Digestion in The Small Intestine
The Small Intestine plays a significant role in digestion of food. The partially digested food from The Stomach passes on into the Small Intestine, where it is acted upon by two other Digestive Juices – The Bile, which comes from the Liver, and the Pancreatic Juice, which is secreted by the Pancreas.
Liver and Pancreas Juices – Biggest Role Players in Digesting the Food in Small Intestine
The Liver and The Pancreas are a pair of large glands which have budded out, one on each side of the Food Tube, about six inches below where the food enters the Small Intestine from the Stomach. The Liver weighs nearly Three Pounds, and the Pancreas about a quarter of a Pound.
Of these two glands, the Pancreas, “though smaller, but is far more important in Digestion; In fact, it is the most powerful digestive gland in the body”.
Its juice, the Pancreatic juice, can do everything that any other Digestive Juice can, and does it better.
- It contains a ferment for turning Starch into Sugar, which is far more powerful than that of the Saliva;
- Also another (Trypsin), which will dissolve Meat-Stuffs nearly twice as fast as the Pepsin of the Stomach can;
- And still another, not possessed by either Mouth or Stomach Glands, which will melt Fat, so that it can be sucked up by the Lining Cells of The Intestine.
The Small Intestine – “The Real Center of Digestion”
What does this great combination of powers in the Pancreas mean? It means that we have now reached the “Real Centre and Chief Seat of Digestion”, namely, The Small Intestine, or Upper Bowel. This is where the food is really absorbed, taken up into the blood, and distributed to the body. All changes before this have been merely preparatory; all after it are simply a picking up of the pieces that remain.
In general appearance, this division of the food tube is very simple – merely a tube about Twenty Feet Long and an Inch in diameter, thrown into coils, so as to pack into small space.
The Other Digestive Juices
The Small Intestine also is provided with Glands that pour out a juice known as the Intestinal Juice, which, although not very active in digestion, helps to melt down still further some of the Sugars, and helps to prevent Putrefaction, or Decay of the food from the bacteria which swarm in this part of the tube.
By the time the food has gone a third of the way down the Small Intestine, a good share of the Starches in it have been turned into sugar and absorbed by the blood vessels in its wall; and the meats, milk, eggs, and similar foods have been digested in the same way.
There still remain the bulk of the fats to be disposed of. These fats are attacked by the Pancreatic juice and the bile, and made ready for digestion.
Turning of Food into Blood
All these different Food Substances, in the process of Digestion, do not simply soak through the lining cells of the food tube, as through a Blotting Paper or Straining Cloth, but are actually eaten by the cells and very much changed in the process, and are then passed through the other side of the cells, either into the blood vessels of the wall of the intestine or into the lymph vessels, practically ready for use by the living tissues of the body. It is in the cells then that our food is turned into blood, and it is there that what we have eaten becomes really a part of us. It may even be said that we are living upon the leavings of the little cell citizens that line our food tube; but they are wonderfully decent, devoted little comrades of the rest of our body cells, and generous in the amount of food they pass on to the blood vessels.
As the Food-Pulp is squeezed on from one coil to another through the Small Intestine, it naturally has more and more of its nourishing matter sucked out of it; until, by the time it reaches the last loop of the twenty feet of the Small Intestine, it has lost over two-thirds of its Food Value.