As food is digested and absorbed

We already said that the food is subjected to mechanical and chemical processing. In the mouth the main role plays the preparation machining - teeth turn food into a finely pounded wet mush. However, already in the mouth begins under the action of saliva and her enzymes splitting of complex carbohydrates. Starch bread, potatoes, various groups under the action of the enzyme amylase turns into maltose. Carbohydrate this consists of just two parts of glucose, which is under the action of the enzyme Maltese split with the formation of monosaccharide glucose. The life experience we know that, really, if you hold the bread in his mouth, he gradually acquires sweet taste. However, usually the food in the mouth for a long time is not delayed, and enzymes saliva, swallowed together with the food bundle that continue its work in the stomach. This is very important because of gastric juice on carbohydrates is not valid. Its main parts are the enzyme pepsin and gestrichen that cleave proteins, and hydrochloric acid, without which these enzymes are proteins have virtually no effect. After staying in the stomach 3-8 hours, the food passes into the small intestine, which moves about during 6-7 hours, subjected to the action of enzymes pancreas and intestinal juices. Especially great value pancreatic juice, which, as can be seen from the attached table, affects the proteins and fats, and carbohydrates. Not casually people with sharply reduced gastric secretion can live and work - saves them the activity of the pancreas. Pancreatic juice less than other juices, but it is most valuable. However, no matter how valuable pancreatic juice, without intestinal juice and bile he cannot manifest his power. On the one hand, in laboratories Pavlov was revealed, that in itself trypsin contained in the pancreatic juice, being derived directly from it flow, no effect on proteins. It is, however, to come into contact with the mucous membrane of the intestine, even her piece that surrounds sewn to the skin hole duct, and trypsin gets all his strength. It turned out that cancer of the intestine produce the enzyme enzyme - enterokinase, which makes trypsinogen in the active form. Remember that and pepsin itself is little active and becomes effective only where it is added to hydrochloric acid. Both biologically justified. If pepsin and trypsin was produced immediately in the active form, they splintered would proteins those cells which develop them. Cancer of the stomach and pancreas would have fallen victim to its own juices.
Thus, on the one hand, pancreatic juice helps intestinal juice, on the other hand, it helps the bile. It allows you to properly digest and absorb fats. Although in the bile no enzymes, it activates the functioning of the digestive fat enzyme pancreatic juice. Not without reason in diseases of the liver, the body poorly absorbs fatty foods.
Returning to the intestinal juice, you should specify that it, in addition to assistance trypsin, and has independent significance. It breaks down one of the most important food - sugar. Only intestinal juice split and the most important carbohydrate milk - milk sugar - lactose.
We already said that the chemical processing of food improves its mechanical processing, carried out thanks to the movements of the walls of the digestive tract. It is noted for the movement mainly of two types. First, a process known as the ramp reduction, under which certain segment of intestine becomes thinner and longer, thicker and shorter. While hidden in it food gruel vigorously stirred. Secondly, there is the so-called peristalsis in the direction from the stomach to the intestines run in the entire length of the digestive tube waves of contraction of the muscles, promotes food a lot farther and farther along the narrow "corridor" of the digestive tract. In total food spending on the completion of the whole of this route about a day. The herbivores, which have a much longer bowel transit time of food much more. Food remains are thrown at them in a few days after a meal (the sheep " in a week).
In the process of digestion about 90 % of dietary valuable nutrients are broken down into digestible for the body products. The value of the small intestine is not only a century that it completes the process of digestion, but in what happens here intake. The mucous membrane of the colon has a smooth appearance by the mass of tiny protrusions its called villi. These surface of the mucous membrane increases in 300-500 times. In each hair enter the blood and lymphatic vessels, which do absorbed products of digestion, and also a number of other food substances, which need not be in the digestion of water, salts and vitamins. Do some substances, sometimes harmful for the body.

Digestive juice It enzymes The action of these enzymes Notes
Saliva (about 1 liter per day) Amylase Breaks down starch into maltose Mainly operate in the stomach
Maltese Splits maltose to glucose
Gastric juice (about 3 litres a day) Pepsin Breaks down proteins to albums and peptone (intermediate breakdown products of proteins) Acts only in an acid environment
Lipase Breaks down fats Weak enzyme
Pancreatic juice (up to 2 litres per day) Trypsin
Breaks down proteins to amino acids Activated by enterokinase
Lipase Breaks down fats (the most powerful enzyme of this kind) Activated bile
Similar saliva  
Intestinal juice (about 3.5 l per day) Enterokinase Enzyme enzyme activates trypsin  
Erepsin Splits albumose and gelatin to amino acids (like "had to finish" that was launched by pepsin)  
Lipase Breaks down fats Weak enzyme
Inverting Breaks down sugar for glucose and fructose  
Lactase Breaks down milk sugar into glucose and galactose  
Similar to those of saliva and gastric juice  
Bile (about 1 liter per day) - - Promotes digestion and absorption of fats