Anatomical and physiological features of the gastrointestinal tract in children. Anatomical and physiological features of the digestive system in children

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. amniotic fluid the fetus begins to swallow 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: small size of the oral cavity, big tongue, well-developed muscles of the lips and chewing muscles, transverse folds on the mucous membrane of the lips, ridge-like thickening of the gums, in the cheeks there are lumps of fat (lumps of Bish), 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

Esophagus in children early age has a spindle shape, it is 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 horizontal. As the child grows and develops during the period when the child begins to walk, the stomach gradually takes vertical position, and by 7-10 years 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. It contributes frequent regurgitation in a 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.

in the stomach baby very little lipase is released. 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 abdominal cavity at the level of the X thoracic vertebra, at an older age it is at the level of the I lumbar vertebra. Her intensive growth occurs before the age of 14.

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-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, 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 most big 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) carries out barrier function;

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

6) in prenatal 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 spindle shape, its length reaches 3 cm. pear-shaped it acquires 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. inner surface 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, main function which is to create an area reduced 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 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 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 the intestinal microflorain children

The gastrointestinal tract of the fetus is sterile. When the child comes into contact with 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, when artificial feeding the carbohydrate composition of the food was changed. Vitamins are also absorbed in the small intestine.

Young children (especially newborns) have a number of morphological features common to all parts of the gastrointestinal tract: 1) thin, delicate, dry, easily damaged 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 does not correspond to the age of the child, reduce the barrier function 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. 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, fatty bodies (Bish's lumps) in the thickness of the cheeks, which are characterized by considerable 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.

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, which must be taken into account when carrying out a number of medical and diagnostic procedures.

Stomach. 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 (Fig. 10-12). 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. Cardiac sphincter at infants it 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 aerophagy"). 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 (Table 3), which not only affects digestion, but also determines the low barrier function of the stomach. 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 last 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.

As can be seen from Table. 3, acidity indicators fluctuate significantly, which is explained by the individual characteristics of the formation of gastric secretion and the age of the child.

Determination of acidity is carried out by the fractional method using as an irritant 7% cabbage broth, meat broth, 0.1 % histamine or pentagastrin solution. 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. However, the importance of gastric juice lipase in the digestion of fats is small due to its extremely low content in it and low activity. This deficiency is filled with lipase, which is found in women's milk, as well as in the pancreatic juice of the child. Therefore, in infants who receive only cow's milk, fats in the stomach do not break down. 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. 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.

Pancreas. 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 (a- and (beta-amylase, maltase, lactase, etc.). The rhythm of pancreatic secretion is regulated by neuro-reflex and humoral mechanisms. Secretin, which stimulates the separation of the liquid part of pancreatic juice and bicarbonates, and pancreozymin, enhances the secretion of enzymes along with other hormones (cholecystokinin, hepatokinin, etc.) produced by the mucosa 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 secreted juice and its composition depend on the amount and the 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 liver is relatively large, its weight in newborns is 4-6% of body weight (in adults - 3%). The liver parenchyma is poorly differentiated, the lobulation of the structure is revealed only by the end of the first year of life, it is full-blooded, as a result of which it rapidly increases in size with various pathologies, especially with infectious diseases and intoxications. By the age of 8, the morphological and histological structure of the liver is the same as in adults.

The liver performs various and very important functions: 1) produces bile, which is involved in intestinal digestion, stimulates the motor activity of the intestine and sanitizes its contents; 2) stores nutrients, mainly excess glycogen; 3) performs a barrier function, protecting the body from exogenous and endogenous pathogenic substances, toxins, poisons, and takes part in the metabolism of medicinal substances; 4) participates in the metabolism and conversion of vitamins A, D, C, B12, K; 5) during the period prenatal development is a hematopoietic organ.

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 newborns gallbladder located deep in the thickness of the liver and has a spindle shape, its length is about 3 cm.

it acquires a 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.

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), 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 intestinal secretory apparatus is generally formed at 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 stools of healthy newborns who are on breastfeeding, have a mushy texture, golden- yellow coloration, 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. 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 feeding with mother's milk, the main flora is B. bifidum, the growth of which is promoted by (betta-lactose of human milk. When complementary foods are introduced into the diet or the child is transferred to feeding with cow's milk, gram-negative Escherichia coli, which is a conditionally pathogenic microorganism, predominates in the intestine. therefore, dyspepsia is more often observed in formula-fed children.According to modern concepts, the normal intestinal flora performs three main functions: 1) creating 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.

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. Specific gravity 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 importance has an analysis of complaints, knowledge and consideration of the anatomical and physiological characteristics of the child's gastrointestinal tract.

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, at the opposite end, anus. 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 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 material 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 recent months 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 may contribute to the development of thrush of the oral mucosa when improper care for her. 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. Gastric lipase (produced by the pyloric region of the stomach) breaks down into acidic environment together with lipase of human milk 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 increased amount 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 better development circular muscles than longitudinal, 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 bacterial infection phase is 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.

Excursion to physiology

Throughout the entire period of intrauterine development, the digestive system of the fetus is in a state of relative inactivity. The fetus receives the nutrients necessary for its growth and development with maternal blood entering through the placenta. After the umbilical cord is cut, the supply of nutrients through this route is stopped, and there is a need for nutrition through the mouth.

The oral cavity of a newborn child is small, chewing muscles are well developed. In addition, the newborn has special fatty lumps in the thickness of the cheeks and a special structure of the mucous membrane of the lips, which are provided to facilitate the act of sucking and ensure the tightest capture of the breast nipple by the baby's mouth. The sucking reflex in healthy full-term newborns is fully developed, however, to strengthen it, it is necessary to early attachment baby to the breast, literally in the first minutes of life. If, due to some reasons, the child receives nutrition through the nipple in the first hours of life, then the muscles of the oral cavity “remember” the shape of the nipple, and the so-called “nipple” sucking is formed. This can make it much more difficult for the baby to get used to the mother's breast.

Another feature digestive system newborn is that the salivary glands located in the oral cavity are poorly developed, as a result of which saliva is secreted little, and the oral mucosa is not sufficiently moistened. Dryness of the oral mucosa makes it vulnerable to minor damage and infection. Easier infection is also facilitated by the fact that newborns almost completely lack the production of class A immunoglobulins - antibodies responsible for local protection of the mucous membranes, including the oral cavity. It is no coincidence that children in the first months of life so often develop thrush - an inflammatory disease of the oral mucosa caused by yeast fungi of the genus Candida.

Thrush causes the child to experience unpleasant, even painful, sensations when sucking. The baby may cry during feeding, refuse to breastfeed. The nutrient medium for the growth of these fungi is milk, therefore, when a white curdled plaque appears in the child’s mouth (on the mucous membrane of the cheeks, lips and tongue), it is necessary to remove milk residues after each feeding with a cotton swab dipped in a solution of baking soda (1/2 teaspoon per glass water). To do this, you need to purchase sterile cotton wool in a pharmacy and use it only to treat your mouth. But this procedure can be carried out only after consulting a doctor: if signs of thrush appear, you should contact your pediatrician.

The stomach of a newborn baby is located horizontally. The sphincter (muscular “lock”) of its inlet is poorly developed, and the sphincter that separates the stomach from the small intestine (pylorus), on the contrary, is quite well developed. That is why babies spit up so often. The volume of the stomach in a newborn child is very small and is only 30 ml, but gradually, as the baby grows, the capacity of his stomach also increases - in a month the stomach holds about 100 ml, at three - 150 ml, by six months - 200 ml, by year - 250 ml. In accordance with this, the feeding regimen should be organized.

The digestive glands of the stomach of a newborn produce gastric juice, but the activity of digestive enzymes is reduced, so the food that the baby receives should be easily digestible and easily digestible.

The intestines of a newborn are longer in relation to the entire body than in adults. The motor activity of the stomach and intestines of children in the first months of life is reduced due to muscle weakness, which explains the tendency of babies of this age to constipation. However, by four months, the motor activity of the intestine improves, which is manifested by the normalization of the stool and the gradual cessation of regurgitation.

After birth, the baby's intestines are filled with meconium - a thick, very dark-colored original feces. It accumulates in the intestines of the fetus throughout the entire period of intrauterine development and is released during the first two days of the baby's life. The intestine at the time of birth is sterile, its colonization with bacteria begins from the first hours of the baby's life and goes through several stages. The first stage of microbial settlement is very important, because the health of the baby for many months and years largely depends on which bacteria penetrate into the sterile intestines of a child who is still completely unfamiliar with microbes. By putting a baby to the breast in the first minutes of his life, by placing a newly born baby next to his mother, we enable his intestines to be populated by the microorganisms of the mother's body, which creates the basis for the correct formation of the microbial landscape.

The liver plays throughout life huge role in the implementation of the digestive process, releasing bile, which is involved in the digestion of food in the small intestine. At an early age of a child, the liver secretes bile in small quantities, so the inclusion of a baby in the diet is excessive fatty foods may lead to indigestion. In addition to producing bile, the liver plays a major role in the disposal of toxins. Considering the functional immaturity of the liver during the first months of a child's life, one should be especially careful when taking medications both by the infant and the breastfeeding mother.

How and what to feed?

Taking everything into account age features digestive system of a newborn, there is no doubt about the expediency and vital necessity breastfeeding from the very first minutes of a child's life. Mother's milk the best way suitable for baby feeding. Its composition is so balanced that this food is easily digested, minimizing the risk of allergic reactions. Besides, mother's milk has the most suitable temperature and is normally sterile, which makes the feeding process convenient for both mother and baby.

In the first three days after childbirth, colostrum is secreted from the mammary glands of the mother. Its composition is characterized by a high protein content and a higher energy value than mature milk. This makes sense because the amount of colostrum is small, the volume of the stomach of a newborn baby is very small. Receiving about 10 ml of colostrum in one feeding on the first day of life, the child satisfies his needs for nutrients, no additional feeding is required for the baby. Colostrum is a truly invaluable product for feeding children in the first days of life, for the reason that it contains immunoglobulins (antibodies) to many infectious diseases with which the mother had been ill during her life. Receiving colostrum, the child receives a kind of vaccination against these diseases.

On average with fourth day after childbirth, transitional milk begins to be secreted from the mammary glands of the mother. Gradually, the volume of the stomach of the newborn increases, and with it the amount of milk secreted from the mammary glands also increases. The content of proteins in its composition decreases, the content of carbohydrates gradually increases, the energy value approaches that of mature milk, which is produced from the end of the second week after the birth of a child. Thus, the mother's body regulates the compliance of the composition and quantity of milk with the needs of the newborn. During the period of lactation, it is very important cohabitation mother with a child so that she can apply the newborn to the breast in a free mode on demand. This stimulates lactation and ensures that the child gets used to the mother's breast.

From birth until the child is four to five months old, breast milk is the only necessary nutrition for the baby. In cases where insufficient milk is produced, it is necessary to continue to feed the baby on demand with obligatory night feedings until lactation improves. In those rare cases when hypogalactia (insufficient amount of milk in the mammary glands) is primary and true, it is necessary to decide on the introduction of supplementary feeding with artificial milk mixtures. Making such a decision is a very responsible step. In any case, it is necessary to consult a pediatrician in order for this decision to be justified and expedient.

There are some peculiarities of digestion in young children, so babies often suffer from hiccups, regurgitation, pain, coli. Parents just need to know about this so that the reaction to what is happening is adequate. It is the peculiarities of digestion in children that cause sleepless nights, frequent crying.

Let's look deeper: during the period of intrauterine development, all the necessary substances were delivered to the baby thanks to the placenta and umbilical cord, and in an already split form. Having been born, the child's body receives everything it needs with food, whether it is breast milk or milk formula. Problems arise in the background rapid growth and accelerated metabolic processes.

Salivary glands

To understand the problem, you need to know what the process of digestion is. As you know, it originates in oral cavity, where the main role is allocated to the salivary glands. The peculiarities of digestion in children during the neonatal period suggest a small amount of saliva secreted, because this is necessary due to the fact that this does not play a role for the absorption of milk. Excessive dryness of the lining of the oral cavity is the cause of weak salivation, and therefore there is a tendency to damage. By the way, by the age of four months, saliva secretion increases, but the baby still does not know how to swallow it, therefore, at this stage of development, it is noted.

Children's stomach

Features of digestion in children are also in the horizontal arrangement of the stomach, which persists for about a year. This is what causes regurgitation in the first months of a baby's life. This is also facilitated by poorly developed stomach muscles, as well as a wide entrance. Regurgitation also appears due to swallowing air during feeding, incorrectly organized feeding, incorrectly selected nipple.

As for the volume of the stomach, we can say that in relation to the body weight of the baby, it is up to 60 ml at the age of up to three months, then - 100 ml, and at the age of one year - two and a half times more.

Have you ever wondered why newborns don't eat the same things we do? It's all about, as well as the low activity of gastric enzymes. Digestion of food in the baby's stomach lasts no more than three hours (assuming breastfeeding), so babies often eat.

Intestine in digestion

The stomach is followed by the duodenum. Intestinal digestion is being used, where they are already taking Active participation and biliary system, and pancreas. Suction useful substances takes place in the intestine. The rate of movement of the contents through the intestines directly depends on the nature of feeding.

If the child is fed cow's milk, stool have a thick texture light color, specific smell. In infancy, it can occur from 2 to 5 times, and by the year - 1-2. This is due to the absolute sterility of the intestinal flora. The settlement of beneficial microorganisms occurs during the first days of life.