AFO of the digestive system of the newborn. Anatomical and physiological features of the digestive system in children. Research methodology. Semiotics of lesions Physiological features of the digestive system in children

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 child infancy. 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. 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, exposure neighboring bodies. 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, and 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, lining 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 at breastfeeding after 1-1.5 hours, and with artificial - 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 children early age it is very mobile, but by the age of 7, adipose tissue appears around it, which fixes the intestine and reduces 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 (bile comes from the liver through the bile ducts).

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.

In the small intestine baby contains a relatively large amount of gases, which gradually decrease in volume and disappear by the age of 7 (adults normally do not have gases 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 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 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 released 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 pancreatic secretions containing 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.

Structural features of the intestinal wall and its relatively large area are determined in children younger age higher than in adults, absorption capacity, and at the same time, due to high permeability, 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 coming 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 (motor) 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 reached 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 has relatively big sizes: 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 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 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, endothelium of the portal vein) are part of the reticuloendothelial apparatus, which has phagocytic functions and accepts Active participation in iron and cholesterol metabolism.

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.

SEMIOTICS OF LESIONS OF THE DIGESTIVE ORGANS

Diseases of the digestive system in children of preschool and school age are 79.3 cases per 1000 children. The proportion of functional disorders of the digestive system decreases with age in children, and at the same time the frequency of organic diseases increases. For the diagnosis of diseases of the digestive system, the analysis of complaints, knowledge and consideration of the anatomical and physiological characteristics of the gastrointestinal tract of a child are important.

ANATOMICAL AND PHYSIOLOGICAL FEATURES OF THE GASTROINTESTINAL TRACT 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. Normal fetus swallows a large number 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 considerable 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 to comply with proper care behind the mouth.

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 assigning various kinds nutrition for the 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 secretory apparatus of the intestine by the time of the birth of the child is generally formed, the intestinal juice contains the same enzymes 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 maternal 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 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 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. The 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 decay processes in the feces, there are a lot of Escherichia coli, fermentative flora (bifidoflora, lactic acid bacilli) is present in a smaller amount.

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 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 determined. The fetus begins to swallow amniotic fluid by 16-20 weeks of pregnancy. Digestive processes occur in the intestines of the fetus, where an accumulation of the original feces - meconium - is formed.

FEATURES OF THE MOUTH

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

The salivary glands in children after birth are underdeveloped; 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 ESOPHAGUS

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, at 7 years old is 8 mm, at 12 years old - 15 mm.

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 STOMACH

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? n,

where n is the age in months.

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

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 - curdling of milk.

In the stomach of an infant, very little lipase is secreted. 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 lingers in the stomach for 2-3 hours.

FEATURES OF THE PANCREAS

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? 1.3? 0.5;

2) 5 months - 7.0? 1.5? 0.8;

3) 1 year - 9.5? 2.0? 1.0.

The pancreas is richly supplied with blood vessels. Its capsule is less dense than in adults, and consists of fine-fibrous 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, trace elements and electrolytes, enzymes necessary for the 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

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 is 10 times.

The liver performs the following functions:

1) produces bile involved in intestinal digestion;

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

3) deposits nutrients;

4) performs a barrier function;

5) participates in metabolism, including - in the conversion of vitamins A, D, C, B 12, K;

6) in the prenatal period is a hematopoietic organ.

After birth, further formation of liver lobules occurs. 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 GALL BLADDER

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 stand out than in young 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? 1.0? 0.68 cm;

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

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

4) 12 years - 7.7? 3.7? 1.5 cm.

FEATURES OF THE SMALL INTESTINE

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 old - 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 cm 2, in an adult - 3.3? 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

The large intestine consists 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, 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 years, the rectum assumes 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 INTESTINAL MICROFLORA

The gastrointestinal tract of the fetus is sterile. When a child comes into contact with environment 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 ?-lactose in breast milk. With artificial feeding, opportunistic gram-negative E. coli dominates in the intestine. The normal intestinal flora performs 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, 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. Human milk contains ?-lactose, cow's milk contains ?-lactose. In this regard, with artificial feeding, the carbohydrate composition of food is changed. Vitamins are also absorbed in the small intestine.

Anatomical and physiological features. In young children 1) thin, delicate, dry, easily injurious mucous membrane; 2) richly vascularized submucosal layer, consisting mainly of loose fiber; 3) underdeveloped, elastic and muscle tissue; 4) low secretory function of the glandular tissue, which separates a small amount of digestive juices with a low content of enzymes. These features make it difficult to digest food if the latter is not appropriate for the age of the child, reduce the barrier function of the gastrointestinal tract and lead to frequent illnesses, create the prerequisites for a general systemic reaction to any pathological effect and require very careful and careful care of the mucous membranes.

Oral cavity. providing the act of sucking, 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, fatty bodies of the cheek (Bish's lumps). The salivary glands are underdeveloped. at the age of 3-4 months, physiological salivation due to the automatism of swallowing it that has not yet been developed.

Esophagus. In young children, the esophagus is funnel-shaped. Its length in newborns is 10 cm, in children 1 year old - 12 cm, 10 years old - 18 cm, diameter - 7-8, 10 and 12-15 mm, respectively.

Stomach. In infants, the stomach is horizontal, with the pyloric portion near the midline and the lesser curvature facing posteriorly. When 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 year 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 sphincter functions satisfactorily - regurgitation ("physiological aerophagy"). children of the first months of life should be kept upright for some time. Secretory - the 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 determines the low barrier function of the stomach. This makes it absolutely essential to meet dietary requirements according to the age of the child and to carefully observe the sangig regimen during feeding of children (toilet breasts, clean hands, proper expression of milk, sterility of nipples and bottles).

In children of the first months of life, intragastric pH reflects a neutral environment or is close to it, and only by the end of the first year of life does it decrease to 2.0, providing maximum pepsin activity.

The main active enzyme of gastric juice is chymosin (rennet, labenzyme), which provides the first phase of digestion - curdling of milk. Pepsin (in the presence of hydrochloric acid) and lipase continue the hydrolysis of proteins and fats of curdled milk. Nevertheless, its peculiarities in children of the first year of life, which consist in the fact that it can also show its activity in a neutral environment, in the absence of bile acids, contribute to the hydrolysis of a certain part of the fats of human milk in the stomach. The maturation of the secretory apparatus of the stomach occurs earlier and more intensively in formula-fed children. 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 buffering properties of milk).

Pancreas. The newborn has a small size (length 5-6 cm, by the age of 10 - three times more), 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 well supplied with blood vessels, intensive growth and differentiation of its structure continue up to 14 years. The capsule of the organ is less dense than in adults, consists of fine-fibrous 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. 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 -kih a- and (3-amylase, maltase, lactase, etc.). The secretory activity of the gland reaches the level of adult secretion by the age of 5.

The liver mass in newborns is 4-6% of body weight (in adults - 3%). The liver parenchyma is poorly differentiated, the lobulation of the structure is detected only by the end of the first year of life, it is full-blooded, as a result of which it rapidly increases in various pathologies, especially in infectious diseases and intoxications.

By the age of 8, the morphological and histological structure of the liver is the same as in adults, the metabolism of indirect bilirubin released during hemolysis of erythrocytes is not fully carried out, resulting in physiological jaundice.

Gallbladder. In newborns, it 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. the predominance of taurocholic acid over glycocholic acid, as it enhances the bactericidal effect of bile and accelerates the separation of pancreatic juice. Bile emulsifies fats, dissolves fatty acids, improves peristalsis.

Intestines. 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. The cecum and appendix are mobile, the latter is often located atypically, thereby making it difficult to diagnose inflammation. The sigmoid colon is relatively larger length than in adults, and in some children even forms loops, which contributes to the development of habitual constipation.With age, these anatomical features disappear.Due to 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 of intestinal loops, 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. and an abundance of small lymphatic follicles.

The intestinal secretory apparatus is generally formed at the time of the birth of the child, and even in the smallest, the same enzymes are determined in the intestinal juice as in adults (enterokinase, alkaline phosphatase, erepsin, lipase, amylase, maltase, lactase, nuclease), but much 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 the small intestine, especially in its proximal sections, vitamins A, D, C, group B are absorbed.

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, microorganisms 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. In infants, defecation occurs reflexively, in the first 2 weeks of life up to 3-6 times a day, then less often, a year by 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, 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.

Microflora. 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. According to modern concepts, the normal intestinal flora performs three main functions: 1) the creation of an immunological barrier; 2) final digestion of food residues and digestive enzymes; 3) 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.

Significant structural and functional differences in the digestive organs of children compared with those of adults are observed only in the first years of life. The morphofunctional features of the digestive system depend to a large extent on the type of nutrition and food composition. Adequate food for children of the first year of life, especially the first 4 months, is mother's milk. By the time of the birth of the child, the secretory apparatus of the digestive tract is formed according to milk feeding. The number of secretory cells and enzymatic activity of digestive juices are insignificant. In infants, in addition to parietal, intracellular and abdominal digestion, which are not active enough (especially abdominal), there is also autolytic digestion due to human milk enzymes. By the end of the first year of life, with the start of complementary foods and the transition to definitive nutrition, the formation of one's own digestive mechanisms is accelerated. Complementary feeding at 5-6 months ensures the further development of the digestive glands and their adaptation to the nature of the food.

Digestion in the mouth children of different ages is carried out with the help of mechanical and chemical processing of food. Since teething begins only from the 6th month of life after birth, chewing until this process is completed (up to 1.5-2 years) is ineffective. The mucous membrane of the oral cavity in children of the first 3–4 months. life is relatively dry, due to the underdevelopment of the salivary glands and the deficiency of saliva. The functional activity of the salivary glands begins to increase at the age of 1.5–2 months. in 3-4-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 salivary glands of the newborn secrete very little saliva, from 4-6 months. secretion increases significantly, which is associated with the start of complementary foods: mixed nutrition with thicker food is a stronger irritant of the salivary glands. The secretion of saliva in newborns outside the periods of feeding is very low, while sucking it increases to 0.4 ml / min.

The glands during this period develop rapidly and by the age of 2 years are close in structure to those of adults. Children under 1 year old - 1.5 years old cannot swallow saliva, so they experience salivation. During suckling, saliva wets the nipple and provides a seal, making sucking more effective. The role of saliva lies in the fact that it is a sealant of the child's oral cavity, providing, as it were, gluing the nipple to the oral mucosa, which creates the vacuum necessary for sucking. Saliva, mixed with milk, promotes the formation of looser casein flakes in the stomach.

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.

The larynx in infants 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.

Digestion in the stomach.

The shape of the stomach, characteristic of adults, is formed in a child by the age of 8-10 years. The cardiac sphincter is underdeveloped, but the muscular layer of the pylorus is expressed, so regurgitation and vomiting are often observed in infants. The capacity of the stomach of a newborn is 40-50 ml, by the end of the first month 120-140 ml, by the end of the first year 300-400 ml.

In infants, the volume of gastric juice is not large, because. the complex reflex phase of gastric secretion is poorly expressed, the receptor apparatus of the stomach is poorly developed, mechanical and chemical effects do not have a pronounced stimulating effect on the secretion of the glands.

The pH of the gastric contents of a newborn baby ranges from slightly alkaline to slightly acidic. During the first day, the environment in the stomach becomes acidic (pH 4 - 6). The acidity of the gastric juice is created not by HCl (free HCl in the juice is negligible), but by lactic acid. The acidity of the gastric juice is provided by lactic acid until about 4-5 months of age. The intensity of HCl secretion increases by about 2 times with mixed feeding and 2-4 times with the transfer to artificial feeding. Acidification of the stomach environment is also stimulated by its proteolytic enzymes.

First 2 months In the life of a child, fetal pepsin plays the main role in the breakdown of proteins, then pepsin and gastrixin (enzymes of an adult). Fetal pepsin has the ability to curdle milk.

The activity of stomach pepsins for plant proteins is quite high from the 4th month of a child's life, and for animal proteins - from the age of 7 months.

In the slightly acidic environment of the stomach of young infants, proteolytic enzymes are inactive, due to which various milk immunoglobulins are not hydrolyzed and absorbed in the intestine in a native state, providing the proper level of immunity. In the stomach of a newborn, 20-30% of the incoming proteins are digested.

Under the influence of saliva and gastric juice in the presence of calcium ions, caseinogen protein dissolved in milk, lingering in the stomach, turns into insoluble loose flakes, which are then exposed to the action of proteolytic enzymes.

Emulsified milk fats are well split by gastric lipase from the moment the child is born, and this lipase is filtered from the capillaries of the gastric mucosa. The lipase of the saliva of the child and breast milk also participate in this process, the lipase of breast milk is activated by the lipokinase of the gastric juice of the child.

Carbohydrates in milk in the stomach of the child are not broken down, since the gastric juice does not contain the appropriate enzymes, and saliva alpha-amylase does not have this property. In the slightly acidic environment of the stomach, the amylolytic activity of the saliva of the child and mother's milk can be preserved.

The activity of all enzymes of the stomach reaches the norm of adults at the age of 14-15.

Contractions of the stomach in a newborn, continuous, weak, but with age they increase, periodic stomach motility appears on an empty stomach.

Women's milk stays in the stomach for 2-3 hours, the nutritional mixture with cow's milk - 3-4 hours. Regulatory mechanisms are immature, local mechanisms are somewhat better formed. Histamine begins to stimulate the secretion of gastric juice from the end of the first month of life.

Digestion in the duodenum carried out with the help of pancreatic enzymes, the duodenum itself, the action of bile. In the first 2 years of life, the activity of proteases, lipases and amylases of the pancreas and duodenum is low, then it increases rapidly: the activity of proteases reaches a maximum level by 3 years, and lipases and amylases - by 9 years of age.

The liver of a newborn and an infant is large, a lot of bile is secreted, but it contains little bile acids, cholesterol and salts. Therefore, with early feeding in infants, fats may not be absorbed enough and appear in the feces of children. Due to the fact that little bilirubin is secreted in newborns with bile, they often develop physiological jaundice.

Digestion in the small intestine. 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.

The mucous membrane is thin, richly vascularized and has increased permeability, especially in children of the first year of life. 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 the blood directly.

Enzymatic activity the mucosa of the small intestine is high - membrane digestion predominates. Intracellular digestion also plays an important role in digestion. Intracavitary digestion in newborns is not formed. With age, the role of intracellular digestion decreases, but the role of intracavitary increases. There is a set of enzymes for the final stage of digestion: dipeptidases, nucleases, phosphatases, disaccharases. Proteins and fats of women's milk are digested and absorbed better than cow's milk: women's milk proteins are digested by 90-95%, and cow's - by 60-70%. The peculiarities of protein assimilation in young children include the high development of pinocytosis by epitheliocytes of the intestinal mucosa. As a result, milk proteins in children of the first weeks of life can pass into the blood in an unmodified form, which can lead to the appearance of antibodies to cow's milk proteins. In children older than a year, proteins undergo hydrolysis to form amino acids.

A newborn baby is able to absorb 85-90% fat female milk. However lactose cow's milk is digested better than women's. Lactose is broken down into glucose and galactose, which are absorbed into the blood. The inclusion of pureed fruits and vegetables in the diet enhances the secretory and motor activity of the small intestine. When switching to definitive nutrition (typical of an adult) in the small intestine, the production of invertase and maltase increases, but the synthesis of lactase decreases

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.

Suction 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.

The peculiarity of the absorption of hydrolysis products in children in early ontogenesis is determined by the peculiarity of food digestion - mainly membrane and intracellular, which facilitates absorption. Absorption is also facilitated by the high permeability of the mucous membrane of the gastrointestinal tract. In children different years life, absorption in the stomach occurs more intensively than in adults.

Digestion in the large intestine. The intestines of a newborn contain primordial feces (meconium), which includes the remains of amniotic fluid, bile, exfoliated intestinal epithelium, and thickened mucus. It disappears from the feces within 4-6 days of life. 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 of the first months of life is involuntary - 5-7 times a day, by the year it becomes arbitrary and occurs 1-2 times a day.

Microflora of the gastrointestinal tract The intestines of the fetus and newborn are sterile during the first 10-20 hours (aseptic phase). Then 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 bifidum, Lactobacillus acidophilus

The microflora of the gastrointestinal tract in a newborn child mainly depends on the type of feeding, it performs the same functions as the microflora of an adult. For the distal small intestine and the entire large intestine, the bifidoflora is the main one. Stabilization of microflora in children ends by 7 years of age.

Human milk contains p-lactose, which breaks down more slowly than a-lactose in cow's milk. Therefore, in the case of breastfeeding, part of the undigested p-lactose enters the large intestine, where it undergoes cleavage by the bacterial flora, and thus a normal microflora develops in the large intestine. With early feeding with cow's milk, lactose does not enter the large intestine, which can be the cause of dysbacteriosis in children.

Neuroendocrine activity of the gastrointestinal tract.

Regulatory peptides produced by the endocrine apparatus of the gastrointestinal tract in the fetus stimulate the growth and differentiation of mucous membranes. The production of enteral hormones in a newborn increases sharply immediately after the first feeding and increases significantly in the first days. The formation of the intramural nervous apparatus, which regulates the secretory and motor activity of the small intestine, is completed at the age of 4-5 years. In the process of maturation of the central nervous system, its role in the regulation of the activity of the gastrointestinal tract increases. However, the conditioned reflex secretion of digestive juices begins in children already in the first years of life, as in adults, subject to a strict diet - a conditioned reflex for a while, which must be taken into account.

The products of hydrolysis absorbed into the blood and lymph are included in the process of anabolism.