Digestion is the process by which foods with complex substances are transformed into simpler substances, so that they can be taken up by each of the body's cells.
The digestive system is where digestion is carried out, in order to fulfill its mission properly, it has a series of structures whose synchronized operation allows it to be carried out. The digestive system is made up of the digestive tract and its attached glands.
The digestive tract is an elongated tube-like structure, comprising five organs: the mouth (are the teeth and tongue), the pharynx, the esophagus, the stomach, and the intestines (small and large). The attached glands are organs that produce substances that facilitate the digestion process, these are: the liver (secretes bile), the pancreas (secretes gastric juice) and the salivary glands (secretes saliva).
Digestion consists of a series of mechanical and chemical processes. The first are chewing, insalivation and movements that take place in the digestive tract. Through these processes, food is crumbled, emulsified and circulates through the digestive tract until waste products are eliminated.
In chemical processes, food is transformed into assimilable substances for cells by the action of enzymes, these are found in saliva, gastric juice, intestinal juice and pancreatic juice. For each food group there is a class of enzymes: carbohydrases or amylases act on carbohydrates; lipases act on lipids; and proteases act on protids.
Digestion takes place in the mouth, stomach, and small intestine. The food to be ingested must be crushed and divided by the joint action of the teeth, the tongue and the chewing muscles, in this way they mix with the saliva and form a mass called the food bolus, which passes to the pharynx, the esophagus and reaches the stomach; This process is called swallowing.
In the stomach, the food bolus is mixed with the gastric juice secreted by the gastric glands by means of peristaltic movements. This juice is made up of water, hydrochloric acid, and enzymes that break down large food molecules into simpler molecules. At the end of the stomach or gastric digestion, the food bolus has been transformed into a thick liquid called chyme, which reaches the duodenum, the first portion of the small intestine, and bile, pancreatic juice and intestinal juice act on it.
The rest of the food that is not absorbed by the intestinal villi, together with the water, pass to the large intestine, where the water is progressively absorbed and the content thus becomes more solid, constituting the feces, which are expelled outside throughout the year. This process is called defecation.
