Features of the digestive system of preschool children. Features of the digestive system in children

Morphological and physiological characteristics digestive organs in children are especially pronounced in infancy. In this age period, the digestive apparatus is adapted mainly for assimilation breast milk, the digestion of which requires the least amount of enzymes (lactotrophic nutrition). A child is born with a well-defined sucking and swallowing reflex. The act of sucking is ensured by the anatomical features of the oral cavity of a newborn and infant. When sucking, the baby's lips tightly grasp the mother's breast nipple 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 child's oral cavity is relatively small and filled with the tongue. The tongue is short, wide and thick. When the mouth is closed, it comes into contact with the cheeks and hard palate. The lips and cheeks are relatively thick, with fairly developed muscles and dense fatty lumps of Bisha. There are roller-shaped 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 under 3-4 months of age. The oral mucosa is easily vulnerable, which should be taken into account when performing oral hygiene. The development of the salivary glands ends by 3-4 months, and from this time 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 saliva reaction in newborns is neutral or slightly acidic. From the first days of life it contains an amylolytic enzyme. It promotes 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 velum and is connected to the oral cavity; Thanks 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 into the stomach.

Esophagus. At the beginning of development, the esophagus has the appearance of a tube, the lumen of which is filled due to the proliferation of cell mass. At 3-4 months intrauterine development There is a formation of glands that begin to actively secrete. This promotes the formation of a lumen in the esophagus. Violation of the recanalization process is the cause of congenital narrowings and strictures of the esophagus.

In newborns, the esophagus is a spindle-shaped muscular tube lined with mucous membrane on the inside. The entrance to the esophagus is located at the level of the disc between the III and IV cervical vertebrae, by 2 years - at the level of the IV-V cervical vertebrae, at 12 years - at the level of the 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).

There are three anatomical narrowings in the esophagus - in the initial part, at the level of the tracheal bifurcation and the diaphragmatic one. Anatomical narrowing of the esophagus in newborns and children of the first year of life is relatively weakly expressed. Features of the esophagus include complete absence glands and underdevelopment muscle-elastic tissue. Its mucous membrane is tender and richly supplied with blood. Outside of the act of swallowing, the transition from the pharynx to 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 cardiac 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 midway between the navel and the xiphoid process. This position varies significantly 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 muscular layer, the nature of nutrition, and the influence of neighboring organs. In infants, the stomach is positioned horizontally, but as soon as the child begins to walk, it takes on a more vertical position.

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

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

The mucous membrane of the stomach is tender, rich in blood vessels, poor in elastic tissue, contains little digestive glands. The muscle layer is underdeveloped. There is scanty secretion of gastric juice, which has low acidity.

The digestive glands of the stomach are divided into fundic (main, parietal and accessory) glands that secrete hydrochloric acid, pepsin and mucus, cardiac (accessory cells) that secrete mucin, and pyloric (main and accessory cells). Some of them begin to function in utero (lining 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 enzyme in infants) curdles milk.

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

An important role in the implementation of the motor function of the stomach belongs to the activity of the pylorus, thanks to the reflex periodic opening and closing of which 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, and the gas bubble is enlarged. In infants, there may be an increase in the tone of the stomach muscles in the pyloric region, the maximum manifestation of which is pyloric spasm. Cardiospasm sometimes occurs in older people.

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

The intestine starts from the pylorus of the stomach and ends at the anus. There are small and large intestines. The first is divided into the 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 rounded shape. By the age of 12, it descends to the III-IV lumbar vertebra. The length of the duodenum up to 4 years is 7-13 cm (in adults up to 24-30 cm). In young children, it is very mobile, but by the age of 7, adipose tissue appears around it, which fixes the intestine and reduces its mobility.

In the upper part of the duodenum, the acidic gastric chyme is alkalized, prepared for the action of enzymes that come from the pancreas and formed in the intestines, 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 excluding 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 cecum, 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 a variable position, which depends on the degree of its filling, body position, intestinal tone and peritoneal muscles. Compared to adults, it is relatively long, and the intestinal loops lie more compactly due to the relatively large liver and underdevelopment of the pelvis. After the first year of life, as the pelvis develops, the location of the small intestinal loops becomes more constant.

The small intestine of an infant 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 intestinal features in infants and young children include:

· greater permeability of the intestinal epithelium;
· poor development of the muscle layer and elastic fibers of the intestinal wall;
· tenderness of the mucous membrane and a high content of blood vessels in it;
· good development of villi and folding of the mucous membrane with insufficiency of the secretory apparatus and incomplete development of the nerve pathways.

This makes it easier to develop functional disorders and favors the penetration into the blood of undigested components food, toxic-allergic substances and microorganisms.

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

The mesentery, which is very thin in newborns, increases significantly in length during the first year of life and descends along with the intestine. This, apparently, causes relatively frequent intestinal volvulus and intussusception in the child.

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

The large intestine is as long as the child is tall. The parts of the large intestine are developed to varying degrees. The newborn has no omental processes, the bands of the colon are barely visible, and haustra are absent until six months of age. The anatomical structure of the colon after 3-4 years of age is the same as in an adult.

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

The appendix in a newborn has a cone 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 a 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), and 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, length from 4 to 27 cm; By the age of 2, it approaches a horizontal position. The mesentery of the transverse colon is thin and relatively long, due to which the intestine moves easily when filling the stomach and small intestine.

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 poorly mobile and rarely has a mesentery.

The sigmoid colon is the most mobile and relatively long part of the colon (12-29 cm). Up to 5 years it is usually located in abdominal cavity due to an underdeveloped 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 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, the 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, young children often experience its loss.

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

The process of digestion, which begins in the mouth and stomach, continues in the small intestine under the influence of pancreatic juice and bile secreted into the duodenum, as well as intestinal juice. The intestinal secretory apparatus is generally formed. Even in the smallest children, the same enzymes are detected in the intestinal juice secreted by enterocytes 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 breakdown and absorption of nutrients are carried out with the combined action of intestinal juice, bile and pancreatic secretions.

Split 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 cavity intracellular digestion, adapted to lactotropic nutrition, and intracellular digestion, carried out by pinocetosis. The breakdown of foods occurs mainly under the influence of pancreatic secretions containing trypsin (acting proteolytically), amylase (breaks down polysaccharides and converts them into monosaccharides) and lipase (breaks down fats). Due to the low activity of the lipolytic enzyme, the process of fat digestion is especially intense.

Absorption is closely related to parietal digestion and depends on the structure and function of the cells of the superficial layer of the mucous membrane of the small intestine; it is the most important function of the small intestine. Proteins are absorbed in the form of amino acids, but in children in the first months of life they may be partially absorbed unchanged. Carbohydrates are absorbed in the form of monosaccharides, fats - in the form of fatty acids.

The structural features of the intestinal wall and its relatively large area determine in young children a higher absorption capacity than in adults, and at the same time, due to high permeability, insufficient barrier function of the mucous membrane. The easiest to digest components of human milk are the proteins and fats of which are partially absorbed undigested.

In the colon, 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 inhabiting the large intestine. The secretion of juice from the colon is insignificant; however, it increases sharply with mechanical irritation of the mucous membrane. Feces are formed in the large intestine.

The motor function of the intestine (motility) consists of pendulum-like 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 colon is also characterized by antiperistaltic movements that thicken and form feces.

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 a voluntary act. In the first 2-3 days after birth, the baby secretes meconium (original feces) of a greenish-black color. It consists of bile, epithelial cells, mucus, enzymes, and swallowed amniotic fluid. On days 4-5, stool takes on a normal appearance. Feces of healthy newborns who are natural feeding, have a mushy consistency, golden-yellow or yellow-greenish color, and a sour odor. The golden-yellow color of stool in the first months of a child’s life is explained by the presence of bilirubin, while the greenish color is due to biliverdin. In older children, stool is formed, 1-2 times a day.

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

The pancreas is a parenchymal organ of external and internal secretion. In a newborn, it is located deep in the abdominal cavity, at the level of the Xth thoracic vertebra, its length is 5-6 cm. In young and older children, the pancreas is located at the level of the Ith lumbar vertebra. The gland grows most intensively in the first 3 years and in puberty. By birth and in the first months of life, it is insufficiently differentiated, abundantly vascularized and poor in connective tissue. In a newborn, the head of the pancreas is the most developed. IN early age The surface of the pancreas is smooth, and by the age of 10-12 years, tuberosity appears, caused by the separation of the boundaries of the lobules.

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

Due to the different rate of increase in liver and body weight in children from 1 to 3 years of age, the edge of the liver emerges from under the right hypochondrium and is easily palpable 1-2 cm below the costal arch along the midclavicular line. From 7 years in a lying position bottom edge the liver is not palpable, and along the midline it does not extend beyond the upper third of the distance from the navel to the xiphoid process.

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 observed already in a 3-month-old fetus, but bile production at an early age is still insufficient.

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

The liver stores nutrients, mainly glycogen, but also fats and proteins. These substances enter the blood as needed. Individual cellular elements of the liver (stellate reticuloendothelial cells, or Kupffer cells, portal vein endothelium) are part of the reticuloendothelial apparatus, which has phagocytic functions and receives Active participation in the exchange of iron and cholesterol.

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

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

In young children, the liver is in a state of functional failure, its enzymatic system is especially incompetent, resulting in transient jaundice of newborns due to incomplete metabolism of free bilirubin formed during hemolysis of red blood cells.

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 splenic pulp is based on reticular tissue, which forms its stroma.

afo gastrointestinal tract in children

The beginning of the organization of digestion occurs on early stage embryonic development. Already by 7-8 days from the endoderm → the primary gut, from which on the 12th day 2 parts are formed: intraembryonic(future digestive tract), extraembryonic(yolk sac).

From the 4th week of embryogenesis, the formation of various sections begins:

from the foregut the pharynx, esophagus, stomach and part of the duodenum with the rudiments of the pancreas and liver develop;

from the midgut a part of the duodenum, jejunum and ileum is formed;

from the back– all parts of the large intestine develop.

afo

Oral cavity has features that ensure the act of sucking:

relatively small volume of the oral cavity;

big tongue;

good development of the muscles of the mouth and cheeks;

roller-like duplications of the gum mucosa;

fat bodies (Besh's lumps);

the salivary glands are underdeveloped.

Esophagus formed at birth. The entrance to the esophagus in a newborn is at the level between the III and IV cervical vertebrae, at 12 years old - at the level of VI-VII vertebrae. Funnel-shaped. The length of the esophagus increases with age. Anatomical narrowings are weakly expressed.

The transition of the esophagus to the stomach in all periods of childhood at the level of the X-XI thoracic vertebrae.

Stomach in infants it is located horizontally. As the child begins to walk, the axis of the stomach becomes vertical.

newborns have poor development of the fundus and cardiac region

the cardiac sphincter is very poorly developed, and the pyloric sphincter functions satisfactorily  tendency to regurgitate;

there are few glands in the mucosa  the secretory apparatus is underdeveloped and its functional abilities are low;

the composition of gastric juice is the same, but the acid and enzyme activity is lower;

the main enzyme of gastric juice is chymosin (rennet enzymes), which ensures the curdling of milk;

there is little lipase and its activity is low;

the timing of food evacuation from the stomach depends on the type of feeding;

Gastrointestinal motility is slow, peristalsis is sluggish;

physiological volume is less than anatomical capacity and at birth is 7 ml. On the 4th day – 40-50 ml, by the 10th day – up to 80 ml. By the end of 1 year – 250 ml, by 3 years – 400-600 ml. At the age of 4-7 years, the stomach capacity increases slowly, by 10-12 years it is 1300-1500 ml.

With the start of enteral nutrition, the number of gastric glands begins to increase rapidly. If a fetus has 150-200 thousand glands per 1 kg of body weight, a 15-year-old has 18 million.

Pancreas by birth the pancreas is not fully formed;

at birth the weight is  3 g, in an adult it is 30 times more. The gland grows most intensively in the first 3 years and during puberty.

at an early age, the surface of the gland is smooth, and by 10-12 years, tuberosity appears, which is due to the separation of the boundaries of the lobules. In newborns, the head of the pancreas is most developed;

trypsin and chymotrypsin begin to be secreted in utero; from week 12 – lipase, phospholipase A; amylase only after birth;

the secretive activity of the gland reaches the level of secretion of adults by 5 years of age;

Liver parenchyma is poorly differentiated;

lobulation is detected only by 1 year;

by 8 years, the morphological and histological structure of the liver is the same as in adults;

the enzymatic system is incompetent;

at birth, the liver is one of the largest organs (1/3 - 1/2 of the volume of the abdominal cavity, and weight = 4.38% of the total weight); the left lobe is very massive, which is explained by the peculiarities of the blood supply;

the fibrous capsule is thin, there are delicate collagen and elastic fibers;

in children 5-7 years old, the lower edge extends from under the edge of the right costal arch by 2-3 cm;

a newborn’s liver contains more water, but at the same time less protein, fat, and glycogen;

There are age-related changes in the microstructure of liver cells:

in children, 1.5% of hepatocytes have 2 nuclei (in adults - 8.3%);

the granular reticulum of the hepatocyte is less developed;

many freely lying ribosomes in the endoplasmic reticulum of the hepatocyte;

glycogen is found in the hepatocyte, the amount of which increases with age.

Gallbladder in a newborn it is hidden by the liver, has a spindle-shaped shape  3 cm. Bile is different in composition: low in cholesterol; bile acids, the content of bile acids in the liver bile in children aged 4-10 years is less than in children of the first year of life. At the age of 20 years, their content again reaches its previous level; salts; rich in water, mucin, pigments. With age, the ratio of glycocholic and taurocholic acids changes: an increase in the concentration of taurocholic acid increases the bactericidal activity of bile. Bile acids in the hepatocyte are synthesized from cholesterol.

Intestines relatively longer in relation to body length (in a newborn 8.3:1; in an adult 5.4:1). In young children, in addition, the intestinal loops lie more compactly, because the small pelvis is not developed.

in young children there is a relative weakness of the ileocecal valve, and therefore the contents of the cecum, the richest in bacterial flora, can be thrown into the ileum;

due to weak fixation of the rectal mucosa, prolapse can often occur in children;

the mesentery is longer and more easily extensible easily = torsion, intussusception;

short omentum  diffuse peritonitis;

the structural features of the intestinal wall and its large area determine a higher absorption capacity and, at the same time, an insufficient barrier function due to the high permeability of the mucosa to toxins and microbes;

In children of all ages, maltase activity of the mucous membrane of the small intestine is high, while its sucrase activity is much lower. Lactase activity of the mucosa, noted in the first year of life, gradually decreases with age, remaining at a minimum level in adults. Disaccharidase activity in older children is most pronounced in the proximal parts of the small intestine, where monosaccharides are mainly absorbed.

In children over 1 year of age, as in adults, protein hydrolysis products are absorbed primarily in the jejunum. Fats begin to be absorbed in the proximal ileum.

Vitamins and minerals are absorbed in the small intestine. Its proximal sections are the main site of absorption of nutrients. The ileum is a reserve zone of absorption.

The length of the large intestine in children of different ages is equal to the length of the child’s body. By the age of 3-4 years, the structure of the sections of the child’s large intestine becomes similar to the anatomy of the corresponding sections of the adult’s intestine.

Juice secretion by the glands of the large intestine in children is weakly expressed, but it increases sharply with mechanical irritation of the mucous membrane.

motor activity is very energetic (increased bowel movements).

By birth all enzymes membrane digestion, have high activity, topography of enzymatic activity throughout the small intestine or distal shift, which reduces the reserve capacity of membrane digestion. In the same time intracellular digestion, carried out by pinocytosis in children of the 1st year of life, is expressed much better.

Transient dysbacteriosis goes away on its own from the 4th day

60-70% - pathogenetic staphylococcus

in 30-50% - enterobacterial, Candida

10-15% - Proteus

Excreta:

Meconium (intestinal contents, I. Aseptic (sterile) phase).

accumulated before childbirth and before II. Phase of colonization by flora (disbacteri-

first breastfeeding; oz coincides with toxic erytherma).

consists of cells of intestinal III. The phase of displacement of bifidobacteria flora

epithelium, amniotic fluid). teria.

Transitional stool (after day 3)

Newborn stool (from the 5th day

birth).

Features of digestion in children

By birth, the salivary glands are formed, but secretory function is low for 2-3 months. Salivary α-amylase is low. By 4-5 months, profuse salivation is observed.

By the end of the 1st year, hydrochloric acid appears in the gastric juice. Among the proteolytic enzymes, the action of renin (chymosin) and gastricsin predominates. Relatively high activity of gastric lipase.

At birth, the endocrine function of the pancreas is immature. Pancreatic secretion increases rapidly after the introduction of complementary foods (with artificial feeding, the functional maturation of the gland is ahead of that with natural feeding). Particularly low amylolytic activity.

Liver at birth is relatively large, but functionally immature. The secretion of bile acids is small, at the same time, the liver of a child in the first months of life has a greater “glycogen capacity”.

Intestines in newborns, it seems to compensate for the insufficiency of those organs that provide distant digestion. Of particular importance is membrane digestion, the enzymes of which are highly active. The topography of enzymatic activity throughout the small intestine in newborns has a distal shift, which reduces the reserve capabilities of membrane digestion. In the same time intracellular digestion, carried out by pinocytosis, is expressed much better in children of the 1st year than in older children.

Rapid development occurs during the first year of life distant digestion, the importance of which increases every year.

Disaccharides (sucrose, maltose, isomaltose), like lactose, are hydrolyzed in the small intestine by the corresponding disaccharidases.

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Federal State Autonomous Educational Institution of Higher Professional Education "North-Eastern Federal University named after. M.K. Ammosova"

Medical Institute

discipline: “Hygiene”

On the topic: “Anatomical and physiological features of the digestive organs in children and adolescents”

Completed by: Gotovtseva

Ulyana Afanasyevna

Group: LD 306-1

Checked by: Fedoseeva

Lyudmila Romanovna

Yakutsk 2014

Introduction

Food contains substances that, without prior processing, cannot penetrate from the digestive organs into the blood. Food is exposed physical changes(grinding, grinding, moistening, dissolving) and chemical (digestion). The path through which food passes is called the digestive tract. Its length in humans is 6-8 m. The wall of the tract, consisting mainly of smooth muscle tissue, is covered from the inside with a mucous membrane. Its cells produce mucus. Food processing begins in the oral cavity: here it is moistened with saliva and crushed by the teeth.

Food entering the mouth and then into subsequent sections digestive system, undergoes complex physical and chemical transformations. And as a result of physical and chemical processing, nutrients are broken down into simpler ones and absorbed into the blood. Consequently, the importance of digestion lies in replenishing the body with the necessary building (plastic) substances and energy. digestion physiological esophagus intestinal

As the child grows and develops, the need for nutrients ah increases. At the same time, the body of young children cannot assimilate all foods. The child’s food in quantity and quality must meet the characteristics of digestive tract, satisfy his need for plastic substances and energy (contain in sufficient quantities necessary for the child proteins, fats, carbohydrates, minerals, water and vitamins).

The system of the digestive organs of children is not only functional, but also differs in linear dimensions and volume of cavities from the digestive organs of an adult.

1. The period of intrauterine formation of the digestive organs

The formation of the digestive organs occurs at a very early stage of embryonic development: from the 7th day to the 3rd month intrauterine life fetus By day 7-8, the organization of the primary intestine begins from the endoderm, and on the 12th day, the primary intestine is divided into 2 parts: intraembryonic (future digestive tract) and extraembryonic (yolk sac). Initially, the primary gut has oropharyngeal and cloacal membranes. At the 3rd week of intrauterine development, the oropharyngeal membrane melts, and at the 3rd month, the cloacal membrane melts. During development, the intestinal tube goes through the stage of a tight “cord”, when the proliferating epithelium completely closes the intestinal lumen. Then the process of vacuolization occurs, ending with the restoration of the lumen of the intestinal tube. When vacuolization is partially or completely impaired, the intestinal lumen remains (almost or completely) closed, leading to either stenosis or atresia and obstruction. By the end of 1 month. intrauterine development, 3 parts of the primary intestine are outlined: anterior, middle and posterior; the primary intestine closes in the form of a tube. From the 1st week, the formation of various parts of the digestive tract begins: from the foregut the pharynx, esophagus, stomach and part of the duodenum with the rudiments of the pancreas and liver develop; from the midgut, part of the duodenum, jejunum and ileum are formed, from the hindgut all parts of the large intestine develop.

In the antenatal period, the foregut develops most intensively and gives many bends. In the third month of intrauterine development, a process of movement of the small intestine (from right to left, behind the superior mesenteric artery) and large intestine (from left to right from the same artery) occurs, which is called intestinal rotation.

There are three periods of intestinal rotation:

1) turn 90°, the large intestine is on the left, the small intestine is on the right; 2) turn by 270º, the large and small intestines have a common mesentery; 3) fixation of the intestine ends, the small intestine acquires a separate mesentery.

If the process of intrauterine intestinal rotation stops at the first stage, midgut volvulus may occur. The time of occurrence of volvulus varies: from the intrauterine period to old age. If the second period of rotation is disrupted, the following may occur: failed intestinal rotation, duodenal obstruction and other anomalies. If the third stage of rotation is disrupted, the fixation of the intestine changes, which leads to the formation of mesenteric defects, as well as various pockets and bags, predisposing to strangulation of intestinal loops and internal hernias.

At the same time, vessels leading to yolk sac and intestinal tract. The arteries arise from the aorta. The veins go directly to the venous sinus.

At the 10th week, the formation of the gastric glands begins, but their differentiation, both morphologically and functionally, is not completed by the birth of the child.

Between the 10th and 22nd weeks of intrauterine development, the formation of intestinal villi occurs - most membrane digestive enzymes appear, but the activation of some of them, for example lactase, occurs only by 38-40 weeks of pregnancy.

From the 16-20th week, the system begins to function as a digestive organ: the swallowing reflex is already expressed, gastric juice contains pepsinogen, intestinal juice contains trypsinogen.

The fruit swallows and digests a large number of amniotic fluid, which is close in composition to extracellular fluid and serves the fetus additional source nutrition (amniotic nutrition).

2. Anatomical and physiological features of the digestive organs

The morphological and physiological characteristics of the digestive organs in children are especially pronounced in infancy. In this age period, the digestive apparatus is adapted mainly for the absorption of breast milk, the digestion of which requires the least amount of enzymes (lactotrophic nutrition). A child is born with a well-defined sucking and swallowing reflex. The act of sucking is ensured by the anatomical features of the oral cavity of a newborn and infant. When sucking, the baby's lips tightly grasp the mother's breast nipple 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.

Oral cavity. 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 muscles of the lips and masticatory muscles, transverse folds on the mucous membrane of the lips, roller-like thickening of the gums, in the cheeks there are lumps of fat (Bishat lumps), which give the cheeks elasticity.

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

Anatomical narrowing of the esophagus in newborns and children of the first year of life is relatively weakly expressed. Features of the esophagus include the complete absence of glands and insufficient development of muscle-elastic tissue. Outside of the act of swallowing, the transition from the pharynx to the esophagus is closed. The transition of the esophagus to the stomach in all periods of childhood is located at the level of the X-XI thoracic vertebrae.

Stomach. Located in the left hypochondrium, its cardiac 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 midway between the navel and the xiphoid process. In infants, the stomach is positioned horizontally, but as soon as the child begins to walk, it takes on a more vertical position.

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

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

The gastric mucosa is delicate, rich in blood vessels, poor in elastic tissue, and contains few digestive glands. The muscle layer is underdeveloped. There is scanty secretion of gastric juice, which has low acidity.

The digestive glands 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.

Functional deficiency 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 characteristics of the stomach correspond to those of an adult.

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

The jejunum occupies 2/5 and the ileum 3/5 of the length of the small intestine excluding the duodenum. There is no clear boundary between them.

Other intestinal features in infants and young children include:

· greater permeability of the intestinal epithelium;

· poor development of the muscle layer and elastic fibers of the intestinal wall;

· tenderness of the mucous membrane and a high content of blood vessels in it;

· good development of 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 facilitates the penetration into the blood of undigested 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.

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

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

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), and begins to increase after a year.

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 poorly mobile and rarely has a mesentery.

The sigmoid colon is the most mobile and relatively long part of the colon (12-29 cm). Until 5 years of age, 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 shortening of the mesentery and the accumulation of adipose tissue around it.

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

The intestinal secretory apparatus is generally formed. Even in the smallest children, the same enzymes are detected in the intestinal juice secreted by enterocytes as in adults (enterokinase, alkaline phosphatase, erepsin, lipase, amylase, maltase, nuclease), but their activity is low.

The infant has a special cavity intracellular digestion, adapted to lactotropic nutrition, and intracellular digestion, carried out by pinocetosis. The breakdown of foods occurs mainly under the influence of pancreatic secretions containing trypsin (acting proteolytically), amylase (breaks down polysaccharides and converts them into monosaccharides) and lipase (breaks down fats). Due to the low activity of the lipolytic enzyme, the process of fat digestion is especially intense.

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 a voluntary act. In the first 2-3 days after birth, the baby secretes meconium (original feces) of a greenish-black color. It consists of bile, epithelial cells, mucus, enzymes, and swallowed amniotic fluid. On days 4-5, stool takes on a normal appearance. The stool of healthy newborns who are breastfed has a mushy consistency, golden-yellow or yellow-greenish color, and a sour odor. The golden-yellow color of stool in the first months of a child’s life is explained by the presence of bilirubin, while the greenish color is due to biliverdin. In older children, stool is formed, 1-2 times a day.

The intestines of the fetus and newborn are free of 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 infants receiving breastfeeding, a normal level of intestinal microflora is achieved with a predominance of B. bifidus, with artificial feeding - B. Coli, B. Acidophilus, B Bifidus and enterococci.

The pancreas is a parenchymal organ of external and internal secretion. In a newborn, it is located deep in the abdominal cavity, at the level of the Xth thoracic vertebra, its length is 5-6 cm. In young and older children, the pancreas is located at the level of the Ith lumbar vertebra. The gland grows most intensively in the first 3 years and during puberty. By birth and in the first months of life, it is insufficiently differentiated, abundantly vascularized and poor in connective tissue. In a newborn, the head of the pancreas is the most developed. At an early age, the surface of the pancreas is smooth, and by the age of 10-12 years, tuberosity appears due to the separation of the boundaries of the lobules.

Due to the different rate of increase in liver and body weight in children from 1 to 3 years of age, the edge of the liver emerges from under the right hypochondrium and is easily palpable 1-2 cm below the costal arch along the midclavicular line. From the age of 7, in the supine position, the lower edge of the liver is not palpable, and along the midline it does not extend 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 at the end of the first year of life. The liver is full of blood, as a result of which it quickly enlarges during infection and intoxication, circulatory disorders and easily degenerates under the influence of unfavorable factors. By the age of 8, the morphological and histological structure of the liver is the same as that of 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 observed already in a 3-month-old fetus, but bile production at an early age is still insufficient.

The liver stores nutrients, mainly glycogen, but also fats and proteins. These substances enter the blood as needed. Individual 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 takes an active part in the metabolism of iron and cholesterol.

The liver performs a barrier function, neutralizes a number of endogenous and exogenous harmful substances, including toxins coming 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 the period of intrauterine development it is also a hematopoietic organ. In young children, the liver is in a state of functional failure, its enzymatic system is especially incompetent, resulting in transient jaundice of newborns due to incomplete metabolism of free bilirubin formed during hemolysis of red blood cells.

Features of the gallbladder in children

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

The main function of the gallbladder is the accumulation and secretion of hepatic bile. The composition of a child's bile differs from that of an adult. It contains little bile acids, cholesterol, salts, a lot of water, mucin, and pigments. During 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, and improves peristalsis.

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

For children in the first months of life, the nutrients that come with mother’s milk and are digested by substances contained in human 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. Fats cow's milk contain long-chain fats, which 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 rim of the intestinal epithelium. Women's milk contains lactose, cow's milk contains lactose. In this regard, during artificial feeding, the carbohydrate composition of food is changed. Vitamins are also absorbed in the small intestine.

3 . Prevention of gastrointestinal disorders

1. Rational and regular nutrition

· Dietary regimen, that is, adaptation of the nature of nutrition, frequency and frequency of food intake to the daily rhythms of work and rest, to the physiological patterns of the gastrointestinal tract. The most rational thing is to eat four meals a day at the same hours of the day. The interval between meals should be 4-5 hours. This achieves the most uniform functional load on the digestive apparatus, which helps create conditions for complete processing of food. It is recommended to have an evening meal of easily digestible food no later than 3 hours before going to bed. Dry food, snacks, and large evening meals have an unfavorable effect.

· Balanced diet, providing the body with daily intake of foods containing proteins, fats, carbohydrates, vitamins, minerals and trace elements. The diet should include: meat, fish, vegetables, fruits, milk and dairy products, herbs, berries, cereals. Dietary restrictions on easily digestible carbohydrates (sweets, baked goods), freeze-dried foods, animal fats, preservatives, dyes. Do not allow your child to consume chips, crackers, carbonated drinks (especially Coca-Cola, Fanta, Pepsi-Cola, etc.), chewing gum.

2. Wash your hands thoroughly with soap after: walking outside, traveling public transport, visiting the toilet; before eating.

3. Maintain personal hygiene and oral hygiene.

4. Eating well-washed vegetables and fruits, thoroughly fried meat, boiled water.

5. Increasing the body’s defenses: air baths, hardening, healthy image life (compliance with the daily routine, morning exercises, physical education, walking (according to SANP).

6. Dosed exercise stress(walking, swimming, tennis, cycling, skating and skiing, etc.).

7. Favorable psychological climate in the family and children's team.

8. Optimal forms of recreation and leisure activities.

9. When bathing a child in a pool, river, or sea, explain that the water should not be swallowed; An adult should ensure that the child does not swallow water.

10. Frequent ventilation premises.

11. Daily wet cleaning.

12. Carpets should be vacuumed daily, beaten out and wiped periodically wet brush, and dry clean once a year.

13. Toys in group I of early age should be washed twice a day with hot water, a brush, soap or a 2% solution of baking soda, in specially designed (marked) basins; then rinse with running water (temperature 37 degrees C) and dry. Toys for older children should be washed daily at the end of the day. Doll clothes are washed and ironed when dirty.

14. Annual examination of children for helminthic infestations.

15. Timely request for qualified medical care if a child has complaints.

16. Prevention Chronic gastritis(+ to the above):

Timely detection and treatment of foci of chronic infection;

Measures aimed at eliminating seasonal exacerbations.

Conclusion

Digestion is the process of breaking down food structures into components that have lost their species specificity and can be absorbed in the gastrointestinal tract.

One of the most important elements of the digestive system are teeth. In a child, they usually begin to erupt at 6-7 months of life.

The digestive organs begin to function long before birth. However, until the end of the prenatal period, the secretory function of the digestive tract is very weakly expressed, since there are no stimuli that stimulate secretion. The gastric juice of a newborn contains little pepsin, but is rich in chymosin, or rennet.

The newborn's stomach is located horizontally in the left hypochondrium. Its capacity is very small. Under the influence of incoming food, the stomach always stretches somewhat. Repeated stretching of the stomach with each feeding, as well as its motor activity, contribute to increased growth of the gastric wall.

The small intestine in newborns is only 2 times shorter than in adults. Digestive juices pouring into the small intestine already in the first days contain all the necessary enzymes that ensure the digestion process. The pancreas is relatively very small, and the juice it produces is less active than in subsequent months.

The child’s food, in its quantity and quality, must meet the characteristics of the digestive tract and satisfy its need for plastic substances and energy.

Bibliography

1. Kabanov A.N., Chabovskaya A.P. Anatomy, physiology and hygiene of children preschool age. ? M., Education, 1975.

2. Leontyeva N.N., Marinova K.V. Anatomy and physiology child's body. ? M., Education, 1986.

3. Lipchenko V.Ya., Samsuev R.P. Atlas of human anatomy. M., Alliance-V, 1998.

4. Matyushonok M.T., Turik G.G., Kryukova A.A. Physiology and hygiene of children and adolescents. ? Mn., Higher School, 1975.

5. Obreimova N.I., Petrukhin A.S. Fundamentals of anatomy, physiology and hygiene of children and adolescents. ? M., Academy, 2000.

6. Tonkova-Yampolskaya R.V. and others. Fundamentals of medical knowledge. ? M., Education, 1986.

7. Chabovskaya A.P. Fundamentals of pediatrics and hygiene of preschool children. ? M., Education, 1980

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The digestive organs include oral cavity, esophagus, stomach and intestines. The pancreas and liver take part in digestion. The digestive organs are formed in the first 4 weeks of the intrauterine period; by 8 weeks of pregnancy, all parts of the digestive organs are defined. 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 first-grade 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 ensure the act of sucking. These features are: small size of the oral cavity, large tongue, well-developed muscles of the lips and masticatory muscles, transverse folds on the mucous membrane of the lips, roller-like thickening of the gums, in the cheeks there are lumps of fat (Bishat lumps), which give the cheeks elasticity.

The salivary glands in children are not sufficiently developed after birth; Little saliva is produced in the first 3 months. The development of the salivary glands is completed by 3 months of life.

Features of the esophagusin children

The esophagus in young children has a spindle-shaped 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 - 18 cm. Its width, respectively, is at 7 years - 8 mm, at 12 years - 15 mm.

There are no glands on the mucous membrane of the esophagus. It has thin walls, poor development of muscle and elastic tissue, and is well supplied with blood. The entrance to the esophagus is located high. He has no physiological restrictions.

Features of the stomachin children

In infancy, the stomach is located horizontally. As the child grows and develops during the period when he begins to walk, the stomach gradually takes on a vertical position, and by the age of 7–10 years it is positioned 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 age in months.

A feature of the stomach in children is the poor development of its fundus and cardiac sphincter against the background good development pyloric department. This contributes to frequent regurgitation in the baby, especially when air enters the stomach during sucking.

The mucous membrane of the stomach is relatively thick, which is why the gastric glands are poorly developed. As the child grows, the active glands of the gastric mucosa are formed and enlarge 25 times, as in adults. Due to these features, the secretory apparatus in children of the first year of life is not sufficiently developed. The composition of gastric juice in children is similar to that of adults, but its acid and enzymatic activity is much lower. The barrier activity of gastric juice is low.

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

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

Absorption in the stomach is insignificant and concerns substances such as salts, water, glucose, and protein breakdown products are only partially absorbed. The timing of food evacuation from the stomach depends on the type of feeding. Human milk is retained 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 years it triples. The pancreas is located deep in the abdominal cavity at the level of the X thoracic vertebra; in older age, it is located at the level of the I lumbar vertebra. Her intensive growth occurs before age 14.

Dimensions 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 and vessels. Its capsule is less dense than that of adults and consists of fine fibrous structures. Its excretory ducts are wide, which provides good drainage.

The child's pancreas has exocrine and intrasecretory functions. It produces pancreatic juice, consisting of albumins, globulins, trace elements and electrolytes, enzymes necessary for digesting food. The enzymes include proteolytic enzymes: trypsin, chymotrypsin, elastase, as well as lipolytic enzymes and amylolytic enzymes. Regulation of the pancreas is provided by secretin, which stimulates the secretion of the liquid part of 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 performed through 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 large 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 liver weight increases 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) stores nutrients;

4) performs a barrier function;

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

6) in prenatal period is a hematopoietic organ.

After birth, further formation of the liver organs occurs. The functional capabilities of the liver in young children are low: in newborns, the metabolism of indirect bilirubin is not complete.

Features of the gallbladder in children

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

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

Dimensions 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 - 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 to the length of the body in a newborn is 8.3: 1, in the first year of life - 7.6: 1, at 16 years - 6.6: 1.

The length of the small intestine in a child of the first year of life is 1.2-2.8 m. The area of the internal surface of the small intestine in the first week of life is 85 cm2, in an adult - 3.3 x 103 cm2. The area of the small intestine increases due to the development of 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 and absorption of its ingredients occurs in the small intestine. The intestinal mucosa is rich in blood vessels, and 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 consists of different sections and develops after birth. In children under 4 years of age, the ascending colon is longer than the descending colon. The sigmoid colon is relatively longer. Gradually these features disappear. The cecum and appendix are mobile, the appendix is often located atypically.

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

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

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

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

Features of intestinal microflorain children

The fetal gastrointestinal tract is sterile. When contacting a child with environment it is colonized by microflora. The microflora in the stomach and duodenum 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, the growth of which is stimulated by lactose in breast milk. During artificial feeding, opportunistic gram-negative Escherichia coli dominates in the intestine. 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

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.

The duodenum in newborns has the shape of a ring. By six months, her descending and ascending sections are determined. The duodenum in children is mobile.

Digestion in the duodenum in children, as in adults, occurs under the influence of pancreatic juice, intestinal juice and bile. The contents of the stomach in the form of food gruel, soaked in acidic gastric juice, partially digested, are moved by movements of the stomach to its pyloric section and pass in portions from the stomach into the duodenum, where the common bile duct and pancreatic duct open. A mixture of secretions from the pancreas, duodenum and liver forms duodenal juice. The activity of duodenal juice enzymes increases with age.

Pancreas. Unlike the stomach, the cellular development of the pancreas ends in the first months of a child’s life, which explains its special importance in the early period of development, since the pancreas is the main place for the production of digestive enzymes. During the first year of life, the mass of the pancreas increases 3 times, and pancreatic secretion increases 10 times. The growth and development of the pancreas continues up to 11 years.

Pancreatic juice contains:

? enzymes: trypsinogen, amylase, maltase, lipase (nuclease is absent in children);
? inorganic substances: salts of sodium, potassium, calcium, iron and others, creating an alkaline reaction in the juice.

The mechanism for regulating juice secretion is the same as in adults: humoral (secretin, cholecystokinin) and reflex. The humoral mechanism in children plays the greatest role in the process of regulating digestion.

The liver has insufficient parenchymal differentiation. Liver cells in children are smaller than in adults. Lobulation in the structure of the liver is detected already by the first year of life. Liver is rich in iron.

From the age of eight, the liver has almost the same structure as that of an adult. The liver size in children is relatively larger (4% of body weight) than in adults (2.5%).

The functions of the liver (especially barrier and antitoxic) in the first years of a child’s life are not sufficiently developed, this also applies to storage (in relation to the regulation of the amount of circulating blood) and regulatory (in relation to carbohydrate, fat and water-mineral metabolism) functions.

Bile formation is observed already in a three-month fetus. The intensity of bile formation and bile secretion increases with age. Bile is rich in water, mucin, pigments, and, during the neonatal period, urea, but is poor in bile acids, cholesterol, lecithin and salts, which causes insufficient absorption of fats when feeding with milk. The amount of bile secreted in a child relative to his weight is 4 times greater than in an adult.

The small intestine in children is relatively longer than in adults and has a well-developed mucous membrane with a weak muscle layer. The length of the intestine in an infant is 6 times greater than the length of the body (in an adult - 4.5 times). The most vigorous growth of the small intestine is observed in the first five years, especially between the ages of one and three years due to the transition from dairy foods to a mixed diet.

The mucous membrane is thinner, more delicate, but the folding is well expressed, there are fewer villi, the intestines have a well-developed circulatory and lymphatic system. The villi of the small intestine and the lymphatic apparatus are well developed, the myelination of the nerve plexuses is not complete, the enzymatic power of the digestive glands is insignificant in newborns, but increases with age. The muscle layer and elastic fibers in the intestinal wall are poorly developed. Intestinal juice contains all the enzymes necessary for intestinal digestion, and unlike older children, they are less active, i.e. there is some insufficiency of the secretory apparatus.

Composition of intestinal juice:

? mucus - 40-50%, NaHC0 3 - 2%, NaCl - 0.6% (juice reaction is alkaline, ranges from 7.3 to 7.6);
? enzymes: erepsin, lipase, amylase, maltase, sucrase, nuclease, enterokinase, alkaline phosphatase (about 22 in total).

Lactase in the small intestine hydrolyzes lactose in cow's milk more easily than in women's milk (with a deficiency of this enzyme, undigested lactose increases the osmotic pressure of the chyme, which leads to diarrhea and dehydration). With the transition to definitive nutrition, the synthesis of maltase and sucrase increases, and lactase production decreases. Proteins in human milk are more fully absorbed in the intestines (90-95%) than in cow's milk (60-70%). When feeding vegetables early, the activity of enterokinase and alkaline phosphatase increases, causing a retention of calcium and magnesium salts in the body. Regulation of intestinal secretion is carried out by reflex and humoral pathways.

In infancy, the low intensity of cavity digestion is compensated by the high activity of membrane digestion. A relatively large portion of the small intestine is involved in nutrient hydrolysis. Its mucous membrane is highly permeable, so not only low molecular weight, but also high molecular weight substances such as immunoglobulins and breast milk hormones are easily absorbed by the child. However, this circumstance, combined with the low level of hydrochloric acid production in the stomach, is the cause of easy development of poisoning when low-quality food enters the gastrointestinal tract.

Thus, the anatomical and physiological characteristics of the children’s intestines contribute to the easy occurrence of functional disorders its motility and secretion.

The fetal large intestine is sterile and colonization by microorganisms occurs on the first day of life. Stabilization of the microflora occurs by the second week. The mucous membrane does not produce cavity enzymes. Digestion is carried out by enzymes coming from the small intestine. The breakdown of chyme occurs due to the activity of the intestinal microbial flora, which has protective antitoxic functions, affects the rate of renewal of epithelial cells, participates in the inactivation of physiologically active substances and enzymes, and promotes the synthesis of vitamins.

Rotting in the intestines of healthy people infants the first months of life is completely absent, and they do not produce such toxic products as indole, skatole, phenol, etc. In the intestines of older children, processes of both fermentation and putrefaction simultaneously occur. Their nature and intensity depends on the characteristics of the child’s food and intestinal bacterial flora.

Between the ages of 10 and 15, intestinal growth occurs again, mainly due to the large intestine.

The motor function of the intestines is low: with breastfeeding, chyme is evacuated in 12-13 hours, with mixed feeding - in 14.5 hours, with artificial feeding - in 16 hours, if the food is vegetable - in 15 hours. This partly explains the tendency to constipation in children. However, the total time for food to pass through the gastrointestinal tract in a child is less than in an adult, which depends on the relative length of the digestive tract, as well as on the type of feeding.

Thus, the functions of the gastrointestinal tract in children are subject to the same physiological laws as in adults. The breakdown of food, which begins in the mouth and stomach, continues in the intestines. Peptones and a certain amount of native (natural, retaining their structure) proteins that have not yet been broken down in the stomach undergo peptic digestion, partly bringing them to the stage of amino acids, partly to the stage of polypeptides of varying complexity. The latter undergo hydrolysis due to the action of erepsin. The effect of trypsin in children is more significant than that of pepsin, since peptic digestion at an early age is of secondary importance.

Gastric, pancreatic and intestinal lipase, in combination with human milk lipase, break down fats into fatty acids and glycerol. The aminolytic action of the pancreas is significantly expanded and supplemented by maltase, lactase, invertase and other enzymes.

In children, as in adults, there is parietal digestion, which is even more active than cavity digestion. In newborns, unlike older children, fermentation rather than putrefaction predominates.

Consequently, the immaturity of the child’s digestive system is expressed in the insufficiency and originality of the enzymatic apparatus in various parts of the gastrointestinal tract. This feature requires a kind of nutrition, especially during the first year of life. Great importance have a frequency of feeding the child during the day, recording the quantity and chemical composition milk consumed by the child.