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The Liver BookA Comprehensive Guide to Diagnosis, Treatment, and Recovery
By Sanjiv Chopra
Atria BooksCopyright © 2002 Sanjiv Chopra
All right reserved.
Chapter One: What Is the Liver? What Does It Do?
There, inside, you filter and apportion
You separate and divide,
You multiply and lubricate
You raise and gather
The threads, the grams of life.
-- PABLO NERUDA, "Ode to the Liver"
The liver is a powerful organ that has long been linked to human bravery, courage, and strength. People who are called chicken-livered or lily-livered are thought to be fainthearted and cowardly. Those possessed of a robust liver, in contrast, are thought to have both physical might and spiritual integrity. Indeed, the liver is considered by some to be the seat of the soul. In ancient times, augurs used animal organs to portend the future, and a deep red, healthy liver was an omen that all would be well. Today, with all of our scientific and medical advances and know-how, we still look to the liver as a measure of our vitality, for it has a unique and essential role in sustaining life.
If you've recently been diagnosed with a liver disease, you may be thinking about this all-important organ for the very first time. In this chapter, I'd like to share with you some basic details regarding where your liver is situated in your body and its essential functions. Once you have a clear idea of what this organ is all about, in the next chapter I'll tell you what you can expect if you visit your primary care physician or liver specialist and you are told that something in your liver may have gone awry. Then, in the chapters that follow, you'll find a guide to the symptoms, diagnosis, and treatment of major liver diseases.
WHERE IS YOUR LIVER?
If you take your right forefinger and trace the bottom of your right rib cage, you're very close indeed to the bottom of your liver, which lies for the most part just beneath your lower ribs. The top of your liver is roughly at the level of your nipples. Situated in the right upper part of your abdomen, your liver is sheltered by your rib cage on the right side. It rests below your lungs and above your kidneys.
Beneath the liver is your gallbladder. This tiny pear-shaped, saclike organ receives bile, a yellowish green fluid that the liver produces to help digest and absorb fats. The gallbladder concentrates bile before passing it into the small intestine via a tube called the common bile duct.
Blood also travels through the liver in fairly copious amounts. About two-thirds of the liver's blood supply enters this organ through the portal vein; the remaining third arrives, well oxygenated, via the hepatic artery. Hepatic means liver, and the hepatic artery is the only artery that enters the liver from the aorta, which carries blood from the heart. As blood exits the liver, the hepatic veins carry it away to the right side of the heart.
WHAT IS THE LIVER LIKE?
Your liver is the largest organ in your body. It weighs about three pounds and in some people is about as large as a standard-size football. In adults it represents roughly one-fiftieth of total body weight; in infants it's relatively larger, comprising one-eighteenth of body weight.
Your liver is composed of two major lobes: a left lobe and a right lobe that is five to six times bigger than the left. These lobes are separated by a smooth membrane called the falciform ligament. On the outside, a healthy liver is smooth and reddish brown because of its rich blood supply. (In medical jargon, we would say that it's a very "vascular" organ.) On the inside, the liver consists of a busy and intricate network of ducts, veins, and liver cells. The liver cells are called hepatocytes.
WHY IS THE LIVER SO IMPORTANT?
A healthy liver, which is so critical to our well-being, is akin to a master conductor who is orchestrating a number of essential functions. It acts as a central manufacturing factory, toxic-waste-processing plant, and warehouse. It's also a site where many ingenious transformations occur.
The Liver as a Factory
Albumin and blood-clotting proteins
The liver produces a major protein in the blood called albumin, which is key to regulating the fluid balance within our bodies. It is also the place where the major coagulation, or blood-clotting, factors are produced. In the next chapter, I'll tell you how doctors measure these proteins in your blood to determine how well your liver is functioning.
Throughout history, the connections that man has made between the liver and the human spirit have extended to one of this organ's important products: a substance called bile. People once spoke of "having bile" when they were referring to either a fiery temper or melancholia. Today the term is still used to mean an inclination to anger. Another term for bile, gall, has long been associated with wrath and rancor.
In truth, bile doesn't have anything to do with a sour mood. Rather, it's a fluid -- consisting of water, bile salts, a pigment called bilirubin, and other substances -- that is necessary for the breakdown of fats by the intestines. The liver produces bile continuously, and its flow to the intestines is very important. Blockage of the flow of bile can lead to a condition called cholestasis. This problem is associated with several disorders, including one called primary biliary cirrhosis, which I'll tell you about later in this book.
Ammonia is a chemical that is produced as a by-product of digestion. One of the liver's many tasks is to break this substance down. In doing so, it forms a waste product called urea. If the liver isn't functioning well, ammonia can build up in the body and can cause mental confusion.
THE LIVER AS AN INGENIOUS ENGINE THAT PERFORMS MAGIC
The liver magically transforms quite a number of substances such as cholesterol and fats into other substances. These "metabolic" processes result in the production of essential substances that the body needs as well as waste products that it can readily dispose of. Let's look more closely at the materials that the liver refashions.
Red blood cells, which carry oxygen through your body, only live for 90 to 120 days. When they die, they release a pigment called bilirubin, which is taken up by the liver and metabolized into a water-soluble substance that is excreted in bile. The bile flows in the bile ducts and is transported into the intestines. Bilirubin breakdown is a normal activity of a healthy liver. If your liver is damaged and it fails to keep up with such tasks, this bile pigment can accumulate in your blood, causing your skin and the whites of your eyes to look yellow, or jaundiced.
Your liver also synthesizes steroids, including cholesterol (a fatty substance that can clog the arteries and is the main constituent of the major kinds of gallstones encountered in the West). Your liver is the sole organ that removes cholesterol from the body. Cholesterol within the liver is converted into bile acids (which are essential for fat digestion), bile salts, and phospholipids, which are fats that are essential for cell maintenance and important sources of fuel for the body.
The liver plays a pivotal role in maintaining blood sugar concentrations within a relatively narrow range. It transforms sugars such as galactose and fructose to another kind of sugar called glucose. Glucose, in turn, is converted to a substance called glycogen, which you might think of as a box that is used to store carbohydrate energy in the warehouse of the liver.
THE LIVER AS WAREHOUSE
In addition to its creative and transforming capacities, the liver serves as a storage place for extra amounts of energy and iron.
Glycogen, the storage unit of carbohydrate energy that I mentioned earlier, is housed in the liver. You may have heard of marathon runners who practice "carbo loading," or consumption of large amounts of carbohydrates, such as bread and pasta, before a race. When they need a boost of energy, the glycogen is converted back to glucose and is sent to the muscles and other organs.
Lastly, most of the body's stores of iron are found in the liver. In a disorder known as iron overload, excessive amounts of this trace mineral are absorbed by the gastrointestinal tract and then deposited in the liver, where a buildup of too much iron can cause liver damage (see chapter 11).
THE LIVER AS A PURIFICATION PLANT
The last significant role of the liver that I'd like to tell you about is that of purification, or detoxification.
Blood flowing from your intestines into the liver is contaminated by bacteria. Inside the liver, cells called Kupffer cells filter and remove bacteria from your blood.
As I said earlier, ammonia, a toxic chemical produced in the intestines when we digest foods, finds its way to the liver, where it is converted to a substance called urea that can be excreted by the kidneys. If a diseased liver fails to purge this poison from the body, ammonia can build up in the blood and affect the central nervous system to the extent that it can cause sleepiness, confusion, and even coma.
As you'll read in chapter 8, alcohol, like many other toxins, is broken down and converted to other substances by your liver. In its attempts to clear this chemical from the body, the liver creates a substance called acetaldehyde. This by-product of alcohol metabolism can be quite damaging to liver cells.
In addition to dangerous chemicals like ammonia and alcohol, the liver is responsible for "detoxifying" all kinds of drugs, including many antibiotics, sedatives, tranquilizers, and drugs used to lower cholesterol or thin the blood. If your liver is not functioning well, major drug reactions can occur.
Now that you know where the liver is located and how it functions when it's working properly, let's move on to chapter 2, where you'll find a brief run-through of what you can expect when you go to your doctor's office because of a liver problem.
Copyright © 2001 by Sanjiv Chopra
Excerpted from The Liver Book by Sanjiv Chopra Copyright © 2002 by Sanjiv Chopra.
Excerpted by permission.
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