Digestion in the Stomach: When food is swallowed, it goes to the stomach. The stomach is a thin bag. In a man, it holds about three pints. Like the mouth, it does three things to the food.
First, the stomach gently stirs and mixes the food.
Second, it pours fluid over the food. This fluid is called gastric juice. The gastric juice is sour and bitter.
Third, the gastric juice changes some of the albumins in food to a liquid form.
If the mouth has done its work well, the stomach does its work easily, and we do not know it. But if the mouth has eaten food too fast and has not chewed it well, then the stomach must do the work of the mouth too. In that case, it gets tired and aches.
The intestine. The food stays in the stomach for only a little while. All the time, a little keeps trickling into the long coil of the tube. This tube is called the intestine or the bowels. Hence, three or four hours after a hearty meal, the stomach is empty. Some of the food has been changed to a liquid, but most of it has only been ground into smaller pieces and mixed with a great deal of water. Now it all must be changed to a liquid.
What the intestine does Like the mouth and stomach, the intestine does three things.
First, it mixes the food and makes it pass down the tube.
Second, two sets of cells behind the stomach make two liquids and pour them into the intestine. One set of cells is the sweetbread, or pancreas, and its liquid is the pancreatic juice. The other is the liver, and its fluid is the bile.
Third, the pancreatic juice makes three changes in food. First, like the mouth, it changes starch to sugar. Second, like the stomach, it makes albumin a liquid. It divides fat into fine drops. These drops then mix with water and do not float on top.
Bile: The bile is yellow and bitter. It helps the pancreatic juice do its work. It also helps to keep the inside of the intestine clean.
Digestion of simple water and minerals Water and the mineral parts of food do not need to be changed at all but can become part of the blood just as they are. So, seeds, husks, and tough strings of flesh all pass the length of the intestine and are not changed.
How food gets into the blood By the time food is halfway down the intestine, it is mostly liquid and ready to become part of the blood. Moreover, that liquid soaks through the sides of the intestine and into the blood tubes. At last, the food reaches the end of the intestine. Most of its liquid has then soaked into the blood tubes, and only some solid waste is left.
Work of the Liver Well, you know the food is now in the blood but didn’t become a part of it. It is carried to the liver. The liver changes the food into good blood, and then the blood hurries on and feeds the cells of the body. Because spoiled food may be swallowed and taken into the blood with good-quality food, the liver takes out the poisons and sends them back again with the bile. The liver keeps us from getting poisoned.
Bad Food: Sometimes the stomach and intestine cannot digest the food. They cannot digest green apples, but they try hard to do so. They stir the apples faster and faster until there is great pain. Sometimes the stomach throws up the food, and then the pain and sickness stop. Spoiled food makes us sick in the same way.
Don’t eat fast. When the food stays too long in the stomach or intestine, it sours or decays, just as it does outside of the body. This makes us very sick. When we eat too much or when we do not chew the food into small pieces. The stomach may take a long time to digest the food. Then it may become sour and make us sick.
Biliousness. When the food is poor or becomes sour, it is poorly digested. Then the liver has more work to do and does not change the food into blood as it should. It also lets some of the sour poison pass by. These poison the whole body and cause headaches. We call this biliousness. The tongue is then covered with a white or yellow coat, and the mouth tastes bad. These are signs of sickness. The stomach and liver are out of order.
Rules of Eating for Digestion in the Stomach If we eat as we should, our stomach will digest the food. We must follow three rules.
First, we must chew the food in the mouth until all the lumps are fine. Then the food will be ready for the stomach.
Second, we must eat bit by bit. If we eat fast, we cannot chew the food well. The stomach cannot take care of food if it comes too quickly. Hence, you must swallow all of one mouthful before we put another into the mouth.
Third, we must eat only at mealtimes. The stomach needs a rest. Even a little candy, apples, or nuts will keep the stomach at work and tire it out.
A child needs to eat more often than his father. So, besides his meals, he should have something to eat in the middle of the morning and some more in the afternoon. But he should not be eating at all hours. He ought not to eat little bits just before dinner, for that spoils his meal.
What to Learn from Digestion in the Stomach
The stomach and intestine stir and rub the food and mix it with juices.
The juices change albumin to a liquid and starch to sugar. They also change fat into tiny drops.
The digested food soaks through the sides of the intestine into the blood tubes.
The blood carries the food to the liver.
The liver changes food into blood.
Blood goes to all parts of the body and feeds the cells.
The liver keeps poisons from getting into the blood.
Water and minerals become part of the blood without being digested.
When food is not well digested, the liver cannot make it into good blood.
This makes us bilious. If food is not soon digested, it sours and decays. This makes us sick. We can make food digest quickly by chewing it well and eating slowly.