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General Practice 2023

Digestive systemório: funções, órgãos and digestive process

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Digestive systemório: funções, órgãos and digestive process
Digestive systemório: funções, órgãos and digestive process
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The digestive system, also called digestive or gastrointestinal (GI) is one of the main systems of the human body and is responsible for processing food and absorbing nutrients, allowing the body to function properly. This system is made up of several organs, such as the mouth, esophagus, stomach, small and large intestine, rectum and anus, which work together so that their function can be performed.

The digestive process starts with the release of enzymes secreted by these organs, starting when the food is consumed and ending when there is elimination through the feces.

It is important that any change in the functioning of the digestive system, such as pain or burning in the stomach, abdominal pain, cramps or diarrhea, for example, is communicated to the gastroenterologist, who is the doctor responsible for evaluating and treating all related changes with that system.

Functions of the digestive system

The digestive system is made up of several organs that work together in order to perform the following main functions:

  • Promote the digestion of proteins, carbohydrates and lipids from the foods and beverages consumed;
  • Absorb liquids and micronutrients;
  • Provide a physical and immunological barrier to microorganisms, foreign bodies and antigens consumed with food.

In this way, the digestive system is responsible for regulating metabolism and the immune system, in order to maintain the proper functioning of the organism.

Which doctor to consult?

If signs or symptoms are identified that may be related to the digestive process, such as excessive gas, constipation or diarrhea, weakness, abdominal pain, increased abdominal volume, cramps or the presence of blood in the stool, for For example, it is important that the gastroenterologist is consulted so that tests are carried out that help to identify the alteration in the digestive system and, thus, it is possible to start the most appropriate treatment.Learn more about the gastroenterologist.

Organs of the digestive system

The digestive system is made up of organs that allow the transport of ingested food or drink and, along the way, absorption of nutrients essential for the proper functioning of the organism. This system extends from the mouth to the anus, and its constituent organs are:

  1. Mouth: responsible for receiving the food and reducing the size of the particles so that it can be digested and absorbed more easily, in addition to mixing it with saliva;
  2. Esophagus: responsible for transporting food and liquids from the oral cavity to the stomach;
  3. Stomach: plays a key role in the temporary storage and digestion of ingested food;
  4. Small intestine: responsible for most of the digestion and absorption of food and receives secretions from the pancreas and liver, which help this process;
  5. Large intestine: this is where the absorption of water and electrolytes takes place. This organ is also responsible for temporarily storing end products of digestion that serve as a means for bacterial synthesis of some vitamins;
  6. Retum and anus: are responsible for controlling defecation.

In addition to the organs, the digestive system is made up of several enzymes that ensure the correct digestion of food, the main ones being:

  • Salivary amylase, or ptyalin, which is present in the mouth and is responsible for the initial digestion of starch;
  • Pepsin, which is the main enzyme in the stomach and is responsible for the breakdown of proteins;
  • Lipase, which is also present in the stomach and promotes the initial digestion of lipids. This enzyme is also secreted by the pancreas and performs the same function;
  • Trypsin, which is found in the small intestine and leads to the degradation of fatty acids and glycerol.

Many nutrients cannot be absorbed in their natural form due to their size or the fact that they are not soluble. Thus, the digestive system is responsible for transforming these large particles into smaller and soluble particles capable of being quickly absorbed, which happens mainly due to the production of several digestive enzymes.

How digestion happens

The digestive process begins with the ingestion of food or drink and ends with the release of feces. Carbohydrate digestion begins in the mouth, although digestion is minimal, while protein and lipid digestion begins in the stomach. Most digestion of carbohydrates, proteins and fats takes place in the initial portion of the small intestine.

The digestion time of food varies according to the total volume and characteristics of the food consumed, and can last up to 12 hours for each meal, for example.

1. In the mouth and pharynx

In the mouth, the teeth crush and crush the ingested food into smaller particles and the food bolus formed is moistened by saliva. In addition, there is the release of a digestive enzyme, salivary amylase or ptyalin, which initiates the digestion of the starch that makes up carbohydrates. The digestion of starch in the mouth by the action of amylase is minimal and its activity is inhibited in the stomach due to the presence of acidic substances.

The bolus passes through the pharynx, under voluntary control, and the esophagus, under involuntary control, reaching the stomach, where it is mixed with gastric secretions.

2. In the stomach

In the stomach, the secretions produced are rich in hydrochloric acid and enzymes and are mixed with food. In the presence of food in the stomach, pepsin, which is one of the enzymes present in the stomach, is secreted in its inactive form (pepsinogen) and converted into pepsin by the action of hydrochloric acid.This enzyme plays a fundamental role in the process of digestion of proteins, changing their shape and size. In addition to the production of pepsin, there is also the production, to a lesser extent, of lipase, which is an enzyme responsible for the initial degradation of lipids.

Gastric secretions are also important for increasing intestinal availability and absorption of vitamin B12, calcium, iron and zinc.

After processing the food by the stomach, the food bolus is released in small amounts in the small intestine according to the contractions of the stomach. In the case of liquid meals, gastric emptying lasts around 1 to 2 hours, while for solid meals it lasts about 2 to 3 hours and varies according to the total volume and characteristics of the food ingested.

3. In the small intestine

The small intestine is the main organ for digestion and absorption of food and nutrients and is divided into three parts: duodenum, jejunum and ileum.In the initial part of the small intestine, digestion and absorption of most of the ingested food occurs due to the stimulation of enzyme production by the small intestine, pancreas and gallbladder.

Bile is secreted by the liver and gallbladder and facilitates digestion and absorption of lipids, cholesterol and fat-soluble vitamins. The pancreas is responsible for secreting enzymes that are able to digest all major nutrients. Enzymes produced by the small intestine reduce lower molecular weight carbohydrates and medium and large sized peptides, in addition to triglycerides.

Most of the digestive process is completed in the duodenum and upper jejunum, and absorption of most nutrients is almost complete by the time the material reaches the middle of the jejunum. The entry of partially digested food stimulates the release of various hormones and, consequently, of enzymes and fluids that interfere with gastrointestinal motility and satiety.

Along the small intestine almost all macronutrients, vitamins, minerals, trace elements and liquids are absorbed before reaching the colon. The colon and rectum absorb most of the remaining fluid from the small intestine. The colon absorbs electrolytes and a small amount of remaining nutrients.

Remaining fiber, resistant starches, sugar and amino acids are fermented by the colon's brush border, resulting in short-chain fatty acids and gas. Short-chain fatty acids help maintain normal mucosal function, release a small amount of energy from some of the residual carbohydrates and amino acids, and facilitate the absorption of s alt and water.

Intestinal contents take 3 to 8 hours to reach the ileocecal valve, which serves to limit the amount of intestinal material that passes from the small intestine to the colon and prevents its return.

What can interfere with digestion

There are several factors that can cause digestion not to be carried out correctly, resulting in consequences for the person's he alth. Some of the factors that can affect digestion are:

  • Quantity and composition of food ingested, because depending on the characteristics of the food, the digestion process can be faster or slower, which can influence the feeling of satiety, for example.
  • Psychological factors, such as appearance, smell and taste of food. This is because these sensations increase the production of saliva and stomach secretions, in addition to favoring muscle activity in the SGI, causing food to be poorly digested and absorbed. In the case of negative emotions, such as fear and sadness, for example, the opposite occurs: there is a decrease in the release of gastric secretions as well as a reduction in perist altic bowel movements;
  • Digestive microbiota, which may suffer interference due to the use of drugs such as antibiotics, inducing bacterial resistance, or situations that lead to a decrease in the production of hydrochloric acid by the stomach, which can result in gastritis.
  • Food processing, as the way food is consumed can interfere with the speed of digestion. Cooked foods are usually digested more quickly than foods eaten raw, for example.

If you notice any symptoms related to the gastrointestinal system, such as excess gas, heartburn, feeling of abdominal swelling, constipation or diarrhea, for example, it is important to go to the gastroenterologist so that exams are carried out with the aim of identify the cause of symptoms and initiate the best treatment.

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