Key Control Center

Take the heart, for instance. I regulate the blood flow to it. Should there be a temporary surge of blood, I swell, absorbing the excess that might smother its pumping action. Then I emit the blood gradually so the heart can handle it. Being the vascular sponge that I am, I can soak up some three pints of blood, or I may hold as little as a few ounces.

I am also keenly interested in your food. The food you eat passes from your stomach to your intestines, where it is broken down, and usable materials are sent into the bloodstream. I am so situated that these materials first come to me. They are delivered to me by the large portal vein, which connects with the network of intestinal veins.

Portal is an appropriate name for this vein. It serves as a ‘port’ or ‘gateway’ through which food materials must pass before reaching the tissues of the body. And since the portal vein flows into me, I am able to monitor all of these materials, converting them into a form usable by the cells of the body.

My strategic position also allows me to protect you from harmful bacteria absorbed into the portal bloodstream. I have what are called “Kupffer cells.” These act somewhat like scavenger white blood cells. They capture, engulf and destroy bacteria as they pass through me. If it were not for this protection that I afford, a serious infection might develop somewhere in your body.

I also protect you from other toxic substances, such as caffeine and various drugs. If you were to inject such substances into my exit blood vessel that leads to the heart, you might be dead in minutes. But since they must first pass through me, I am able to safeguard you.

Also, ammonia is constantly being formed as your body cells burn protein. The ammonia is absorbed into the portal bloodstream and comes to me. If it were allowed to accumulate in your body, you would die. But I take good care of you. I form urea from the ammonia and pass it along to the kidneys for elimination.

But due to the manifold and complex biochemical reactions involved, any description of my processes must be an extreme simplification.

For example, I receive sugar by way of portal blood in the form of glucose. This serves as fuel for your body. But if too much is fed into the bloodstream, you will go into a coma and die. So I see that this does not happen.

If there is sufficient glucose in the bloodstream, I convert the excess glucose I receive to glycogen. This is a convenient, compact form of storage for glucose, which, in its own form, would take up too much room. Then as the body needs fuel throughout the day, I change the glycogen back to glucose and send it out bit by bit. Such transformation, one doctor writes, “involves a highly interrelated and complex sequence of enzymatically controlled events.” Yet for me it is a simple, basic procedure.

I also produce the fibrinogen and prothrombin that clot your blood. You would bleed to death from a minor cut without them! Yet, at the same time, I figure in the manufacture of heparin, which keeps the blood from getting fatally thick. One doctor likened this action of mine to making atom bombs and fuses simultaneously, without an accident or fatal explosion. Be grateful that I don’t get mixed up in what I’m doing!

Another substance I make is albumin. It keeps fluid from leaking out of your blood vessels into surrounding tissues. And to provide you resistance against infectious disease I make globulin, which contains immune bodies.

Yet another of my marvelous productions is bile​—that bitter, green-yellow liquid. I form it continuously​—up to a quart a day—​dribbling it into your nearby gallbladder for storage. It’s amazing what goes into it. For instance, each second ten million of your red blood cells die. As they pass through me, I pick them out, salvage parts for making new blood cells, and use some of the debris in bile production!

By means of bile I expel unwanted materials from your body. The bile is discharged into the intestinal tract, and from there it finds its way out of your body.

But bile is also important in the digestion of fats, being passed into your intestinal tract at mealtime. It aids, too, in the absorption of fat particles and vitamins from the intestinal tract into the bloodstream. Thus, I make and deliver bile to the intestinal tract so that important nutrients can be released and sent back to me by way of the bloodstream!

After I finish processing food materials, producing the nutrients your body needs, I may send them immediately into the bloodstream. This food-laden blood goes up to your heart, from where it is pumped to every cell of your body. Or, if they are not needed immediately, I store nutrients for later use​—sugars, fats, proteins, vitamins and iron being my principal storage staples. Then when these are needed, I send them out. I can also convert nutrients from one form to another​—sugars into fats or fats into sugars—​to satisfy your body’s needs.

And what causes cirrhosis? Overindulgence in alcohol is a principal factor. I convert alcohol into carbon dioxide and water, preventing a fatal buildup of it in your blood. But when a person daily consumes large amounts of alcohol, his liver cannot take it. It breaks down, becoming shrunken, hard and knobby. If this is not stopped, death will ensue.