Digestion The digestive system. Digestive system: how it all works. Main functions of the digestive system

The digestive system (gastrointestinal tract) includes: oral cavity, pharynx, esophagus, stomach, large and small intestines, liver, pancreas. Each of these organs plays its own, special role in the process of digestion - a complex physiological act, due to which the pig entering the digestive tract undergoes physical and chemical changes, and the food contained in it nutrients absorbed into the blood or lymph.

Processing and assimilation of food occur, as noted above, in the digestive tract (Figure 1), which is a tube about 9 m long with two openings - the mouth through which food enters, and the anal (anus) opening through which waste.

It should be noted that the process of digestion of food begins as soon as it enters the mouth, and as a result, food is converted into energy necessary for our body.

As food passes through the entire gastrointestinal tract, which takes a day or two, enzymes (from Latin fermentum - fermentation, fermentation) - substances produced by living cells and facilitating chemical transformations - mix with food, accelerating its breakdown. Only then is the body able to use energetic resources eaten food.

The organs that make up the digestive system are located in the head, neck, chest and abdominal cavities, and pelvis.

In the region of the head and neck are the oral cavity, pharynx and the beginning of the esophagus; most of the esophagus lies in the chest cavity; in the abdominal - the final section of the esophagus, stomach, small, blind, colon, liver, pancreas; in the pelvic area - the rectum.

The beginning of the digestive system is the oral cavity. Here, with the help of teeth, food is crushed, chewed, and mixed with saliva, which enters the oral cavity from salivary glands. From the oral cavity, partially processed food through the pharynx, and then the esophagus is sent to the stomach.

In the stomach, the food mass, lingering for several hours, is exposed to gastric juice, liquefies, actively mixes, and digests.

AT small intestine, where the food gruel - chyme - enters from the stomach, its further chemical processing with bile, secrets of the pancreas and intestinal glands continues. Bile, produced by the liver, and pancreatic juice, secreted by the pancreas, are poured into the beginning of the small intestine - the duodenum.

In the jejunum and ileum, the food slurry is actively mixed, which ensures its complete chemical processing, and then the effective absorption of nutrients into the blood and lymphatic capillaries that lie in the walls of the intestines. Further, undigested and unabsorbed food mass enters the large intestine, consisting of the cecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum. In the large intestine, water is absorbed and feces are formed from the remnants (slags) of the food mass.

Figure 2 shows the abdomen. In the future, when describing the symptoms of intestinal diseases, these names will be used.

We briefly reviewed the structure and function of the organs of the digestive system. Now let's talk in more detail about the intestine, which, as you know, consists of the small and large intestines.

Digestion

Digestion process- This is the process of splitting food into smaller components, necessary for its further assimilation and absorption, with the subsequent intake of the necessary nutrients for the body into the blood. The length of the human digestive tract is about 9 meters. The process of complete digestion of food in humans takes 24-72 hours and varies from person to person. Digestion can be divided into three phases: the head phase, the gastric phase, and the intestinal phase. head phase of digestion begins at the sight of food, at the sensation of its smell or idea of it. In this case, stimulation of the cerebral cortex occurs. Taste and smell signals are sent to the hypothalamus and the medulla oblongata. After that, the signal passes through the vagus nerve, acetylcholine is released. In this phase, gastric secretion rises to 40% of the maximum. AT this moment acidity in the stomach is not yet extinguished by food. In addition, the brain sends signals and the digestive tract begins to secrete enzymes and saliva in the mouth.

Gastric phase of digestion lasts 3 to 4 hours. It is stimulated by the presence of food in the stomach and its distension, the pH level decreases. Distension of the stomach activates reflexes of the muscular membrane.

Digestive organs

In turn, this process activates the release of a greater level of acetylcholine, which increases the secretion of gastric juice. When proteins enter the stomach, they bind to hydrogen ions, which causes the pH to rise. Increased inhibition of gastrin and gastric juice. This activates G cells to release gastrin, which in turn stimulates parietal cells to secrete gastric acid. Gastric acid contains approximately 0.5% hydrochloric acid, which lowers the pH to the desired 1-3. Acid secretion is also caused by acetylcholine and histamine.

Intestinal phase of digestion consists of two stages: excitatory and inhibitory.

Partially digested food (chyme) in the stomach fills the duodenum. This causes the release of intestinal gastrin. The enterogastrin reflex along the vagus nerve sets in motion fibers that cause the pyloric sphincter to tighten, which inhibits the flow of more food into the intestines.

Stages of digestion

Digestion is a form of catabolism, and in a global sense, it can be divided into two processes - the mechanical and chemical process of digestion. The mechanical process of digestion consists in the physical grinding of large pieces of food (chewing) into smaller ones, which can then be available for splitting by enzymes. Chemical digestion is the breakdown of food by enzymes into molecules that are available for absorption by the body. It is worth noting that the process of chemical digestion starts even when a person just looked at food or smelled it. The sense organs trigger the secretion of digestive enzymes and saliva.

When a person eats, it enters the mouth, where the process of mechanical digestion takes place, that is, food is ground into smaller particles by chewing, and it is also wetted with saliva. Human saliva is a liquid secreted by the salivary glands, which contains salivary amylases - enzymes that break down starch. Saliva also acts as a lubricant for better passing food further down the esophagus. After the process of chewing and starch fermentation, the food in the form of a moistened lump passes further into the esophagus and further into the stomach under the action of wave-like movements of the muscles of the esophagus (peristalsis). Gastric juice in the stomach starts the process of digestion of proteins. Gastric juice consists mainly of hydrochloric acid and pepsin. These two substances do not corrode the walls of the stomach due to the protective mucous layer of the stomach. At the same time, protein fermentation occurs in the process of peristalsis, during which food is mixed and mixed with digestive enzymes. After about 1-2 hours, the resulting thick liquid called chyme enters the duodenum through the opening sphincter. There, the chyme mixes with the digestive enzymes of the pancreas, then the chyme passes through the small intestine, where the digestion process continues. When this gruel is completely digested, it is absorbed into the blood. 95% of nutrient absorption occurs in the small intestine. In the process of digestion in the small intestine, bile secretion processes are launched, pancreatic juice and intestinal juice. Water and minerals are absorbed back into the blood in the large intestine, where the pH is between 5.6 and 6.9. The colon also absorbs some of the vitamins, such as biotype and vitamin K, which are produced by bacteria in the intestine. The movement of food in the large intestine is much slower than in other parts of the digestive tract. Waste is eliminated through the rectum during a bowel movement.

It is worth noting that the walls of the intestines are lined with villi, which play a role in the absorption of food. Villi significantly increase the surface area of the suction surface during digestion.

The human digestive system.

Digestion- the process of mechanical and chemical processing of food. The chemical breakdown of nutrients into their constituent simple components, which can pass through the walls of the digestive canal, is carried out under the action of enzymes that make up the juices of the digestive glands (salivary, liver, pancreas, etc.). The process of digestion is carried out in stages, sequentially. Each section of the digestive tract has its own environment, its own conditions necessary for the breakdown of certain food components (proteins, fats, carbohydrates). alimentary canal, the total length of which is 8–10 m., consists of the following departments:

Oral cavity- contains teeth, tongue and salivary glands. AT oral cavity food is mechanically crushed with the help of teeth, its taste and temperature are felt, it is formed food bolus with the help of language. The salivary glands secrete their secret through the ducts - saliva, and already in the oral cavity the primary breakdown of food occurs. The saliva enzyme ptyalin breaks down starch into sugar. In the oral cavity, in the holes of the jaws are teeth. Newborns have no teeth. By about the 6th month, they begin to appear, milky at first. By the age of 10–12, they are replaced by permanent ones. An adult has 28–32 teeth. The last teeth - wisdom teeth grow by the age of 20-22. Each tooth has a crown protruding into the oral cavity, a neck and a root located deep in the jaw. There is a cavity inside the tooth. The crown of the tooth is covered with hard enamel, which serves to protect the tooth from abrasion and the penetration of microbes. Most of the crown, neck, and root is made up of dentin, a dense, bone-like substance. In the cavity of the tooth, blood vessels branch and nerve endings. The soft part in the center of the tooth. The structure of the teeth is related to the functions performed. There are 4 incisors in front on the upper and lower jaws. Behind the incisors are fangs - long, deep-set teeth.

Like incisors, they have simple single roots. The incisors and fangs are used to bite off food. Behind the fangs on each side there are 2 small and 3 large molars. The molars are tuberous chewing surface and roots with multiple processes. With the help of molars, food should be crushed and crushed. In case of dental disease, digestion is disturbed, since in this case food that is not chewed enough and not prepared for further chemical processing enters the stomach. That's why it's so important to take care of your teeth.

Pharynx It is funnel-shaped and connects the oral cavity and esophagus. It consists of three sections: the nasal part (nasopharynx), oropharynx and laryngeal part of the pharynx. The pharynx is involved in swallowing food, this happens reflexively.
Esophagus- the upper part of the alimentary canal, is a tube 25 cm long. Top part the tube consists of a striated, and the lower one - of a smooth muscle tissue. The tube is lined squamous epithelium. The esophagus transports food to the stomach cavity. The movement of the food bolus through the esophagus occurs due to wave-like contractions of its wall. The contraction of individual sections alternates with relaxation.
Stomach- an expanded part of the alimentary canal, the walls consist of smooth muscle tissue, lined with glandular epithelium. Glands produce gastric juice. The main function of the stomach is the digestion of food. Gastric juice is produced by numerous glands in the gastric mucosa. There are approximately 100 glands in 1 mm2 of the mucous membrane. Some of them produce enzymes, others produce hydrochloric acid, and others secrete mucus.

The human digestive and excretory system.

Mixing food, soaking it with gastric juice and moving into the small intestine is carried out by contracting the muscles - the walls of the stomach.
digestive glands: liver and pancreas. The liver produces bile, which enters the intestines during digestion. The pancreas also secretes enzymes that break down proteins, fats, carbohydrates and produces the hormone insulin.

Intestines starts duodenum into which the ducts of the pancreas and gallbladder open.
Small intestine- the longest part of the digestive system. The mucous membrane forms villi, which are suitable for blood and lymphatic capillaries. Absorption takes place through the villi. Scattered throughout the mucosa of the small intestine big number small glands that secrete intestinal juice. The movement of food in the small intestine occurs as a result of longitudinal and transverse contractions of the muscles of its wall. This is where the final digestion and absorption of nutrients takes place.
Colon- has a length of 1.5 m, it produces mucus, contains bacteria that break down fiber. Initially, the large intestine forms a sac-like protrusion - the caecum, from which the appendix extends downwards.
The appendix is a small organ 8–15 cm long, it is the underdeveloped end of the caecum. When it hits undigested food, cherry, grape and plum seeds, it can become inflamed. There is an acute disease and surgical intervention is necessary.

End department- rectum - ends with an anus, through which undigested food residues are removed.

Definition of the digestive system.

Digestive system (systema digestorium) - complex hollow (tubular) organs and excretory glands, related in origin, development and structure and providing the functions of mechanical and chemical processing of food, absorption of the processed and its assimilation, production of hormones and the release of unprocessed residues. The system provides the body with plastic and energy materials.

The hollow organs of the system successively pass one into another, making up an extended (8-12 m) alimentary canal or tract, in which different levels fall into ducts of large digestive glands: salivary - into the oral cavity liver and pancreas- into the duodenum. Millions small digestive glands small salivary, pharyngeal, esophageal, gastric, intestinal are located in the mucous membrane of hollow organs, opening into the digestive tract throughout its entire length.

The epithelium of the mucous and serous membranes is able to secrete into the lumen of organs and cavities nitrogenous slags which is taken into account in practice in the treatment of a number of diseases.

Cells of the mucous membrane of the digestive tract and its glands have endocrine function, generating hormones(gastrins, enterins, endorphins, vascular intestinal peptides) , vitamins and other active compounds, necessary both for the regulation of the work of the system itself and the whole organism.

General functions of the digestive system

The oral cavity is the beginning of the digestive system. Here with teeth food is crushed, crushed and with the help of language mixed up. Saliva wets, impregnates the food bolus and begins chemical processing in it (in particular, the breakdown of carbohydrates). From the oral cavity, food passes through the pharynx and then the esophagus to the stomach. In the stomach, the food mass lingers for several hours and undergoes chemical effect of gastric juice, liquefied, actively mixed, digested. In the small intestine, where food gruel - chyme - enters from the stomach, further chemical processing it with bile, secrets of the pancreas and intestinal glands. Bile, produced by the liver, and pancreatic juice, secreted by the pancreas, are poured into the beginning of the small intestine - the duodenum. In the jejunum and ileum, there is an active mixing of food gruel, which ensures its complete chemical processing, including intestinal juice, efficient suction into the blood and lymphatic capillaries that lie in the villi of the small intestine. Further, the undigested and unabsorbed food mass enters the large intestine, which consists of the caecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. Occurs in the large intestine absorption of water, formation and excretion of feces from the remains (slags) of the food mass.

Regular processes in the phylogenesis of the digestive system.

The simplest organisms have intracellular digestion. In vertebrates, the digestive system develops from the endoderm - the epithelium of the primary intestine and gland, from mesoderm — the remaining layers in the wall of the primary intestine - a pattern, characteristic of man. In education oral cavity and anus rectum ectoderm is involved, which is also noted in humans.

In cyclostomes, jaws are absent, but there is a digestive tube with an extended endodermal lining and a non-extended ectodermal epithelium in the region of the mouth and anus. Mollusks have an intestine in which the length of the ectodermal epithelium increases due to the anterior and posterior sections of the intestine, and the extent of the endodermal epithelium in the middle section of the intestine decreases. In arthropods, the reduction in the endodermal lining reaches its maximum. Beginning with chordates, the endodermal lining grows again, reaching its maximum length in higher vertebrates. The distribution scheme of the ento- and ectodermal epithelium during the phylogenesis of the digestive tube resembles hourglass, the bottleneck of which falls on arthropods.

Jaws first appear in transverse and sturgeon fish and contain teeth. The opening of the mouth in connection with this moves to the lower parts of the head.

Lips are absent. The tongue is poorly developed, does not contain muscles. They appear in the amphibian language. The formation of the palate and the separation of the nasal cavity and the mouth begins with reptiles, and the complete separation occurs in mammals.

Clinical significance of knowledge of the sources of the lining of the alimentary canal.

In the mouth and rectum epithelial lining has a dual origin ectodermal and endodermal, which leads to the formation of epithelium of different structure. Front two thirds of the oral cavity and its organs develop on the basis of visceral arches and covered with epithelium of ectodermal origin. The posterior one third of the oral cavity develops from pharyngeal part of the primary intestine and is covered with epithelium of endodermal origin. Along the border, there is a docking of a heterogeneous epithelial tissue. A similar picture is observed in rectum, where the mucous membrane of the ampoule is lined with endodermal epithelium, and the mucous membrane of the anus (anal canal) is covered with ectodermal epithelium.

Numerous clinical observations have revealed the following regularities: chronic pathogenic processes develop in the epithelium of ectodermal origin, acute ones develop in the epithelium of ectodermal origin, and tumors appear at the junction of epithelia.

What is the yolk duct, yolk stalk, yolk sac?

In the first week of development, two original tissues appear: endoderm and ectoderm. The endoderm develops from the internal cells of the germinal nodule and limits endoblastic vesicle or yolk vesicle which develops into a yolk sac as it grows. From the ectoderm, an amniotic sac is formed, located nearby. Both sacs develop into extra-embryonic organs. As an early extra-embryonic organ yolk sac before the formation of the placenta, through its vessels it delivers nutrition from the uterus to the embryo and serves as the original source for the formation of many internal organs and vessels.

From the intestinal endoderm of the yolk sac on the 4th week, the primary intestine arises, which is first connected to it by a wide fistula. Back department the intestine is connected to the allantois (cloaca). The primary intestine is located rectilinearly along the chord, that is, at the posterior wall of the coelom, and the yolk sac lies along the anterior wall. Very soon, he begins to lag behind the intestine in growth, but does not lose contact with it for a long time. A wide fistula between the sac and the intestine gradually turns into a narrow one. vitelline duct, and the yolk sac itself decreases in size, grows into ventral stalk, where it finally atrophies and becomes empty.

The ventral or yolk stalk consists of the umbilical vessels, the empty yolk sac, and the yolk duct.. Over time, the ventral stalk lengthens, becomes relatively thin, and is later called umbilical cord. In the fetal period, the lumen of the sac and duct gradually overgrows. The yolk stalk with a neglected duct and sac dissolves and loses contact with the intestine. But with violations of embryogenesis, this connection can be preserved in the form of a saccular protrusion of the ileum wall (Meckel's diverticulum) or umbilical-intestinal fistula (rarely).

What develops from the splanchnopleura in the wall of the alimentary canal?

All organs of the digestive system, with the exception of the oral cavity and anus, develop from the primary intestine, the epithelial lining of which arises from the germinal intestinal endoderm yolk sac, and all other layers of the membranes - from the medial plate unsegmented mesoderm - splanchnopleura.

From the intestinal endoderm formed epithelium digestive tube and digestive glands : liver, pancreas and numerous small glands of the mucous membrane - pharyngeal, esophageal, gastric and intestinal.

What organs does the digestive system consist of?

The mucous membrane, in addition to the epithelial cover, the submucosa, muscular and connective tissue (serous or adventitial) membranes are formed from splanchnopleuron (visceropleuron).

What is a splanchnopleura? The ventral part of the mesoderm is not divided into segments, but is represented on the right and left sides by two plates: medial and lateral. The space between the plates of non-segmented mesoderm turns into the body cavity of the embryo, from which the peritoneal, pleural and pericardial cavities arise. The dorsal mesoderm is segmented.

Medial (visceral) plate ventral mesoderm adjacent to the endoderm of the primary intestine and is called the splanchnopleura, as it already consists from mesoderm and endoderm. The lateral (outer) plate is adjacent to the wall of the body of the embryo and to the ectoderm. She got the name somatopleuron, consisting of mesoderm and ectoderm. From the splanchno- and somatopleura, the mesothelium of the serous membranes develops: visceral and parietal, and the cells that emerge from them between the germ layers give rise to a more differentiated tissue - mesenchyme.

Topic: "DIGESTION"

4th grade students

Lyceum No. 10

All the substances necessary to perform physical and mental work, maintain body temperature, as well as the growth and restoration of deteriorating tissues and other functions, the body receives in the form of food and water.

Food products consist of nutrients, the main of which are proteins, fats, carbohydrates, mineral salts, vitamins, water. These substances are part of the cells of the body. Majority food products cannot be used by the body without pre-treatment. It consists in the mechanical processing of food and its chemical breakdown into simple soluble substances that enter the bloodstream and are absorbed from it by cells. This processing of food is called digestion.

The digestive system is the digestive organs of animals and humans. In humans, the digestive system is represented by the oral cavity, pharynx, esophagus, stomach, intestines, liver and pancreas.

In the oral cavity, food is crushed (chewed), then subjected to complex chemical processing by digestive juices, those that are in our stomach. The salivary glands secrete saliva, the glands of the stomach, pancreas and intestinal glands - various juices and the liver is bile. As a result of exposure to these juices, proteins, fats and carbohydrates are broken down into simpler soluble compounds.

But this is possible only with the movement of food through the digestive canal and its thorough mixing. Moving and mixing food is carried out due to powerful contractions of the muscles of the walls of the digestive canal. The transition of nutrients into the blood is carried out by the mucous membrane of individual sections of the digestive canal.

All substances that could not be processed by the enzymes of the gastrointestinal tract go to the large intestine, where, with the help of microorganisms, they undergo additional splitting (partial or complete), while some of the products of this splitting are absorbed into the blood of the macroorganism, and some goes to feed the microflora.

The final stage of digestion is the formation of feces and their evacuation.

Digestion is a set of processes that provide mechanical grinding and chemical breakdown of nutrients ready for absorption and participation in the metabolism of animals and humans. The food entering the body is comprehensively processed under the action of various digestive enzymes synthesized by specialized cells, and the breakdown of complex nutrients (proteins, fats and carbohydrates) into ever smaller fragments occurs with the addition of a water molecule to them.

Organs of the digestive system

Proteins are ultimately broken down into amino acids, fats into glycerol and fatty acids, carbohydrates into monosaccharides.

These are relatively simple substances are absorbed, and complex organic compounds are again synthesized from them in organs and tissues. This process is carried out throughout the gastrointestinal tract.

The digestive tract consists of the following sections: the upper one, consisting of the mouth and larynx, the middle one, consisting of the esophagus and stomach, and the lower one, the small and large intestine.

Upper digestive tract

Mouth

Mouth- the first part of the digestive tract. It contains: hard and soft palate, lips, muscles, teeth, salivary glands and tongue.
The hard and soft palate form the upper wall of the oral cavity. The hard palate is formed by the maxilla and palatine bone and lies in front of the mouth. The soft palate is composed of muscles and lies at the back of the mouth, forming an arch with the uvula.

Lips- extremely mobile formations - are the entrance to the oral cavity. They are composed of muscle tissue and have a plentiful blood supply, which provides their color, and many nerve endings, allowing them to determine the temperature of food and liquid entering the mouth.

Muscles - three main muscles of the face are involved in chewing:

Cheek muscles
Chewing muscles on the sides of the face
Temporal muscles

Teeth. Children have 20 milk teeth, which are replaced by 32 permanent teeth between the ages of 6 and 25. An adult has 16 upper teeth growing from the tooth cells of the upper jaw, and 16 in the lower jaw.

There are three types of teeth:

Anterior incisors
Fangs shaped like a cone
The posterior premolar and molar teeth are flatter than the rest.

Salivary glands- contain cells that produce a thick watery liquid - saliva. Saliva is made up of water, mucus, and the enzyme salivary amylase.

There are three pairs of salivary glands:

Ears located under the ears
Sublingual
Submandibular

Language- formed by skeletal muscles and attached to the hyoid bone and lower jaw. Its surface is covered with small papillae that have sensitive cells. Because of this, they are called taste buds.

Pharynx

The pharynx connects the digestive and respiratory systems and has three parts:

The nasopharynx is the passage for air inhaled through the nose. Associated with the respiratory system rather than the digestive system.
Oropharynx - located behind the soft palate and nasopharynx and is a channel for air, food and fluid entering through the mouth.
The hypopharynx is a continuation of the oropharynx leading further into the digestive tract.

Tonsils in the throat and adenoids on the back of the nose protect the body from infection that enters it with food, liquid and air.

Middle and lower digestive tract

Medium and lower divisions The digestive tract is a single structure from the esophagus to the anus. In its course, it changes in accordance with its functions.

The digestive tract is made up of four main layers:

The peritoneum is a tough outer layer that secretes a lubricant that keeps the organs of the digestive system gliding.
Muscle layers - muscle fibers are arranged in two layers. The inner layer is a circular layer of the muscular membrane, the outer one is longitudinal. The contraction and relaxation of these muscles is called peristalsis and is a wave-like movement that moves food through the digestive tract.
The submucosal layer is composed of loose connective tissue containing elastic fibers lymphatic vessels and nerves that are involved in the life of the digestive tract, nourishing it and providing its sensitivity.

Esophagus

The esophagus is a long tube (about 25 cm) that runs from the throat to the stomach. It lies behind the trachea, in front of the spine. The empty esophagus is flat. The muscular structure allows it to expand when food enters. The muscular layer contracts, propelling food down the esophagus (peristalsis) through a circular muscle called the cardiac sphincter into the stomach.

Stomach

The stomach is a comma-shaped bag and lies under the diaphragm on the left side. The lining of the stomach has many folds that allow it to stretch when full and contract when empty. In the same layer are the gastric glands, which produce gastric juice that dissolves food.

The muscular layer of the digestive tract is thickest in the stomach, since here it carries out movements during the digestion of food. At the end of the stomach is another circular muscle - the pyloric sphincter. It controls the passage of digested food to the lower digestive system.

Small intestine

The small intestine is by no means small. It is about 6 meters long. It coils around itself and fills the abdominal cavity.

The general structure of the small intestine is the same as that of other digestive organs, except that it has tiny protective villi on its inner mucosa. They contain glands that produce digestive juices; blood capillaries, which take nutrients from digested food; lymphatic capillaries, called lactiferous vessels, which absorb food fats.

The small intestine is also associated with additional organs of the digestive system. The gallbladder and pancreas are connected to the small intestine in the duodenum by the bile and pancreatic ducts, respectively.

Colon

The large intestine is wider and shorter than the small intestine. It is about 1.5 meters long and is divided into 5 sections.

The caecum is separated from the ileum small intestine ileocecal sphincter. Attached to the caecum is an appendix formed by lymphatic tissue. It is not involved in digestion, but protects the system from infections.
The colon is divided into four parts: ascending, transverse and descending, the position of which corresponds to the names, and the sigmoid, connecting the colon with the rectum.
The rectum comes from the sigmoid colon and lies next to the sacrum.
The anal canal is a continuation of the rectum.
The intestine ends with an anus formed by two muscles: internal and external sphincters.

The structure of additional organs

The liver, gallbladder and pancreas are also part of the digestive system. They also have functions associated with other systems that make them important links in the body.

Liver

The liver is the largest internal organ. It lies directly below the diaphragm in the upper right side of the abdomen. The liver has a large right side and a smaller left side. The parts of the liver are called lobes; The right lobe is connected to the gallbladder by a canal. The liver is one of the most important connecting links in the body, having an abundant blood supply. It receives oxygenated blood through the hepatic artery, which is a branch of the descending aorta, and nutrient-rich venous blood through the hepatic portal vein, which is part of the portal circulation. As a result, the liver performs many functions, not all of which are related to the digestive system.

Filtration - blood from the hepatic portal vein is filtered as it passes through the liver; old and damaged red blood cells and other unnecessary substances, including excess proteins, are removed from it.
Detoxification - The liver removes toxins from the blood, such as drugs and alcohol.
Breakdown - The liver breaks down damaged, dead blood cells to form bilirubin, which is involved in the production of bile. The liver also breaks down waste particles (toxins and extra proteins) to form urea, which is excreted from the body in the form of urine.
Storage - The liver stores some of the vitamins, glycogen and iron that the body gets from food to be used later, such as muscle glycogen.
Production - The liver produces bile, which is stored in the gallbladder. Bile helps maintain body temperature by producing heat and breaks down damaged and dead red blood cells, resulting in waste products in the liver.

gallbladder

The gallbladder is shaped like a saddle. It is located just above the duodenum and below the liver and is connected to both organs by tributaries. The gallbladder receives bile from the liver for storage until the duodenum needs it to digest food. Bile is made up of water, bile salts used in digestion, and bile pigments, including bilirubin, which gives feces their characteristic color. gallstones formed from large particles of bile, which can block its passage into the duodenum; this causes severe pain.

Pancreas

The pancreas is a long, thin organ that lies across the abdominal cavity on the left side.

This gland has a dual function:

It is endocrine, i.e. produces hormones that are released into the blood as part of the excretory system.
She is exocrine. those. produces a liquid substance - pancreatic juice, which enters the duodenum through the ducts and is involved in digestion. Pancreatic juice is made up of water, minerals and enzymes.

The digestive system relies on the interaction of all its parts to perform its functions.

Functions of the digestive system

swallowing

This includes eating, chewing and grinding food in the mouth. The food comes in the form of a soft ball called a bolus.

This process involves:

Lips - the nerve endings of the lips assess the temperature of food and liquid entering the oral cavity, and the movements of the muscles of the upper and lower lips ensure their tight closure.
Teeth - incisors can bite off large pieces of food; sharp fangs break food; molars grind it.
Muscles - The cheek muscles move the cheeks inward; chewing muscles lift lower jaw to the top, thereby pressing on the food in the mouth; temporalis muscles close the mouth.
Saliva binds and moistens food, preparing it for swallowing. Saliva dissolves food so that we can taste it and cleans the mouth and teeth.
Tongue - tastes food by moving it around the mouth during chewing, before moving the finished bolus to the back of the mouth for swallowing. The taste buds on the surface of the tongue have tiny nerves that determine whether we want to continue the process by sending the appropriate signal to the brain, which interprets the taste.
Pharynx - The muscles of the pharynx contract and push the bolus down into the esophagus. During swallowing, all other pathways are closed. The soft palate rises and closes the nasopharynx. The epiglottis closes the entrance to the trachea. Thus, this muscle coordination ensures the correct direction of food movement.

digestion

Digestion is the breakdown of food into tiny particles that can be absorbed by cells.

There are 2 processes in digestion:

Mechanical digestion - chewing food to break up and form food boluses (boluses) that occurs in the mouth.
Chemical digestion, which is the breakdown of food by digestive juices containing enzymes, occurring in the mouth, stomach, and duodenum. During this time, the food bolus is transformed into chyme.
The saliva produced in the mouth by the salivary glands contains the enzyme amylase. In the mouth, amylase begins the breakdown of carbohydrates.
In the stomach, the glands present produce gastric juices, which contain the enzyme pepsin. It breaks down proteins.
The gastric glands also produce hydrochloric acid, which stops the action of salivary amylase and also kills harmful particles that have entered the stomach. When the level of acidity in the stomach reaches a certain point, the pyloric sphincter passes a small part of the digested food into the first section of the lower digestive tract - the duodenum.
Pancreatic juices from the pancreas through the duct enter the duodenum. They contain enzymes. Lipase breaks down fats, amylase continues the digestion of carbohydrates, trypsin breaks down proteins.
In the duodenum itself, mucosal villi produce digestive juices; they contain the enzymes maltose, sucrose and lactose, which break down sugar, as well as erepsin, which completes the processing of proteins.
At the same time, bile produced in the liver and stored in the gallbladder enters the duodenum. Bile breaks down fats into smaller particles during the emulsification process.

During the process of digestion, the food we eat undergoes a series of changes from solid food in the mouth to bolus and liquid chyme. Carbohydrates, proteins and fats must be broken down by enzymes so that the following processes can take place.

Absorption

Absorption is the process by which nutrients move from the digestive system into the blood to be distributed throughout the body. Absorption occurs in the stomach, small and large intestines.

From the stomach limited quantity water, alcohol and narcotic substances directly into the blood stream and carried throughout the body.
With peristaltic movements of the muscles of the small intestine, chyme passes through the duodenum, jejunum, and ileum. At the same time, the villi of the mucous membrane ensure the absorption of digested nutrients. The villi contain blood capillaries that take digested carbohydrates, proteins, vitamins, minerals, and water into the blood stream. The villi also contain lymphatic capillaries called lactiferous vessels that absorb digested fats before they enter the bloodstream. The blood carries the received substances throughout the body in accordance with its requests and after that it is cleared by the liver, leaving excess nutrients for storage. When the chyme reaches the end of the duodenum, most of the nutrients have already been absorbed by the blood and lymph, leaving only indigestible food particles, water and a small amount of nutrients.
When the chyme reaches the ileum, the end of the small intestine, the ileocecal sphincter allows it to pass into the large intestine and closes to prevent backflow. All the remaining nutrients in it are absorbed, and feces are obtained from the remains. Peristaltic movements of the muscles push them along the colon into the rectum. The rest of the water is absorbed along the way.

Excretion

Excretion is the removal of indigestible food residues from the body.

When feces reach the rectum, we reflexively feel the need to empty the bowels. Peristaltic movements push feces through the anus and the internal sphincter relaxes. The movements of the external sphincter are voluntary, and at this moment we can choose whether to empty the bowels or close the muscle until a more appropriate moment.

This whole process takes from several hours to several days, depending on its complexity. Nutritious, dense foods are digested more slowly and stay in the stomach longer than lighter, softer foods. In the next few hours, absorption occurs, and then excretion. All these processes are more efficient if the body is not overloaded. The digestive system needs rest when blood from the muscles can move to it, which is why we feel sleepy after eating, and suffer from indigestion when we exercise too much.

Possible violations

Possible disorders of the digestive system from A to Z:

Anorexia - lack of appetite, leading to exhaustion, and in severe cases - to death.
APPENDICITIS - inflammation of the appendix. Acute appendicitis occurs suddenly and the appendix is removed surgically. Chronic appendicitis may last several months without the need for surgery.
CROWN'S DISEASE - see ILITIS.
BULIMIA is a disorder associated with overeating, as a result of which one begins to induce vomiting and / or take laxatives. Like anorexia, bulimia is a psychological problem, and normal food intake can only be restored after it has been corrected.
A prolapse is a displacement of an organ, such as the rectum.
Gastritis is irritation or inflammation of the stomach. May be caused by eating certain foods or drinks.
GASTROENTERITIS - inflammation of the stomach and intestines, leading to vomiting and diarrhea. Dehydration and exhaustion can set in very quickly, so care must be taken to replenish lost fluids and nutrients.
HEMORRHOIDS - swelling of the veins of the anus, painful and discomfort. Bleeding from these veins can lead to anemia due to the loss of iron.
GLUTEN DISEASE - intolerance to gluten (a protein found in wheat).
HERNIATION - a rupture in which the body goes beyond its protective shell. In men, a hernia of the colon is common.
DIARRHEA - too frequent bowel movements as a result of a peristaltic "attack", leading to dehydration and malnutrition, since the body does not get enough water and nutrients.
DYSENTHERIA is an infection of the colon leading to severe diarrhea.
JAUNDICE - yellow discoloration of the skin, which in adults is a sign of a serious illness. Yellow caused by bilirubin, which is produced when red blood cells are destroyed in the liver.
GALL STONES - hard formations from particles of bile in the gallbladder, which can cause obstruction of bile into the duodenum. In difficult cases, removal of the gallbladder is sometimes required.
CONSTIPATION - Irregular bowel movements due to dry, hard feces when too much water is absorbed.
HICCUP - repetitive involuntary spasms of the diaphragm.
ILITIS - inflammation of the ileum. Another name is Crohn's disease.
ACID REGURGITATION - a condition where the contents of the stomach, along with hydrochloric acid and digestive juices, return to the esophagus, causing a burning sensation.
COLITIS is an inflammation of the large intestine leading to diarrhea. In this case, stools with blood and mucus are observed due to damage to the mucous membrane.
Flatulence - the presence of air in the stomach and intestines, which was swallowed with food. May be associated with certain gassy foods.
Indigestion - Pain associated with eating certain foods that are difficult to digest. It can also be caused by overeating, hunger, or other causes.
OBESITY - being overweight as a result of overeating.
PROCTITIS - inflammation of the lining of the rectum, causing both pain during the passage of feces and the need to empty the intestines.
INTESTINAL CANCER - Colon cancer. It can form in any part of it and block patency.
ESOPHAGEAL CARCINOMA - malignant tumor along the length of the esophagus. It most often occurs in the lower esophagus in middle-aged men.
MUCOUS COLITIS is a disease usually associated with severe stress. Symptoms are alternating periods of diarrhea and constipation.
Cirrhosis of the liver is hardening of the liver, usually caused by alcohol abuse.
Esophagitis is inflammation of the esophagus, often characterized by heartburn (burning in the chest).
ULCER - opening the surface of any part of the body. Usually occurs in the digestive tract, where its lining is broken due to an excess of acid in the digestive juices.

Harmony

The efficient functioning of the digestive system ensures that cells, organs and systems of the body receive the optimal amount of nutrients and water. The digestive system, in addition to the state of its own components, depends on its connections with other systems.

Liquid

The body loses about 15 liters of fluid per day: through the kidneys with urine, through the lungs when exhaling, through the skin with sweat and feces. The body produces about a third of a liter of water per day in the process of energy production in cells. Therefore, the minimum need of the body for water - a little more than a liter - allows you to maintain fluid balance and avoid dehydration. Drinking water prevents constipation: when feces stagnate in the intestines, most of the water is absorbed and they dry out. This makes bowel movements difficult, painful, and can lead to strain on the lower digestive tract. Constipation affects other body systems as well, leading to flaccidity of the skin if the toxins in the feces are retained in the body.

Food

The task of the digestive system is to break down food into substances that can be absorbed by the body - part natural process sustaining life. Food can be divided into:

Carbohydrates are broken down to glucose and transported by the blood to the liver. The liver directs some of the glucose to the muscles, and it is oxidized in the process of energy production. Part of the glucose is stored in the liver in the form of glycogen and sent to the muscles later. The rest of the glucose is carried by the blood stream to the cells, its excess is deposited in the form of fats. There are fast-burning carbohydrates: in sugar, candy and most foods fast food, which give a short burst of energy, and are slowly consumed: in cereals, vegetables and fresh fruit, which provide a longer charge.
Proteins (proteins) - are broken down into amino acids, which ensure the growth and restoration of the body. The proteins we get from eggs, cheese, meat, fish, soy, lentils and legumes are broken down into different amino acids during digestion. Further, these amino acids are absorbed by the blood and enter the liver, after which they are either removed or used by cells. Liver cells convert them into plasma proteins; proteins change; are broken down (unnecessary proteins are destroyed and pass into urea, which enters the kidneys with blood and is removed from there in the form of urine).
Fats - get into lymphatic system through the lactiferous vessels during the emulsification process, before lymphatic ducts enter the blood. They are another source of energy and material for the formation of cells. extra fat removed from the blood and deposited. There are two main sources of fat: hard fats from dairy and meat, and soft fats from vegetables, nuts, and fish. Hard fats are not as healthy as soft fats.
Vitamins A, B, C, D, E and K are absorbed from the digestive system and are involved in all processes occurring in the body. Extra vitamins can be stored in the body until needed, such as during a diet. Vitamins A and BJ2 are stored in the liver, fat-soluble vitamins A, D, E and K are stored in fat cells.
Minerals (iron, calcium, soda, chlorine, potassium, phosphorus, magnesium, fluorine, zinc, selenium, etc.) are absorbed like vitamins and are also necessary for various processes in the body. Excess minerals are not absorbed and are removed either c. faeces or urine through the kidneys.
Fibers are dense fibrous carbohydrates that cannot be digested. Insoluble fibers found in wheat bran, fruits and vegetables make it easier for feces to pass through the colon, increasing their mass. This mass absorbs water, making the feces softer. The muscular layer of the large intestine is stimulated and waste products are removed from the body faster, reducing the risk of constipation and infections.
It is clear that in order to fulfill my functions, the digestive system requires a balanced supply of nutrients. Ignoring the body's need for food entails rapid dehydration into exhaustion. Over time, it leads to even more major changes resulting in illness or even death.

Relaxation

The body needs rest so that the digestive system can process the food received. Before and immediately after a meal, the body needs a short period of rest so that the digestive tract can do its job. The digestive system needs an abundant supply of blood to function naturally and efficiently. During rest, a large amount of blood can flow into the alimentary canal from other systems. If the body remains active during and immediately after eating, insufficient blood is involved in the process of digestion. Due to inefficient digestion, heaviness, nausea, flatulence, and indigestion occur. Rest also allows time for the absorption of nutrients. In addition, after a good rest, the cleansing of the body is much more effective.

Activity

Activity becomes possible when food and liquid have been broken down, digested and assimilated. During digestion, proteins, fats and carbohydrates obtained from food are broken down so that after digestion they can be used to produce energy in cells (cellular metabolism). When the body is deficient in nutrients, it draws on reserves from the muscles, liver, and fat cells. Eating more food than necessary leads to weight gain, and eating less food leads to weight loss. The energy value products are calculated in kilocalories (Kcal) or kilojoules (kJ). 1 kcal = 4.2 kJ; the average daily requirement for a woman and 2550 kcal / 10,600 kJ for a man. To maintain body weight, it is necessary to commensurate the amount of food consumed with the body's need for energy. Required amount energy for each person varies depending on age, gender, physique and physical activity. It changes during pregnancy, lactation or illness. The body responds with a feeling of hunger to the growing need for energy. However, often this feeling misleads us, and we eat out of boredom, out of habit, in company, or simply because of the availability of food. In addition, we very often ignore satiety signals and indulge ourselves.

Air

The air from the atmosphere contains oxygen, which is necessary to activate the energy received from food. The way we breathe determines the amount of activated energy and should be related to the needs of the body. When the body needs a lot of energy, breathing quickens, with a decrease in this need, it slows down significantly. It is important to breathe more calmly during meals so that too much air does not enter the digestive tract, and to increase breathing when it is necessary to activate the energy received from food. Although breathing is an involuntary process carried out by the respiratory and nervous systems, we can control its quality to some extent. If more attention were paid to the art of breathing, the body would be much less prone to stress and injury, which in turn would prevent the occurrence of many diseases or mitigate their syndromes (mucous colitis is greatly relieved with proper breathing).

With age, the body's energy needs change: children need more energy than older people. With aging, the processes in the body slow down, and this is reflected in the need for food, which changes in proportion to the decrease in the level of activity. Middle-aged people often have excess weight because they ignore the need to reduce food intake. Changing your eating habits can be difficult, especially if eating is associated with pleasure. In addition, age affects digestion: it is difficult due to a decrease in the absorption of nutrients.

Color

The digestive tract occupies a significant part of the body, stretching from the mouth down to the anus. It goes through five chakras, from the fifth to the first. Thus, the digestive system is associated with the colors corresponding to these chakras:

Blue, the color of the fifth chakra, is associated with the throat.
Green - the color of the fourth chakra - brings the system into harmony.
Yellow, associated with the third chakra, purifies by affecting the stomach, liver, pancreas and small intestine, aiding digestion and absorption of nutrients.
Orange - the color of the second chakra - continues the cleansing process and promotes the removal of decay products through the small and large intestines.
Red - the color of the first chakra - affects excretion, preventing sluggishness in the lower digestive system.

Knowledge

Knowing what role the digestive system plays in the overall health of the body is the key to healthy eating. In addition, when we understand the signals of our body, it is easier to achieve a balance between the physical and psychological need for food. Children intuitively know what they need to eat and when, and when left alone with sufficient food and water supplies, they never go hungry or overeat. Starting to live according to the laws of society, which, in general, do not take into account the needs of the digestive system, we very quickly lose this ability. What's the point of skipping breakfast when we need the most nutrients for the day in the morning? And why eat a three-course dinner at the end of the day when we won't need energy at all for another 12 hours or so?

special care

The care the digestive system receives affects the health of the whole organism. A digestive system that is taken care of will take care of the entire body. It prepares the "fuel" for the body, and the quality and quantity of this "fuel" is correlated with the time required to grind, digest and assimilate food. Stress destroys the balance necessary for the efficient production of "fuel" and is one of the main causes of digestive disorders. Stress, as it were, turns off the digestive system until the situation returns to normal. In addition, it affects the feeling of hunger. Some people eat to calm down, while others lose their appetite in stressful situations.

For the well-being of the digestive system, the following is necessary:

Regular meals to provide the body with enough energy to perform its functions.
Balanced nutrition for healthy work organism.
At least a liter of water per day to avoid dehydration.
Fresh, unprocessed food containing maximum amount nutrients.
Dedicated time for eating to avoid indigestion.
Time for a regular bowel movement.
Avoid increased activity immediately after a meal.
Eat when you are hungry, not out of boredom or out of habit.
Chew food thoroughly for efficient mechanical digestion.
Avoid stressful situations that can adversely affect digestion, assimilation and excretion.
Avoid sources of free radicals - fried foods - which cause premature aging.

Think about how often you gobble up food, eat on the run, or even skip meals, and then eat fast food when you're hungry, but too tired, lazy, or busy to make a proper meal. No wonder so many people have digestive problems!

The digestive system is a complex of organs, the function of which is the mechanical and chemical processing of ingested nutrients, the absorption of processed and the release of the remaining undigested food components. It includes the oral cavity, pharynx, esophagus, stomach, small and large intestine, liver, gallbladder and pancreas (Fig. 2). The esophagus, stomach, and entire intestine form the gastrointestinal tract.

Rice. 2. General plan of the structure of the digestive system.

Oral cavity It is divided into two sections: the vestibule of the mouth and the oral cavity itself. mouth vestibule called the space located between the lips and cheeks on the outside and the teeth and gums on the inside. Through the mouth opening, the vestibule of the mouth opens outward.

Oral cavity extends from the teeth anteriorly and laterally to the posterior pharyngeal inlet. From above, the oral cavity is limited by the hard and soft palate, the bottom is formed by the diaphragm of the mouth and is occupied by the tongue. The ducts of three pairs of large salivary glands open into the oral cavity: parotid, submandibular and sublingual. In addition, there are numerous small glands in the oral mucosa, which, by the nature of the secret, can be serous, mucous, or mixed.

The sky consists of two parts (Fig. 3). The anterior two thirds of it have a bone base (the palatine process of the upper jaw and the horizontal plate palatine bone), this is - solid sky; back third - soft sky(is a muscle formation). The free posterior edge of the soft palate hangs down freely, having a protrusion in the middle - uvula, and on the sides passes into two pairs of folds, forming two pairs of arches, between which are located palatine tonsils (tonsils). In the thickness of the soft palate there are muscles that determine its participation in swallowing and sound production.

Rice. 3. The structure of the oral cavity.

1 - upper lip, 2, 9 - gums, 3 - teeth, 4 - hard palate, 5 - soft palate, 6 - tongue, 7 - tonsil, 8 - tongue, 10 - frenulum of the lower lip, 11 - lower lip 12 - frenulum upper lip, 13 - pharynx.

The opening, bounded from the sides by the arches of the soft palate, from above by the tongue, and from below by the initial section of the tongue, is called pharynx. Thanks to him, the oral cavity communicates with the pharynx.

Language is a muscular organ. It has three parts - root, top and between them body. Numerous lymphoid accumulations are located at the root of the tongue - lingual tonsil. The upper surface of the tongue is called back of the tongue it contains numerous papillae, which contain receptors that determine the sensitivity of the tongue to touch, pain, temperature, perception and taste identification.

Teeth(Fig. 4) are ossified papillae of the mucous membrane, which serve for the mechanical processing of food. In humans, the change of teeth occurs 2 times, therefore, milk teeth and permanent teeth are distinguished.

Rice. 4. The structure of the tooth.

Number permanent teeth equals 32, 16 each in the top and bottom row. Each half of the dentition has 8 teeth. Human tooth development begins around the 7th week of embryonic life. The teeth are located in the cells of the alveolar processes of the upper and lower jaws.

The fabric that covers alveolar processes, is called gums. Each tooth consists of a crown, neck and root. Crown protrudes above the gum neck covered by the gum, and root sits in the dental alveolus and ends at the top, on which there is a small hole. Vessels and nerves enter the tooth through this opening. Inside the crown of the tooth there is a cavity that is filled with dental pulp ( pulp), rich in vessels and nerves. The solid substance of the tooth consists of dentin, enamel and cementum. The bulk of the tooth is dentin. Enamel covers the outside of the crown, and the root is covered with cement. A fully developed and preserved chewing apparatus of an adult contains 32 teeth, forming the upper and lower dentition. Each half of the dentition contains 8 teeth: 2 incisors, 1 canine, 2 small molars (premolars) and 3 large molars (molars). The third root is called the wisdom tooth and is the last to erupt.

The number of teeth is usually represented by a dental formula in which upper teeth are indicated in the numerator, and the lower ones - in the denominator. The teeth are marked starting from the middle, and since the right and left halves are symmetrical, only the left is taken into account. The first digit indicates the number of incisors, the second - canines, the third - small molars and the fourth - large molars.

Formula of permanent teeth:

Milk teeth formula:

In dental practice, the following digital formulas are used:

On right Left

The number 1 indicates the medial incisor, the number 8 - the third large molar. Based on this formula, individual teeth are designated as follows:

- right upper first molar;

- left upper canine;

- lower right first small molar;

In the oral cavity there are three pairs of large glands - parotid, sublingual and submandibular, which produce digestive enzymes and mucus that are secreted through the excretory ducts into the oral cavity.

Pharynx (Fig. 5) - part of the digestive tube and respiratory tract, which is the connecting link between the oral cavity and nose on the one hand, the esophagus and larynx on the other. It starts from the base of the skull and ends at the level of 6-7 cervical vertebrae. Inner space pharynx makes up the pharyngeal cavity. The pharynx is located behind the nasal and oral cavities and larynx. According to the organs located anterior to the pharynx, it can be divided into three parts: nasal, oral, laryngeal.

Rice. 5. The cavity of the pharynx.

bow(nasopharynx)- This is the upper section, which has nothing to do with digestion and is functionally part of the respiratory system. Through choan the pharynx communicates with the nasal cavity. On the lateral walls of the nasopharynx are openings of the auditory (Eustachian) tubes connecting this department with the middle ear cavity. At the entrance to the throat is ring of lymphoid formations: tonsil of the tongue, two palatine, two tubal and pharyngeal tonsils. The mucous membrane of the nasal part of the pharynx is covered with ciliated epithelium in accordance with the respiratory function of this part of the pharynx.

Mouth (oropharynx) represents middle department pharynx, which communicates in front through the pharynx with the oral cavity. The opening of the pharynx is located under the choanae. In this section, the respiratory and digestive tracts cross. Here, the mucous membrane acquires a smooth surface that facilitates the sliding of the food bolus during swallowing. This is also facilitated by the secret of the glands embedded in the mucous membrane and the muscles of the pharynx, located longitudinally (dilators - dilators) and circularly (narrowers - constrictors).

Laryngeal part (larynx) is the lower part of the pharynx, located behind the larynx and extending from the entrance to the larynx to the entrance to the esophagus. On the front wall there is a hole - the entrance to the larynx, limited by the epiglottis. The basis of the pharyngeal wall is a fibrous membrane, which is attached to the bones of the base of the skull at the top. From the inside, the pharynx is covered with a mucous membrane, outside of it there is a muscular membrane, and behind it is a thin fibrous one that connects the wall of the pharynx with the surrounding organs. Level VI cervical vertebra the pharynx passes into the esophagus.

Throat function consists in conducting air from the nasal cavity to the entrance to the larynx, and the food bolus from the oral cavity to the esophagus, as well as in isolating the airways during swallowing.

The act of swallowing . In the oral cavity, mechanical and initial chemical processing of food takes place. As a result, a food lump is formed, which moves to the root of the tongue, causing irritation of its receptors. At the same time, the soft palate rises reflexively and blocks communication with the nasopharynx. By contraction of the muscles of the tongue, the food bolus is pressed against the back of the tongue against the hard palate and pushed through the pharynx. At the same time, the muscles located above the hyoid bone pull the larynx upward, and the root of the tongue descends downward (due to muscle contraction) and presses on the epiglottis, lowering it and thereby blocking the entrance to the larynx. Next, there is a consistent contraction of the constrictor muscles of the pharynx, as a result of which the food bolus is pushed towards the esophagus.

Lymphatic pharyngeal ring. Alien substances and microorganisms constantly penetrate into the human body, their sources are air and food. These substances must be detained or rendered harmless. This role is performed by six tonsils located in the oral cavity at the entrance to the pharynx (pharyngeal, lingual, paired tubal and palatine), forming lymphatic pharyngeal ring (Pirogov's ring). Acute infection palatine tonsils called angina, the growth of the pharyngeal tonsil - adenoids.

Esophagus is the initial section of the gastrointestinal tract. It is a narrow and long tube 23-25 cm long, located between the pharynx and the stomach and helping to move food from the pharynx to the stomach. The esophagus begins at the level of the VIth cervical vertebra and ends at the level of the XIth thoracic. The esophagus, starting in the neck, passes into the chest cavity and, piercing the diaphragm, enters the abdominal cavity, so it distinguishes between the cervical, thoracic and abdominal parts.

Starting from the stomach, all sections of the digestive tract, along with its large glands(liver, pancreas), as well as the spleen and genitourinary system located in the abdominal cavity and in the pelvic cavity.

abdominal cavity called the space located in the trunk below the diaphragm and filled abdominal organs. Aperture is upper wall abdominal cavity and separates it from the chest cavity. The anterior wall is formed by tendon extensions of the three broad abdominal muscles and the rectus abdominis muscles. The lateral walls of the abdomen include the muscular parts of the three broad abdominal muscles, and the lumbar part serves as the back wall. spinal column and quadratus lumborum. Below, the abdominal cavity passes into the pelvic cavity. pelvic cavity limited behind the anterior surface of the sacrum, and in front and laterally by parts pelvic bones with muscles attached to them. The abdominal cavity is divided into the peritoneal cavity and the retroperitoneal space. The walls of the abdominal cavity are lined with a serous membrane - the peritoneum.

Peritoneum is a closed serous sac, which only in women communicates with the external environment through the openings of the fallopian tubes. The peritoneum consists of two sheets: parietal parietal and splanchnic or visceral. The parietal sheet lines the walls of the abdominal cavity, and the visceral sheet covers the insides, forming their serous cover over a greater or lesser extent. Between the leaves is peritoneal cavity, which contains a small amount of serous fluid that moisturizes the surface of the organs and facilitates their movement relative to each other. The peritoneum, passing from the walls of the abdominal cavity to the organs, from one organ to another, forms ligaments, mesentery, omentums. By using ligaments the abdominal organs are fixed to each other and to the wall of the abdomen. mesentery serve to fix the position of the abdominal organs, they pass through the vessels and nerves going to the organ. Oil seals are folds of the peritoneum, between the sheets of which contains a large amount of fatty tissue. The space between the fascia covering the muscles and the peritoneum on the back abdominal wall called retroperitoneal. It contains the pancreas and kidneys.

Stomach (Fig. 6) is a bag-like expansion of the digestive tract, food accumulates in the stomach after passing it through the esophagus and the first stages of its digestion proceed when the solid components of the food turn into a liquid or mushy mixture. In the stomach, anterior and back wall. The concave edge of the stomach, facing up and to the right, is called lesser curvature, convex edge facing down and to the left - great curvature. The stomach is divided into the following parts:

- cardiac part(cardia) - the initial section, the place of entry of the esophagus into the stomach;

- bottom- the domed part of the stomach cavity, located at the very top to the left of the cardia;

- body- the largest department in which food is "storage" at the time of its digestion;

- pyloric part, located behind the body and ending pyloric sphincter which separates the stomach cavity from the duodenal cavity.

The wall of the stomach consists of three membranes: mucous, muscular and serous.

mucous membrane The stomach is lined with a single-layer cylindrical epithelium, forms many folds, which are smoothed out when the stomach is full. It has special gastric glands that produce gastric juice containing pepsin and hydrochloric acid.

Rice. 6. Stomach.

Muscular membrane well expressed and consists of three layers: longitudinal, oblique and circular. When leaving the stomach, the circular muscle layer forms a powerful pyloric sphincter, which blocks the communication between the stomach and duodenum.

Serous membrane is a visceral sheet of peritoneum and covers the stomach from all sides. When performing some exercises (for example, hanging, hanging hanging, handstand), the stomach can shift and change its shape compared to its original position during normal standing.

The main functions of the stomach are enzymatic breakdown (hydrolysis) of proteins and other nutrients in an acidic environment, further grinding and softening of food (mechanical processing), deposition (food is in the stomach from 3 to 10 hours), carrying food to the intestines, absorption medicinal substances, bactericidal action.

Small intestine (Fig. 2) is the section of the alimentary canal following the stomach. It occupies the entire middle and lower sections of the abdominal cavity, forming a large number of loops, and passes into the region of the right iliac fossa into the large intestine. In a living person, the length of the small intestine does not exceed 2.7 m, in corpses - 6.5-7 m. In the small intestine, mechanical (promotion) and further chemical processing of food takes place in an alkaline environment, as well as the absorption of nutrients. Therefore, in the small intestine there are special adaptations for the secretion of digestive juices (glands located both in the intestinal wall and outside it) and for the absorption of digested substances ( intestinal villi and folds). The small intestine is divided into three sections: the duodenum, jejunum, and ileum.

Duodenum(Fig. 7) starts from the pylorus of the stomach, goes around the head of the pancreas in a horseshoe shape and at the level of the 2nd lumbar vertebra on the left passes into the jejunum. The excretory ducts of the liver and pancreas open into the lumen of the duodenum, the secret of which contains a number of important enzymes involved in intestinal digestion. Often these ducts open with one common opening. In the area where the ducts of the liver and pancreas enter the duodenum, there are 2 sphincters that regulate the flow of bile and pancreatic juice into the lumen of the duodenum. If there is no need for juices, then these sphincters are in a reduced state.

Jejunum is a continuation of the duodenum. Going down, it forms bends and loops, located mainly in the umbilical region and in the left side of the abdomen.

Ileum is a continuation of the jejunum and at the level of the right sacroiliac joint, it flows into the large intestine. This place is located ileocecal valve, which regulates the movement of food from the small intestine into the large intestine and prevents its reverse passage.

Rice. 7. Duodenum.

The wall of the small intestine consists of three membranes: mucous with a well-defined submucosal layer, muscular and serous.

mucous membrane characterized by the presence of a large number of circular folds, especially pronounced in the duodenum. Throughout the small intestine, the mucous membrane forms numerous protrusions - intestinal villi(Fig. 8), increasing the absorption surface of the mucous membrane by 25 times. Outside, the intestinal villus is covered with epithelium, in the center of it are blood and lymphatic capillaries. Proteins and carbohydrates enter the bloodstream venous vessels go to the liver, and fats go to the lymphatic vessels.

Rice. 8. Intestinal villus.

Muscular membrane consists of smooth muscle cells that form two layers: the inner circular and the outer longitudinal. Contractions of muscle fibers are peristaltic in nature, they consistently spread towards the lower end, while the circular fibers narrow the lumen, and the longitudinal ones, shortening, contribute to its expansion.

Serous membrane covers the small intestine from almost all sides.

Colon (Fig. 2, 9) begins in the right iliac fossa, where the ileum passes into it. The length of the large intestine is 1.5-2 m, it absorbs water and forms feces.

The wall of the large intestine is made up of three layers. mucous membrane forms sparse semilunar folds, there are no villi in the large intestine, but there are much more intestinal crypts than in the small intestine. Outside of the mucosa are located two muscle layers: inner circular and outer longitudinal. The longitudinal layer is not continuous; it forms three longitudinal bands. Protrusions form between the tapes - gaustra. Outside, the large intestine is covered peritoneum.

Rice. 9. Large intestine.

In the large intestine, the following are distinguished departments: caecum with appendix, colon (ascending, transverse, descending and sigmoid colon) and rectum.

Cecum is the initial section of the large intestine. It is located in the right iliac fossa. From the posterior surface of the caecum departs appendix(appendix), in the mucous membrane of which there are accumulations of lymphoid tissue. At the point where the large intestine enters the small intestine ileocecal valve, containing a layer of circular muscles.

Colon consists of four parts. Ascending colon is a continuation of the caecum. It rises up to the liver, forms a bend to the left and passes into transverse colon, which runs across the abdominal cavity and reaches the spleen with its left end, where it forms a left bend, passing into descending colon. The latter is located on the left on the posterior abdominal wall and stretches to the iliac crest, from where it continues into sigmoid colon, which is located in the left iliac fossa and at the level of the 3rd sacral vertebra passes into the rectum. The mesentery attaches the transverse colon to the posterior abdominal wall.

Rectum(Fig. 9) begins at the level of the 3rd sacral vertebra and is the final section of the large intestine. It ends with an anus. The rectum is located in the small pelvis. An expansion is formed in the middle part of the intestine - ampoule, in which they accumulate stool. Mucous the shell forms transverse and longitudinal folds. In the anus, in the thickness of the mucous membrane, there are a large number of veins that form hemorrhoidal plexus. The fibers of the muscular membrane of the rectal wall are arranged longitudinally and circularly. In the region of the anus, the fibers of the circular layer thicken and form internal anal sphincter, unmanaged arbitrarily. Slightly below it is external sphincter, controlled by the arbitrary efforts of man.

The digestive system includes two large glands - the liver and pancreas.

Liver is the largest gland in the human body. Its weight reaches 1.5 kg, the substance of its soft consistency, red-brown color.

Liver functions diverse:

o how the digestive gland, the liver, produces bile, which enters the duodenum through the excretory duct and promotes the digestion of fats;

o barrier (protective) function - poisonous products of protein metabolism are neutralized in the liver, which are brought there with venous blood through the portal vein;

o has phagocytic properties, i.e. properties to absorb and neutralize toxic substances absorbed in the intestines. These properties are possessed by cells of the reticuloendothelial system, i.e. capillary endothelium and the so-called Kupffer cells;

o participates in all types of metabolism, in particular carbohydrate, being a “depot” of glycogen (carbohydrates absorbed by the intestinal mucosa are converted into glycogen in the liver;

o in the embryonic period, it performs the function of hematopoiesis, since during this period it produces red blood cells;

o performs hormonal functions.

Rice. 10. Lobes and gates of the liver.

Thus, the liver is both an organ of digestion, circulation and all types of metabolism, including hormonal, and also performs a protective function.

The liver is located directly under the diaphragm, in the upper part of the abdominal cavity on the right (in the right hypochondrium). Two surfaces are distinguished on it: the upper one is the diaphragmatic and the lower one is the visceral and two edges: the anterior acute and the posterior blunt.

On the diaphragmatic surface of the liver adjacent to bottom surface diaphragm, distinguish two lobes (right and left), separated by a falciform ligament.

On the visceral surface, facing down and back, there are two longitudinal and one transverse grooves that divide the liver into four lobes: right, left, square and caudate (Fig. 10). The longitudinal grooves contain the gallbladder and the inferior vena cava.

In the transverse furrow are gate of the liver(Fig. 10) , those. a place through which vessels, nerves and other formations enter and leave the organ. The gates of the liver include the portal vein, hepatic artery and nerves. From the gate exit the common hepatic duct and lymphatic vessels. The common hepatic duct drains bile from the liver.

Almost the entire liver, with the exception of the posterior part of the diaphragmatic surface, is covered by the peritoneum. Under the serous membrane there is a thin fibrous membrane, which in the region of the gate of the liver, together with the vessels, enters the substance of the liver and continues into the thin layers of connective tissue surrounding hepatic lobules, which are the structural and functional unit of the liver (Fig. 11). The lobule has a transverse size of 1-2 mm and consists, in turn, of hepatic beams, which are located radially from the axial part of the lobule to the periphery. The hepatic beams are built from two rows of hepatic cells, between which the bile capillary passes. The hepatic beams are a kind of tubular glands. Between the liver cells that make up the liver lobules are bile ducts. Leaving the lobule, they fall into interlobular ducts, which merge together to form right and left hepatic ducts. From the confluence of the right and left ducts, common hepatic duct, which exits the gates of the liver and carries bile out of it.

The liver (unlike other internal organs) receives rich in oxygen blood from hepatic artery and nutrient-rich blood from the portal vein (from the stomach, spleen, small and large intestines). Arterial and venous blood is mixed in special capillaries (sinusoids) located between the beams of the liver. In the sinusoids, blood is washed through special holes in the liver cells, cleaned, and then poured into the central vein located in the center of the lobule. Central veins, merging together, form 3-4 hepatic veins that exit the liver (not from the gate) and flow into the inferior vena cava.

Rice. 11. Hepatic lobule.

gallbladder (Fig. 10) has a pear-shaped shape, it distinguishes the bottom, body and neck, which continues into the cystic duct.

From the confluence of the cystic duct and the common hepatic duct, common bile duct which opens into the lumen of the duodenum.

Ways of excretion of bile . Since bile is produced in the liver around the clock, and enters the intestines as needed, there was a need for a reservoir for storing bile. This reservoir is the gallbladder. The bile produced in the liver flows out of it through the common hepatic duct (Fig. 10). If necessary, it enters immediately into the duodenum through the common bile duct. This duct is formed by the confluence of the common hepatic and cystic ducts. If this is not necessary, then the common bile duct and its sphincter are in a contracted state and do not let bile into the intestine, as a result of which bile can only be directed to the cystic duct and then to the gallbladder. When food enters the stomach and a corresponding reflex occurs, the muscular wall of the gallbladder contracts and at the same time the muscles of the common bile duct and sphincters relax, as a result of which bile enters the lumen of the duodenum 12.

Pancreas (Fig. 7, 12) is the second largest gland of the digestive tract. Its weight in an adult is 70-80g, length - 12-15cm. The gland lies retroperitoneally, behind the stomach on the posterior abdominal wall. It is divided into head, body and tail. The head is covered by the duodenum. Structurally, the pancreas is a complex alveolar glands. It has a lobed structure. Excretory duct The pancreas goes inside the gland along its length and receives numerous small ducts extending from the lobules. By connecting with the common bile duct, it opens with a common opening into the duodenum.

Rice. 12. Pancreas.

In iron, they distinguish two components: the main mass of the gland has an exocrine function, releasing its secret through the excretory duct into the duodenum; the smaller part of the gland in the form of pancreatic islets (islets of Langergaans) refers to endocrine formations (i.e., to glands that do not have excretory ducts, the secrets of which are called hormones). The cells of these islets secrete into the blood pancreatic hormones - insulin and glucagon, which regulate blood sugar levels.

AT oral cavity going on primary processing food, which consists in its mechanical grinding with the help of the tongue and teeth and turning into a food lump. The salivary glands secrete saliva, the enzymes of which begin the breakdown of carbohydrates contained in food. Then, through the pharynx and esophagus, food enters the stomach, where it is digested by the action of gastric juice.

The stomach is a thick-walled muscular sac located under the diaphragm in the left side of the abdominal cavity. By contracting the walls of the stomach, its contents are mixed. Many glands, concentrated in the mucous wall of the stomach, secrete gastric juice containing enzymes and hydrochloric acid. After that, partially digested food enters the anterior part of the small intestine - the duodenum.

Small intestine consists of the duodenum, jejunum and ileum. AT duodenum food is exposed to the action of pancreatic juice, bile, and also the juices of the glands located in its wall. In skinny and ileum final digestion of food and absorption of nutrients into the blood occurs.

Undigested leftovers enter the large intestine. Here they accumulate and must be removed from the body. The initial part of the large intestine is called the cecum. A vermiform appendix departs from it - appendix.

to the digestive glands salivary glands, microscopic glands of the stomach and intestines, pancreas and liver. The liver is the largest gland human body. It is located on the right under the diaphragm. Bile is produced in the liver, which enters the gallbladder through the ducts, where it accumulates and, as needed, enters the intestines. The liver retains toxic substances and protects the body from poisoning.

The digestive glands that secrete juices and convert complex nutrients into simpler and more soluble in water include pancreas. It is located between the stomach and duodenum. Pancreatic juice contains enzymes that break down proteins, fats and carbohydrates. 1-1.5 liters of pancreatic juice is secreted per day.

If stale foods or toxic substances (arsenic, copper compounds, natural poisons) enter the digestive system, food poisoning occurs. Acute poisoning require urgent action to quick removal poison even before the arrival of the doctor: gastric lavage, inducing vomiting, etc.

After all, during our life we eat about 40 tons of different products that directly affect almost all aspects of our life. It is no coincidence that in ancient times they said: "Man is what he eats."

human digestive system carries out the digestion of food (through its physical and chemical processing), absorption of products, splitting through the mucous membrane into and lymph, as well as the removal of undigested residues.

The process of grinding food begins in the mouth. There it is softened by saliva, chewed with teeth and sent down the throat. Then the formed food bolus enters the stomach through the esophagus.

Thanks to the acidic gastric juice in this muscular organ, a very complex enzymatic process of digestion of food begins.

Enzymes are proteins accelerating chemical processes in cells.

The structure of the digestive system

The human digestive system consists of the organs of the gastrointestinal tract and auxiliary organs (salivary glands, liver, pancreas, gallbladder, etc.).

There are three divisions of the digestive system.

The anterior section includes the organs of the oral cavity, pharynx and esophagus. Here, mainly mechanical processing of food is carried out.
The middle section consists of the stomach, small and large intestines, liver and pancreas, in this section the chemical processing of food, the absorption of nutrients and the formation of feces are predominantly carried out.
The posterior section is represented by the caudal part of the rectum and ensures the excretion of feces from the body.

Organs of the digestive system

We will not consider all the organs of the digestive system, but we will give only the main ones.

Stomach

The stomach is a muscular bag, the volume of which in adults is 1.5-2 liters. The gastric juice contains caustic hydrochloric acid, so every two weeks the inner lining of the stomach is replaced by a new one.

Food moves through the digestive tract by contraction of the smooth muscles of the esophagus, stomach, and intestines. This is called peristalsis.

Small intestine

The small intestine is the part of the human digestive tract located between the stomach and the large intestine. From the stomach, food enters the 6-meter small intestine (12 duodenal, jejunum and ileum). Digestion of food continues in it, but already with pancreatic and liver enzymes.

Pancreas

The pancreas is the most important organ of the digestive system; largest gland. Its main function of external secretion is to secrete pancreatic juice, which contains the digestive enzymes necessary for the proper digestion of food.

Liver

The liver is the largest internal human organ. It cleanses the blood of toxins, "monitors" the level of glucose in the blood and produces bile, which breaks down fats in the small intestine.

gallbladder

The gallbladder is an organ that stores bile from the liver for release into the small intestine. Anatomically, it is part of the liver.

Colon

The large intestine is the lower, final part of the digestive tract, namely Bottom part intestines, in which there is mainly water absorption and the formation of formed feces from food slurry (chyme). The muscles of the colon work independently of the will of the person.

Soluble sugars and proteins are absorbed through the walls of the small intestine and enter the bloodstream, while undigested residues move on to the large intestine (caecum, colon and rectum).

There, water is absorbed from the food masses, and they gradually become semi-solid and, in the end, are excreted from the body through the rectum and anus.

Interesting facts about the digestive system

When chewing food, the jaw muscles develop a force of up to 72 kg on the molars, and up to 20 kg on the incisors.

By the age of three, a child has 20 milk teeth. From the age of six or seven, milk teeth fall out, and permanent ones grow in their place. There are 32 of these teeth in humans.

What are vitamins

Vitamins (from Latin vita- life) - these are substances without which the full-fledged work of all human organs is impossible. They are contained in different products but mainly in vegetables, fruits and herbs. Vitamins are denoted by the letters of the Latin alphabet: A, B, C, etc.

Together with food, we get a supply of “fuel” that provides energy to cells (fats and carbohydrates), “building material” necessary for the growth and repair of our body (proteins), as well as vitamins, water and minerals.

The lack of one or another substance can adversely affect human health.

The human digestive system is an extremely important and complex mechanism. If you have any discomfort after eating, and this discomfort has been observed for a long time, be sure to consult a gastroenterologist.

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