The concept of comfortable digestion in children. transverse striation of the mucous membrane of the lips. The food of the child in its quantity and quality must meet the characteristics of the digestive tract, satisfy his need for plastic substances and energy.

24.05.2019

Age features of digestion in children.

The formation of the digestive organs begins from the 3-4th week of the embryonic period, when the primary intestine is formed from the endodermal plate. At the front end of it, a mouth opening appears on the 4th week, and a little later, an anus appears at the opposite end. The intestine quickly lengthens, and from the 5th week of the embryonic period, the intestinal tube is delimited into two sections, which are the basis for the formation of the small and large intestines. During this period, the stomach begins to stand out - as an extension of the primary intestine. At the same time, the mucous, muscular and serous membranes of the gastrointestinal tract are being formed, in which blood and lymphatic vessels, nerve plexuses, and endocrine cells are formed.

In the first weeks of pregnancy, the endocrine apparatus of the gastrointestinal tract is laid in the fetus and the production of regulatory peptides begins. In the process of intrauterine development, the number of endocrine cells increases, the content of regulatory peptides in them increases (gastrin, secretin, motilin, gastric inhibitory peptide (GIP), vasoactive intestinal peptide (VIP), enteroglukzhagon, somatostatin, neurotensin, etc.). At the same time, the reactivity of target organs with respect to regulatory peptides increases. In the prenatal period, peripheral and central mechanisms of nervous regulation of the activity of the gastrointestinal tract are laid.

In the fetus, the gastrointestinal tract begins to function already at the 16-20th week of intrauterine life. By this time, the swallowing reflex is expressed, amylase is found in the salivary glands, pepsinogen in the stomach, and secretin in the small intestine. A normal fetus swallows a large amount of amniotic fluid, the individual components of which are hydrolyzed in the intestine and absorbed. The undigested part of the contents of the stomach and intestines goes to the formation of meconium.

During intrauterine development, before implantation of the embryo into the uterine wall, its nutrition occurs at the expense of reserves in the cytoplasm of the egg. The embryo feeds on the secrets of the uterine mucosa and the material of the yolk sac (histotrophic type of nutrition). Since the formation of the placenta, hemotrophic (transplacental) nutrition, provided by the transport of nutrients from the mother's blood to the fetus through the placenta, is of primary importance. It plays a leading role until the birth of a child.

From 4-5 months of intrauterine development, the activity of the digestive organs begins and, together with hemotrophic, amniotrophic nutrition occurs. The daily amount of liquid absorbed by the fetus in the last months of pregnancy can reach more than 1 liter. The fetus absorbs amniotic fluid containing nutrients (proteins, amino acids, glucose, vitamins, hormones, salts, etc.) and hydrolyzing enzymes. Some enzymes enter the amniotic fluid from the fetus with saliva and urine, the second source is the placenta, the third source is the mother's body (enzymes through the placenta and bypassing it can enter the amniotic fluid from the blood of a pregnant woman).

Part of the nutrients are absorbed from the gastrointestinal tract without prior hydrolysis (glucose, amino acids, some dimers, oligomers and even polymers), since the intestinal tube of the fetus has a high permeability, fetal enterocytes are capable of pinocytosis. This is important to consider when organizing the nutrition of a pregnant woman in order to prevent allergic diseases. Some of the nutrients of the amniotic fluid are digested by its own enzymes, that is, the autolytic type of digestion plays an important role in the amniotic nutrition of the fetus. Amniotrophic nutrition of the type of own abdominal digestion can be carried out from the 2nd half of pregnancy, when pepsinogen and lipase are secreted by the cells of the stomach and pancreas of the fetus, although their level is low. Amniotrophic nutrition and the corresponding digestion are important not only for the supply of nutrients to the blood of the fetus, but also as a preparation of the digestive organs for lactotrophic nutrition.

In newborns and children in the first months of life, the oral cavity is relatively small, the tongue is large, the muscles of the mouth and cheeks are well developed, in the thickness of the cheeks there are fatty bodies (Bish's lumps), which are distinguished by significant elasticity due to the predominance of solid (saturated) fatty acids in them. These features provide full breast sucking. The mucous membrane of the oral cavity is tender, dryish, rich in blood vessels (easily vulnerable). The salivary glands are poorly developed, produce little saliva (submandibular, sublingual glands function to a greater extent in infants, in children after a year and adults - parotid). The salivary glands begin to function actively by the 3-4th month of life, but even at the age of 1 year, the volume of saliva (150 ml) is 1/10 of the amount in an adult. The enzymatic activity of saliva at an early age is 1/3-1/2 of its activity in adults, but it reaches the level of adults within 1-2 years. Although the enzymatic activity of saliva at an early age is low, its action on milk contributes to its curdling in the stomach with the formation of small flakes, which facilitates the hydrolysis of casein. Hypersalivation at 3-4 months of age is due to teething, saliva may flow from the mouth due to the inability of children to swallow it. The reaction of saliva in children of the first year of life is neutral or slightly acidic - this can contribute to the development of thrush of the oral mucosa if it is not properly cared for. At an early age, saliva contains a low content of lysozyme, secretory immunoglobulin A, which determines its low bactericidal activity and the need for proper oral care.

The esophagus in young children has a funnel-shaped form. Its length in newborns is 10 cm, with age it increases, while the diameter of the esophagus becomes larger. At the age of one year, the physiological narrowing of the esophagus is weakly expressed, especially in the area of the cardial part of the stomach, which contributes to the frequent regurgitation of food in children of the 1st year of life.

The stomach in infants is located horizontally, its bottom and cardia are poorly developed, which explains the tendency of children of the first year of life to regurgitation and vomiting. As the child begins to walk, the axis of the stomach becomes more vertical, and by 7-11 years it is located in the same way as in an adult. The capacity of the stomach in a newborn is 30-35 ml, by the year it increases to 250-300 ml, by the age of 8 it reaches 1000 ml. The secretory apparatus of the stomach in children of the 1st year of life is not sufficiently developed, they have fewer glands in the gastric mucosa than in adults, and their functional abilities are low. Although the composition of gastric juice in children is the same as in adults (hydrochloric acid, lactic acid, pepsin, rennet, lipase), but the acidity and enzymatic activity are lower, which determines the low barrier function of the stomach and the pH of gastric juice (4-5, in adults 1.5-2.2). In this regard, proteins are not sufficiently cleaved in the stomach by pepsin, they are cleaved mainly by cathepsins and gastrixin produced by the gastric mucosa, their optimum action is at pH 4-5. Lipase of the stomach (produced by the pyloric part of the stomach) breaks down in an acidic environment, together with lipase of human milk, up to half of the fats of human milk. These features must be taken into account when prescribing various types of nutrition to a child. With age, the secretory activity of the stomach increases. Motility of the stomach in children of the first months of life is slowed down, peristalsis is sluggish. The timing of the evacuation of food from the stomach depends on the nature of feeding. Women's milk lingers in the stomach for 2-3 hours, cow's - 3-4 hours, which indicates the difficulties of digesting the latter.

The intestines in children are relatively longer than in adults. The caecum is mobile due to the long mesentery, therefore the appendix can be located in the right iliac region, shift to the small pelvis and to the left half of the abdomen, which creates difficulties in diagnosing appendicitis in young children. The sigmoid colon is relatively long, which predisposes to constipation in children, especially if the mother's milk contains an increased amount of fat. The rectum in children in the first months of life is also long, with weak fixation of the mucous and submucosal layers, and therefore, with tenesmus and persistent constipation, it may prolapse through the anus. The mesentery is longer and more easily distensible, which can lead to torsion, intussusception, and other pathological processes. The weakness of the ileocecal valve also contributes to the occurrence of intussusception in young children. A feature of the intestines in children is the better development of the circular muscles than the longitudinal ones, which predisposes to intestinal spasms and intestinal colic. A feature of the digestive organs in children is also the weak development of the lesser and greater omentum, and this leads to the fact that the infectious process in the abdominal cavity (appendicitis, etc.) often leads to diffuse peritonitis.

The intestinal secretory apparatus is generally formed by the time of the birth of the child, the same enzymes are found in the intestinal juice as in adults (enterokinase, alkaline phosphatase, lipase, erypsin, amylase, maltase, lactase, nuclease, etc.), but their activity low. Under the influence of intestinal enzymes, mainly the pancreas, there is a breakdown of proteins, fats and carbohydrates. However, the pH of duodenal juice in young children is slightly acidic or neutral, so the breakdown of protein by trypsin is limited (for trypsin, the optimal pH is alkaline). Especially intense is the process of digestion of fats due to the low activity of lipolytic enzymes. In children who are breastfed, lipids emulsified by bile are cleaved by 50% under the influence of breast milk lipase. Digestion of carbohydrates occurs in the small intestine under the influence of pancreatic amylase and intestinal juice disaccharidases. The processes of putrefaction in the intestines do not occur in healthy infants. The peculiarities of the structure of the intestinal wall and its large area determine in young children a higher absorption capacity than in adults and, at the same time, an insufficient barrier function due to the high permeability of the mucous membrane for toxins and microbes.

The motor function of the gastrointestinal tract in young children also has a number of features. The peristaltic wave of the esophagus and the mechanical irritation of its lower section with a food lump cause a reflex opening of the entrance to the stomach. Motility of the stomach consists of peristalsis (rhythmic waves of contraction from the cardiac section to the pylorus), peristoles (resistance exerted by the walls of the stomach to the tensile action of food) and fluctuations in the tone of the stomach wall, which appears 2-3 hours after eating. Motility of the small intestine includes pendulum movement (rhythmic oscillations that mix intestinal contents with intestinal secretions and create favorable conditions for absorption), fluctuations in the tone of the intestinal wall and peristalsis (worm-like movements along the intestine that promote the promotion of food). Pendulum and peristaltic movements are also noted in the large intestine, and antiperistalsis in the proximal sections, which contributes to the formation of fecal masses. The time of passage of food gruel through the intestines in children is shorter than in adults: in newborns - from 4 to 18 hours, in older ones - about a day. It should be noted that with artificial feeding, this period is extended. The act of defecation in infants occurs reflexively without the participation of a volitional moment, and only by the end of the first year of life does defecation become arbitrary.

A newborn in the first hours and days of life allocates the original feces, or meconium, in the form of a thick mass of dark olive color, odorless. In the future, the feces of a healthy infant are yellow in color, sour reaction and sour smell, and their consistency is mushy. At an older age, the chair becomes decorated. Stool frequency in infants - from 1 to 4-5 times a day, in older children - 1 time per day.

The intestines of a child in the first hours of life are almost free from bacteria. In the future, the gastrointestinal tract is populated by microflora. In the oral cavity of an infant, staphylococci, streptococci, pneumococci, Escherichia coli and some other bacteria can be found. E. coli, bifidobacteria, lactic acid bacilli, etc. appear in the feces. With artificial and mixed feeding, the phase of bacterial infection occurs faster. Gut bacteria contribute to the processes of enzymatic digestion of food. With natural feeding, bifidobacteria, lactic acid bacilli predominate, and in a smaller amount - Escherichia coli. Feces are light yellow with a sour smell, ointment. With artificial and mixed feeding, due to the predominance of putrefaction processes in feces, there are a lot of E. coli, fermentative flora (bifidoflora, lactic acid bacilli) are present in smaller quantities.

The liver in children is relatively large, in newborns it is about 4% of body weight (in adults - 2% of body weight). In young children, bile formation is less intense than in older children. The bile of children is poor in bile acids, cholesterol, lecithin, salts and alkali, but rich in water, mucin, pigments and urea, and also contains more taurocholic than glycocholic acid. It is important to note that taurocholic acid is an antiseptic. Bile neutralizes the acidic food slurry, which makes possible the activity of pancreatic and intestinal secretions. In addition, bile activates pancreatic lipase, emulsifies fats, dissolves fatty acids, turning them into soaps, and enhances peristalsis of the large intestine.

Thus, the system of the digestive organs in children is distinguished by a number of anatomical and physiological features that affect the functional ability of these organs. In a child in the first year of life, the need for food is relatively greater than in older children. Although the child has all the necessary digestive enzymes, the functional capacity of the digestive organs is limited and can only be sufficient if the child receives physiological food, namely human milk. Even small deviations in the quantity and quality of food can cause digestive disorders in an infant (they are especially frequent in the 1st year of life) and ultimately lead to a lag in physical development.

The main structural elements of the digestive system are formed in humans by 3-4 months of uterine existence. There is reason to believe that the fetal digestive system is subjected to a “functional load” very early due to the entry of amniotic fluid into the gastrointestinal tract. It is possible that the absorption of amniotic fluid is to some extent associated with the regulation of their volume. The fluid, absorbed in the intestines of the fetus, returns through the placenta to the mother's blood. It is not excluded that part of the amniotic fluid protein can be absorbed, undergoing hydrolysis, and part can be absorbed unchanged. This is a kind of training of the secretory and motor activity of the digestive canal. The antenatal period is characterized by the rapid development and improvement of individual components of the digestive functions, and the development proceeds asynchronously for different parts of the digestive system.

The functional activity of the salivary glands is manifested with the appearance of milk teeth, at the age of 5-6 months. A particularly significant increase in salivation is found at the end of the first year of life. During the first two years, the formation of milk teeth is intensively going on. At the age of 2-2.5 years, the child already has 20 teeth and can eat relatively coarse food that requires chewing. Approximation of the structure of the salivary glands to the definitive structure occurs approximately at this age. However, saliva secretion begins immediately after birth. Its physiological meaning lies in the fact that saliva, as it were, glues the nipple to the tongue and the walls of the mouth and contributes to the creation of the vacuum necessary for sucking milk. In addition, mixing milk with saliva contributes to the formation in the stomach of not compact, but very small, loose clots of casein, more accessible for further processing. In a newborn child, the rate of saliva secretion during sucking increases many times over in comparison with secretion on an empty stomach. With age, the amount of secreted saliva increases. Its maximum amylolytic activity is observed at the age of 2-7 years. The activity of salivary amylase in the elderly is somewhat reduced, but not more than 30-40% even at the age of 80 years or more. With age, the mineral composition of saliva changes. The content of potassium in it remains constant for a long time, only after 40 years it slightly increases. The concentration of sodium up to 5 years increases slightly. In puberty, the level of this cation in boys becomes higher than in girls. Some excess sodium in men persists after 40 years. The content of calcium and inorganic phosphorus in human mixed saliva with basal secretion tends to increase with age.

The differentiation of the gastric glands in children is completed mainly by the age of 7, i.e. to the period of replacement of milk teeth with permanent ones, which is important for determining the "biological age". In connection with the final approximation of the qualitative composition of food to the diet of an adult, the functions of the entire digestive system are transformed during this period. The function of hydrochloric acid synthesis is detected earlier than enzyme formation, which is associated with an earlier development of parietal cells. However, the acidity of gastric juice in preschool children remains relatively low. The number of enzymes that break down protein increases especially intensively from 1.5 to 3 years, then at 5-6 years and at school age up to 12-14 years. The content of hydrochloric acid increases up to 15-16 years. Its low concentration causes weak bactericidal properties of gastric juice in children under 6-7 years old, which contributes to easier susceptibility of children of this age to gastrointestinal diseases.

Due to the low acidity of gastric juice in infants, pepsin is able to break down only milk protein. Rennin, or rennet, causes milk to curdle. Lipase of gastric juice in infants breaks down no more than 25% of milk fats, however, breast milk lipase is also involved in the breakdown of fats, which becomes active in the stomach. With age, lipase activity increases. The amount and composition of gastric juice depends on the food. So, a lot of juice with high acidity is allocated to meat, little - to fat. When feeding on mother's milk, children secrete gastric juice with low acidity and little digestive power. Up to 10 years, the concentration of free hydrochloric acid in gastric juice increases, then stabilizes and remains constant for 3 years. During puberty, the secretion of hydrochloric acid increases, which is more pronounced in boys.

Sex differences persist until the age of 80, when the amount of free hydrochloric acid in the gastric juice in men decreases and becomes the same as in women. At the same time, not only the acidity of gastric juice decreases, but also the content of pepsin in it. In the first two decades of life, enzyme formation increases, reaching a maximum by the age of 21-40. Between 40 and 60 years, the concentration of the enzyme decreases sharply, and then, until old age, a slow decrease in the enzymatic activity of the juice follows. In children under 10 years of age, absorption processes are actively going on in the stomach, while in adults these processes are carried out mainly only in the small intestine,

Amylolytic activity of duodenal contents is low during the first year of life, and then, due to the secret of the pancreas, it exceeds the level of an adult. Lipolytic activity does not reach the level of an adult even by the age of 12, and proteolytic activity during childhood is even higher than in an adult, and only by the age of 12 does it decrease to this level. At the age of 60-70 years, the lipolytic and proteolytic activity of the pancreatic secretion decreases. There is evidence of a violation of parietal digestion in the small intestine in the elderly, which is due to a weakening of intestinal motility. At the same time, the absorption function also suffers.

The liver of a child produces in early childhood an ample amount of bile to carry out the part of digestion that is dependent on it, especially the assimilation of milk containing emulsified fat. Bubble bile in a child of the first years of life is slightly alkaline, the rate of emptying of the gallbladder is much higher than in adults. Accelerated emptying of the gallbladder is also observed in the elderly compared with mature age. In general, it can be noted that changes in the digestive system in old age, compared with changes, for example, in the vessels and muscles of the body, to a greater extent retain a sufficient, albeit reduced, “margin of safety”.

In the extrauterine period, the gastrointestinal tract is the only source of obtaining nutrients and water necessary both for maintaining life and for the growth and development of the fetus.

Features of the digestive system in children

Anatomical and physiological features of the digestive system

Young children (especially newborns) have a number of morphological features common to all parts of the gastrointestinal tract:

thin, tender, dry, easily injured mucous membrane;
richly vascularized submucosal layer, consisting mainly of loose fiber;
underdeveloped elastic and muscle tissue;
low secretory function of the glandular tissue that separates a small amount of digestive juices with a low content of enzymes.

These features of the digestive system make it difficult to digest food if the latter does not correspond to the age of the child, reduce the barrier function of the gastrointestinal tract and lead to frequent diseases, create the preconditions for a general systemic reaction to any pathological effect and require very careful and thorough care of the mucous membranes.

Child's oral cavity

In a newborn and a child in the first months of life, the oral cavity has a number of features that ensure the act of sucking. These include: a relatively small volume of the oral cavity and a large tongue, good development of the muscles of the mouth and cheeks, roller-like duplication of the mucous membrane of the gums and transverse folds on the mucous membrane of the lips, fat bodies (Bish's lumps) in the thickness of the cheeks, which are characterized by significant elasticity due to the predominance of they contain solid fatty acids. The salivary glands are underdeveloped. However, insufficient salivation is mainly due to the immaturity of the nerve centers that regulate it. As they mature, the amount of saliva increases, and therefore, at the age of 3-4 months, the child often has the so-called physiological salivation due to the automatism of swallowing it that has not yet been developed.

In newborns and infants, the oral cavity is relatively small. The lips of newborns are thick, on their inner surface there are transverse ridges. The circular muscle of the mouth is well developed. The cheeks of newborns and young children are rounded and convex due to the presence between the skin and the well-developed buccal muscle of a rounded fat body (Bish's fat lumps), which subsequently, starting from the age of 4, gradually atrophies.

The hard palate is flat, its mucous membrane forms weakly expressed transverse folds, and is poor in glands. The soft palate is relatively short, located almost horizontally. The palatine curtain does not touch the posterior pharyngeal wall, which allows the child to breathe during sucking. With the appearance of milk teeth, a significant increase in the size of the alveolar processes of the jaws occurs, and the arch of the hard palate rises, as it were. The tongue of newborns is short, wide, thick and inactive; well-defined papillae are visible on the mucous membrane. The tongue occupies the entire oral cavity: when the oral cavity is closed, it comes into contact with the cheeks and hard palate, protrudes forward between the jaws in the vestibule of the mouth.

The mucous membrane of the oral cavity

The mucous membrane of the oral cavity in children, especially at an early age, is thin and easily vulnerable, which must be taken into account when treating the oral cavity. The mucous membrane of the bottom of the oral cavity forms a noticeable fold, covered with a large number of villi. A protrusion in the form of a roller is also present on the mucous membrane of the cheeks in the gap between the upper and lower jaws. In addition, there are transverse folds (rollers) on the hard palate, roller-like thickenings on the gums. All these formations provide sealing of the oral cavity in the process of sucking. On the mucous membrane in the area of the hard palate along the midline in newborns there are Bohn's nodules - yellowish formations - retention cysts of the salivary glands, disappearing by the end of the first month of life.

The mucous membrane of the oral cavity in children of the first 3-4 months of life is relatively dry, which is due to the insufficient development of the salivary glands and the deficiency of saliva. The salivary glands (parotid, submandibular, sublingual, small glands of the oral mucosa) in the newborn are characterized by low secretory activity and secrete a very small amount of thick, viscous saliva necessary for gluing the lips and sealing the oral cavity during sucking. The functional activity of the salivary glands begins to increase at the age of 1.52 months; in 34-month-old children, saliva often flows out of the mouth due to the immaturity of the regulation of salivation and swallowing of saliva (physiological salivation). The most intensive growth and development of the salivary glands occurs between the ages of 4 months and 2 years. By the age of 7, a child produces as much saliva as an adult. The reaction of saliva in newborns is often neutral or slightly acidic. From the first days of life, saliva contains osamylase and other enzymes necessary for the breakdown of starch and glycogen. In newborns, the concentration of amylase in saliva is low; during the first year of life, its content and activity increase significantly, reaching a maximum level at 2-7 years.

Throat and larynx in a child

The pharynx of a newborn has the shape of a funnel, its lower edge is projected at the level of the intervertebral disc between C I | and C 1 V . By adolescence, it descends to the level C vl -C VII. The larynx in infants also has a funnel-shaped shape and is located differently than in adults. The entrance to the larynx is located high above the lower posterior edge of the palatine curtain and is connected to the oral cavity. Food moves to the sides of the protruding larynx, so the baby can breathe and swallow at the same time without interrupting sucking.

Sucking and swallowing in a child

Sucking and swallowing are innate unconditioned reflexes. In healthy and mature newborns, they are already formed by the time of birth. When suckling, the baby's lips tightly grasp the nipple of the breast. The jaws squeeze it, and the communication between the oral cavity and the outside air stops. Negative pressure is created in the child's oral cavity, which is facilitated by the lowering of the lower jaw along with the tongue down and back. Then breast milk enters the rarefied space of the oral cavity. All elements of the chewing apparatus of a newborn are adapted for the process of breast sucking: the gingival membrane, pronounced palatine transverse folds and fatty bodies in the cheeks. The adaptation of the oral cavity of the newborn to sucking is also physiological infantile retrognathia, which later turns into orthognathia. In the process of sucking, the child makes rhythmic movements of the lower jaw from front to back. The absence of the articular tubercle facilitates the sagittal movements of the child's mandible.

Child's esophagus

The esophagus is a spindle-shaped muscular tube lined from the inside with a mucous membrane. By birth, the esophagus is formed, its length in a newborn is 10-12 cm, at the age of 5 years - 16 cm, and at 15 years - 19 cm. The ratio between the length of the esophagus and body length remains relatively constant and is approximately 1:5. The width of the esophagus in a newborn is 5-8 mm, at 1 year old - 10-12 mm, by 3-6 years old - 13-15 mm and by 15 years old - 18-19 mm. The dimensions of the esophagus must be taken into account during fibro-esophago-gastroduodenoscopy (FEGDS), duodenal sounding and gastric lavage.

Anatomical narrowing of the esophagus in newborns and children of the first year of life is weakly expressed and is formed with age. The wall of the esophagus in a newborn is thin, the muscular membrane is poorly developed, it grows intensively up to 12-15 years. The mucous membrane of the esophagus in infants is poor in glands. Longitudinal folds appear at the age of 2-2.5 years. The submucosa is well developed, rich in blood vessels.

Outside the act of swallowing, the passage of the pharynx into the esophagus is closed. Peristalsis of the esophagus occurs during swallowing movements.

Gastrointestinal tract and size of the esophagus in children depending on age.

During anesthesia and intensive care, probing of the stomach is often performed, so the anesthesiologist must know the age dimensions of the esophagus (table).

Table. The size of the esophagus in children depending on age

In young children, there is a physiological weakness of the cardiac sphincter and, at the same time, a good development of the muscle layer of the pylorus. All this predisposes to regurgitation and vomiting. This must be remembered during anesthesia, especially with the use of muscle relaxants, since in these cases regurgitation is possible - a passive (and therefore late noticed) leakage of the contents of the stomach, which can lead to its aspiration and the development of severe aspiration pneumonia.

The capacity of the stomach increases in proportion to age up to 1-2 years. A further increase is associated not only with the growth of the body, but also with the peculiarities of nutrition. Approximate values of the capacity of the stomach in newborns and infants are presented in the table.

Table. Gastric capacity in young children

What is the size of the esophagus in children?

These values are very approximate, especially in pathological conditions. For example, with obstruction of the upper gastrointestinal tract, the walls of the stomach can stretch, which leads to an increase in its capacity by 2-5 times.

The physiology of gastric secretion in children of different ages, in principle, does not differ from that in adults. The acidity of the gastric juice may be somewhat lower than in adults, but this often depends on the nature of the diet. pH of gastric juice in infants is 3.8-5.8, in adults at the height of digestion up to 1.5-2.0.

Motility of the stomach under normal conditions depends on the nature of nutrition, as well as on neuroreflex impulses. High activity of the vagus nerve stimulates gastrospasm, and the splanchnic nerve stimulates pyloric spasm.

The time of passage of food (chyme) through the intestines in newborns is 4-18 hours, in older children - up to a day. Of this time, 7-8 hours are spent passing through the small intestine and 2-14 hours through the large intestine. With artificial feeding of infants, the digestion time can reach up to 48 hours.

baby stomach

Features of the stomach of a child

The stomach of a newborn has the shape of a cylinder, a bull horn or a fishhook and is located high (the inlet of the stomach is at the level of T VIII -T IX, and the pyloric opening is at the level of T x1 -T x | 1). As the child grows and develops, the stomach descends, and by the age of 7 years, its inlet (with the body upright) is projected between T X | and T X|| , and the output - between T x || and L. In infants, the stomach is located horizontally, but as soon as the child begins to walk, it gradually assumes a more vertical position.

Cardiac part, fundus and pyloric part of the stomach in a newborn are weakly expressed, the pylorus is wide. The inlet part of the stomach is often located above the diaphragm, the angle between the abdominal part of the esophagus and the wall of the fundus of the stomach adjacent to it is not sufficiently pronounced, the muscular membrane of the cardial part of the stomach is also poorly developed. Gubarev's valve (a mucosal fold protruding into the esophageal cavity and preventing the return of food) is almost not expressed (it develops by 8-9 months of life), the cardiac sphincter is functionally inferior, while the pyloric section of the stomach is functionally well developed already at birth.

These features determine the possibility of reflux of the contents of the stomach into the esophagus and the development of peptic lesions of its mucous membrane. In addition, the tendency of children of the first year of life to regurgitation and vomiting is associated with the absence of a tight grasp of the esophagus by the legs of the diaphragm, as well as impaired innervation with increased intragastric pressure. Swallowing air during sucking (aerophagia) also contributes to regurgitation with improper feeding technique, a short frenulum of the tongue, greedy sucking, and too rapid release of milk from the mother's breast.

In the first weeks of life, the stomach is located in an oblique frontal plane, completely covered in front by the left lobe of the liver, and therefore the fundus of the stomach in the supine position is located below the antral-pyloric section, therefore, to prevent aspiration after feeding, children should be given an elevated position. By the end of the first year of life, the stomach lengthens, and in the period from 7 to 11 years, it acquires a shape similar to that of an adult. By the age of 8, the formation of its cardiac part is completed.

The anatomical capacity of the stomach of a newborn is 30-35 cm3, by the 14th day of life it increases to 90 cm3. Physiological capacity is less than anatomical, and on the first day of life is only 7-10 ml; by the 4th day after the start of enteral nutrition, it increases to 40-50 ml, and by the 10th day - up to 80 ml. Subsequently, the capacity of the stomach increases monthly by 25 ml and by the end of the first year of life is 250-300 ml, and by 3 years - 400-600 ml. An intensive increase in the capacity of the stomach begins after 7 years and by 10-12 years is 1300-1500 ml.

The muscular membrane of the stomach in a newborn is poorly developed, it reaches its maximum thickness only by the age of 15-20. The mucous membrane of the stomach in a newborn is thick, the folds are high. During the first 3 months of life, the surface of the mucous membrane increases by 3 times, which contributes to better digestion of milk. By the age of 15, the surface of the gastric mucosa increases 10 times. With age, the number of gastric pits increases, into which openings of the gastric glands open. By birth, the gastric glands are morphologically and functionally underdeveloped, their relative number (per 1 kg of body weight) in newborns is 2.5 times less than in adults, but rapidly increases with the onset of enteral nutrition.

The secretory apparatus of the stomach in children of the first year of life is underdeveloped, its functional abilities are low. The gastric juice of an infant contains the same components as the gastric juice of an adult: hydrochloric acid, chymosin (curdles milk), pepsins (break down proteins into albumoses and peptones) and lipase (breaks down neutral fats into fatty acids and glycerol).

Children in the first weeks of life are characterized by a very low concentration of hydrochloric acid in gastric juice and its low total acidity. It increases significantly after the introduction of complementary foods, i. when switching from lactotrophic nutrition to normal. In parallel with the decrease in the pH of gastric juice, the activity of carbonic anhydrase, which is involved in the formation of hydrogen ions, increases. In children of the first 2 months of life, the pH value is mainly determined by the hydrogen ions of lactic acid, and subsequently by hydrochloric acid.

The synthesis of proteolytic enzymes by the chief cells begins in the antenatal period, but their content and functional activity in newborns are low and gradually increase with age. The leading role in the hydrolysis of proteins in newborns is played by fetal pepsin, which has a higher proteolytic activity. In infants, significant fluctuations in the activity of proteolytic enzymes were noted depending on the nature of feeding (with artificial feeding, activity indicators are higher). In children of the first year of life (unlike adults), a high activity of gastric lipase is noted, which ensures the hydrolysis of fats in the absence of bile acids in a neutral environment.

Low concentrations of hydrochloric acid and pepsins in the stomach in newborns and infants determine the reduced protective function of gastric juice, but at the same time contribute to the preservation of Ig, which come with mother's milk.

In the first months of life, the motor function of the stomach is reduced, peristalsis is sluggish, and the gas bubble is enlarged. The frequency of peristaltic contractions in newborns is the lowest, then it actively increases and after 3 years it stabilizes. By the age of 2, the structural and physiological features of the stomach correspond to those of an adult. In infants, an increase in the tone of the muscles of the stomach in the pyloric region is possible, the maximum manifestation of which is pylorospasm. At an older age, cardiospasm is sometimes observed. The frequency of peristaltic contractions in newborns is the lowest, then it actively increases and after 3 years it stabilizes.

In infants, the stomach is horizontal, with the pyloric portion near the midline and the lesser curvature facing posteriorly. As the child begins to walk, the axis of the stomach becomes more vertical. By the age of 7-11, it is located in the same way as in adults. The capacity of the stomach in newborns is 30 - 35 ml, by the age of 1 it increases to 250 - 300 ml, by the age of 8 it reaches 1000 ml. The cardiac sphincter in infants is very poorly developed, and the pyloric one functions satisfactorily. This contributes to the regurgitation often observed at this age, especially when the stomach is distended due to swallowing air during sucking ("physiological aerophagia"). In the gastric mucosa of young children, there are fewer glands than in adults. And although some of them begin to function even in utero, in general, the secretory apparatus of the stomach in children of the first year of life is underdeveloped and its functional abilities are low. The composition of gastric juice in children is the same as in adults (hydrochloric acid, lactic acid, pepsin, rennet, lipase, sodium chloride), but the acidity and enzyme activity are much lower, which not only affects digestion, but also determines a low barrier stomach function. This makes it absolutely necessary to carefully observe the sanitary and hygienic regime during feeding of children (breast toilet, clean hands, proper expression of milk, sterility of nipples and bottles). In recent years, it has been established that the bactericidal properties of gastric juice are provided by lysozyme produced by the cells of the superficial epithelium of the stomach.

The maturation of the secretory apparatus of the stomach occurs earlier and more intensively in formula-fed children, which is associated with the body's adaptation to more indigestible food. The functional state and enzymatic activity depend on many factors: the composition of the ingredients and their quantity, the child's emotional tone, his physical activity, and his general condition. It is well known that fats suppress gastric secretion, while proteins stimulate it. Depressed mood, fever, intoxication are accompanied by a sharp decrease in appetite, i.e., a decrease in the secretion of gastric juice. Absorption in the stomach is insignificant and mainly concerns substances such as salts, water, glucose, and only partially - protein breakdown products. Motility of the stomach in children of the first months of life is slowed down, peristalsis is sluggish, the gas bubble is enlarged. The timing of the evacuation of food from the stomach depends on the nature of feeding. So, women's milk lingers in the stomach for 2-3 hours, cow's - for a longer time (3-4 hours and even up to 5 hours, depending on the buffer properties of milk), which indicates the difficulties of digesting the latter and the need to switch to more rare feedings.

Child's intestines

The intestine starts from the pylorus and ends at the anus. Distinguish between small and large intestines. The small intestine is divided into duodenum, jejunum and ileum; large intestine - on the blind, colon (ascending, transverse, descending, sigmoid) and rectum. The relative length of the small intestine in a newborn is large: 1 m per 1 kg of body weight, while in adults it is only 10 cm.

In children, the intestines are relatively longer than in adults (in an infant, it exceeds the length of the body by 6 times, in adults, by 4 times), but its absolute length varies individually within wide limits. The caecum and appendix are mobile, the latter is often located atypically, thereby making it difficult to diagnose inflammation. The sigmoid colon is relatively longer than in adults, and in some children even forms loops, which contributes to the development of primary constipation. With age, these anatomical features disappear. Due to the weak fixation of the mucous and submucosal membranes of the rectum, it may prolapse with persistent constipation and tenesmus in debilitated children. The mesentery is longer and easily stretchable, and therefore torsion, intussusception, etc., easily occur. The omentum in children under 5 years of age is short, so the possibility of localizing peritonitis in a limited area of the abdominal cavity is almost excluded. Of the histological features, it should be noted the good severity of the villi and the abundance of small lymphatic follicles.

All intestinal functions (digestive, absorption, barrier and motor) in children differ from those of adults. The process of digestion, which begins in the mouth and stomach, continues in the small intestine under the influence of pancreatic juice and bile secreted into the duodenum, as well as intestinal juice. The secretory apparatus of the intestinal tract is generally formed by the time of the birth of the child, and even in the smallest children, the same enzymes are determined in the intestinal juice as in adults (enterokinase, alkaline phosphatase, erepsin, lipase, amylase, maltase, lactase, nuclease), but significantly less active. Only mucus is secreted in the large intestine. Under the influence of intestinal enzymes, mainly the pancreas, there is a breakdown of proteins, fats and carbohydrates. The process of digestion of fats is especially intense due to the low activity of lipolytic enzymes.

In children who are breastfed, lipids emulsified by bile are cleaved by 50% under the influence of maternal milk lipase. Digestion of carbohydrates occurs in the small intestine parietal under the influence of pancreatic juice amylase and 6 disaccharidases localized in the brush border of enterocytes. In healthy children, only a small part of the sugars is not subjected to enzymatic breakdown and is converted in the large intestine to lactic acid by bacterial decomposition (fermentation). The processes of putrefaction in the intestines of healthy infants do not occur. Hydrolysis products formed as a result of cavitary and parietal digestion are absorbed mainly in the small intestine: glucose and amino acids into the blood, glycerol and fatty acids into the lymph. In this case, both passive mechanisms (diffusion, osmosis) and active transport with the help of carrier substances play a role.

The structural features of the intestinal wall and its large area determine in young children a higher absorption capacity than in adults and, at the same time, an insufficient barrier function due to the high permeability of the mucous membrane for toxins, microbes and other pathogenic factors. The constituent components of human milk are most easily absorbed, the protein and fats of which in newborns are partially absorbed unsplit.

The motor (motor) function of the intestines is carried out in children very energetically due to pendulum movements that mix food, and peristaltic, moving food to the exit. Active motility is reflected in the frequency of bowel movements. In infants, defecation occurs reflexively, in the first 2 weeks of life up to 3-6 times a day, then less often, by the end of the first year of life it becomes an arbitrary act. In the first 2 to 3 days after birth, the baby excretes meconium (original feces) of a greenish-black color. It consists of bile, epithelial cells, mucus, enzymes, and swallowed amniotic fluid. The feces of healthy breastfed newborns have a mushy texture, a golden yellow color, and a sour smell. In older children, the chair is decorated, 1-2 times a day.

Child's duodenum

The duodenum of a newborn has an annular shape (bends are formed later), its beginning and end are located at the L level. In children older than 5 months, the upper part of the duodenum is at the level of T X | 1; the descending part gradually drops by the age of 12 to the level L IM L IV . In young children, the duodenum is very mobile, but by the age of 7, adipose tissue appears around it, which fixes the intestine, reducing its mobility.

In the upper part of the duodenum, acidic gastric chyme is alkalized, prepared for the action of enzymes that come from the pancreas and are formed in the intestine, and mixed with bile. The folds of the mucous membrane of the duodenum in newborns are lower than in older children, the duodenal glands are small, less branched than in adults. The duodenum has a regulatory effect on the entire digestive system through hormones secreted by the endocrine cells of its mucous membrane.

The small intestine of a child

The jejunum occupies approximately 2/5, and the ileum 3/5 of the length of the small intestine (excluding the duodenum). The ileum ends with an ileocecal valve (Bauhinian valve). In young children, relative weakness of the ileocecal valve is noted, and therefore the contents of the caecum, the richest in bacterial flora, can be thrown into the ileum, causing a high incidence of inflammatory lesions of its terminal section.

The small intestine in children occupies an unstable position, depending on the degree of its filling, the position of the body, the tone of the intestines and the muscles of the anterior abdominal wall. Compared with adults, the intestinal loops lie more compactly (due to the relatively large size of the liver and the underdevelopment of the small pelvis). After 1 year of life, as the pelvis develops, the location of the loops of the small intestine becomes more constant.

The small intestine of an infant contains a relatively large amount of gases, the volume of which gradually decreases until it disappears completely by the age of 7 (in adults, gases are normally absent in the small intestine).

The mucous membrane is thin, richly vascularized and has increased permeability, especially in children of the first year of life. Intestinal glands in children are larger than in adults. Their number increases significantly during the first year of life. In general, the histological structure of the mucous membrane becomes similar to that in adults by the age of 5-7 years. In newborns, single and group lymphoid follicles are present in the thickness of the mucous membrane. Initially, they are scattered throughout the intestine, and later they are grouped mainly in the ileum in the form of group lymphatic follicles (Peyer's patches). Lymphatic vessels are numerous, have a wider lumen than in adults. Lymph flowing from the small intestine does not pass through the liver, and the products of absorption enter directly into the blood.

The muscular coat, especially its longitudinal layer, is poorly developed in newborns. The mesentery in newborns and young children is short, increasing significantly in length during the first year of life.

In the small intestine, the main stages of the complex process of splitting and absorption of nutrients occur with the combined action of intestinal juice, bile and pancreatic secretions. The breakdown of nutrients with the help of enzymes occurs both in the cavity of the small intestine (abdominal digestion) and directly on the surface of its mucous membrane (parietal, or membrane, digestion, which dominates in infancy during the period of milk nutrition).

The secretory apparatus of the small intestine is generally formed by birth. Even in newborns, the same enzymes can be determined in the intestinal juice as in adults (enterokinase, alkaline phosphatase, lipase, amylase, maltase, nuclease), but their activity is lower and increases with age. The peculiarities of protein assimilation in young children include the high development of pinocytosis by epitheliocytes of the intestinal mucosa, as a result of which milk proteins in children in the first weeks of life can pass into the blood in an unmodified form, which can lead to the appearance of AT to cow's milk proteins. In children older than a year, proteins undergo hydrolysis to form amino acids.

Already from the first days of a child's life, all parts of the small intestine have a fairly high hydrolytic activity. Disaccharidases in the intestine appear even in the prenatal period. Maltase activity is quite high at birth and remains so in adults; sucrase activity increases somewhat later. In the first year of life, a direct correlation is observed between the age of the child and the activity of maltase and sucrase. Lactase activity increases rapidly in the last weeks of gestation, and after birth, the increase in activity decreases. It remains high throughout the period of breastfeeding, by the age of 4-5 there is a significant decrease in it, it is the smallest in adults. It should be noted that human milk rlactose is absorbed more slowly than cow's milk oslactose, and partially enters the large intestine, which contributes to the formation of gram-positive intestinal microflora in breastfed children.

Due to the low activity of lipase, the process of digesting fats is especially intense.

Fermentation in the intestines of infants complements the enzymatic breakdown of food. There is no rotting in the intestines of healthy children in the first months of life.

Absorption is closely related to parietal digestion and depends on the structure and function of the cells of the surface layer of the small intestine mucosa.

Large intestine of a child

The large intestine in a newborn has an average length of 63 cm. By the end of the first year of life, it lengthens to 83 cm, and subsequently its length is approximately equal to the height of the child. By birth, the colon does not complete its development. The newborn does not have omental processes (they appear on the 2nd year of the child's life), the bands of the colon are barely visible, the haustras of the colon are absent (they appear after 6 months). Colon bands, haustra and omental processes are finally formed by the age of 6-7 years.

The caecum in newborns has a conical or funnel-shaped shape, its width prevails over its length. It is located high (in a newborn directly under the liver) and descends into the right iliac fossa by the middle of adolescence. The higher the caecum, the more underdeveloped the ascending colon. The ileocecal valve in newborns looks like small folds. The ileocecal opening is annular or triangular, gaping. In children older than a year, it becomes slit-like. The appendix in a newborn has a conical shape, the entrance to it is wide open (the valve is formed in the first year of life). The appendix has great mobility due to the long mesentery and can be placed in any part of the abdominal cavity, including retrocecally. After birth, lymphoid follicles appear in the appendix, reaching their maximum development by 10-14 years.

The colon surrounds the loops of the small intestine. The ascending part of the newborn is very short (2-9 cm) and increases after the colon takes its final position. The transverse part of the colon in a newborn usually has an oblique position (its left bend is located higher than the right one) and only by the age of 2 takes a horizontal position. The mesentery of the transverse part of the colon in a newborn is short (up to 2 cm), within 1.5 years its width increases to 5-8.5 cm, due to which the intestine becomes able to move easily when the stomach and small intestine are filled. The descending part of the colon in a newborn has a smaller diameter than other parts of the colon. It is weakly mobile and rarely has a mesentery.

The sigmoid colon in a newborn is relatively long (12-29 cm) and mobile. Up to 5 years, it is located high in the abdominal cavity due to underdevelopment of the small pelvis, and then descends into it. Its mobility is due to the long mesentery. By the age of 7, the intestine loses its mobility as a result of the shortening of the mesentery and the accumulation of adipose tissue around it. The large intestine provides water resorption and evacuation-reservoir function. It completes the absorption of digested food, breaks down the remaining substances (both under the influence of enzymes coming from the small intestine and the bacteria that inhabit the large intestine), and the formation of feces occurs.

The mucous membrane of the large intestine in children is characterized by a number of features: deepened crypts, flatter epithelium, higher rate of its proliferation. Juice secretion of the colon under normal conditions is insignificant; however, it sharply increases with mechanical irritation of the mucous membrane.

The rectum of a child

The rectum of a newborn has a cylindrical shape, does not have an ampulla (its formation occurs in the first period of childhood) and bends (they form simultaneously with the sacral and coccygeal bends of the spine), its folds are not expressed. In children of the first months of life, the rectum is relatively long and poorly fixed, since fatty tissue is not developed. The rectum occupies the final position by 2 years. In a newborn, the muscular membrane is poorly developed. Due to the well-developed submucosa and weak fixation of the mucous membrane relative to the submucosa, as well as the insufficient development of the anal sphincter in young children, prolapse often occurs. The anus in children is located more dorsally than in adults, at a distance of 20 mm from the coccyx.

Functional features of the intestines of the child

The motor function of the intestine (motor) consists of pendulum movements that occur in the small intestine, due to which its contents are mixed, and peristaltic movements that move the chyme towards the large intestine. The colon is also characterized by anti-peristaltic movements, thickening and forming feces.

Motor skills in young children are more active, which contributes to frequent bowel movements. In infants, the duration of the passage of food gruel through the intestines is from 4 to 18 hours, and in older children - about a day. High motor activity of the intestine, combined with insufficient fixation of its loops, determines the tendency to intussusception.

Defecation in children

During the first hours of life, meconium (original feces) is passed - a sticky mass of dark green color with a pH of about 6.0. Meconium consists of desquamated epithelium, mucus, remnants of amniotic fluid, bile pigments, etc. On the 2nd-3rd day of life, feces are mixed with meconium, and from the 5th day, feces take on the appearance characteristic of a newborn. In children of the first month of life, defecation usually occurs after each feeding - 5-7 times a day, in children from the 2nd month of life - 3-6 times, in 1 year - 12 times. With mixed and artificial feeding, defecation is more rare.

Cal in children who are breastfed, mushy, yellow in color, sour reaction and sour smell; with artificial feeding, the feces have a thicker consistency (putty-like), lighter, sometimes with a grayish tint, neutral or even alkaline reaction, more pungent odor. The golden yellow color of feces in the first months of a child's life is due to the presence of bilirubin, greenish - biliverdin.

In infants, defecation occurs reflexively, without the participation of the will. From the end of the first year of life, a healthy child is gradually accustomed to the fact that defecation becomes an arbitrary act.

Pancreas

The pancreas, a parenchymal organ of external and internal secretion, is small in newborns: its mass is about 23 g, and its length is 4-5 cm. Already by 6 months, the mass of the gland doubles, by 1 year it increases by 4 times, and by 10 years - 10 times.

In a newborn, the pancreas is located deep in the abdominal cavity at the level of T x, i.e. higher than that of an adult. Due to weak fixation to the posterior wall of the abdominal cavity in a newborn, it is more mobile. In children of early and older age, the pancreas is at the level of L n . Iron grows most intensively in the first 3 years and in the puberty period.

By birth and in the first months of life, the pancreas is not sufficiently differentiated, abundantly vascularized and poor in connective tissue. At an early age, the surface of the pancreas is smooth, and by the age of 10-12, tuberosity appears, due to the isolation of the boundaries of the lobules. The lobes and lobules of the pancreas in children are smaller and few in number. The endocrine part of the pancreas is more developed at birth than the exocrine part.

Pancreatic juice contains enzymes that ensure the hydrolysis of proteins, fats and carbohydrates, as well as bicarbonates, which create the alkaline reaction of the environment necessary for their activation. In newborns, a small volume of pancreatic juice is secreted after stimulation, amylase activity and bicarbonate capacity are low. Amylase activity from birth to 1 year increases several times. When switching to a normal diet, in which more than half of the calorie requirement is covered by carbohydrates, amylase activity increases rapidly and reaches maximum values by 6-9 years. The activity of pancreatic lipase in newborns is low, which determines the great role of salivary gland lipase, gastric juice and breast milk lipase in the hydrolysis of fat. The activity of duodenal content lipase increases by the end of the first year of life, reaching the level of an adult by the age of 12. The proteolytic activity of the secret of the pancreas in children during the first months of life is quite high, it reaches a maximum at the age of 4-6 years.

The type of feeding has a significant effect on the activity of the pancreas: with artificial feeding, the activity of enzymes in the duodenal juice is 4-5 times higher than with natural feeding.

In a newborn, the pancreas is small (length 5-6 cm, by the age of 10 it is three times larger), located deep in the abdominal cavity, at the level of the X thoracic vertebra, in subsequent age periods - at the level of the I lumbar vertebra. It is richly vascularized, intensive growth and differentiation of its structure continues up to 14 years. The capsule of the organ is less dense than in adults, consists of fine-fibred structures, and therefore, in children with inflammatory edema of the pancreas, its compression is rarely observed. The excretory ducts of the gland are wide, which provides good drainage. Close contact with the stomach, the root of the mesentery, the solar plexus and the common bile duct, with which the pancreas in most cases has a common outlet to the duodenum, often leads to a friendly reaction from the organs of this zone with a wide irradiation of pain.

The pancreas in children, as in adults, has external and intrasecretory functions. The exocrine function is to produce pancreatic juice. It contains albumins, globulins, trace elements and electrolytes, as well as a large set of enzymes necessary for digestion of food, including proteolytic (trypsin, chymopsin, elastase, etc.), lipolytic (lipase, phospholipase A and B, etc.) and amylolytic (alpha- and beta-amylase, maltase, lactase, etc.). The rhythm of pancreatic secretion is regulated by neuro-reflex and humoral mechanisms. Humoral regulation is carried out by secretin, which stimulates the separation of the liquid part of pancreatic juice and bicarbonates, and pancreozymin, which enhances the secretion of enzymes along with other hormones (cholecystokinin, hepatokinin, etc.) produced by the mucous membrane of the duodenum and jejunum under the influence of hydrochloric acid. The secretory activity of the gland reaches the level of adult secretion by the age of 5. The total volume of separated juice and its composition depend on the amount and nature of the food eaten. The intrasecretory function of the pancreas is carried out by the synthesis of hormones (insulin, glucagon, lipocaine) involved in the regulation of carbohydrate and fat metabolism.

Liver in children

The size of the liver in children

The liver at the time of birth is one of the largest organs and occupies 1/3-1/2 of the volume of the abdominal cavity, its lower edge protrudes significantly from under the hypochondrium, and the right lobe can even touch the iliac crest. In newborns, the mass of the liver is more than 4% of body weight, and in adults - 2%. In the postnatal period, the liver continues to grow, but more slowly than body weight: the initial mass of the liver doubles by 8-10 months and triples by 2-3 years.

Due to the different rate of increase in the mass of the liver and body in children from 1 to 3 years of age, the edge of the liver comes out from under the right hypochondrium and is easily palpated 1-3 cm below the costal arch along the midclavicular line. From the age of 7, the lower edge of the liver does not come out from under the costal arch and is not palpable in a calm position; in the midline does not go beyond the upper third of the distance from the umbilicus to the xiphoid process.

The formation of liver lobules begins in the fetus, but by the time of birth, the liver lobules are not clearly demarcated. Their final differentiation is completed in the postnatal period. The lobulated structure is revealed only by the end of the first year of life.

The branches of the hepatic veins are located in compact groups and do not intersperse with the branches of the portal vein. The liver is plethoric, as a result of which it rapidly increases with infections and intoxications, circulatory disorders. The fibrous capsule of the liver is thin.

About 5% of the volume of the liver in newborns is accounted for by hematopoietic cells, subsequently their number decreases rapidly.

In the composition of the liver, the newborn has more water, but less protein, fat and glycogen. By the age of 8, the morphological and histological structure of the liver becomes the same as in adults.

Functions of the liver in the child's body

The liver performs various and very important functions:

produces bile, which is involved in intestinal digestion, stimulates the motor activity of the intestine and sanitizes its contents;
stores nutrients, mainly excess glycogen;
performs a barrier function, protecting the body from exogenous and endogenous pathogenic substances, toxins, poisons, and takes part in the metabolism of medicinal substances;
participates in the metabolism and conversion of vitamins A, D, C, B12, K;
during fetal development is a hematopoietic organ.

The formation of bile begins already in the prenatal period, but bile formation at an early age is slowed down. With age, the ability of the gallbladder to concentrate bile increases. The concentration of bile acids in the hepatic bile in children of the first year of life is high, especially in the first days after birth, which leads to the frequent development of subhepatic cholestasis (bile thickening syndrome) in newborns. By the age of 4-10, the concentration of bile acids decreases, and in adults it increases again.

The neonatal period is characterized by the immaturity of all stages of the hepato-intestinal circulation of bile acids: insufficiency of their uptake by hepatocytes, excretion through the tubular membrane, slowing of bile flow, dyscholia due to a decrease in the synthesis of secondary bile acids in the intestine and a low level of their reabsorption in the intestine. Children produce more atypical, less hydrophobic, and less toxic fatty acids than adults. The accumulation of fatty acids in the intrahepatic bile ducts causes an increased permeability of intercellular junctions and an increased content of bile components in the blood. The bile of a child in the first months of life contains less cholesterol and salts, which determines the rarity of stone formation.

In newborns, fatty acids combine mainly with taurine (in adults - with glycine). Taurine conjugates are more soluble in water and less toxic. A relatively higher content of taurocholic acid in bile, which has a bactericidal effect, determines the rarity of the development of bacterial inflammation of the biliary tract in children of the first year of life.

Enzymatic systems of the liver, which provide adequate metabolism of various substances, are not mature enough at birth. Artificial feeding stimulates their earlier development, but leads to their disproportion.

After birth, the child's albumin synthesis decreases, which leads to a decrease in the albumin-globulin ratio in the blood.

In children, transamination of amino acids occurs much more actively in the liver: at birth, the activity of aminotransferases in the child's blood is 2 times higher than in the mother's blood. At the same time, the processes of transamination are not mature enough, and the number of essential acids for children is greater than for adults. So, in adults there are 8 of them, children under 5-7 years old need additional histidine, and children in the first 4 weeks of life also need cysteine.

The urea-forming function of the liver is formed by the age of 3-4 months; before that, children have a high excretion of ammonia in the urine at a low concentration of urea.

Children of the first year of life are resistant to ketoacidosis, although they receive a diet rich in fat, and at the age of 2-12 years, on the contrary, they are prone to it.

In a newborn, the content of cholesterol and its esters in the blood is much lower than in the mother. After the start of breastfeeding for 3-4 months, hypercholesterolemia is noted. In the next 5 years, the concentration of cholesterol in children remains lower than in adults.

In newborns in the first days of life, insufficient activity of glucuronyl transferase is noted, with the participation of which conjugation of bilirubin with glucuronic acid and the formation of water-soluble "direct" bilirubin occur. Difficulty in the excretion of bilirubin is the main cause of physiological jaundice in newborns.

The liver performs a barrier function, neutralizes endogenous and exogenous harmful substances, including toxins from the intestines, and takes part in the metabolism of medicinal substances. In young children, the neutralizing function of the liver is not sufficiently developed.

The functionality of the liver in young children is relatively low. Its enzymatic system is especially untenable in newborns. In particular, the metabolism of indirect bilirubin released during hemolysis of erythrocytes is incomplete, resulting in physiological jaundice.

Gallbladder in a child

The gallbladder in newborns is usually hidden by the liver, its shape can be different. Its dimensions increase with age, and by the age of 10-12 years, the length increases by about 2 times. The rate of excretion of gallbladder bile in newborns is 6 times less than in adults.

In newborns, the gallbladder is located deep in the thickness of the liver and has a spindle-shaped shape, its length is about 3 cm. It acquires a typical pear-shaped shape by 6-7 months and reaches the edge of the liver by 2 years.

The bile of children differs in composition from the bile of adults. It is poor in bile acids, cholesterol and salts, but rich in water, mucin, pigments, and in the neonatal period, in addition, urea. A characteristic and favorable feature of the bile of a child is the predominance of taurocholic acid over glycocholic acid, since taurocholic acid enhances the bactericidal effect of bile, and also accelerates the separation of pancreatic juice. Bile emulsifies fats, dissolves fatty acids, improves peristalsis.

The intestinal microflora of a child

During fetal development, the intestines of the fetus are sterile. Its colonization by microorganisms occurs first during the passage of the mother's birth canal, then through the mouth when children come into contact with surrounding objects. The stomach and duodenum contain a meager bacterial flora. In the small and especially the large intestine, it becomes more diverse, the number of microbes increases; microbial flora depends mainly on the type of feeding of the child. When breastfeeding, the main flora is B. bifidum, the growth of which is promoted by (3-lactose of human milk. When complementary foods are introduced into the diet or the child is transferred to cow's milk feeding, gram-negative Escherichia coli, which is a conditionally pathogenic microorganism, predominates in the intestine. therefore, dyspepsia is more common in formula-fed children.According to modern concepts, the normal intestinal flora performs three main functions:

Creation of an immunological barrier;

Final digestion of food residues and digestive enzymes;

Synthesis of vitamins and enzymes.

The normal composition of the intestinal microflora (eubiosis) is easily disturbed under the influence of infection, improper diet, as well as the irrational use of antibacterial agents and other drugs, leading to a state of intestinal dysbacteriosis.

Historical data on the intestinal microflora

The study of the intestinal microflora began in 1886, when F. Escherich described Escherichia coli (Bacterium coli centipae). The term "dysbacteriosis" was first introduced by A. Nissle in 1916. Later, the positive role of the normal intestinal microflora in the human body was proved by I. I. Mechnikov (1914), A. G. Peretz (1955), A. F. Bilibin (1967), V. N. Krasnogolovets (1968), A. S. Bezrukova (1975), A. A. Vorobyov et al. (1977), I.N. Blokhina et al. (1978), V. G. Dorofeichuk et al. (1986), B. A. Shenderov et al. (1997).

Characteristics of the intestinal microflora in children

The microflora of the gastrointestinal tract takes part in digestion, prevents the development of pathogenic flora in the intestine, synthesizes a number of vitamins, participates in the inactivation of physiologically active substances and enzymes, affects the rate of renewal of enterocytes, enterohepatic circulation of bile acids, etc.

The intestines of the fetus and newborn are sterile during the first 10-20 hours (aseptic phase). Then the colonization of the intestine by microorganisms begins (second phase), and the third phase - stabilization of the microflora - lasts at least 2 weeks. The formation of intestinal microbial biocenosis begins from the first day of life, by the 7-9th day in healthy full-term children, the bacterial flora is usually represented mainly by Bifidobacterium bifldum, Lactobacillus acidophilus. With natural feeding, B. bifidum prevails among the intestinal microflora, with artificial feeding, L. acidophilus, B. bifidum and enterococci are present in almost equal amounts. The transition to a diet typical for adults is accompanied by a change in the composition of the intestinal microflora.

Intestinal microbiocenosis

The center of the human microecological system is the intestinal microbiocenosis, which is based on the normal (indigenous) microflora, which performs a number of important functions:

Indigenous microflora:

participates in the formation of colonization resistance;
produces bacteriocins - antibiotic-like substances that prevent the reproduction of putrefactive and pathogenic flora;
normalizes intestinal peristalsis;
participates in the processes of digestion, metabolism, detoxification of xenobiotics;
possesses universal immunomodulatory properties.

Distinguish mucoid microflora(M-microflora) - microorganisms associated with the intestinal mucosa, and cavity microflora(P-microflora) - microorganisms localized mainly in the intestinal lumen.

All representatives of the microbial flora with which the macroorganism interacts are divided into four groups: obligate flora (the main intestinal microflora); facultative (conditionally pathogenic and saprophytic microorganisms); transient (random microorganisms incapable of prolonged stay in the macroorganism); pathogenic (causative agents of infectious diseases).

Obligate microflora intestines - bifidobacteria, lactobacilli, full-fledged E. coli, propionobacteria, peptostreptococci, enterococci.

Bifidobacteria in children, depending on age, range from 90% to 98% of all microorganisms. Morphologically, they are gram-positive, immobile rods with a club-shaped thickening at the ends and bifurcation at one or both poles, anaerobic, not forming spores. Bifidobacteria are divided into 11 species: B. bifidum, B. ado-lescentis, B. infantis, B. breve, B. hngum, B. pseudolongum, B. thermophilum, B. suis, B. asteroides, B. indu.

Dysbacteriosis is a violation of the ecological balance of microorganisms, characterized by a change in the quantitative ratio and qualitative composition of the indigenous microflora in the microbiocenosis.

Intestinal dysbacteriosis is a violation of the ratio between anaerobic and aerobic microflora towards a decrease in the number of bifidobacteria and lactobacilli, normal E. coli and an increase in the number of microorganisms found in small numbers or usually absent in the intestine (opportunistic microorganisms).

Methodology for the study of the digestive system

The state of the digestive organs is judged by complaints, the results of questioning the mother and the data of objective research methods:

examination and observation in dynamics;

palpation;

percussion;

laboratory and instrumental indicators.

Complaints of the child

The most common of these are complaints of abdominal pain, loss of appetite, regurgitation or vomiting, and bowel dysfunction (diarrhea and constipation).

Questioning a child

A doctor-directed questioning of the mother allows you to clarify the time of onset of the disease, its relationship with the characteristics of nutrition and regimen, past diseases, and family-hereditary nature. Of particular importance is the detailed clarification of feeding issues.

Abdominal pain is a common symptom that reflects a variety of childhood pathologies. Pain that arose for the first time requires, first of all, the exclusion of surgical pathology of the abdominal cavity - appendicitis, intussusception, peritonitis. They can also be caused by acute infectious diseases (influenza, hepatitis, measles), viral and bacterial intestinal infections, inflammation of the urinary tract, pleuropneumonia, rheumatism, pericarditis, Shenlein-Genoch disease, periarteritis nodosa. Recurrent abdominal pain in older children are observed in diseases such as gastritis, duodenitis, cholecystitis, pancreatitis, peptic ulcer of the stomach and duodenum, ulcerative colitis. Functional disorders and helminthic invasion can also be accompanied by abdominal pain.

Reduced or prolonged loss of appetite (anorexia) in children is often the result of psychogenic factors (school overload, family conflict, neuroendocrine dysfunction during puberty), including improper feeding of the child (forced feeding). However, usually a decrease in appetite indicates a low secretion of the stomach and is accompanied by trophic and metabolic disorders.

Vomiting and regurgitation in newborns and infants may be due to pyloric stenosis or pylorospasm. In healthy children of this age, aerophagia leads to frequent regurgitation, which is observed in violation of the feeding technique, a short frenulum of the tongue, and a tight chest in the mother. In children 2-10 years old, suffering from neuro-arthritic diathesis, acetonemic vomiting may periodically occur due to acute reversible metabolic disorders. Emergence of vomiting in connection with damage of TsNS, infectious diseases, poisonings is possible.

Diarrhea in children of the first year of life often reflects intestinal dysfunction due to qualitative or quantitative feeding errors, regimen violations, overheating (simple dyspepsia) or is accompanied by an acute febrile illness (parenteral dyspepsia), but can also be a symptom of enterocolitis with intestinal infection.

Constipation - rare bowel movements occurring after 48 hours or more. They can be the result of both a functional disorder (dyskinesia) of the large intestine, and its organic damage (congenital narrowing, anal fissures, Hirschsprung's disease, chronic colitis) or inflammatory diseases of the stomach, liver and biliary tract. Nutritional (food intake, poor fiber) and infectious factors are of some importance. Sometimes constipation is associated with the habit of delaying the act of defecation and the resulting violation of the tone of the lower segment of the colon, and in infants with chronic malnutrition (pyloric stenosis). In children with sufficient weight gain, breastfed, stools are sometimes rare due to good digestion and a small amount of toxins in the intestines.

When examining the abdomen, pay attention to its size and shape. In healthy children of different ages, it slightly protrudes above the level of the chest, and subsequently flattens somewhat. An increase in the size of the abdomen can be due to a number of reasons:

hypotension of the muscles of the abdominal wall and intestines, which is especially often observed in rickets and dystrophies;
flatulence that develops with diarrhea of various etiologies, persistent constipation, intestinal dysbacteriosis, pancreatitis, pancreatic cystic fibrosis;
an increase in the size of the liver and spleen in chronic hepatitis, systemic blood diseases, circulatory failure and other pathologies;
the presence of fluid in the abdominal cavity due to peritonitis, ascites;
neoplasm of the abdominal cavity and retroperitoneal space.

The shape of the abdomen also has a diagnostic value: its uniform increase is observed with flatulence, hypotension of the muscles of the anterior abdominal wall and intestines ("frog" abdomen - with rickets, celiac disease), local bulging with hepatolienal syndrome of various etiologies, tumors of the abdominal cavity and retroperitoneal space. Retraction of the abdomen can be observed when the child is starving, pyloric stenosis, meningitis, diphtheria. On examination, you can determine the condition of the navel in newborns, the expansion of the venous network in liver cirrhosis, the divergence of the muscles of the white line and hernial protrusions, and in malnourished children in the first months of life, intestinal motility, which increases with pyloric stenosis, intussusception and other pathological processes.

Palpation of the abdomen and abdominal organs of the child

Palpation of the abdomen and abdominal organs is best done in the position of the patient on his back with legs slightly bent, with a warm hand, starting from the navel, and it is necessary to try to distract the child's attention from this procedure. Superficial palpation is carried out with light tangential movements. It makes it possible to determine the condition of the skin of the abdomen, muscle tone and tension of the abdominal wall. With deep palpation, the presence of painful points, infiltrates is detected, the size, consistency, nature of the surface of the lower edge of the liver and spleen, an increase in mesenteric lymph nodes in tuberculosis, lymphogranulomatosis, reticulosis and other diseases, spastic or atonic state of the intestine, accumulation of feces.

Palpation is also possible in the vertical position of the child with a half-tilt forward and lowered arms. At the same time, the liver and spleen are well probed, free fluid in the abdominal cavity is determined. In older children, bimanual palpation of the abdominal organs is used.

Percussion of the child's abdomen

Examination of the child's abdomen

Lastly, the child's mouth and pharynx are examined. At the same time, attention is paid to the smell from the mouth, the condition of the mucous membranes of the cheeks and gums (the presence of aphthae, ulcers, bleeding, fungal overlays, Filatov-Koplik spots), teeth, tongue (macroglossia with myxedema), papillary crimson - with scarlet fever, coated - with diseases of the gastrointestinal tract, "geographic" - with exudative-catarrhal diathesis, "varnished" - with hypovitaminosis B12).

The area of the anus is examined in younger children in the position on the side, in the rest - in the knee-elbow position. On examination, the following are revealed: anal fissures, a decrease in the tone of the sphincter and its gaping with dysentery, prolapse of the rectum with persistent constipation or after an intestinal infection, irritation of the mucous membrane during pinworm invasion. A digital examination of the rectum and sigmoid colonoscopy can detect polyps, tumors, strictures, fecal stones, ulcers of the mucous membrane, etc.

Of great importance in assessing the state of the digestive system is a visual examination of the stool. In infants with intestinal enzyme dysfunction (simple dyspepsia), dyspeptic stools are often observed, which look like chopped eggs (liquid, greenish, mixed with white lumps and mucus, acid reaction). Very characteristic stool in colitis, dysentery. Bloody stool without admixture of feces against the background of an acutely developed severe general condition may be in children with intestinal intussusception. Discolored stool indicates a delay in the flow of bile into the intestine and is observed in children with hepatitis, blockage or atresia of the bile ducts. Along with determining the quantity, consistency, color, odor and pathological impurities visible to the eye, the characteristics of the stool are supplemented by microscopy (coprogram) data on the presence of leukocytes, erythrocytes, mucus in the feces, as well as helminth eggs, lamblia cysts. In addition, bacteriological and biochemical studies of feces are carried out.

Laboratory and instrumental research

These studies are similar to those conducted in adults. The most important is endoscopy, which is currently widely used, which allows visually assessing the condition of the mucous membranes of the stomach and intestines, making a targeted biopsy, detecting neoplasms, ulcers, erosions, congenital and acquired strictures, diverticula, etc. Endoscopic examinations of children of early and preschool age are carried out under general anesthesia. Ultrasound examination of parenchymal organs, radiography of the biliary tract and gastrointestinal tract (with barium), gastric and duodenal sounding, determination of enzymes, biochemical and immunological blood parameters, biochemical analysis of bile, rheohepatography, laparoscopy with targeted liver biopsy and subsequent morphological study of the biopsy are also used. .

Of particular importance are laboratory and instrumental research methods in the diagnosis of diseases of the pancreas, which, due to its location, is not amenable to direct methods of physical examination. The size and contours of the gland, the presence of stones in the excretory ducts, developmental anomalies are detected by relaxation duodenography, as well as retrograde pancreatocholangiography, echopancreatography. Violations of exocrine function observed in cystic fibrosis, post-traumatic cysts, biliary atresia, pancreatitis, are accompanied by a change in the level of the main enzymes that are determined in the blood serum (amylase, lipase, trypsin and its inhibitors), in saliva (isoamylase), urine and duodenal contents. An important indicator of insufficiency of exocrine pancreatic function is persistent steatorrhea. The intrasecretory activity of the pancreas can be judged on the basis of studying the nature of the glycemic curve.

Importance of digestion.

Metabolism is a complex complex of various interdependent and interdependent processes that occur in the body from the moment these substances enter it and until the moment they are released. Metabolism is a necessary condition for life. It is one of its mandatory manifestations. For the normal functioning of the body, it is necessary to supply organic food material, mineral salts, water and oxygen from the external environment. For a period equal to the average life expectancy of a person, he consumes 1.3 tons of fat, 2.5 tons of proteins, 12.5 tons of carbohydrates and 75 tons of water. Metabolism consists of the processes of substances entering the body, their changes in the digestive tract, absorption, transformations inside cells and excretion of their decay products. The processes associated with the transformation of substances inside cells are called intracellular or intermediate metabolism. As a result of intracellular metabolism, hormones, enzymes and a wide variety of compounds are synthesized, which are used as a structural material for building cells and intercellular substance, which ensures the renewal and growth of a developing organism. The processes that result in the formation of living matter are called anabolism or assimilation. The other side of the metabolism is that the substances that form the living structure undergo splitting. This process of destruction of living matter is called catabolism or dissimilation. The processes of assimilation and dissimilation are very closely related, although they are opposite in their final results. Thus, it is known that the breakdown products of various substances contribute to their enhanced synthesis. Oxidation of cleavage products serves as a source of energy that the body constantly spends even in a state of complete rest. In this case, the same substances that are used for the synthesis of larger molecules can undergo oxidation. For example, in the liver, glycogen is synthesized from part of the breakdown products of carbohydrates, and the energy for this synthesis is provided by another part of them, which is included in metabolic or metabolic processes. The processes of assimilation and dissimilation occur with the obligatory participation of enzymes.

The role of vitamins in nutrition

Vitamins were discovered at the turn of the 19th and 20th centuries as a result of research into the role of various nutrients in the life of the body. The founder of vitaminology can be considered the Russian scientist N.I. Lunin, who in 1880 was the first to prove that in addition to proteins, fats, carbohydrates, water and minerals, some other substances are needed, without which the body cannot exist. These substances were called vitamins (vita + amin - "amines of life" from Latin), since the first vitamins isolated in their pure form contained an amino group in their composition. And although later it turned out that not all vitamin substances contain an amino group and nitrogen in general, the term "vitamin" has taken root in science.

According to the classical definition, vitamins are low molecular weight organic substances necessary for normal life that are not synthesized by an organism of a given species or are synthesized in an amount insufficient to ensure the life of the organism.

Vitamins are necessary for the normal course of almost all biochemical processes in our body. They provide the functions of the endocrine glands, that is, the production of hormones, increase mental and physical performance, support the body's resistance to the effects of adverse environmental factors (heat, cold, infections, and many others).

All vitamin substances are conditionally divided into vitamins proper and vitamin-like compounds, which are similar in their biological properties to vitamins, but are usually required in larger quantities. In addition, deficiency of vitamin-like substances is extremely rare, since their content in everyday food is such that even in the case of a very unbalanced diet, a person receives almost all of them in sufficient quantities.

According to their physical and chemical properties, vitamins are divided into two groups: fat-soluble and water-soluble. Each of the vitamins has a letter designation and a chemical name. In total, 12 true vitamins and 11 vitamin-like compounds are currently known.

At present, vitamins can be characterized as low-molecular organic compounds, which, being a necessary component of food, are present in it in extremely small quantities compared to its main components.

Vitamins are a necessary element of food for humans and a number of living organisms because they are not synthesized or some of them are synthesized in insufficient quantities by this organism. Vitamins are substances that ensure the normal course of biochemical and physiological processes in the body. They can be attributed to the group of biologically active compounds that have an effect on the metabolism in negligible concentrations.

Diseases of the gastrointestinal tract in children

Recently, there has been a significant increase in the number of diseases of the digestive system in children. Many factors contribute to this:

1. bad ecology,

2. unbalanced diet,

3. heredity.

Sweets and confectionery products with a high content of preservatives and artificial colors, fast food, carbonated drinks, so beloved by many, cause great harm to the child's body. The role of allergic reactions, neuropsychic factors, and neuroses is growing. Doctors note that intestinal diseases in children have two age peaks: at 5-6 years and at 9-11 years. The main pathological conditions are:

Constipation, diarrhea

Chronic and acute gastritis and gastroenteritis

Chronic duodenitis

Chronic enterocolitis

Peptic ulcer of the stomach and duodenum

· Chronic cholecystitis

· Chronic pancreatitis

Diseases of the biliary tract

Chronic and acute hepatitis

Of great importance in the occurrence and development of gastrointestinal diseases is the insufficient ability of the child's body to resist infections, since the child's immunity is still weak. The formation of immunity is greatly influenced by proper feeding in the first months of life.

The best option is breast milk, with which protective bodies are passed from mother to child, increasing the ability to resist various infections. Formula-fed babies are more susceptible to various diseases and have a weakened immune system. The cause of violations in the digestive system can be irregular feeding or overfeeding of the child, early introduction of complementary foods, non-compliance with hygiene standards.

A separate group consists of acute intestinal diseases in children (dysentery, salmonellosis). Their main clinical manifestations are dyspeptic disorders, dehydration (dehydration) of the body and symptoms of intoxication. Such manifestations are very dangerous and require immediate hospitalization of a sick child.

Intestinal infections are especially often diagnosed in childhood, this is due to the imperfection of protective mechanisms, the physiological characteristics of the digestive organs and the lack of sanitary and hygienic skills in children. Especially negative acute intestinal infections affect young children and can lead to a significant decrease in immunity, delayed physical development, and complications.

Their onset is accompanied by characteristic signs: a sharp increase in temperature, abdominal pain, diarrhea, vomiting, loss of appetite. The child becomes restless, or, on the contrary, lethargic and inhibited. The clinical picture largely depends on which parts of the intestine are affected. In any case, the child needs emergency medical care and antibiotic therapy.

The treatment of diseases of the digestive system in babies is handled by a pediatric gastroenterologist, it is he who should be contacted when unfavorable symptoms appear.

Age features of the digestive system in children and adolescents.

The most significant morphological and functional differences between the digestive organs of an adult and a child are observed only in the first years of postnatal development. The functional activity of the salivary glands is manifested with the appearance of milk teeth (from 5-6 months). A particularly significant increase in salivation occurs at the end of the first year of life. During the first two years, the formation of milk teeth is intensively going on. At the age of 2-2.5 years, the child already has 20 teeth and can eat relatively coarse food that requires chewing. In subsequent years, starting from the age of 5-6, milk teeth are gradually replaced by permanent ones. In the first years of postnatal development, the formation of other digestive organs is intensively going on: the esophagus, stomach, small and large intestines, liver and pancreas. Their size, shape and functional activity change. Thus, the volume of the stomach from birth to 1 year increases 10 times. The shape of the stomach in a newborn is round, after 1.5 years the stomach becomes pear-shaped, and from 6-7 years old its shape is no different from the stomach of adults. The structure of the muscular layer and the mucous membrane of the stomach changes significantly. In young children, there is a weak development of muscles and elastic elements of the stomach. The gastric glands in the first years of a child's life are still underdeveloped and few in number, although they are able to secrete gastric juice, in which the content of hydrochloric acid, the number and functional activity of enzymes are much lower than in an adult. So, the number of enzymes that break down proteins increases from 1.5 to 3 years, then at 5-6 years and at school age up to 12-14 years. The content of hydrochloric acid increases up to 15-16 years. A low concentration of hydrochloric acid causes weak bactericidal properties of gastric juice in children under 6-7 years of age, which contributes to an easier susceptibility of children of this age to gastrointestinal infections. In the process of development of children and adolescents, the activity of the enzymes contained in it also changes significantly. The activity of the enzyme chymosin, which acts on milk proteins, changes especially significantly in the first year of life. In a child of 1-2 months, its activity in arbitrary units is 16-32, and in 1 year it can reach 500 units, in adults this enzyme completely loses its significance in digestion. With age, the activity of other enzymes of gastric juice also increases, and at senior school age it reaches the level of an adult organism. It should be noted that in children under 10 years of age, absorption processes are actively going on in the stomach, while in adults these processes are carried out mainly only in the small intestine. The pancreas develops most intensively up to 1 year and at 5-6 years. According to its morphological and functional parameters, it reaches the level of an adult organism by the end of adolescence (at the age of 11-13, its morphological development is completed, and at the age of 15-16, its functional development). Similar rates of morphofunctional development are observed in the liver and all parts of the intestine. Thus, the development of the digestive organs goes in parallel with the general physical development of children and adolescents. The most intensive growth and functional development of the digestive organs is observed in the 1st year of postnatal life, in preschool age and in adolescence, when the digestive organs in their morphological and functional properties approach the level of an adult organism. In addition, in the course of life, children and adolescents easily develop conditioned food reflexes, in particular, reflexes for the time of eating. In this regard, it is important to accustom children to strict adherence to the diet. Important for normal digestion is the observance of "food aesthetics".

43. Age features of the structure of the digestive organs in children.

The development of the digestive organs in children occurs in parallel with the development of the whole organism. And this development is divided into periods of the first year of life, preschool age and adolescence. At this time, the work of the digestive organs is controlled by the nervous system and depends on the state of the cerebral cortex. In the process of the formation of the digestive system in children, reflexes are easily developed for the time of eating, its composition and quantity. The esophagus in young children has the shape of a spindle. It is short and narrow. In children in the year of life, its length is 12 cm. There are no glands on the mucosa of the esophagus. Its walls are thin, but it is well supplied with blood. The stomach in young children is located horizontally. And as the child develops, he takes a vertical position. By the age of 7-10, the stomach is already positioned as in adults. The gastric mucosa is thick, and the barrier activity of gastric juice is low compared to adults. The main enzyme of gastric juice is rennet. It provides curdling of milk. The pancreas of a young child is small. In a newborn, it is 5-6 centimeters. In 10 years, it will triple in size. This organ is well supplied with blood vessels. The pancreas produces pancreatic juice. The largest organ of the digestive system of a young child, occupying a third of the abdominal cavity, is the liver. At 11 months, its mass doubles, by 2-3 years it triples. The capabilities of the liver of a child at this age are low. The gallbladder at an early age reaches a size of 3 centimeters. It acquires a pear-shaped form by 7 months. Already at 2 years old, the child's gallbladder reaches the edge of the liver. For children up to a year, substances that come with mother's milk are of great importance. With the introduction of complementary foods to the child, the mechanisms of the child's enzyme systems are activated.

Importance of digestion.

The body needs a regular supply of food. Food contains nutrients: proteins, carbohydrates and fats. In addition, the composition of food includes water, mineral salts and vitamins. Nutrients are necessary for building the living matter of body tissues and serve as a source of energy, due to which all vital processes are performed (muscle contractions, heart function, nervous activity, etc.). In short, nutrients are plastic and energy material for the body. Water, mineral salts and vitamins are not nutrients and a source of energy, but are part of cells and tissues and participate in various life processes. Proteins, carbohydrates and fats in food are complex organic substances and are not absorbed by the body in this form. In the digestive canal, food is subjected to mechanical and chemical influences, as a result of which nutrients are broken down into simpler and more water-soluble substances that are absorbed into the blood or lymph and absorbed by the body. This process of processing food in the alimentary canal is called digestion. Mechanical processing of food consists in its crushing and grinding, which contributes to mixing with digestive juices (food liquefaction) and subsequent chemical processing. Chemical processing - the breakdown of complex substances into simpler ones - occurs under the influence of special substances contained in digestive juices - digestive enzymes. Water, mineral salts and vitamins are not subjected to special treatment in the digestive canal and are absorbed in the form in which they arrive.

44. Neurohumoral regulation of the digestive system.

45. Importance of metabolism and energy.

The digestive organs include the mouth, esophagus, stomach and intestines. The pancreas and liver are involved in digestion. The digestive organs are laid in the first 4 weeks of the prenatal period; by 8 weeks of pregnancy, all departments of the digestive organs are identified. The fetus begins to swallow amniotic fluid by 16-20 weeks of pregnancy. Digestive processes occur in the intestines of the fetus, where the accumulation of the original feces - meconium - is formed.

Features of the oral cavity in children

The main function of the oral cavity in a child after birth is to provide the act of sucking. These features are: the small size of the oral cavity, a large tongue, well-developed musculature of the lips and chewing muscles, transverse folds on the mucous membrane of the lips, ridge-like thickening of the gums, there are lumps of fat (Bish lumps) in the cheeks, which give the cheeks elasticity.

The salivary glands in children after birth are not sufficiently developed; little saliva is secreted in the first 3 months. The development of the salivary glands is completed by 3 months of age.

Features of the esophagusin children

The esophagus in young children is spindle-shaped, narrow and short. In a newborn, its length is only 10 cm, in children at 1 year of age - 12 cm, at 10 years old - 18 cm. Its width, respectively, is 8 mm at 7 years old, and 15 mm at 12 years old.

There are no glands on the mucous membrane of the esophagus. It has thin walls, poor development of muscle and elastic tissues, and a good blood supply. The entrance to the esophagus is located high. He has no physiological constrictions.

Features of the stomachin children

In infancy, the stomach is located horizontally. As the child grows and develops during the period when the child begins to walk, the stomach gradually assumes a vertical position, and by the age of 7-10 it is located in the same way as in adults. The capacity of the stomach gradually increases: at birth it is 7 ml, at 10 days - 80 ml, per year - 250 ml, at 3 years - 400-500 ml, at 10 years - 1500 ml.

V = 30 ml + 30 x n,

where n is the age in months.

A feature of the stomach in children is the weak development of its fundus and cardiac sphincter against the background of a good development of the pyloric section. This contributes to frequent regurgitation in the child, especially when air enters the stomach during suckling.

The mucous membrane of the stomach is relatively thick, against this background there is a weak development of the gastric glands. The active glands of the gastric mucosa, as the child grows, form and increase 25 times, as in the adult state. In connection with these features, the secretory apparatus in children of the first year of life is underdeveloped. The composition of gastric juice in children is similar to adults, but its acidic and enzymatic activity is much lower. Barrier activity of gastric juice is low.

The main active enzyme of gastric juice is rennet (labenzyme), which provides the first phase of digestion - milk curdling.

Very little lipase is excreted in the stomach of an infant. This deficiency is compensated by the presence of lipase in breast milk, as well as in the pancreatic juice of the child. If a child receives cow's milk, its fats in the stomach do not break down.

Absorption in the stomach is negligible and concerns substances such as salts, water, glucose, and protein breakdown products are only partially absorbed. The timing of the evacuation of food from the stomach depends on the type of feeding. Women's milk stays in the stomach for 2-3 hours.

Features of the pancreas in children

The pancreas is small. In a newborn, its length is 5-6 cm, and by the age of 10 it triples. The pancreas is located deep in the abdominal cavity at the level of the X thoracic vertebra; at an older age it is located at the level of the I lumbar vertebra. Its intensive growth occurs up to 14 years.

The size of the pancreas in children in the first year of life (cm):

1) newborn - 6.0 x 1.3 x 0.5;

2) 5 months - 7.0 x 1.5 x 0.8;

3) 1 year - 9.5 x 2.0 x 1.0.

The pancreas is richly supplied with blood vessels. Its capsule is less dense than in adults, and consists of fine-fibred structures. Its excretory ducts are wide, which provides good drainage.

The pancreas of a child has exocrine and intrasecretory functions. It produces pancreatic juice, consisting of albumins, globulins, microelements and electrolytes, enzymes necessary for digestion of food. Enzymes include proteolytic enzymes: trypsin, chymotrypsin, elastase, as well as lipolytic enzymes and amylolytic enzymes. The regulation of the pancreas is provided by secretin, which stimulates the release of the liquid part of the pancreatic juice, and pancreozymin, which enhances the secretion of enzymes along with other hormone-like substances that are produced by the mucous membrane of the duodenum and small intestine.

The intrasecretory function of the pancreas is carried out due to the synthesis of hormones responsible for the regulation of carbohydrate and fat metabolism.

LIVER: features in children

The liver of a newborn is the largest organ, occupying 1/3 of the volume of the abdominal cavity. At 11 months, its mass doubles, by 2-3 years it triples, by 8 years it increases 5 times, by 16-17 years the mass of the liver - 10 times.

The liver performs the following functions:

1) produces bile, which is involved in intestinal digestion;

2) stimulates intestinal motility, due to the action of bile;

3) stores nutrients;

4) performs a barrier function;

5) participates in metabolism, including the conversion of vitamins A, D, C, B12, K;

6) in the intrauterine period is a hematopoietic organ.

After birth, further formation of liver cells takes place. The functionality of the liver in young children is low: in newborns, the metabolism of indirect bilirubin is not completely carried out.

Features of the gallbladder in children

The gallbladder is located under the right lobe of the liver and has a fusiform shape, its length reaches 3 cm. It acquires a typical pear-shaped shape by 7 months, by 2 years it reaches the edge of the liver.

The main function of the gallbladder is to store and secrete hepatic bile. The bile of a child differs in its composition from the bile of an adult. It has few bile acids, cholesterol, salts, a lot of water, mucin, pigments. In the neonatal period, bile is rich in urea. In the bile of a child, glycocholic acid predominates and enhances the bactericidal effect of bile, and also accelerates the separation of pancreatic juice. Bile emulsifies fats, dissolves fatty acids, improves peristalsis.

With age, the size of the gallbladder increases, bile of a different composition begins to be secreted than in younger children. The length of the common bile duct increases with age.

The size of the gallbladder in children (Chapova O.I., 2005):

1) newborn - 3.5 x 1.0 x 0.68 cm;

2) 1 year - 5.0 x 1.6 x 1.0 cm;

3) 5 years - 7.0 x 1.8 x 1.2 cm;

4) 12 years old - 7.7 x 3.7 x 1.5 cm.

Features of the small intestine in children

The intestines in children are relatively longer than in adults.

The ratio of the length of the small intestine and body length in a newborn is 8.3:1, in the first year of life - 7.6:1, at 16 years - 6.6:1.

The length of the small intestine in a child of the first year of life is 1.2-2.8 m. The area of the inner surface of the small intestine in the first week of life is 85 cm2, in an adult - 3.3 x 103 cm2. The area of the small intestine increases due to the development of the epithelium and microvilli.

The small intestine is anatomically divided into 3 sections. The first section is the duodenum, the length of which in a newborn is 10 cm, in an adult it reaches 30 cm. It has three sphincters, the main function of which is to create an area of low pressure where food comes into contact with pancreatic enzymes.

The second and third sections are represented by the small and ileal intestines. The length of the small intestine is 2/5 of the length to the ileocecal angle, the remaining 3/5 is the ileum.

Digestion of food, absorption of its ingredients occurs in the small intestine. The intestinal mucosa is rich in blood vessels, the epithelium of the small intestine is rapidly renewed. Intestinal glands in children are larger, lymphoid tissue is scattered throughout the intestine. As the child grows, Peyer's patches form.

Features of the large intestine in children

The large intestine is made up of various sections and develops after birth. In children under 4 years of age, the ascending colon is longer than the descending one. The sigmoid colon is relatively longer. Gradually, these features disappear. The caecum and appendix are mobile, and the appendix is often located atypically.

The rectum in children of the first months of life is relatively long. In newborns, the rectal ampulla is undeveloped, the surrounding fatty tissue is poorly developed. By the age of 2, the rectum takes its final position, which contributes to prolapse of the rectum in early childhood with straining, with persistent constipation and tenesmus in debilitated children.

The omentum in children under 5 years of age is short.

Juice secretion in children in the large intestine is small, but with mechanical irritation it increases sharply.

In the large intestine, water is absorbed and feces are formed.

Features of the intestinal microflorain children

The gastrointestinal tract of the fetus is sterile. When a child comes in contact with the environment, it is populated by microflora. In the stomach and duodenum, the microflora is poor. In the small and large intestines, the number of microbes increases and depends on the type of feeding. The main microflora is B. bifidum, whose growth is stimulated by breast milk lactose. With artificial feeding, the opportunistic Gram-negative Escherichia coli dominates in the intestine. The normal intestinal flora has two main functions:

1) creation of an immunological barrier;

2) synthesis of vitamins and enzymes.

Features of digestion in young children

For children in the first months of life, the nutrients that come with mother's milk and are digested due to substances contained in women's milk itself are of decisive importance. With the introduction of complementary foods, the mechanisms of the child's enzyme systems are stimulated. The absorption of food ingredients in young children has its own characteristics. Casein first curdles in the stomach under the influence of rennet. In the small intestine, it begins to break down into amino acids, which are activated and absorbed.

Digestion of fat depends on the type of feeding. Cow's milk fats contain long chain fats that are broken down by pancreatic lipase in the presence of fatty acids.

Absorption of fat occurs in the final and middle sections of the small intestine. The breakdown of milk sugar in children occurs in the border of the intestinal epithelium. Women's milk contains lactose, cow's milk contains lactose. In this regard, during artificial feeding, the carbohydrate composition of food is changed. Vitamins are also absorbed in the small intestine.

Morphological and physiological features of the digestive organs in children are especially pronounced in infancy. In this age period, the digestive apparatus is adapted mainly for the assimilation of breast milk, the digestion of which requires the least amount of enzymes (lactotrophic nutrition). The baby is born with a well-defined sucking and swallowing reflex. The act of sucking is provided by the anatomical features of the oral cavity of the newborn and infant. When sucking, the baby's lips tightly grasp the nipple of the mother's breast with the areola. The jaws squeeze it, and the communication between the oral cavity and the outside air stops. A cavity with negative pressure is created in the child's mouth, which is facilitated by the lowering of the lower jaw (physiological retrognathia) along with the tongue down and back. Breast milk enters the rarefied space of the oral cavity.

The oral cavity of a child is relatively small, filled with the tongue. The tongue is short, wide and thick. When the mouth is closed, it comes into contact with the cheeks and the hard palate. The lips and cheeks are relatively thick, with sufficiently developed muscles and dense fatty lumps of Bish. There are ridge-like thickenings on the gums, which also play a role in the act of sucking.

The mucous membrane of the oral cavity is delicate, richly supplied with blood vessels and relatively dry. Dryness is caused by insufficient development of the salivary glands and a deficiency of saliva in children up to 3-4 months of age. The oral mucosa is easily vulnerable, which should be taken into account when carrying out the toilet of the oral cavity. The development of the salivary glands ends by 3-4 months, and from that time on, an increased secretion of saliva begins (physiological salivation). Saliva is the result of the secretion of three pairs of salivary glands (parotid, submandibular and sublingual) and small glands of the oral cavity. The reaction of saliva in newborns is neutral or slightly acidic. From the first days of life, it contains an amylolytic enzyme. It contributes to the sliming of food and foaming, from the second half of life its bactericidal activity increases.

The entrance to the larynx in an infant lies high above the lower edge of the palatine curtain and is connected to the oral cavity; due to this, food moves to the sides of the protruding larynx through the communication between the oral cavity and the pharynx. Therefore, the baby can breathe and suck at the same time. From the mouth, food passes through the esophagus to the stomach.

Esophagus. At the beginning of development, the esophagus looks like a tube, the lumen of which is filled due to the proliferation of cell mass. At 3-4 months of intrauterine development, the laying of glands is observed, which begin to actively secrete. This contributes to the formation of a lumen in the esophagus. Violation of the recanalization process is the cause of congenital narrowing and strictures in the development of the esophagus.

In newborns, the esophagus is a spindle-shaped muscular tube lined from the inside with a mucous membrane. The entrance to the esophagus is located at the level of the disk between the III and IV cervical vertebrae, by 2 years - at the level of IV-V cervical vertebrae, at 12 years old - at the level of VI-VII vertebrae. The length of the esophagus in a newborn is 10-12 cm, at the age of 5 years - 16 cm; its width in a newborn is 7-8 mm, by 1 year - 1 cm and by 12 years - 1.5 cm (the dimensions of the esophagus must be taken into account when conducting instrumental studies).

In the esophagus, three anatomical narrowings are distinguished - in the initial part, at the level of the bifurcation of the trachea and diaphragmatic. Anatomical narrowing of the esophagus in newborns and children of the first year of life are relatively weakly expressed. The features of the esophagus include the complete absence of glands and insufficient development of muscular-elastic tissue. Its mucous membrane is tender and richly supplied with blood. Outside the act of swallowing, the passage of the pharynx into the esophagus is closed. Peristalsis of the esophagus occurs during swallowing movements. The transition of the esophagus to the stomach in all periods of childhood is located at the level of the X-XI thoracic vertebrae.

The stomach is an elastic sac-like organ. It is located in the left hypochondrium, its cardial part is fixed to the left of the X thoracic vertebra, the pylorus is located near the midline at the level of the XII thoracic vertebra, approximately in the middle between the navel and the xiphoid process. This position varies considerably depending on the age of the child and the shape of the stomach. The variability of the shape, volume and size of the stomach depends on the degree of development of the muscle layer, the nature of nutrition, and the impact of neighboring organs. In infants, the stomach is located horizontally, but as soon as the child begins to walk, he assumes a more vertical position.

By the birth of a child, the fundus and cardial section of the stomach are not sufficiently developed, and the pyloric section is much better, which explains frequent regurgitation. Regurgitation is also facilitated by the swallowing of air during sucking, with improper feeding technique, a short frenulum of the tongue, greedy sucking, too rapid release of milk from the mother's breast.

The capacity of the stomach of a newborn is 30-35 ml, by the age of 1 year it increases to 250-300 ml, by the age of 8 it reaches 1000 ml.

The mucous membrane of the stomach is tender, rich in blood vessels, poor in elastic tissue, and contains few digestive glands. The muscular layer is underdeveloped. There is a meager secretion of gastric juice, which has low acidity.

The digestive glands of the stomach are divided into fundic (main, parietal and accessory), secreting hydrochloric acid, pepsin and mucus, cardiac (additional cells) that secrete mucin, and pyloric (main and accessory cells). Some of them begin to function in utero (parietal and main), but in general, the secretory apparatus of the stomach in children of the first year of life is underdeveloped and its functional abilities are low.

The stomach has two main functions - secretory and motor. The secretory activity of the stomach, consisting of two phases - neuro-reflex and chemical-humoral - has many features and depends on the degree of development of the central nervous system and the quality of nutrition.

The gastric juice of an infant contains the same components as the gastric juice of an adult: rennet, hydrochloric acid, pepsin, lipase, but their content is reduced, especially in newborns, and increases gradually. Pepsin breaks down proteins into albumins and peptones. Lipase breaks down neutral fats into fatty acids and glycerol. Rennet (the most active of the enzymes in infants) curdles milk.

The total acidity in the first year of life is 2.5-3 times lower than in adults, and is 20-40. Free hydrochloric acid is determined during breastfeeding after 1-1.5 hours, and with artificial - after 2.5-3 hours after feeding. The acidity of gastric juice is subject to significant fluctuations depending on the nature and diet, the state of the gastrointestinal tract.

An important role in the implementation of the motor function of the stomach belongs to the activity of the pylorus, due to the reflex periodic opening and closing of which the food masses pass in small portions from the stomach to the duodenum. In the first months of life, the motor function of the stomach is poorly expressed, peristalsis is sluggish, the gas bubble is enlarged. In infants, it is possible to increase the tone of the muscles of the stomach in the pyloric region, the maximum manifestation of which is pylorospasm. At an older age, sometimes there is cardiospasm.

Functional insufficiency decreases with age, which is explained, firstly, by the gradual development of conditioned reflexes to food stimuli; secondly, the complication of the child's diet; thirdly, the development of the cerebral cortex. By the age of 2, the structural and physiological features of the stomach correspond to those of an adult.

The intestine starts from the pylorus and ends at the anus. Distinguish between small and large intestine. The first is subdivided into a short duodenum, jejunum and ileum. The second - on the blind, colon (ascending, transverse, descending, sigmoid) and rectum.

The duodenum of a newborn is located at the level of the 1st lumbar vertebra and has a rounded shape. By the age of 12, it descends to the III-IV lumbar vertebra. The length of the duodenum up to 4 years is 7-13 cm (in adults up to 24-30 cm). In young children, it is very mobile, but by the age of 7, adipose tissue appears around it, which fixes the intestine and reduces its mobility.

The jejunum occupies 2/5, and the ileum 3/5 of the length of the small intestine without the duodenum. There is no clear boundary between them.

The ileum ends at the ileocecal valve. In young children, its relative weakness is noted, and therefore the contents of the caecum, the richest in bacterial flora, can be thrown into the ileum. In older children, this condition is considered pathological.

The small intestine in children occupies an unstable position, which depends on the degree of its filling, body position, tone of the intestines and abdominal muscles. Compared to adults, it is relatively long, and the intestinal loops are more compact due to the relatively large liver and underdevelopment of the small pelvis. After the first year of life, as the pelvis develops, the arrangement of the loops of the small intestine becomes more constant.

The small intestine of an infant contains a relatively large amount of gas, which gradually decreases in volume and disappears by the age of 7 (adults normally do not have gas in the small intestine).

Other features of the gut in infants and young children include:

Greater permeability of the intestinal epithelium;
Poor development of the muscular layer and elastic fibers of the intestinal wall;
tenderness of the mucous membrane and a high content of blood vessels in it;
Good development of the villi and folding of the mucous membrane with insufficiency of the secretory apparatus and incomplete development of the nerve pathways.

This contributes to the easy occurrence of functional disorders and favors the penetration into the blood of unsplit food components, toxic-allergic substances and microorganisms.

After 5-7 years, the histological structure of the mucous membrane no longer differs from its structure in adults.

The mesentery, very thin in newborns, increases significantly in length during the first year of life and descends along with the intestine. This, apparently, causes the child to have relatively frequent torsion of the intestines and intussusceptions.

The lymph flowing from the small intestine does not pass through the liver, so the products of absorption, along with the lymph through the thoracic duct, enter directly into the circulating blood.

The large intestine has a length equal to the height of the child. Parts of the colon are developed to varying degrees. The newborn has no omental processes, the bands of the colon are barely marked, haustra are absent until the age of six months. The anatomical structure of the colon after 3-4 years of age is the same as in an adult.

The caecum, which has a funnel-shaped shape, is located the higher, the younger the child. In a newborn, it is located directly under the liver. The higher the caecum is located, the more underdeveloped the ascending one. The final formation of the cecum ends by the year.

The appendix in a newborn has a conical shape, a wide open entrance and a length of 4-5 cm, by the end of 1 year - 7 cm (in adults 9-12 cm). It has greater mobility due to the long mesentery and can be located in any part of the abdominal cavity, but most often occupies the retrocecal position.

The colon in the form of a rim surrounds the loops of the small intestine. The ascending part of the colon in a newborn is very short (2-9 cm), begins to increase after a year.

The transverse part of the colon in a newborn is located in the epigastric region, has a horseshoe shape, a length of 4 to 27 cm; by the age of 2, it approaches a horizontal position. The mesentery of the transverse part of the colon is thin and relatively long, due to which the intestine moves easily when the stomach and small intestine are full.

The descending colon in newborns is narrower than the rest of the colon; its length doubles by 1 year, and by 5 years it reaches 15 cm. It is slightly mobile and rarely has a mesentery.

The sigmoid colon is the most mobile and relatively long part of the large intestine (12-29 cm). Up to 5 years, it is usually located in the abdominal cavity due to an underdeveloped small pelvis, and then descends into the small pelvis. Its mobility is due to the long mesentery. By the age of 7, the intestine loses its mobility as a result of the shortening of the mesentery and the accumulation of adipose tissue around it.

The rectum in children of the first months is relatively long and, when filled, can occupy the small pelvis. In a newborn, the ampulla of the rectum is poorly differentiated, fatty tissue is not developed, as a result of which the ampulla is poorly fixed. The rectum occupies its final position by the age of 2 years. Due to the well-developed submucosal layer and weak fixation of the mucous membrane, prolapse is often observed in young children.

The anus in children is located more dorsally than in adults, at a distance of 20 mm from the coccyx.

The process of digestion, which begins in the mouth and stomach, continues in the small intestine under the influence of pancreatic juice and bile secreted into the duodenum, as well as intestinal juice. The secretory apparatus of the intestine as a whole is formed. Even the smallest in the intestinal juice secreted by enterocytes, the same enzymes are determined as in adults (enterokinase, alkaline phosphatase, erepsin, lipase, amylase, maltase, nuclease), but their activity is low.

The duodenum is the hormonal center of digestion and exerts a regulatory influence on the entire digestive system through hormones secreted by the glands of the mucous membrane.

In the small intestine, the main stages of the complex process of splitting and absorption of nutrients are carried out with the combined action of intestinal juice, bile and pancreatic secretions.

The breakdown of food products occurs with the help of enzymes both in the cavity of the small intestine (cavitary digestion) and directly on the surface of its mucous membrane (parietal or membrane digestion). The infant has a special abdominal intracellular digestion, adapted to lactotropic nutrition, and intracellular, carried out by pinocetosis. The breakdown of foodstuffs occurs mainly under the influence of the secret of the pancreas, which contains trypsin (acting proteolytically), amylase (breaks down polysaccharides and turns them into monosaccharides) and lipase (breaks down fats). Due to the low activity of the lipolytic enzyme, the process of digesting fats is especially intense.

Absorption is closely related to parietal digestion and depends on the structure and function of the cells of the surface layer of the mucous membrane of the small intestine; it is the main function of the small intestine. Proteins are absorbed in the form of amino acids, but in children of the first months of life, their partial absorption in unchanged form is possible. Carbohydrates are digested as monosaccharides, fats as fatty acids.

The peculiarities of the structure of the intestinal wall and its relatively large area determine in young children a higher absorption capacity than in adults, and at the same time, due to high permeability, an insufficient barrier function of the mucous membrane. The components of women's milk are most easily absorbed, the proteins and fats of which are partially absorbed unsplit.

In the large intestine, the absorption of digested food and mainly water is completed, and the remaining substances are broken down under the influence of both enzymes from the small intestine and bacteria that inhabit the large intestine. Juice secretion of the colon is insignificant; however, it sharply increases with mechanical irritation of the mucous membrane. In the large intestine, feces are formed.

The motor function of the intestine (motility) consists of pendulum movements that occur in the small intestine, due to which its contents are mixed, and peristaltic movements that promote the movement of chyme towards the large intestine. The large intestine is also characterized by anti-peristaltic movements, which thicken and form fecal masses.

Motor skills in young children are very energetic, which causes frequent bowel movements. In infants, defecation occurs reflexively; in the first 2 weeks of life up to 3-6 times a day, then less often; by the end of the first year of life, it becomes an arbitrary act. In the first 2-3 days after birth, the baby excretes meconium (original feces) of a greenish-black color. It consists of bile, epithelial cells, mucus, enzymes, swallowed amniotic fluid. On day 4-5, the stool becomes normal. The stools of healthy breastfed newborns have a mushy texture, golden yellow or yellow-greenish color, sour smell. The golden-yellow color of feces in the first months of a child's life is due to the presence of bilirubin, greenish - biliverdin. In older children, the chair is decorated, 1-2 times a day.

The intestines of the fetus and newborn are free from bacteria for the first 10-20 hours. The formation of intestinal microbial biocenosis begins from the first day of life, by the 7-9th day in healthy full-term breastfed babies, a normal level of intestinal microflora is achieved with a predominance of B. bifidus, with artificial feeding - B. Coli, B. Acidophilus, B Bifidus and enterococci.

The pancreas is a parenchymal organ of external and internal secretion. In a newborn, it is located deep in the abdominal cavity, at the level of the Xth thoracic vertebra, its length is 5-6 cm. In infants and older children, the pancreas is located at the level of the 1st lumbar vertebra. Iron grows most intensively in the first 3 years and in the puberty period. By birth and in the first months of life, it is not sufficiently differentiated, abundantly vascularized and poor in connective tissue. In a newborn, the head of the pancreas is most developed. At an early age, the surface of the pancreas is smooth, and by the age of 10-12, tuberosity appears, due to the isolation of the boundaries of the lobules.

The liver is the largest digestive gland. In children, it is relatively large: in newborns - 4% of body weight, while in adults - 2%. In the postnatal period, the liver continues to grow, but more slowly than body weight.

Due to the different rate of increase in liver and body weight in children from 1 to 3 years of age, the edge of the liver comes out from under the right hypochondrium and is easily palpable 1-2 cm below the costal arch along the mid-clavicular line. From the age of 7, in the supine position, the lower edge of the liver is not palpable, and along the midline does not go beyond the upper third of the distance from the navel to the xiphoid process.

The liver parenchyma is poorly differentiated, the lobular structure is revealed only by the end of the first year of life. The liver is full-blooded, as a result of which it rapidly increases with infection and intoxication, circulatory disorders and is easily reborn under the influence of adverse factors. By the age of 8, the morphological and histological structure of the liver is the same as in adults.

The role of the liver in the body is varied. First of all, it is the production of bile, which is involved in intestinal digestion, stimulating the motor function of the intestine and sanitizing its contents. Bile secretion is noted already in a 3-month-old fetus, however, bile formation at an early age is still insufficient.

Bile is relatively poor in bile acids. A characteristic and favorable feature of the bile of a child is the predominance of taurocholic acid over glycocholic acid, since taurocholic acid enhances the bactericidal effect of bile and accelerates the separation of pancreatic juice.

The liver stores nutrients, mainly glycogen, but also fats and proteins. As needed, these substances enter the bloodstream. Separate cellular elements of the liver (stellate reticuloendotheliocytes, or Kupffer cells, portal vein endothelium) are part of the reticuloendothelial apparatus, which has phagocytic functions and is actively involved in the metabolism of iron and cholesterol.

The liver performs a barrier function, neutralizes a number of endogenous and exogenous harmful substances, including toxins from the intestines, and takes part in the metabolism of medicinal substances.

Thus, the liver plays an important role in carbohydrate, protein, bile, fat, water, vitamin (A, D, K, B, C) metabolism, and during fetal development it is also a hematopoietic organ.

In young children, the liver is in a state of functional insufficiency, its enzymatic system is especially untenable, resulting in transient neonatal jaundice due to incomplete metabolism of free bilirubin formed during hemolysis of erythrocytes.

The spleen is a lymphoid organ. Its structure is similar to the thymus gland and lymph nodes. It is located in the abdominal cavity (in the left hypochondrium). The pulp of the spleen is based on reticular tissue that forms its stroma.