Apparatus appointed to the nutrition, or to the ingestion of nourishing substances; to the digestion, or to their degradation in simple molecules; to the absorption, that is to the transfer of these mixtures to the circulatory apparatus and the lymphatic system; and finally to the excretion of the solid refusals. The organs that constitute the digestive apparatus are the mouth, the pharynx, the esophagus, the stomach, the slim bowel and the crass bowel; to these they are attached the salivary glands, the liver and the pancreas.

The digestion includes both trials mechanics how chemical; the first ones are the mastication, that reduces the food in particles, the action of remixing of the stomach and the intestinal peristalsi. These strengths push the food through the digestive pipe and they mix him/it with various secretions. The fundamental chemical trials, involved in the digestion and all catalizzatis by specific enzymes, I am the conversion of the carbohydrates in simple sugars, the degradation of the proteins in amminoacidi and the division of the trigliceridis in fat acids and glicerolo.

When the food is ingested and chewed, the salivary glands produce the saliva that mixes him with the food. The saliva fluidifica the solid foods, mostly making them susceptible to the following action of the gastric and intestinal secretions, and it contains enzymes that separate the starches in destrina and maltosio; besides it lubricates the mouth and it facilitates the swallowing.

The gastric juices contain substances as the hydrochloric acid and some enzymes, among which the pepsina, the I curdle and traces of lipasi, that would be able to also practice his/her own action of degradation on the walls of the stomach, if these didn't come protected from the mucous covering. The pepsina separates the proteins in peptidi of various dimensions, the I curdle it separates the milk in a solid portion and one liquid, and the lipasis act on the fats. After the gastric digestion the ingested substances are gradually freed in the superior part of the slim bowel, where the digestion is completed. The secretion of the gastric juice is stimulated by the mastication, from the swallowing and from the presence of food in the stomach, as well as, of reflex, from the simple sight or from the thought of the food. The gastric secretions, to them it turns, they stimulate the production of digestive substances from the slim bowel, while some constituent ones of the gastric juice are activated only when they come to contact with the alkaline environment of the first intestinal line.

The digestion is completed in the slim bowel, where the most greater part of the alimentary products subsequently come idrolizzata and absorbed. The predigested material furnished by the stomach is exposed to the action of three powerful digestive juices: the juice pancreatico, the intestinal juice and the bile, that neutralize the gastric acid putting an end to the gastric phase of the digestion.

The juice pancreatico, that comes in the slim bowel through various scholars, contains the tripsina and the chimotropsina, two enzymes that separate the complex proteins in composed simpler, absorbed and riutilizzati for the synthesis of new bodily proteins. The steapsina, also it foresees in the juice pancreatico, it degrades the fats, while the amilopsina idrolizza the starches in maltosio, subsequently separated in glucose and fructose. The secretion of the juice pancreatico is stimulated by the ingestion of the proteins and the fats.

The intestinal juice, that is secreted by the slim bowel and it contains many enzymes, completes the trial begun by the juice pancreatico and its flow you/he/she is stimulated by the mechanical pressure practiced by the food partially digested in the bowel.

The role of the bile in the digestion is that to favor the absorption of the fats reducing them to more accessible structures from the lipasis. Secreted by the liver and preserved in the colecisti, the bile reaches in the bowel in answer the presence of fats in the stomach and in the superior part of the bowel. The obstructive jaundice is a pathology, characterized by the obstruction of the bilious canalicolis of the liver, in which the bile cannot be freed in the bowel and therefore the digestion of the fats is very difficult.

The products of the digestion come, therefore, actively transported or passively through the intestinal wall to be assimilated by the organism. The sodium, the glucose and many amminoacidis come, for instance actively transported, and the mucous intestinal works from selective filter towards the different nourishing substances. The stomach and the colon are also them able to absorb some types of substances, what the water, some salts, the alcohol and launchings types of medicines or drugs. In the newborn he believes that the intestinal barrier can also be crossed by some whole proteins. The intestinal absorption introduces another unusual characteristic: many nourishing are absorbed in more efficient way when the body has a greater need of it. In the adult, the surface of absorption of the bowel, broadly convolute, it is equal to around 140 m2s, distributed on a length of around 3-4 ms.

The substances idrosolubili, mineral comprendenti, amminoacidi and carbohydrates, pass in the venous system that drains the bowel and, through the vases of the circulation portal, directly to the liver. Because of their insolubility in the watery solutions, the fats come, assimilated in more complex way instead, and initially they are picked from the lymphatic system and transported by the sap in the general circulation through the system of the vein it extracts.

In the colon, the material not digested assumes the form of a solid mass because of the bodily reabsorption of the water. If this mass is too quickly pushed, semiliquida remains and gives diarrhea place; vice versa, an insufficient activity of the musculature of the colon provokes constipation. I did her you/they are picked up in the straight one up to the moment in which I/you/they are expelled through the anus.

The alterations of the absorption of the foods have called in their complex malassorbimento illnesses.