The process of digestion in the human body: what the stomach, small and large intestines consist of

The path that food takes from entering the body to leaving the body is long and winding. To ensure that a person receives all the necessary nutrients, a processing plant called the “Gastrointestinal Tract” works tirelessly inside him. Remember the common phrase: “There are no irreplaceable people”? So this one is not about the digestive system. Every element is important here, and there is no alternative to any. In this article we tell you how the gastrointestinal tract works so that the food from your plate turns into “molecules of life”.

The structure of the digestive system

To understand what digestion is, it is necessary to consider the structure and functions of the digestive system.
It consists of organs and departments:

• oral cavity and salivary glands;
• pharynx;
• esophagus;
• stomach;
• small intestine;
• colon;
• liver;
• pancreas.

The listed organs are structurally interconnected and represent a kind of tube, 7–9 meters long. But the organs are laid out so compactly that with the help of loops and bends they are located from the oral cavity to the anus.

The main function of the digestive process is to digest food and gradually process it in the body to form nutrients that are absorbed into the lymph and blood.

But besides this, digestion performs a number of other important tasks:

• motor or motor is responsible for grinding food, mixing with the secretions of the digestive glands and further movement through the gastrointestinal tract;
• secretory ensures the breakdown of nutritional components into mucous membranes, electrolytes, monomers and final metabolic products;
• absorption promotes the movement of nutrients from the tract cavity into the blood and lymph;
• protective consists of creating barriers using the mucous membrane;
• excretory removes toxic substances and foreign bodies from the body;
• endocrine produces biologically active substances to regulate digestive functions;
• Vitamin-forming ensures the production of vitamins B and K.

Digestive functions include sensory, motor, secretory and absorption. Among non-digestive tasks, scientists distinguish protective, metabolic, excretory and endocrine.

Methods for diagnosing dysphagia

Diagnostic studies of dysphagia are aimed at clarifying symptoms, identifying connections and causes, and establishing the level of damage to the swallowing act. General tests of blood, feces and urine make it possible to detect the primary disease against which the pathology arose. For an accurate diagnosis, differential diagnosis is carried out.

The doctor prescribes liver tests and an ECG; to identify the pharyngeal form, the main indicators are obtained using:

• Screening test. The patient is given 150 ml of water to drink as soon as possible and the number of sips and time are counted. The data obtained makes it possible to calculate the rate of swallowing and the volume of the sip. This method is quite reliable.
• Examination of the upper esophageal sphincter using fluoroscopy during the period of contrast diagnostics;
• Esophagogastroduodenoscopy. Gives the opportunity to visually evaluate the internal surfaces of the esophagus, stomach and duodenum, and take a tissue specimen for biopsy.
• Checking the motor activity of the esophagus. The study is carried out using a four- or eight-channel device called a water-perfusion catheter. The device allows you to determine the tone of the upper and lower esophageal sphincters, the thoracic region;
• 3d manometry. Is a more accurate way. Allows you to obtain not only indicators, but also color images of peristalsis in the form of waves;
• Method of radionuclide scintigraphy of the esophagus. The method is based on measurements of radioactivity after ingestion of a liquid containing technetium in 99 patients;
• Differential diagnosis. This involves performing an ultrasound of the abdominal organs, MRI of brain structures, and electroencephalography of the brain. Consultations with a gastroenterologist, neurologist, and otolaryngologist are provided;
• Laryngoscopy. The method allows you to examine the posterior walls of the larynx.

Esophageal dysphagia is quite difficult to identify due to the need to exclude various ailments that contribute to the formation of a mechanical obstruction. The doctor must make sure that there are no malignant neoplasms.

In the presence of a tumor, long-term dysphagia (more than 4 months), a progressive course, severe symptoms when consuming non-liquid foods, and a sharp decrease in the patient’s weight are recorded.

Contrast radiography reveals abnormalities in the contours of the esophagus, signs of ulcers or tumors, diverticulitis, achalasia and other organic pathologies.

Lack of timely treatment for dysphagia can cause:

• Asphyxia with respiratory arrest;
• Aspiration pneumonia, abscess;
• Cancer in the throat, esophagus and stomach;
• Severe inflammatory process in the esophagus;
• Alimentary cachexia, which appears as a result of prolonged fasting.

Table of time for digestion of food in the stomach.

Below is a table in which you can see a list of products and their absorption time.

All products can be divided into four groups according to the duration of their processing by the stomach. How long does it take to digest what we eat?

Group 1. This includes mainly carbohydrates, processing time: 30-35 minutes. These are broths, light salads, natural juices, as well as fresh (raw) vegetables and fruits.

Group 2. This category contains proteins and some fats, processing time: 1-2 hours. This group includes eggs, milk, poultry, lean fish and seafood.

Group 3. These are products containing starch and complex carbohydrates, processing time: 2-3 hours. This includes nuts, legumes, cottage cheese, hard cheese, potatoes and cereals.

Group 4. This list includes foods that take longer to digest than others or are not digested at all. This includes coffee, canned food, stewed meat, mushrooms, bread and pasta.

The table shows that the body digests carbohydrates the fastest. Next in ascending order are proteins and fats.

In addition to the types of foods, other factors also play an important role in the speed of digestion.

Features of the large intestine

The stages of human digestion in the oral cavity, where the grinding of food for further processing begins, are important processes. Products interact with saliva, microorganisms and enzymes, after which the taste of food appears and starchy substances are broken down into sugars. The processing process involves teeth and tongue.

Partially digested food, along with gastric juice, moves in small portions into the small intestine. This is where more important digestive cycles take place. Intestinal juice consists of an alkaline environment due to the intake of bile, secretions of the intestinal walls and pancreatic juice. The digestion process in the intestines may slow down due to a lack of lactase, which hydrolyzes milk sugar.

During digestion, the duodenum receives bile formed in the liver. Due to the compounds of bile and pancreatic juice, proteins and polypeptides are broken down into simple particles: elastase, aminopeptidase, trypsin, carboxypeptidase and chymotrypsin. They are absorbed into the intestines.

The remains of undigested food enter the large intestine. They stay in it for 10 – 15 hours. During this period, water absorption and microbial metabolization of nutrients occur. Thanks to the microflora of the large intestine, dietary fiber, which is classified as indigestible biochemical components, is destroyed in this section.

Among them are:

• wax,
• resin,
• gum,
• fiber,
• lignin,
• hemicellulose.

Feces are formed in the large intestine. They consist of residues that have not been digested during digestion, mucus, microbes and dead cells of the mucous membrane.

Results

Digestion in the stomach is a complex mechanism consisting of multiple processes. The processing of food in the stomach is carried out by enzymes, hydrochloric acid, insoluble mucus and salts. Through muscle contractions, the formed chyme moves into the small intestine, where the main processes take place.

The speed of food processing depends on its chemical composition, texture, temperature, cooking, and the age of the person. The right combination of foods, medications, and healthy eating behavior help improve digestion.

Hormones that affect digestion

1. Temperature. Hot foods take longer to digest than cold ones. For example, okroshka requires less time to be digested by the stomach than borscht or oven-baked casserole.
2. Meal time. Food is most actively processed during the day, during lunch. Food taken at breakfast and dinner takes longer to reach the intestines.
3. Treatment. In boiled and fried foods, the enzymes characteristic of raw food are destroyed during the cooking process, and the stomach takes one and a half times longer to digest them.
4. Combination. Their processing depends on how and with what a person mixes products. For example, an apple takes half an hour to digest, and hard cheese takes five hours.
5. And the body processes a soft-boiled egg faster than a hard-boiled one.

In addition to the main sections of the gastrointestinal tract, the quality and speed of the digestion process are influenced by biologically active substances.

As we see, the digestion process in the human body is a complex system, without which human life is impossible. Proper absorption of food contributes to the quality of the body. Each organ that makes up the gastrointestinal tract plays an important role. To maintain health, it is necessary to adhere to the principles of rational nutrition and eliminate bad habits. Then the mechanisms will work like clockwork.

Useful tips on proper nutrition.

I want to end my article with interesting facts; I believe that they can change our eating behavior and at the same time improve our health.

You should know it:

• – water drunk on an empty stomach enters the intestines within a few minutes.
• – fats in the form of oils are not absorbed in the body, and by enveloping food, they complicate its dissolution by stomach acid.
• – Do not drink water, tea or other drinks when there is food in the stomach. Additional liquid entering the stomach dilutes the gastric juice, which makes it more difficult to digest food. This leads to the fact that by increasing the load on the gastrointestinal tract, undigested foods enter the intestines along with liquid and begin to ferment and even rot.
• – to speed up the digestion process and improve it, you need to chew your food thoroughly.
• – it is better to eat protein foods warm, since warm food is digested in about 2-3 hours, and the time for protein breakdown is also within this time.
• – if nuts and seeds are soaked in water overnight and then crushed, they are digested faster.

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Often tasty and healthy food are mutually exclusive concepts. Even so-called haute cuisine often consists of products with different times of absorption by the body. Therefore, a restaurant menu suitable for special occasions should not be your everyday food.

It is useful to eat foods with the same digestion time at one time. And only after complete absorption of the nutrients received by the body, begin the next meal. A diet that contains mixed foods with different digestion times leads to “cluttering” of the gastrointestinal tract, since some foods have already been digested, while others have not yet been digested.

With such inconsistent nutrition, the processes of fermentation and putrefaction begin, which are accompanied by bloating, belching and flatulence. Next, waste accumulates in the intestines. Over time, they will interfere with the absorption of food, as the intestinal walls become clogged. Digestive disorders are also possible.

The principles of separate nutrition are based on the following rules:

• a single serving should contain compatible products that are consumed at the same time;
• the interval between meals should be at least 2 hours (the only exception is fruit);
• Do not mix solid food with drinks;
• liquid foods should be consumed before meals, not after them;
• Chew food slowly and thoroughly, and do not swallow in chunks.
• You should definitely add dry herbs and a variety of spices to your food, as they promote the production of enzymes.

All this will help the functioning of the gastrointestinal tract, good health, and ease. This way you will avoid overeating and diseases associated with the digestive system.

We often try to pamper ourselves by including foods that have little or no compatibility in our diet. But eating tasty food does not mean eating right. Here you need to think through the menu in order to combine business with pleasure. Unfortunately, we do not always have enough time, energy and desire for this. However, in order not to make your body sick, you should take the time to develop a balanced daily menu.

Site doctor: Anton Palaznikov

Gastroenterologist, therapist

Work experience more than 7 years.

Professional skills: diagnosis and treatment of diseases of the gastrointestinal tract and biliary system.

Role of the liver

An important role in the process of digestion in the human body (we will briefly mention this) is played by the liver, in which bile is formed. The peculiarity of the digestive process in the small intestine is due to the assistance of bile in emulsifying fats, absorbing triglycerides, activating lipase, also helps stimulate peristalsis, inactivate pepsin in the duodenum, has a bactericidal and bacteriostatic effect, increases hydrolysis and absorption of proteins and carbohydrates.

Bile does not contain digestive enzymes, but is important in the dissolution and absorption of fats and fat-soluble vitamins. If bile is not produced enough or is secreted into the intestines, then the processes of digestion and absorption of fats are disrupted, as well as an increase in their excretion in their original form with feces.

Along with studying the digestive organs and their functions, we will also analyze the path taken by food from the moment it enters the oral cavity.

The main function of converting food into substances necessary for the human body, as has already become clear, is performed by the gastrointestinal tract. It’s called a tract for a reason, because... is a nature-designed path for food, and its length is about 8 meters! The gastrointestinal tract is filled with all sorts of “regulatory devices”, with the help of which food, making stops, gradually goes its way.

Oral cavity

The beginning of the digestive tract is the oral cavity, in which solid food is moistened with saliva and ground by the teeth. Saliva is secreted into it by three pairs of large and many small glands. During the process of eating, the secretion of saliva increases many times. In general, the glands secrete approximately 1 liter of saliva in 24 hours.

Saliva is required to wet bolus food so that it can move further more easily, and also supplies an important enzyme - amylase or ptyalin, with the help of which carbohydrates begin to break down already in the oral cavity. In addition, saliva removes from the cavity any substances that irritate the mucous membrane (they enter the cavity by accident and are not food).

Lumps of food, chewed by teeth and moistened with saliva, when a person makes swallowing movements, pass through the mouth into the pharynx, bypass it and then go into the esophagus.

Esophagus

The esophagus can be described as a narrow (about 2-2.5 cm in diameter and about 25 cm in length) vertical tube that connects the pharynx and stomach. Despite the fact that the esophagus is not actively involved in food processing, its structure is similar to the structure of the underlying sections of the digestive system - the stomach and intestines: each of these organs has walls consisting of three layers.

What are these layers?

• The inner layer is formed by the mucous membrane. It contains different glands that differ in their characteristics in all parts of the gastrointestinal tract. Digestive juices are secreted from the glands, thanks to which food products can be broken down. They also secrete mucus, which is necessary to protect the inner surface of the digestive canal from the effects of spicy, rough and other irritating foods.
• The middle layer lies under the mucous membrane. It is a muscular sheath composed of longitudinal and circular muscles. The contractions of these muscles allow the food lumps to be tightly grasped, and then, using wave-like movements (these movements are called peristalsis), to push them further. Note that the muscles of the digestive canal are muscles of the smooth muscle group, and their contraction occurs involuntarily, unlike the muscles of the limbs, torso and face. For this reason, a person cannot relax or contract them at will. You can intentionally contract only the rectum with striated, not smooth, muscles.
• The outer layer is called the serosa. It has a shiny and smooth surface, and is composed mainly of dense connective tissue. A wide connective tissue plate called the mesentery originates from the outer layer of the stomach and intestines along its entire length. With its help, the digestive organs are connected to the posterior wall of the abdominal cavity. The mesentery contains lymphatic and blood vessels - they supply lymph and blood to the digestive organs and nerves that are responsible for their movement and secretion.

These are the main characteristics of the three layers of the walls of the digestive tract. Of course, each department has its own differences, but the general principle is the same for everyone, starting with the esophagus and ending with the rectum.

After passing through the esophagus, which takes about 6 seconds, the food enters the stomach.

Stomach

The stomach is a so-called pouch that has an elongated shape and an oblique location in the upper region of the abdominal cavity. The main part of the stomach is located to the left of the central section of the torso. It begins at the left dome of the diaphragm (the muscular septum that separates the abdominal and thoracic cavities). The entrance to the stomach is where it connects to the esophagus.

To put it figuratively, the stomach seems to “know” that food will soon enter it. And he begins to prepare for her new intake even before the moment when the food enters his mouth. Remember that moment when you see some tasty dish and your mouth begins to water. Along with these “drools” that occur in the mouth, digestive juice begins to be released in the stomach (this is exactly what happens before a person begins to eat directly).

By the way, this juice was called by Academician I.P. Pavlov igniting or appetizing juice, and the scientist assigned it a large role in the process of subsequent digestion. Appetizing juice serves as a catalyst for more complex chemical processes that take a major part in the digestion of food entering the stomach.

Note that if the appearance of the food does not evoke appetizing juice, if the eater is absolutely indifferent to the food in front of him, this can create certain obstacles to successful digestion, which means that the food will enter the stomach, which is not sufficiently prepared for its digestion. This is why it is customary to attach such great importance to the beautiful table setting and appetizing appearance of the dishes.

Know that in the central nervous system (CNS) of a person, conditioned reflex connections are formed between the smell and type of food and the work of the gastric glands. These connections help determine a person’s attitude towards food even at a distance, i.e. in some cases he experiences pleasure, and in others - no feelings or even disgust.

It would not be superfluous to note one more side of this conditioned reflex process: in the case when the ignition juice has already been caused for some reason, i.e. If you are already salivating, it is not recommended to delay eating. Otherwise, the connection between the activities of the gastrointestinal tract areas is disrupted, and the stomach begins to work “idle”. If such violations are frequent, the likelihood of certain ailments, such as stomach ulcers or catarrh, will increase.

When food enters the oral cavity, the intensity of secretion from the glands of the gastric mucosa increases; Innate reflexes in the work of the above-mentioned glands come into force. The reflex is transmitted along the sensitive endings of the taste nerves of the pharynx and tongue to the medulla oblongata, and then sent to the nerve plexuses embedded in the layers of the walls of the stomach. Interestingly, digestive juices are released only when only edible foods enter the oral cavity.

It turns out that by the time the crushed food moistened with saliva ends up in the stomach, it is already absolutely ready for work, representing like a machine for digesting food. Lumps of food, entering the stomach and automatically irritating its walls with the chemical elements present in them, contribute to an even more active secretion of digestive juices, affecting individual elements of food.

The digestive juice of the stomach contains hydrochloric acid and pepsin, a special enzyme. Together they break down proteins into albumoses and peptones. The juice also contains chymosin, a rennet enzyme that curdles dairy products, and lipase, an enzyme necessary for the initial breakdown of fats. Among other things, mucus is secreted from some glands, which protects the inner walls of the stomach from the overly irritating effects of food.

Almost no food breakdown products enter the blood vessels from the stomach. For the most part, alcohol and substances containing alcohol, for example, dissolved in alcohol, are absorbed in the stomach.

The “metamorphoses” of food in the stomach are so great that in cases where digestion is somehow disrupted, all parts of the gastrointestinal tract suffer. Based on this, you must always adhere to the correct diet. This can be called the main condition for protecting the stomach from any kind of disorders.

Food stays in the stomach for approximately 4-5 hours, after which it is redirected to another part of the gastrointestinal tract - the duodenum. It passes into it in small parts and gradually.

As soon as a new portion of food has entered the intestine, the pyloric muscle contraction occurs, and the next portion will not leave the stomach until the hydrochloric acid, which ends up in the duodenum along with the already received lump of food, is neutralized by alkalis contained in the intestinal juices.

The duodenum was called the duodenum by ancient scientists, the reason for which was its length - about 26-30 cm, which can be compared with the width of 12 fingers located side by side. The shape of this intestine resembles a horseshoe, and the pancreas is located in its bend.

Digestive juice is secreted from the pancreas, flowing into the cavity of the duodenum through a separate channel. The bile produced by the liver also enters here. Together with the enzyme lipase (found in pancreatic juice), bile breaks down fats.

The pancreatic juice also contains the enzyme trypsin - it helps the body digest proteins, as well as the enzyme amylase - it promotes the breakdown of carbohydrates to the intermediate stage of disaccharides. As a result, the duodenum serves as a place where all the organic components of food (proteins, fats and carbohydrates) are actively affected by a variety of enzymes.