Digestive system of organs: functions and structure

One of the most important components of the human body is its digestive system of organs. This aggregate is thought out and organized by nature in such a way that its possessor is able to extract from the consumed food all that is most necessary for the realization of normal vital activity. And at the same time in the digestive system there are such "magic" mechanisms that save us from infections, neutralize poisons and allow us to even synthesize important vitamins ourselves. Given the importance of this complex of organs, it is necessary to protect it.

Consider what the digestive system is, and the functions of the digestive organs, too, will not be ignored. You will also learn about what must be done in order not to have gastrointestinal diseases.

Which organs are part of the digestive system?

The digestive system consists of the following organs and departments:

• Oral cavity with salivary glands entering into it;
• pharynx;
• Area of the esophagus;
• stomach;
• Thin and large intestine;
• liver;
• pancreas.

Next, we will consider the structure and functions of the organs of the digestive system. The table below provides an overview of the components of the gastrointestinal tract.

If you look at the structure of this system of organs, it can be noted that the digestive tract is a tube 7-9 m in length. Some large glands are located outside the walls of the system and have a message with it.

The peculiarity of this set of organs is that they are packed very compactly. The length of the tract from the mouth to the anus is up to 900 cm, but the capacity of the muscles of the digestive path to form loops and bends has helped to fit them in the human body. However, our task is not only to list the organs of the digestive system. We will carefully study all the processes taking place in each of the departments of the digestive tract.

General scheme of the digestive tract

The oral cavity, pharynx and esophagus have a virtually direct direction.

Now let's briefly consider the sequence of food passage through the organs of the digestive system. Nutrient components enter the human body through the oral opening. Then the mass should be in the throat, in which the digestive tract and respiratory organs intersect. After that, the food lump is sent down the esophagus. Chewed and salted food enters the stomach. In the abdominal region are the organs of the terminal segment of the esophagus: stomach, thin, blind, colon, and glands: liver and pancreas.

In the pelvic area is the direct intestine. Food in the stomach cavity is at different times depending on the type of food, but this period does not exceed several hours. At this time, the so-called gastric juice is secreted into the body cavity . The food becomes liquid, it is stirred and digested. Moving further, the mass enters the small intestine. Here, the activity of enzymes ensures further dissolution of nutrient substances to simple compounds that are absorbed into the bloodstream and into lymph without difficulty.

Further, the residual masses move into the large intestine, where water is absorbed and feces are formed. In fact, these are substances that are not digested and can not be absorbed into the blood and lymph. They are removed into the external environment through the anus.

Why does man need saliva?

On the mucosa of the mouth, from which the sequence of food passage through the organs of the digestive system begins, there are large and small salivary glands. Large are those that are located near the auricles, under the jaws and under the tongue. The last two kinds of salivary glands produce a mixed secret: they secrete both saliva and water. The glands near the ears can only produce mucus. Salivation can be quite intense. For example, with the use of lemon juice can stand out to 7.5 ml per minute.

For the most part, saliva consists of water, but there are enzymes: maltase and amylase. These enzymes start the process of digestion already in the oral cavity: the starch is converted by amylase into maltose, which is further broken down by maltase to glucose. Food is in the mouth for a short time - no more than 20 seconds, and during this time, starch simply does not have time to dissolve completely. Saliva usually has either a neutral or slightly alkaline reaction. Also in this liquid medium is contained a special lysozyme protein, which has a bactericidal property.

Follow the esophagus

Anatomy of the digestive system calls the esophagus following the mouth and throat of the digestive tract. If we consider its wall in a section, then we can clearly distinguish three layers. The median is muscular and is able to contract. This quality allows food to move from the pharynx to the stomach. The musculature of the esophagus produces undulating contractions that extend from the upper part of the organ throughout its duration. When the food lump passes along this tube, the entrance sphincter opens into the stomach.

This muscle keeps food in the stomach and prevents it from moving in the opposite direction. In some cases, the blocking sphincter weakens, and the digested masses can be thrown into the esophagus. There is a reflux, a person feels heartburn.

Stomach and secrets of digestion

We continue to study the order of the digestive system. Behind the esophagus follows the stomach. Its localization is the left hypochondrium in the epigastric region. This organ is nothing but an expansion of the digestive tract with a pronounced musculature of the wall.

The shape and size of the stomach directly depend on its contents. The empty organ has a length of up to 20 cm, the distance between the walls is 7-8 cm. If the stomach is moderately filled, its length will be about 25 cm, and the width - up to 12 cm. The capacity of the organ can also vary depending on the degree of its fullness and Varies from 1.5 liters to 4 liters. When a person swallows, the musculature of the stomach relaxes, and this effect lasts until the end of the meal. But even when the meal is over, the stomach muscles are in a state of activity. Food is rubbed off, it is mechanically and chemically processed by the movement of muscles. The digested food advances towards the small intestine.

From the inside, the stomach is lined with a mucous membrane with many folds in which the glands are located. Their task is to isolate as many digestive juices as possible. Gastric cells produce enzymes, hydrochloric acid and mucoid secret. The food lump is impregnated with all these substances, crushed and mixed. Muscles, cutting, contribute to digestion.

What is gastric juice?

Gastric juice is a colorless liquid with an acid reaction, which is explained by the presence of hydrochloric acid. It has three main enzyme groups:

• Proteases (mainly pepsin) cleave proteins to polypeptide molecules;
• Lipases affecting fat molecules, turning them into fatty acids and glycerin (only emulsified fat of cow's milk is split in the stomach);
• Salivary amylases continue to work on splitting complex carbohydrates to simple sugars (as the food lump is completely saturated with acidic gastric juice, amylolytic enzymes are inactivated).

Hydrochloric acid is a very important element of the digestive secret, as it activates the enzyme pepsin, prepares protein molecules for cleavage, cuts down milk and neutralizes all microorganisms. The secretion of gastric juice occurs mainly with food intake and lasts for 4-6 hours. In total for a day of this liquid is allocated up to 2.5 liters.

It is interesting that the amount and composition of gastric juice depends on the quality of the incoming food. The greatest amount of secretion is excreted for the digestion of albuminous substances, the smallest - when a person absorbs fatty foods. In a healthy body, gastric juice contains a fairly large amount of hydrochloric acid, its pH ranges from 1.5 to 1.8.

Small intestine

When studying the question of which organs enter the digestive system, a further object of investigation is the small intestine. This department of the digestive system originates from the gastric pylorus and has a total length of up to 6 meters. It is divided into several sections:

• The duodenum is the shortest and widest part, its length is about 30 cm;
• The small intestine is characterized by a decrease in lumen and a length of up to 2.5 m;
• The ileum is the narrowest part of the thin section, its length is up to 3.5 m.

The small intestine is located in the abdominal cavity in the form of loops. From the frontal part it is covered with an omentum, and on the sides it is limited to a thick digestive tract. The function of the small intestine is the continuation of chemical transformations of food components, its mixing and further direction to the thick section.

The wall of this organ has a typical structure for all components of the gastrointestinal tract and consists of the following elements:

• Layer of mucosa;
• Submucosal tissue with accumulations of nerves, glands, lymphatic and blood vessels;
• Muscle tissue, which consists of the outer longitudinal and inner circular layers, and between them is a layer of connective tissue with nerves and vessels (the muscle layer is responsible for mixing and moving the digested food along the system);
• The serous membrane is smooth and moist, it prevents friction between the organs.

Features of digestion in the small intestine

The glands that enter the structure of the intestinal tissue secrete a secret. It protects the mucosa from injury and from the activity of digestive enzymes. Mucous tissue forms a variety of folds of circular orientation, and this increases the suction area. The amount of these formations decreases towards the large intestine. From the inside, the small intestine mucosa abounds in villi and grooves that help digestion.

In the 12-finger section a slightly alkaline medium, however, with the ingestion of the contents of the stomach, the pH decreases. The pancreas has a duct in this zone, and its secretion alkalizes the food lump, the medium of which becomes neutral at the same time. Thus, gastric juice enzymes are inactivated here.

A few words about the digestive glands

The digestive system of the organs has ducts of endocrine glands. The pancreas secretes its juice as the person takes food, and its amount depends on the composition of the food. The protein diet provokes the greatest secretion, and fats cause the opposite effect. In just a day, the pancreas produces up to 2.5 liters of juice.

Also in the small intestine secretes its secret gallbladder. Already after 5 minutes from the start of the meal, bile begins to be actively produced, which activates all the enzymes of the intestinal juice. This secret also strengthens the motor functions of the gastrointestinal tract, intensifies the mixing and movement of food. In the 12-finger department, about half of the proteins and sugars supplied with food are digested, as well as a small portion of fats. In the small intestine, the enzymatic decomposition of organic compounds continues, but less intensively, and the absorption of the parietal nature predominates. Most intensively, this process occurs after 1-2 hours from the time of ingestion. It is more effective in the same stage in the stomach.

Large intestine - terminal digestion station

This part of the gastrointestinal tract is terminal, its length is about 2 m. The names of the digestive system take into account their anatomical features, and it is logically clear that this department has the greatest lumen. The width of the large intestine decreases from 7 to 4 cm in the descending colon. On this section of the digestive tract the following zones are distinguished:

• A cecum with a vermicular appendix, or an appendix;
• Ascending colony;
• Transverse colon;
• Descending colonic region;
• Sigmoid colon;
• Straight section, ending with the anal opening.

The digested food gets from the small intestine into the thick through a small hole in the form of a slot located horizontally. There is a kind of valve with a sphincter in the form of the lips, which prevents the contents of the blind section from getting in the opposite direction.

What processes occur in the large intestine?

If the whole process of digesting food lasts from one to three hours, most of it is spent on the presence of a lump in the large intestine. It accumulates the contents, the absorption of necessary substances and water, movement along the tract, formation and removal of stool. The physiological norm is the intake of digested food into the large intestine after 3-3.5 hours after a meal. This department is filled in during the day, then it should be completely emptied in 48-72 hours.

In the large intestine absorption of glucose, amino acids, vitamins and other substances produced by bacteria living in this department occurs, as well as the overwhelming part (95%) of water and various electrolytes.

Inhabitants of the gastrointestinal tract

Virtually all organs and parts of the digestive system are inhabited by microorganisms. Only the stomach has a relative sterility (fasting) due to an acidic environment. The largest number of bacteria is in the large intestine - up to 10 billion / 1 g of feces. The normal microflora of the thick gastrointestinal tract is called eubiosis and plays a huge role in human life:

• Prevents the development of pathogenic microorganisms;
• Synthesis of B and K vitamins, enzymes, hormones and other substances useful to humans;
• Cleavage of cellulose, hemicellulose and pectins.

The quality and quantity of microflora in each person is unique and is regulated by both external and internal factors.

Take care of your health!

Like any part of the human body, the digestive system of organs can be susceptible to various diseases. Often they are associated with the ingress of exogenous pathogens from outside. However, if a person is healthy and his stomach works smoothly, then all harmful bacteria are doomed to die in an acidic environment. If for some reason this organ functions abnormally, almost any infection can develop and lead to serious consequences, such as cancer of the digestive system. Everything starts from small: irrational nutrition, the lack of coarse fibrous food in the diet , the consumption of alcohol and fatty foods, smoking, stress, unbalanced diets, poor ecology and other unfavorable factors gradually destroy our body and provoke the development of diseases.

The digestive system of organs is especially susceptible to destructive influence from the outside. Therefore, do not forget to undergo medical examinations in time and consult a doctor if there is a malfunction in the normal functioning of the body.