Digestion is the process by which food is physically and chemically processed so that it is able to pass through the walls of the digestive tract and move into the blood. Several organs interfere in this process, regulated by nervous and hormonal mechanisms.
General processes of digestion:
- Ingestion: begins in the mouth and includes the processes of chewing, insalivation and swallowing of food.
- Digestion: set of processes that act for the conversion of complex food molecules into simpler units that are admissible and available for use. It starts in the mouth and continues to the small intestine.
- Absorption: process in which nutrients pass through the walls of the digestive tract and are mobilized into the blood. It occurs primarily in relation to the walls of the small intestine.
- Expulsion: the elimination of undigested substances through defecation.
organs and structures that interfere in the digestive process:
- The mouth: in the mouth occurs through chewing, the disintegration of the food crushed by the teeth and displaced by the tongue, a muscular organ that also has the sense of taste. During chewing, the salivary glands come into contact with the food and mix it, to be aware of the taste and prepare the chemical utilization of the starch, transforming it into maltose. The crushed food acquires a thick appearance, called alimentary bolus, which is moved towards the pharynx by the tongue.
- Pharynx: structure located in the neck that connects the oral cavity and the nasal cavity with the esophagus and the larynx respectively. Within it, the ingestion of food takes place, which resides in the movement of the alimentary bolus from the mouth to the pharynx and from the pharynx to the esophagus. In the pharynx there is a cartilaginous wet structure, called epiglottis, which during swallowing wrinkles, to obstruct the transit of parts of the alimentary bolus to the respiratory tract.
- Esophagus: it is a muscular tube that connects the pharynx with the stomach. It has a lower sphincter called cardia, which provides the transit of food from the esophagus to the stomach, and prevents what is already in the stomach from returning to the esophagus.
- Stomach: where gastric digestion takes place, the food bolus accumulates and mixes with gastric acid, then digestive enzymes that degrade proteins intervene. The stomach cells also produce a glycoprotein that yields the assimilation of vitamin B12.
- The mixture, called chyme, is obtained through the action of soft and undulating movements by the muscles of the stomach, where it remains from two to four hours, according to various factors, such as, for example: foods rich in carbohydrates, move quickly, while those rich in fats take more time.
- Pancreas: agent for the production of juices capable of breaking down the carbohydrates, fats and proteins that are part of the food. These juices are conducted to the small intestine, where the chemical disintegration of numerous complex molecules will take place.
- Liver: promotes bile, a digestive juice capable of digesting certain fats and vitamins.
- Gallbladder: where bile from the liver is collected and sent to the small intestine for digestion.
- Small intestine: unit of the digestive tract that connects the stomach with the large intestine. It performs the tasks of digestion, absorption and general defense of the organism.
The chyme, a substance resulting from the processing of food in the stomach, moves to the small intestine, and once there it is mixed with three different liquids:
At this stage, complex molecules are fragmented and transformed into simpler absorbable units that are available for use. These substances pass through the microvilli of the small intestine wall until they reach the blood. The nutrients impregnated by the blood are transported to the liver for filtration, elimination of toxins and processing of nutrients:
- Large intestine: where the wastes of digestion, the useless remains of those of cells and water, undergo conversion to feces, in addition, it gets to synthesize vitamins of group b and vitamin k.
- Rectum: lower end of the large intestine, it is in charge of storing feces until they are expelled during defecation.
Regulators of digestion
Hormonal regulators: the fundamental hormones that regulate the functions of the digestive tract are caused and released from the mucosal cells of the stomach and small intestine.
The hormones involved in digestion are:
- Gastrin: gastrin production is driven by the arrival of food in the stomach. It causes the stomach to produce hydrochloric acid, a substance that dissolves and digests certain foods and interferes with the natural development of the mucosa of the stomach and small intestine.
- Secretin: induces the pancreas to secrete a digestive juice with a high bicarbonate content, stimulates the creation of pepsin, an enzyme that digests proteins and the production of bile.
- Cholecystokinin: stimulates the production of enzymes in the pancreatic juice and the development of the pancreas. It also causes the gallbladder to empty.
- Gastric inhibitory peptide: induces slowing of gastric emptying and promotes insulin secretion.
- Vasoactive inhibitory peptide: causes the production of both enzymes in the pancreas and bile from the gallbladder.
Nerve regulators: the nerves that regulate the functioning of the digestive system are divided into two groups:
- Extrinsic nerves: cause the release of acetylcholine and adrenaline. Acetylcholine: induces the strengthening of the contraction process of the muscles of the digestive tract organs, and the optimization of food and liquids pushing through the digestive tract. It also causes the stomach and pancreas to produce more gastric juices. Adrenaline: it is in charge of relaxing the muscle of the stomach and intestines, decreasing the blood flow to these organs.
- Intrinsic nerves: they are the main ones. They form a network superimposed on the walls of the esophagus, stomach and small intestine. These nerves, when the walls of the organs dilate due to the weight of the food, secrete various different substances that speed up or slow down the movement of the food and the elaboration of juices in the organs of the digestive system.
Recommendations to achieve a good digestion:
- Dose the food to be consumed daily, in four or five light meals.
- Avoid large meals, especially dinner.
- Determine meal times, in order to achieve a stable biological clock.
- Provide a relaxed environment for eating, allowing the individual to eat calmly, chewing food properly.
- Restrict the use of medications.
- Reduce the purchase and consumption of carbonated beverages and junk foods with high percentages of trans fats.
- Consume foods containing vegetable fiber, such as fruits, vegetables and cereals.
- Rest at least one hour after meals.
- Drink more than two liters of water throughout the day.
- Avoid unmoderated consumption of alcoholic beverages.
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