Digestion. Digestion in the mouth

To maintain life, first of all, people need food. Products contain a lot necessary substances: mineral salts, organic elements and water. Nutrient components are construction material for cells and a resource for constant human activity. During the decomposition and oxidation of compounds, a certain amount of energy is released, which characterizes their value.

The digestion process begins in oral cavity. The product is processed by digestive juice, which acts on it with the help of contained enzymes, due to which even when chewing complex carbohydrates, proteins and fats are transformed into molecules that are absorbed. Digestion is a complex process that requires exposure to foods of many components synthesized by the body. Proper chewing and digestion is the key to health.

Functions of saliva in the process of digestion

The digestive tract includes several main organs: the oral cavity, pharynx with esophagus, pancreas and stomach, liver and intestines. Saliva performs many functions:

What happens to food? The main task of the substrate in the mouth is to participate in digestion. Without it, some types of foods would not be broken down by the body or would be dangerous. The liquid moistens the food, the mucin glues it into a lump, preparing it for swallowing and movement through the digestive tract. It is produced depending on the quantity and quality of food: less for liquid food, more for dry food, and is not formed when water is consumed. Chewing and salivation can be attributed to the most important process organism, at all stages of which there is a change in the product consumed and the delivery of nutrients.

Composition of human saliva

Saliva is colorless, tasteless and odorless (see also:). It can be rich, viscous or very rare, watery - it depends on the proteins included in the composition. The glycoprotein mucin gives it the appearance of mucus and makes it easier to swallow. It loses its enzymatic properties soon after entering the stomach and mixing with its juice.

The oral fluid contains no a large number of gases: carbon dioxide, nitrogen and oxygen, as well as sodium and potassium (0.01%). It contains substances that digest some carbohydrates. There are also other components of organic and inorganic origin, as well as hormones, cholesterol, and vitamins. It consists of 98.5% water. The activity of saliva can be explained a huge amount elements contained in it. What functions does each of them perform?

Organic matter

The most important component of intraoral fluid is proteins - their content is 2-5 grams per liter. In particular, these are glycoproteins, mucin, A and B globulins, albumins. It contains carbohydrates, lipids, vitamins and hormones. Most of protein is mucin (2-3 g/l), and due to the fact that it contains 60% carbohydrates, it makes saliva viscous.

The mixed liquid contains about a hundred enzymes, including ptyalin, which is involved in the breakdown of glycogen and its conversion into glucose. In addition to the presented components, it contains: urease, hyaluronidase, glycolytic enzymes, neuraminidase and other substances. Under the influence of the intraoral substance, food is changed and transformed into the form necessary for absorption. For pathology of the oral mucosa, diseases internal organs used frequently laboratory test enzymes to identify the type of disease and the causes of its formation.

What substances can be classified as inorganic?

Mixed oral fluid contains inorganic components. These include:

Mineral components create an optimal reaction of the environment to incoming food and maintain the level of acidity. A significant part of these elements is absorbed by the mucous membrane of the intestines and stomach and sent into the blood. Salivary glands actively participate in maintaining the stability of the internal environment and the functioning of organs.

The process of salivation

The production of saliva occurs both in the microscopic glands of the oral cavity and in large ones: paralingual, submandibular and parotid pairs. Channels parotid glands are located near the second molar from above, the submandibular and sublingual are brought out under the tongue into one mouth. Dry foods cause secretion more saliva than wet. The glands under the jaw and tongue synthesize 2 times more fluid than the parotid glands - they are responsible for the chemical processing of foods.

An adult produces about 2 liters of saliva per day. The secretion of fluid is uneven throughout the day: while consuming foods, active production begins up to 2.3 ml per minute, and during sleep it decreases to 0.05 ml. In the oral cavity, the secretion obtained from each gland is mixed. It washes and moisturizes the mucous membrane.

Salivation is controlled by the autonomic nervous system. Increased fluid synthesis occurs under the influence taste sensations, olfactory stimuli and when irritated by food during chewing. The release slows down significantly under stress, fear and dehydration.

Active enzymes involved in food digestion

The digestive system converts nutrients obtained from foods, turning them into molecules. They become fuel for tissues, cells and organs that continuously perform metabolic functions. Absorption of vitamins and microelements occurs at all levels.

Food is digested from the moment it enters the mouth. Here it is mixed with oral fluid, including enzymes, the food is lubricated and sent to the stomach. Substances contained in saliva break down the product into simple elements and protect the human body from bacteria.

Why do salivary enzymes work in the mouth but stop functioning in the stomach? They only work in alkaline environment, and then, in the gastrointestinal tract, it changes to acidic. Proteolytic elements work here, continuing the stage of absorption of substances.

The enzyme amylase or ptyalin breaks down starch and glycogen

Amylase is a digestive enzyme that breaks down starch into carbohydrate molecules, which are absorbed in the intestines. Under the influence of the component, starch and glycogen are converted into maltose, and with the help of additional substances they are converted into glucose. To detect this effect, eat a cracker - when chewed, the product exhibits sweet taste. The substance works only in the esophagus and mouth, converting glycogen, but loses its properties in the acidic environment of the stomach.

Ptyalin is produced by the pancreas and salivary glands. The type of enzyme produced by the pancreas is called pancreatic amylase. The component completes the stage of digestion and absorption of carbohydrates.

Lingual lipase – for the breakdown of fats

The enzyme helps convert fats into simple compounds: glycerol and fatty acid. The digestion process begins in the oral cavity, and in the stomach the substance stops working. A little lipase is produced by gastric cells; the component specifically breaks down milk fat and is especially important for babies, as it makes the process of assimilation of foods and absorption of elements easier for their underdeveloped digestive system.

Types of protease - for protein breakdown

Protease is a general term for enzymes that break down proteins into amino acids. The body produces three main types:

Stomach cells produce pepsicogen, an inactive component that turns into pepsin upon contact with acidic environment. It breaks peptides - chemical bonds of proteins. The pancreas is responsible for the production of trypsin and chymotrypsin, which enter the small intestine. When food, already processed by gastric juice and fragmentarily digested, is sent from the stomach to the intestines, these substances contribute to the formation of simple amino acids, which are absorbed into the blood.

Why is there a lack of enzymes in saliva?

Proper digestion mainly depends on enzymes. Their deficiency leads to incomplete absorption of food, and diseases of the stomach and liver may occur. Symptoms of their deficiency are heartburn, flatulence and frequent belching. After some time, headaches may appear and work may be disrupted. endocrine system. A small amount of enzymes leads to obesity.

Usually the production mechanisms active substances are genetically determined, so disruption of the glands is congenital. Experiments have shown that a person receives enzyme potential at birth, and if it is spent without replenishing it, it will quickly dry up.

The processes occurring in the body can be controlled. To simplify its work, it is necessary to consume fermented foods: steamed, raw, high-calorie (bananas, avocados).

Reasons for enzyme deficiency include:

• their small supply from birth;
• eating foods grown in soil poor in enzymes;
• eating overcooked, fried food without raw vegetables and fruits;
• stress, pregnancy, diseases and pathologies of organs.

The work of enzymes does not stop in the body for a minute, supporting every process. They protect a person from diseases, increase endurance, destroy and remove fats. When their quantity is small, incomplete breakdown of products occurs, and the immune system begins to fight them as if they were foreign body. This weakens the body and leads to exhaustion.

Organs of the digestive system

The digestive organs include the alimentary canal and digestive glands. The human digestive canal is 8-10 meters long and consists of the following sections: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine. The wall of the digestive canal consists of three layers: outer (connective tissue), middle (muscular), internal (epithelial). The muscular layer of the oral cavity, pharynx and the upper third of the esophagus consists of striated muscles, and muscle layer the underlying sections are represented by smooth muscles. Thanks to the nervous and humoral mechanisms of regulation of functions, the digestive organs are united into unified system.

1. Mechanical and chemical processing food;

2. Absorption of nutrients into internal environment body (blood, lymph);

3. Excretion of undigested and unabsorbed food residues from the body;

Functions of the oral cavity.

Oral cavity - first section digestive system into which food falls. It is limited by the palate, cheeks, and mylohyoid muscle. The ducts of three pairs of large and many small ones open into it. salivary glands. Saliva is secreted into the oral cavity by the parotid, sublingual and submandibular paired glands and smaller ones scattered throughout the oral cavity. All glands secrete about 1 liter of saliva per day. Saliva is 98-99% water and has a slightly alkaline reaction. Saliva contains enzymes: amylase and maltase. Amylase breaks down the carbohydrate polymer - starch - into disaccharides (maltose), and maltase continues the breakdown of maltose into monosaccharides - glucose. Saliva contains protein substance mucin, which makes the food bolus slippery. Saliva also contains lysozyme, a bactericidal substance that partially disinfects food.

The tongue is formed by striated muscles and covered with a mucous membrane. It is involved in mixing food during chewing and helps in swallowing it. In addition, the mucous membrane of the tongue contains numerous taste buds- to determine the taste of food.

Within 10-20 seconds, during which the food is in the oral cavity, it is crushed, soaked in saliva, and the digestion of carbohydrates begins in the food bolus. Chewed food moves to the root using the movement of the cheeks and tongue. The muscles contract - the soft palate rises and closes the path to nasal cavity, and the epiglottic cartilage closes the food path into the larynx. The muscles of the mouth, pharynx and larynx contract and the bolus of food passes into the pharynx and further into the esophagus.

Digestive conveyor concept

Consecutive chain of processes leading to splitting nutrients to monomers that can be absorbed - called the digestive conveyor. The digestive conveyor is a complex chemical conveyor with a pronounced continuity of food processing processes in all departments. It covers all stages from the entry of food into the oral cavity, its grinding to cavity digestion, membrane digestion and further absorption.

Schematically, the digestive system can be represented as a tube that runs along the entire length of the body from the head to its lower end. This tube can be compared to a conveyor belt. As the contents move along the “conveyor” digestive tract in its various parts, certain “operations” of processing food substances and the transition of the final products of digestion into the blood are sequentially performed.

Latest achievements in area basic research The work of the digestive system has significantly changed traditional ideas about the activities of the “digestive conveyor belt”. In accordance with modern concept The digestive conveyor refers to the processes of assimilation of food from its entry into gastrointestinal tract before inclusion in intracellular metabolic processes.

What happens to food during digestion

To maintain metabolism and energy and carry out the vital functions of the body, it is necessary to receive from external environment organic and inorganic substances. Proteins, fats, carbohydrates and other complex proteins contained in food organic matter cannot be absorbed by the human and animal body without prior physical and chemical processing in the gastrointestinal tract, as a result of which depolymerization of nutrient molecules occurs. Oligomers and monomers, devoid of species specificity, formed under the influence of hydrolytic enzymes of digestive juices enter the blood, lymph and tissue fluid and are included in cell metabolism. The complex of processes of mechanical, physicochemical and chemical processing of food, as well as the absorption of the final products of hydrolysis in the digestive tract is called digestion.

Physiology of the oral cavity. Occurs in the oral cavity primary processing food, it is mechanically crushed and a food bolus is formed with the help of the tongue and teeth

In the oral cavity, primary processing of food occurs, it is mechanically crushed and a food bolus is formed with the help of the tongue and teeth. The oral cavity is limited above by the hard and soft palate, which ends with the uvula. The oral cavity is limited in front by the lips, and below by the diaphragm of the mouth. The oral cavity is connected by the pharynx.

In the oral cavity there are the tongue, teeth, on the sides of the soft palate - tonsils. The ducts of the parotid, sublingual and submandibular glands.

Functions of the oral mucosa. The oral mucosa performs a number of functions: protective, plastic, sensory, excretory and absorption.

Protective function the mucous membrane is carried out due to the fact that it is impenetrable to microorganisms (excluding tularemia and foot-and-mouth disease viruses). In addition, in the process of desquamation of the epithelium, which occurs constantly, microorganisms and their metabolic products are removed from the surface of the mucous membrane. Important role in implementation protective function play by leukocytes penetrating into the oral cavity through the epithelium of the periodontal attachment (gingival sulcus). Normally, 1 cm 3 of saliva contains 4000 leukocytes, and in an hour up to 500,000 of them migrate. With diseases of the oral mucosa (gingivitis, periodontitis, etc.), the number of leukocytes increases.

Plastic function The oral mucosa is explained by the high mitotic activity of the epithelium, which is 3-4 times higher than the mitotic activity of skin cells and determines the high regenerative ability of the oral mucosa following various injuries.

Touch function is carried out due to the high sensitivity of the mucous membrane to temperature, pain, tactile and taste stimuli. The mucous membrane is reflexogenic zone glands and muscles of the gastrointestinal tract.

Suction function due to the fact that the oral mucosa has the ability to absorb a number of organic and inorganic compounds(amino acids, carbonates, antibiotics, carbohydrates, etc.).

Excretory function due to the fact that some metabolites, salts are released into the oral cavity heavy metals and some other substances.

Language- muscular organ. The mucous membrane of the tongue is covered with stratified non-keratinizing epithelium. The mucous membrane contains a large number of papillae of different sizes and shapes. Taste buds are located on the surface of the tongue and palate. The muscles of the tongue are located in three mutually perpendicular areas, which ensures changes in the length and width of the tongue. On the lower surface of the tongue there is a frenulum.

Salivary glands. On the sides of the frenulum there are papillae, where the ducts of the submandibular and sublingual salivary glands end. The ducts of the parotid glands end in the buccal mucosa at the level of the second molar upper jaw. The most ancient function of saliva is to moisturize and lick food. In general, the submandibular and sublingual glands secrete a more viscous and thick saliva than the parotid. The amount and composition of saliva secreted by the same iron depends on the properties of the food - its consistency, chemical composition, temperature. Saliva is one of the digestive juices; it contains the enzyme amylase, which breaks down starch into di- and monosaccharides.

Digesting food is enough difficult process, which comes down to the breakdown of large molecules of proteins, fats and carbons into monomers that are easily absorbed by the cells of the body. In different parts of the digestive tract, different compounds break down, which are then absorbed by the mucous membrane of the small intestine and distributed throughout the body. Digestion begins in the oral cavity.

Before considering how digestion occurs, it is necessary to at least briefly familiarize yourself with its structure.

Structure of the oral cavity

In anatomy it is customary to divide it into two sections:

• The vestibule of the mouth (the space between the lips and teeth);
• The oral cavity itself (limited by the teeth, bony palate and diaphragm of the mouth);

Each element of the oral cavity has its own function and is responsible for a specific food processing process.

Teeth are responsible for the mechanical processing of solid foods. With the help of fangs and incisors, a person bites off food, then crushes it with small ones. The function of large molars is to grind food.

The tongue is a large muscular organ that is attached to the floor of the mouth. The tongue is involved not only in food processing, but also in speech processes. Moving, this muscular organ mixes the crushed food with saliva and forms a food bolus. In addition, it is in the tissues of the tongue that taste, temperature, pain and mechanical receptors are located.

The salivary glands are parotid, sublingual and exit into the oral cavity through ducts. Their main function is the production and removal of saliva, which is of great importance for digestive processes. The functions of saliva are as follows:

• Digestive (saliva contains enzymes that help break down carbons);
• Protective (saliva contains lysozyme, which has strong bactericidal properties. In addition, saliva contains immunoglobulins and blood clotting factors. Saliva protects the oral cavity from drying out);
• Excretory (substances such as urea, salts, alcohol, and some drugs are released with saliva);

Digestion in the oral cavity: mechanical phase

A wide variety of food can enter the oral cavity and, depending on its consistency, it either immediately passes into the esophagus during the act of swallowing (drinks, liquid food), or undergoes mechanical processing, which facilitates further digestion processes.

As already mentioned, food is crushed with the help of teeth. Tongue movements are needed to mix chewed foods with saliva. Under the influence of saliva, food softens and becomes coated in mucus. Mucin, which is contained in saliva, takes part in the formation of the food bolus, which subsequently passes into the esophagus.

Digestion in the oral cavity: enzymatic phase

It also includes some enzymes that are involved in the breakdown of polymers. The breakdown of carbons occurs in the oral cavity, which continues already in small intestine.

Saliva contains a complex of enzymes called ptyalin. Under their influence, polysaccharides decompose into disaccharides (mainly maltose). Subsequently, maltose, under the influence of another enzyme, is broken down into glucose monosaccharide.

How longer food is located in the oral cavity and is susceptible to enzymatic action, the easier it is digested in all other parts of the herbal tract. This is why doctors always recommend chewing your food for as long as possible.

This is where digestion in the mouth ends. Food bolus passes further and, reaching the root of the tongue, triggers the reflexive process of swallowing, in which food passes into the esophagus and subsequently enters the stomach.

To summarize, processes such as grinding food, analyzing it, take place in the oral cavity taste qualities, wetting with saliva, mixing and primary breakdown of carbohydrates.