Can you name one thing that the liver does? What are the parts of the liver? Does its size have anything to do with its productivity?

Insights

How big is an average chemical factory? How big is a chemical factory that not only produces new chemicals, but also recycles old ones and turns them into more new chemicals? What if this factory also regulates other factories down the road and stores spare parts?

We're obviously talking about a very big and quite complex factory. Yet the tiny hepatic cell of the liver handles all these tasks and more, occupying a space so small that several hundred cells could fit on the head of a pin!

Located on your right side under the lower rib cage, the liver is actually the biggest gland in your body. It weighs about 1,600 grams (3.5 pounds) and contains millions of cells. Every single cell is its own complete factory, performing every job that needs to be done.

Here is a partial list of what one of these amazing cells can do:

• Make bile and send it down the bile duct. Bile is important for dissolving fats in the digestive tract.
  
• Collect nutrients from the portal vein.
  
• Synthesize important proteins for the blood, such as albumin, which is essential to the blood-clotting process.
  
• Convert extra glucose, the body's primary source of stored energy, into glycogen.
  
• Clean toxins from the blood.

Because of all this activity, the liver needs to be well-connected to the rest of the body. Two highways go into the liver: The portal vein, which carries nutrient-laden blood from the stomach and intestines, and the hepatic artery, which carries oxygen-rich blood from the heart and lungs. Two different kinds of highways lead out from the liver: The hepatic veins, which drain the blood from the liver, and the bile ducts, which take bile from the liver cells to the gall bladder. Every single cell is in close contact with all four of these highways. To get to each cell, each highway must divide into smaller and smaller branches.

The liver is truly a marvelous example of natural engineering. Next time you hear someone talk about recycling or chemical manufacturing, think about the recycling and manufacturing plant in your own body-the liver.

Connections
1. Alcohol abuse can cause serious damage to the liver. Illicit drugs in the bloodstream can create other liver problems. Why might the liver be especially sensitive to the presence of drugs in the bloodstream?
2. Do you see any advantage in the liver's location? Could you find a better location?

Key Words

artery vessel that carries blood from the heart to the body tissues
bile yellowish substance released by the gall bladder into the small intestine to aid in the digestion or breakdown of fats
duct small tube or conduit in the body that carries body fluids from one place to another
gall bladder organ that stores bile until it is needed in the small intestine to aid in digestion
gland organ comprised of similar cells that synthesizes or produces certain substances the body needs
glucose simple sugar that the body uses as an energy source
glycogen complex compound made from glucose for the purposes of energy storage
nutrient any chemical that provides energy or building blocks for the body
portal vein special vein that carries nutrients, absorbed by the gut, to the liver
toxins substances that can harm or destroy body cells and tissues
vein blood vessel that carries blood from body tissues back to the heart

Resources

1. Caselli, G. (1987) The human body and how it works. New York: Grosset and Dunlop.
2. Dorling Kindersley staff. (1991) The visual dictionary of the human body. New York: Dorling Kindersley.
3. Gamlin, L. (1988) The human body. New York: Gloucester Press.
4. Gibbs, W. (1993, Dec) Deliverance: Medicine closes in on an artificial liver device. Scientific American,
   pp. 30-33.
5. Parker, S. (1993) The body atlas. New York: Dorling Kindersley.
6. Sherlock, S. (1991) A color atlas of liver disease (2d ed.). St. Louis: Mosby Year Book.
7. Stein, S. (1992) The body book. New York: Workman Publishing.

Additional sources of information

1. Foundation for Advanced Education in the Sciences
   National Institutes of Health
   9000 Rockville Pike
   Bethesda, MD 20892
   (301) 496-7976
2. American Medical Association
   535 N. Dearborn St.
   Chicago, IL 60610
3. U.S. Public Health Service
   5600 Fishers Lane
   Rockville, MD 20857

Main Activity

The gut uses bile to physically break down fatty substances into smaller pieces. In this way, enzymes can more easily turn the fat chemically into fatty acids, which the small intestine can absorb for body needs. Simple dish detergents act on oils in a manner similar to the way that bile acts on fat. In the following activity, you will get a chance to see this process in action.

Materials

• 2 see-through glass or plastic cups, 240 ml (8 oz) in size
  
• dish detergent (for hand dish-washing)
  
• small amount of vegetable oil
  
• water
  
• 2 stirring rods or spoons

1. Pour about 120 ml (4 oz) of water into each cup.
2. Slowly and gently pour a small amount of vegetable oil into each cup. Pour enough so that there is a layer of about one or two centimeters of oil on top of the water. The exact amount is not crucial, but try to pour so that both cups contain about the same amount.
3. Take some time out to examine the way that the oil reacts with the water. Does the oil stay together as you pour it in? What happens to the oil if you wait two or three minutes?
4. After the oil has collected itself together (approximately five minutes), add a small amount (about seven drops) of the detergent to one of the cups.
5. Gently but quickly stir both of the cups with the stirring rods or spoons. Be careful to keep each stirring device in its own cup. Stir for about 15 seconds.
6. Observe what happens during the first five minutes after the cups have been stirred. Examine the contents in a bright light.
7. If you can, come back an hour later to observe any further changes in the cups.

Questions
1. How did the oil behave in the water before any detergent was added? What effect did the detergent have on the oil after the cups were stirred?
2. What possible benefit is there in breaking up fats physically into smaller pieces before any kind of chemical breakdown occurs, which changes the fat into its simpler components?
3. What use are detergents in washing dishes? Why do they make washing easier?

What does the medical condition known as jaundice have to do with the liver? Do some investigative work on your own. You or somebody you know probably had jaundice as a baby. Why?

The liver converts, produces, stores, excretes, and recycles many different substances. Try writing a job description for a liver cell. Be as complete as you can. Use an encyclopedia for more detailed information if you need it.

How does alcohol affect the liver? Is any amount of alcohol harmful? What is the treatment for cirrhosis of the liver? Call up a nurse or doctor and find out the health scoop on liver and alcohol.

Newton's Apple is a production of KTCA Twin Cities Public Television.
Made possible by a grant from 3M.
Educational materials developed with the National Science Teachers Association.