib cage, where, unlike the rest of your belly, it makes a solid sound when you tap on it firmly. Unlike kidneys, which come in pairs, we each have only one liver, so it’s important to keep it healthy.
But sometimes the liver comes under attack. You may have recently found out that you have a liver disease called hepatitis. In this chapter, you’ll learn first what your liver normally does for your body, and then how hepatitis makes an important difference.
It’s been known since ancient times that a damaged liver can grow back to its full size, or close to it. However, some diseases, including certain forms of hepatitis, can harm the liver and completely destroy it if they aren’t treated properly. If your liver is damaged, it can’t perform the jobs necessary to keep your body healthy, so you need to take care of it to the best of your ability. You absolutely need your liver to survive. Let’s find out why.
The liver’s many functions
The liver is an important passage way for substances moving along from the stomach to the intestines, and finally to the blood stream. Where food is concerned, your liver is like a protein machine shop transforming food into many chemical parts for use in other parts of the body. Some medicines are also changed by the liver. Your liver is also a warehouse for the body. It stores sugar and vitamins so your body can use them when they’re needed. In addition, your liver is a filtering station; it takes some waste and poisons out of your bloodstream.
In with the good
The food we eat travels down the throat into the stomach and then on to the intestines. These organs break up the food into small pieces that can be absorbed into the bloodstream. However, that’s not the last stop in preparing the food for use by the body. About 90% of these small pieces go straight from the intestines to the liver. The liver then sends this nourishment into the bloodstream so that it can be distributed to the cells that need it.
As we said earlier, your liver also stores energy. Carbohydrates, for example, are sugars that your body uses to get quick energy. Your liver stores some of these sugars and releases them between meals whenever your cells need nourishment. This way, the liver makes it easy for you to keep going all day without eating each time you need more energy.
Finally, your liver helps you digest fat and important vitamins stored in fat. Your small intestine cannot handle fat on its own, so your liver makes special substances called bile acids that break fat into pieces, almost the same way that dish detergent cuts through grease. Bile acids are necessary for you to absorb vitamins A, D, and E, all of which are found in fat. Your body uses each of these vitamins every day. Your liver stores other important vitamins, like vitamin B 12 and releases them as you need them.
Out with the bad
Your body needs ways of getting rid of harmful chemicals, and the liver is very important in this process. Any time you take medicine, even an aspirin, it’s your liver’s job to later remove the medicine from your bloodstream. If your liver isn’t functioning correctly, the medicine may stay in your bloodstream longer than it should, and that can cause problems.
Each time you take a drink of alcohol or use an illegal drug (like cocaine or marijuana), your liver goes to work filtering these substances out. The more alcohol or drugs you take, the longer it takes and the harder it is for your liver to get you back to normal again. People who drink too much or take too many drugs can do a lot of harm to their livers, sometimes to the point where the liver cannot heal.
Your body itself also naturally makes a lot of waste products. (Cells and organs are living factories, and they have “toxic waste” they need to get rid of.) Many of these wastes are poisonous and must be quickly broken down or they can cause harm to your heart, brain, kidneys, or other organs. Here again, the liver’s ability to filter is important, and the liver is responsible for breaking down these waste products and making sure that they are sent either to the intestines or to the kidneys to be excreted.
A chemical factory
Just as a factory takes different pieces of metal and builds them into a car, your liver takes natural chemicals such as proteins, carbohydrates, fats, and vitamins and makes them into substances your body needs. All our cells need different kinds of proteins to do different jobs (there are millions of proteins, and they can have very different effects in the body). Your liver takes these different proteins and reshapes them, either by cutting them into smaller pieces or assembling them into larger proteins so that they are just right for use by a particular part of the body. Your liver makes or breaks down thousands of different proteins every day. Here are some of them:
– Fibrinogen, prothrombin, and Factors V, VII, IX, and X. Proteins that are necessary for blood to clot, so that you don’t bleed to death from a small cut.
– Bilirubin is a yellow substance that builds up in your blood as red blood cells age and break down. Your liver is responsible for breaking down bilirubin, and when your liver isn’t functioning properly, you may get too much bilirubin in your system and become jaundiced, which means you have a yellowish color to your eyes and skin.
– Albumin is another important component of blood. It carries other substances around the body and helps prevent swelling.
– Cholesterol, which we often think of as a nuisance, is, however, important. Cholesterol is a key component of the membrane, or outer coat, of your cells. The right amount of cholesterol is necessary for cells to function properly. It is also a building block for sex hormones and vitamins.
– Enzymes are involved in the chemical reactions in the body. Some of these break down molecules the body can no longer use, while others react with other proteins to keep cells healthy.
The liver transforms medicines
Just like the food you eat, any medicine you take to improve your health also passes through your liver. The liver transforms some medicines into a form that your body can handle. For instance, any time you take aspirin, acetaminophen, or cold medicine, the liver changes these medicines, thereby helping them work in your body. Without your liver, these medicines won’t work properly. So how well your liver is working will affect how much and how often you need to take a particular medicine.
Your liver is a warehouse for the body. It stores sugars and some vitamins so your body can call for them when they’re needed.
What happens when my liver is injured?
Most organs get their supply of blood directly from the heart. However, because the liver has such an important role in preparing nutrition for the body, it gets its blood supply from both the heart and the digestive tract directly through a large blood vessel called the portal vein. This blood flows to millions of liver cells, called hepatocytes, which are organized into units called lobules. Each of these lobules is dedicated to carrying out the important body functions we’ve just discussed.
Sometimes, however, certain substances (like alcohol) or infections (like hepatitis) can keep the liver from doing its job. Such substances or infections scar or even kill hepatocytes, and can lead to a condition called cirrhosis. The hepatitis B and C viruses can also sometimes cause cancer, probably because they change the cell’s DNA, which is the part of the cell that tells it what to do. These two serious liver conditions are discussed below. (Viruses, and particularly the effects of chronic hepatitis B and C, are described in more detail in Chapter 3.)
Cirrhosis occurs when repeated damage to the liver results in widespread scarring. Blood cannot flow freely through scarred liver tissue. Eventually, if the damage continues, a high percentage of the liver may become scarred, and only a very small amount of blood can pass through the liver at one time.
Chronic viral hepatitis is a common cause of cirrhosis of the liver. (So is excessive drinking.) About 20% to 30% of patients infected with chronic hepatitis C virus will progress to cirrhosis.
As cirrhosis worsens, other changes that affect your health may start to take place:
– Limited blood flow in the liver may dangerously increase pressure in blood vessels in the stomach and lower throat. Increased pressure may lead to enlargement of the spleen, a small organ on your left side near your stomach.
– Slower blood flow through the liver may also cause increased pressure in your abdomen (from fluid), a condition called ascites.
– Clotting factors normally made by the liver may no longer be sufficient to stop bleeding, both from cuts and bruises on the skin and from internal blood vessels.
– The liver will no longer be able to clear drugs from the bloodstream, and patients will become more sensitive to the effect of the drugs. For instance, if your liver isn’t functioning properly, a normal dose of a sedative drug could make you overly drowsy.
– The liver will lose the ability to clear waste products from the blood. One of the first symptoms of this is often severe, constant itching. Also, the patient’s brain may become affected; thinking can become confused, and if liver damage is severe enough, the patient may lapse into a coma.
Cirrhosis can be stopped and sometimes even prevented. For patients with viral hepatitis, it’s important to prevent greater damage to the liver that will make cirrhosis even worse. Therefore, if you have viral hepatitis, avoid alcohol completely, and closely follow your doctor’s medical instructions about drugs and diet. (See Chapter 8 for more information about proper eating habits.)
As we discussed earlier, when viruses like hepatitis B and C infect cells, they alter parts of the cells, including the cells’ DNA. The damage to the liver cell results from the direct effects of the virus and from the immune system’s response to the infection. It is the damage to the liver cells that leads to the scarring.
There’s increasing reason to believe that this DNA alteration may have an important impact. It appears that while liver cells harbor virus, they go through changes that make it more likely for them to become cancerous. Patients chronically infected with hepatitis B or hepatitis C are at increased risk of hepatocellular carcinoma, a potentially deadly liver tumor. Without proper treatment about 20% of patients with cirrhosis go on to develop liver cancer.
The symptoms of liver cancer are often similar to those of cirrhosis, and are listed below:
– Fatigue and drowsiness
– Weight loss
Patients with liver cancer may find that they sometimes have severe abdominal pain. Liver cancer may also spread through the bloodstream, causing cancer in other tissues throughout the body.
If the cancer is small, it is often treated surgically. Because the liver can regrow, it’s sometimes possible to remove a great deal of liver tissue without long-term ill effects.
However, liver cancer is frequently extensive by the time it is discovered, and cancers may recur after surgery.
Prevention is key
Cirrhosis and liver cancer may take years to develop. In the meantime, it’s important to avoid alcohol, since that may do additional damage to your liver. Alcohol and acetaminophen (an ingredient in some over-the counter pain relievers, and many drug combinations used for colds) taken together can cause a condition called fulminant hepatitis, which can lead to fatal liver failure. Clearly, you should never combine these two substances, and talk to your doctor about any medications you take. (See Chapter 7 for discussions about other medications and alcohol.)
Now that you know more about how your liver works, you may want to learn about the hepatitis virus that has infected your liver, as described next in Chapter 3.
Q. Why is the liver important to nutrition?
A. The liver reconstructs and packages proteins and carbohydrates for use by the body’s cells. The liver stores sugars and vitamins. It breaks down fat and frees up essential vitamins stored in fat.
Q. What other important functions does the liver perform?
A. The liver filters medicines, alcohol, illegal drugs, and waste products from the body. The liver makes important proteins that are essential to the body, such as clotting factors and enzymes.
Q. What are two of the more serious long-term consequences of chronic hepatitis B or C?
A. Cirrhosis and liver cancer.
Q. Why is it important to avoid alcohol when you have hepatitis?
A. Alcohol can do more damage to the liver.
– Avoid alcohol, because it will do additional damage to your liver. In particular, do not combine alcohol and acetaminophen (an ingredient in some over-the-counter pain relievers and cold medicines).
– Be careful with any kind of prescription drug or over-the-counter medication. Liver damage can alter how you respond to these drugs. Ask your doctor about any medications you plan to take and report any change in your response to your physician.
– Find out how seriously the disease has already affected your liver. Be aware of the symptoms of cirrhosis and liver cancer, and consult your doctor if you notice any of these, so you can receive either quick reassurance (most likely you won’t develop these conditions) or treatment.