Process Of Digestion (2)
As part of the mass, being digested by the stomach, assumes a condition that indicates the process of stomach digestion has been completed, it is allowed to pass the pylorus and enter the duodenum, which is a part of the small intestines. Here the food comes in contact with two other digestive juices that are poured forth under normal conditions as needed–the bile and pancreatic juices. The bile is alkaline in character; it neutralizes the gastric juice, emulsifies the fats, making them soluble, and it also has antiseptic qualities which act upon the entire intestinal canal. The pancreatic juice is similar to the saliva of the mouth and performs important offices, though in addition to digesting starchy elements it also digests aluminous–muscle making–and fat.
From the duodenum the food enters the principal part of the small intestines. Here it comes in contact with another fluid called the intestinal juice. This juice possesses the power peculiar to itself of digesting all the various food elements, thus practically completing the work of digestion. The small intestines are supplied with a very large number of glands which absorb large quantities of the nourishment made ready by the various digestive juices with which the food had previously come in contact. From the small intestines the food is slowly forced into the colon where absorption still continues though in a much more limited degree.
For a technical description of the process of absorption of the nourishing elements of the food, I refer you to the following by Dr. J. H. Kellogg:
The process of absorption begins almost as soon as food is taken into the mouth, and continues so long as any soluble nutriment can be extracted from the alimentary mass. The work of absorption is performed by two sets of absorbent vessels, minute veins, and lymphatic, here called lacteals. The venous absorbents take up whatever is held in solution in the food taken into the stomach, and the principal portion of the digested farinaceous, saccharine, and aluminous elements of food. The lacteals absorb the emulsified fats, and some portion of the other elements. The products absorbed by the venous absorbents find their way into the general circulation through the hepatic vein, after passing through the liver, which is apparently a wise arrangement of nature, to provide for a sort of filtration before the more delicate tissues of the body are exposed to the action of whatever deleterious elements the food may happen to contain. It is claimed by physiologists that the liver has also an important function to perform in completing the work of digestion, especially that of starchy substances. The food mingled with venous blood is conveyed to the liver by the portal vein. Those products which are absorbed by the lacteals, reach the general circulation through the thoracic duct, a long, slender lymph vessel which empties “into the large vein from the arm on the left side.
