I hang between your stomach and your duodenum under it, attached to the intestinal mesenteries. I have two different identities in terms of my structure and function. I carry out two very different duties as a compound gland made up of both exocrine and endocrine tissues. So, I am granted a very special structure and chemical abilities to function well. One of my duties is related to the physiology of digestion: I break up the food passing from the stomach to the duodenum by pouring on it the four types of digestive enzymes I have been enabled to produce. These juices are carried through a tiny pipe to your duodenum. Two of them are used for breaking up proteins, one for carbohydrates, and one for fats. You don't even realize it! As the food you take in passes from the stomach to the duodenum, my enzymes begin flowing faster. This is a very fine balance: while food is being digested, neither the enzymes should be wasted, nor should your intestinal walls be harmed. I don't control the release of the enzymes. That duty is given to two hormones produced in your intestinal mucosa by the stimulus of the vagus nerve. When those hormones reach me by the bloodstream, my cells are stimulated and they secrete water, bicarbonate, and the digestive enzymes I mentioned and they flow into your duodenum through my duct.
My second job is the production of insulin and glucagon hormones, as the endocrinal pancreas. My cell clusters, which are also known as islets of Langerhans, have different types as separate groups, which you call alpha and beta. The insulin, which is produced by my beta cells, is used for regulating the glucose level in your blood. The duty of insulin is to stimulate your body cells to take the glucose in your blood and use it.
After you have a meal, the carbohydrates in it are broken down into glucose molecules, pass into the blood, and increase your blood sugar. For your body to function in a healthy way, the amount of glucose should be around 100mg/ml (it varies from 80–120). When the level is above the normal value, I secrete insulin. In this way, the sugar is carried to your cells and burned to produce energy, and its increase in your blood is brought back under control. Also, insulin helps you to store sugar in fat tissues and to turn them into fatty acids, and it slows the breaking down of fatty acids. Moreover, insulin helps you to make protein in your body by holding amino acids within your muscle tissues and storing glucose in your liver and turning it into glycogen.
The failure of my beta cells to secrete insulin is a serious problem; the consequence is "diabetus mellitus," or what we commonly know as diabetes. A person with this disorder must abstain from various delicious foods and drinks. In cases where a strict diet does not solve the problem, patients may have to take insulin shots every day. Diabetes can cause many complications by damaging your nerves and blood vessels; I won't go into types of diabetes so I don't get sidetracked too much. I just wished to make a point: even a substance produced by a tiny cluster of cells can upset the functioning of many of your mechanisms. After having a meal, put your hand to the left of your abdomen below the stomach and remember what a blessing I am!
As for the glucagon hormone I secrete from my alpha cells, it does just the opposite of insulin and causes the sugar stored in your cells to be released into your bloodstream. When your blood sugar decreases-due to hunger, overwork, exercise, and so on-it causes the glycogen in your liver to be used in order to increase the level of your blood sugar. As adrenalin secreted by the adrenal glands helps glycogen to be broken down and to be released into the blood as glucose, they function as an integrated system. Glucagon also slows down the synthesis of glycogen, and it accelerates the break-up of proteins and fat metabolism. I think now you get it, Peter. Insulin and glycagon are parts of a biological feedback mechanism controlling one another. People discovered all these facts after years of lab research; now do you see how ridiculous it is to see me as a work of blind chance?
Like any other organ, I can also contract various diseases. The most common ones are acute or chronic inflammation, tumors, and cysts. I am easily troubled with inflammation in people with alcohol habits. Since enzyme secretions-and therefore digestive processes-are then not carried out properly, some undigested fats and fibers with proteins are excreted with the feces. A problem can arise with the intestines due to digestive deficiency. And if I completely fail to fulfill my duty owing to a chronic inflammation or tumor, then doctors take me out and you become dependent on insulin and a special liquid obtained from the pancreas.
It is sad to say that my cancer is not quickly recognized. It develops very fast and I try to keep up my duty as long as possible. Therefore, it is usually too late when diagnosed. There is nothing much modern medicine can do after it spreads. Although it is not definite yet, I suspect cigarettes play a role in my cancer.
As for diabetes, even though a promising method of treatment has been discovered, certain problems haven't been overcome yet. The transplant of beta cells from the pancreas of someone who has just died-with as much tissue compatibility as possible-has had partial success. As with every other organ transplant, tissue rejection is a challenge. If the human genome project succeeds and the genetic code of the human body is thoroughly solved, it may be possible to cure diabetes by genetic engineering techniques. This is only at research level for now, but if scientists do their best, it is possible to find a way, since there is a treatment for every disease except for old age and death. You see Peter, as the vicegerents on earth, you humans are supposed to explore the secrets of the universe and appreciate the beauties you discover. I think I have said enough now. Thanks for listening, Peter!
Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.