Diseases of the gastrointestinal tract (GIT): how to recognize the enemy in time? Colic in newborns The gastrointestinal tract is formed in a newborn.

Date: 04.03.2020

The viability of the newborn is determined by the successful transition from the period of intrauterine development to the neonatal period of life... The main determining factor in this process is the functional maturity of the gastrointestinal tract (GIT), which is able to provide adequate nutrition. After the birth of a child, his gastrointestinal tract is adapted to the absorption of breast milk and the components it contains, ensures the elimination of foreign antigens, pathogenic microorganisms, as well as some xenobiotics from the body, colonization with intestinal microflora and, together with the kidneys, maintains the necessary water balance.

Have full-term newborns these mechanisms are fully formed and ensure the normal growth and development of the child.

Majority adaptive mechanisms by the time of birth, they function well, however, the final formation of some (for example, the binding and excretion of bilirubin and the metabolism of drugs in the liver) is completed only at the beginning of the neonatal period. After birth, the interaction of the initially sterile gastrointestinal tract with the microorganisms colonizing it is the main stage in the postnatal development of the digestive system.

Relatively late after childbirth, the structure is formed and the function of the esophageal sphincter is established, the secretory function of the stomach is the production of acid and gastric peristalsis, as well as endocrine factors, the absorption of glucose, vitamin B12 and bile salts in the intestine, the formation and accumulation of bile acids, the secretory response in response to action of bacterial toxins. The exocrine function of the pancreas is established approximately 6 months after birth. Endocrine function, expressed in the production of insulin, over a relatively long time interval.

In detail morphogenesis of the gastrointestinal tract human development is described in fundamental guidelines, and GI development has been discussed in detail in several reviews. This chapter provides a detailed description of morphogenesis with an emphasis on modern concepts of the molecular mechanisms of the development of the gastrointestinal tract. The main stages of the structural and functional development of the gastrointestinal tract are summarized in the table.

Stages of development of the gastrointestinal tract in the fetus

Stage	Minimum gestation period
Gastrulation	3rd week
Formation of the primary gut; anlage of the liver and pancreas	4th week
Intestinal tube growth	7th week
Intestinal villi formation	8th week
Immersion of the primary intestine into the abdominal cavity	10th week
Completion of organogenesis	12th week
The appearance of gastric parietal cells, the formation of islets of the pancreas, the secretion of bile, the appearance of intestinal enzymes	12th week
The appearance of swallowing movements	16-17 weeks
Functional maturity	36th week

In the process of cell division from a fertilized egg a blastocyst is formed... The embryo itself develops from the inner cell mass (a compact accumulation of cells on one of the blastocyst walls). Subsequently, the inner cell mass is divided into two layers - the epiblast and the hypoblast, forming a two-layer embryonic disc, from which the embryo develops. At the beginning of the 3rd week of pregnancy, a primary stripe forms, which is a median depression on the surface of the epiblast near the caudal part of the embryonic disc. In the process of gastrulation, the cells located along the primary stripe separate and migrate deeper into the space between the two germ layers.

The gastrulation process leads to the formation of cells endoderm, from which further the formation of the inner lining of the entire gastrointestinal tract occurs. Some of the cells, migrating from the area of the primary stripe, push back the lower germ layer (hypoblast) and form the endoderm. It is in the process of gastrulation that bilateral symmetry of the embryo is established, and the ventral / dorsal (anterior / posterior) and craniocaudal axes of the embryo are formed. The formation of three germ layers is accompanied by the formation of clusters of cells of the same type, from which subsequently, after a cascade of induction interactions, the development of the embryonic organs occurs.

Currently, the molecular mechanisms of most of the listed processes have been studied.

Formation of the intestinal tube occurs as a result of two processes - growth and separation of the embryonic part from the extraembryonic. Tissue sheets formed during the 3rd week of pregnancy continue to differentiate, resulting in the formation of the rudiments of most organ systems. The formation of the trunk folds separating the embryonic and extraembryonic parts, and the rotation of the embryo are very complex processes that are caused by the different growth rates of different parts of the embryo.

As a result of these processes flat germ disc transforms into a three-dimensional structure and the head, lateral and caudal edges of the embryonic disc are located in a certain way relative to the midline ventral line. Subsequently, the layers of endoderm, mesoderm and ectoderm from opposite sides are connected to each other, resulting in the formation of an intestinal tube.

Process formation of trunk folds first leads to the closure of the intestinal tube in the region of the head and caudal ends of the embryo. In the anterior and posterior parts of the developing intestinal tube, the anterior and posterior intestinal gates are formed. Initially, the gut consists of blindly ending cranial and caudal tubes, the anterior gut and the hind gut, which will subsequently be divided by the midgut. The midgut remains associated with the yolk sac. As the lateral trunk folds of the embryo join along the midline ventral line, the midgut rapidly transforms into a tube.

Yolk sac neck undergoes reverse development, turning into the vitelline canal. Sometimes parts of this channel do not undergo reverse development and a Meckel diverticulum is formed.

Below diaphragms three pairs of large blood vessels are formed, which should provide blood supply to the developing abdominal part of the intestinal tube. The zones of blood supply of these arterial trunks constitute the anatomical basis of the division of the abdominal gastrointestinal tract into the anterior, middle and posterior colon. The first artery is the celiac artery, or celiac trunk. As a result of the development of this vessel, arterial branches are formed that supply the anterior intestine with blood from the abdominal esophagus to the descending segment of the duodenum, as well as the liver, gallbladder and pancreas.

Liver development, gallbladder and pancreas also comes from the anterior gut. Due to the superior mesenteric artery, the developing midgut is supplied with blood - from the descending part of the duodenum to the transverse colon. The inferior mesenteric artery is involved in the blood supply to the posterior intestine - the terminal section of the transverse colon, descending, sigmoid and rectum. The separately formed lower part of the anorectal canal is supplied with blood by the branches of the iliac arteries.

At the beginning 4th week of gestation the caudal foregut, located just behind the diaphragm, expands slightly and the stomach begins to form. In the area of the specified fusiform expansion, the posterior wall of the anterior intestine grows faster than the anterior wall, as a result of which a greater curvature of the stomach occurs during the 5th week. The fundus of the stomach is formed due to the continuing characteristic protrusion of the upper part of the greater curvature of the stomach. During the 7th and 8th weeks of gestation, the forming stomach rotates around the longitudinal axis of the embryo by 90 °.

As a result, a peculiar left side of the ventral surface and the right side of the dorsal surface of the stomach are formed. The anterior surface of the stomach in adults is innervated by the left, and the posterior surface is innervated by the right vagus nerve. Subsequently, additional rotation of the stomach along the anteroposterior axis leads to the fact that the greater curvature of the stomach is slightly displaced in the caudal direction, and the lesser curvature is directed towards the head of the embryo.

About 3rd week gestation bowel is a relatively straight tube, divided into three parts: the anterior intestine, from which the pharynx, esophagus, stomach and the initial sections of the duodenum subsequently develop; the middle intestine, communicating along the anterior surface with the yolk sac, subsequently giving rise to the remaining part of the duodenum, small and initial sections of the large intestine; the hindgut is further transformed into the distal colon and rectum. The rudiments of the liver and pancreas are formed on the border of the anterior and middle intestine.

Rapid growth of the midgut leads to its elongation and rotation. By 5 weeks of gestation, the intestine is pulled out and begins to form a loop, which protrudes along with the umbilical cord. Shortly thereafter, the ventral anlage of the pancreas rotates and merges with the dorsal anlage. At 7 weeks, the formed small intestine begins its rotation around the axis formed by the superior mesenteric artery. Rotation is carried out counterclockwise (when looking at the embryo from the front surface) by about 90 °. Starting from 9 weeks, further growth of the intestinal tube leads to a hernial protrusion in the umbilical ring.

Middle intestine continues its turn and lengthening, as a result of which it again plunges into the abdominal cavity. By about 10 weeks of gestation, the bowel rotation angle reaches 180 °. By about 11 weeks, the rotation process continues by another 90 °, reaching a total of 270 °, after which the intestine sinks into the abdominal cavity. This phenomenon is caused not only by intestinal growth processes, but also by regression of the primary kidney and a slowdown in the growth rate of the liver. The mechanism of the process of reverse immersion of the small intestine into the abdominal cavity is not fully understood, but it occurs very quickly. The jejunum sinks first and occupies the left half of the abdominal cavity.

Ileum when immersed, it is located in the right half of the abdominal cavity. In the last place, the initial sections of the large intestine are immersed. The cecum is fixed near the iliac crest, and the ascending and transverse colon are located obliquely in the abdominal cavity - in the direction of the splenic angle. Further development of the colon leads to its elongation and the formation of the hepatic angle and the transverse colon itself. The ordering of the organs in the abdominal cavity is completed after fixation of the ascending colon in the area of the right lateral pocket. This phenomenon is the basis for the formation of a complex innervation and blood supply to the gastrointestinal tract in adults. The main stages of this process are completed by 12 weeks of gestation.

Cloaca serves as the basis for the formation of the rectum and urogenital sinus. In the early stages of embryogenesis, the terminal part of the hind gut protrudes, leading to the formation of a cloaca. In the period between the 4th and 6th weeks of gestation, due to the development of the urerectal septum, the cloaca is divided into the posterior section (rectum) and the anterior section (primary urogenital sinus). Accordingly, the upper and lower parts of the anorectal canal have different embryonic origins. The primary membrane of the cloaca, due to the urerectal septum, is divided into the anterior (urogenital membrane) and posterior (anal membrane). The anal membrane separates the sections of the anorectal canal that form from the endoderm and ectoderm.

Primordial position the anal membrane, which is opened during the 8th week of gestation, corresponds to the scallop line in adults. The terminal parts of the hindgut give rise to the upper 2/3 of the anorectal canal, while intussusception of the ectoderm or proctodeum forms the basis for the lower third of this canal. Some structural abnormalities, such as a non-perforated anus, occur as a result of violations of the described process. The scallop line also represents the border of the blood supply basins of the upper and lower segments of the anorectal canal. The upper (in relation to the scallop line) sections of the anorectal canal are supplied with blood by the branches of the inferior mesenteric artery, and venous drainage is carried out by the veins of the posterior intestine.

Segment located below the scallop line, blood is supplied by the branches of the internal iliac arteries and veins. The innervation of the anorectal canal also reflects the different embryonic origins of its upper and lower sections: the upper section is innervated by the inferior mesenteric ganglion and pelvic celiac nerves, the lower section - by the branches of the inferior rectal nerve.

Hepatic diverticulum initially appears as a small kidney in the caudal foregut. During embryogenesis, the specification of the liver, bile ducts, and pancreas follows an ordered pattern. The liver, gallbladder, pancreas, and duct system develop from endodermal diverticula that bud off from the duodenum between the 4th and 6th weeks of gestation.

At about 30th day of embryonic development the pancreas is represented by two anlages - dorsal (posterior) and ventral (anterior), originating from the endoderm on opposite sides of the duodenum. The dorsal anlage grows faster. In this case, the ventral anlage grows in the direction from the duodenum along the developing common bile duct. Due to the fact that the growth of the duodenum in different parts is not the same, the intestine rotates, as a result of which the anterior anlage of the pancreas moves posteriorly and adjoins the posterior anlage in the region of the dorsal mesentery of the duodenum.

Combining two bookmarks occurs at a gestational age of about 7 weeks. The head and uncinate process of the definitive pancreas develop from the anterior anlage, while the remainder of the body and tail originate from the posterior anlage. Subsequently, the outflow ducts of both anlages merge together and form a Wirsung duct. However, the proximal duct of the posterior pancreas is usually preserved as an accessory Santorini duct. Structural abnormalities such as the annular pancreas are caused by abnormalities in the formation of the pancreas.

Prevertebral sympathetic ganglia develop near the origin of the main branches of the descending aorta. The postganglionic sympathetic axons of the ganglia grow in the peripheral direction along the arterial trunks and innervate the same tissues that are supplied with blood by these vessels. Postganglionic fibers of the celiac ganglion innervate the gastrointestinal tract, developing from the distal segment of the anterior intestine - from the abdominal esophagus to the level of the bile duct orifice in the duodenum. The fibers of the superior mesenteric ganglion are involved in the innervation of the derivatives of the midgut (the remaining segment of the duodenum), the jejunum, the ileum, the colon (ascending colon) and the proximal 2/3 of the transverse colon. Due to the lower mesenteric ganglion, the departments developing from the hind gut are innervated: the distal third of the transverse colon, the descending colon, the sigmoid colon and the upper 2/3 of the anorectal canal.

Digestive tract- phylogenetically, the most ancient system of internal organs - develops mainly from the endoderm. But it forms only the leading, functionally main part of it, namely the inner shell. The initial and insignificant terminal parts of this tract are formed by invaginating ectoderm.

In the embryo, the digestive organs are laid in the form of a longitudinal groove of the endoderm, which protrudes towards the notochord. By closing the ventral edges of this groove at 4 weeks of embryonic development, a primary intestinal tube appears, blindly closed at both ends. At the head end, it abuts against the bottom of the oral fossa, which is a deep invagination of the ectoderm. Soon, the membrane between the oral fossa and the head end of the intestine, consisting of a layer of ectoderm and endoderm, erupts; the oral cavity and pharynx begin to develop. A little later, the posterior end of the tube breaks into the ectodermal anal fossa, from which the final part of the rectum with the anus is formed. The primary intestinal tube in the embryo is divided into the head and trunk intestines. The middle part of the intestine is connected with the yolk sac, and the allantoic outgrowth is clearly visible in its posterior part.

In the process of development, the intestine lengthens, some of its parts move from the starting position. In the process of histogenesis, functional maturation of the gastrointestinal tract occurs. In this case, the endodermal anlage gives rise to the epithelial lining and the glands associated with it, and the connective tissue, blood vessels and the muscular membrane of the intestine are formed from the mesodermal layer.

Head intestine in the process of further development, it undergoes very complex transformations. They begin with the appearance on the lateral walls of its initial section of protrusions - pharyngeal pockets, towards which gill furrows grow from the side of the body integument (ectoderm). In fish, at the junction of the pharyngeal pockets and gill furrows, gill slits with gill arches located between them are formed. In the higher vertebral clefts, with the exception of the first, does not arise, visceral and branchial arches appear, pockets are laid. At the site of the first branchial cleft, the auditory tube, the middle ear cavity and the auditory canal later develop.

In a 30-day-old human embryo, 4 pairs of pharyngeal pockets are formed in the pharyngeal region (Fig. 4.25). The cells that form the pockets migrate into the surrounding tissues and undergo further differentiation. The tympanic cavity and the Eustachian tube are formed from the material of the first pharyngeal pocket. The outgrowth on the ventral pharyngeal wall at the border of the first and second pharyngeal pockets gives rise to the thyroid gland. In the area of the second pair of pharyngeal pockets, accumulations of lymphoid tissue arise, from which the palatine (pharyngeal) tonsils develop. The third and fourth pairs of pharyngeal pockets give rise to the parathyroid and thymus glands. The salivary glands, the anterior lobe of the pituitary gland, the mucous membrane of the oral cavity and tongue develop from the wall of the oral fossa (i.e., due to the ectoderm). The muscles of the tongue arise from the occipital myotomes.

Trunk intestine The embryo is first a straight tube that starts behind the pharyngeal pockets and ends in the anus. The section of the tube that lies between the rudiment of the trachea and the diaphragm turns into esophagus. During 7-8 weeks of embryogenesis, the cells of the epithelium of the esophagus divide intensively, its lumen is almost completely closed. Later, it reappears due to the growth of the esophageal wall and partial death cells in its lumen. The growth of the esophagus in length occurs in parallel with the increase in the size of the lungs and heart in the chest cavity and the lowering of the diaphragm.

The part of the tube located behind the diaphragm expands and forms stomach. In the early stages of development, the stomach is located almost vertically and is connected by the dorsal and ventral mesentery to the walls of the body. The expanding stomach rotates around the longitudinal axis so that its left side becomes anterior, the right - posterior, the longitudinal axis takes an almost transverse position. At the same time, its dorsal mesentery is pulled out and forms a cavity - an omental bursa.

At the end of 2 months of intrauterine development, the formation of the gastric mucosa begins. Folds, pits appear, and then the glands associated with them. From 3 months, secretory cells begin to appear, but neither acid nor pepsin is released into the stomach cavity yet. Although cells acquire the ability to produce enzymes and hydrochloric acid even in the prenatal period, they begin to function actively only after birth.

A newborn has a stomach capacity of 7-10 ml, it cannot function as a depot of nutrients. During the first three weeks, the volume of the stomach increases to 30-35 ml, and by the end of the year up to 250-300 ml. A newborn's stomach may contain a small amount of amniotic fluid. During the first years of life, the shape and volume of the stomach, as well as the glands of its mucous membrane, develop intensively. This is primarily due to the transition from milk feeding to mixed food. By the age of 1 year, the shape of the stomach becomes oblong from rounded, and then, by the age of 7-11, it takes the shape characteristic of adults. In newborns, the mucous membrane is less folded than in adults, the glands are poorly developed, have a wide lumen and a small number of secretory cells.

The part of the intestinal tube of the fetus between the stomach and the anus becomes into the intestines. The border of the small and large intestine passes approximately near the place where the yolk stalk originates. By lengthening rapidly, the intestine bends, loses its middle position and forms loops. The small intestine coagulates spirally and forces the colon against the wall of the abdominal cavity. At the border between the small and large intestine, the rudiment of the cecum is outlined.

The ventral mesentery is preserved only on the stomach and duodenum.

From the outgrowth of the intestine, penetrating between the sheets of its mesentery, the liver develops. The same outgrowth in the dorsal direction gives rise to the pancreas.

The liver is laid already at the end of 1 month of embryogenesis. It is an endodermal protrusion of the intestinal wall that grows into the mesentery. The gallbladder is formed from the caudal hepatic outgrowth. Its cranial part forms numerous branched epithelial cords, from which the hepatic ducts are formed. Blood vessels from the yolk vein grow into the endodermal anlage of the liver from the surrounding mesoderm. It subsequently develops into a portal vein.

The liver of the fetus grows faster than other abdominal organs. Starting from the second month, it becomes a hematopoietic organ in which erythrocytes, granulocytes and platelets develop. In a six-month-old fetus, bile secretion begins. In a newborn baby, the liver occupies half of the abdominal cavity, and its relative weight is twice that of an adult. By contrast, the gallbladder in infants is relatively small. After birth, the liver stops hematopoietic activity.

The pancreas develops in the form of a paired bookmark at the end of 1 month of intrauterine development. The ventral anlage arises from the hepatic outgrowth, and the dorsal - from the duodenal wall

directly behind the stomach. As the anlages grow and the bowel curves form, both outgrowths come closer together, and later merge. In the adult state, in most people, the dorsal anlage of the gland loses its duct, and only 10% of this duct remains.

At the beginning of 2 months of intrauterine development, the formation of the mucous membrane of the small intestine begins. Due to the formation of folds of the epithelium, intestinal villi are formed. During the fetal period, digestive enzymes are synthesized in the cells of the mucous membrane. They are released in a small amount into the lumen.

In newborns and children 1 year of age, the relative length of the small intestine is longer than in adults, the mucous and muscular membranes are thinner, the number of folds, the size and number of villi are smaller. The formation of the elements of the autonomic nervous system lasts up to 3-5 years. The intestines grow intensively in the period from 1 to 3 years in connection with the transition from dairy to mixed food.

In the prenatal period of development (in a 4-month-old fetus), the lumen of the large intestine is much smaller than that of the small intestine, the inner surface is covered with folds and villi. As the intestine develops, the folds and villi are gradually smoothed out and are no longer present in the newborn. Until the age of 40, the intestinal mass gradually increases, and then begins to decrease, mainly due to the thinning of the muscular membrane. In older people, the lumen of the appendix can be completely overgrown.

Lymphoid system represented by the thymus gland, spleen, lymph nodes, circulating lymphocytes, accumulations of lymphoid cells in the tonsils, Peyer's patches of the ileum.

Functions are not well understood. The spleen is the main site of destruction of senescent red blood cells and platelets. It contains partial synthesis of immunoglobulins and antibodies. Lymph nodes are formed from the 2nd month of intrauterine development: first, cervico-subclavian, pulmonary, retroperitoneal, inguinal. The final formation (follicles, sinuses, stroma) continues in the postnatal period. After birth, in connection with antigenic stimulation, the embryonic centers of the lymphoid follicles are enlarged. In the first year, the capsule and trabeculae are insufficiently developed, which creates difficulties in palpation. Their maximum number is reached by the age of 10. The function of the lymph nodes is a barrier; bacteria, foreign bodies brought in with the flow of lymph, are retained in the sinuses of the lymph nodes and are captured by macrophages. In children of the first 2 years of life, the barrier function of the lymph nodes is low, which leads to the generalization of the infection. The first accumulations of lymphoid tissue in the gastrointestinal tract appear in 3-4 months of intrauterine development. The lymphoid apparatus of the gastrointestinal tract (GIT) plays an essential role not only in the synthesis of serum immunoglobulins, but also in local immunity, which protects the body from invasion of infectious agents.

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The digestive tract - phylogenetically the most ancient system of internal organs - develops mainly from the endoderm. But it forms only the leading, functionally main part of it, namely the inner shell. The initial and insignificant terminal parts of this tract are formed by invaginating ectoderm. In the embryo, the digestive organs are laid in the form of a longitudinal groove of the endoderm, which protrudes towards the notochord. By closing the ventral edges of this groove at 4 weeks of embryonic development, a primary intestinal tube appears, blindly closed at both ends. At the head end, it abuts against the bottom of the oral fossa, which is a deep invagination of the ectoderm. Soon, the membrane between the oral fossa and the head end of the intestine, consisting of a layer of ectoderm and endoderm, erupts; the oral cavity and pharynx begin to develop. A little later, the posterior end of the tube breaks into the ectodermal anal fossa, from which the final part of the rectum with the anus is formed. The primary intestinal tube in the embryo is divided into the head and trunk intestines. The middle part of the intestine is connected with the yolk sac, and the allantoic outgrowth is clearly visible in its posterior part.

Digestive system of a 1.5 month old human embryo. 1 - chord; 2 - trachea; 3 - esophagus; 4 - liver; 5 - stomach; 6 - dorsal and 7 - ventral anlage of the pancreas; 8 - peritoneal cavity; 9 - rectum; 10 - postcloacal gut; 11 - genitourinary sinus; 12 - cloacal membrane; 13 - allantois; 14 - yolk stalk; 15 - gallbladder; 16 - hepatic duct; 17 - heart; 18 - Rathke's pocket; 19 - pituitary gland

Head intestine in the process of further development, it undergoes very complex transformations. They begin with the appearance on the lateral walls of its initial section of protrusions - pharyngeal pockets, towards which gill furrows grow from the side of the body integument (ectoderm). In fish, at the junction of the pharyngeal pockets and gill furrows, gill slits with gill arches located between them are formed. In the higher vertebral clefts, with the exception of the first, does not arise, visceral and branchial arches appear, pockets are laid. At the site of the first branchial cleft, the auditory tube, the middle ear cavity and the auditory canal later develop.

In a 30-day-old human embryo, 4 pairs of pharyngeal pockets are formed in the pharyngeal region. The cells that form the pockets migrate into the surrounding tissues and undergo further differentiation. The tympanic cavity and the Eustachian tube are formed from the material of the first pharyngeal pocket. The outgrowth on the ventral pharyngeal wall at the border of the first and second pharyngeal pockets gives rise to the thyroid gland. In the area of the second pair of pharyngeal "pockets, accumulations of lymphoid tissue arise, from which the palatine (pharyngeal) tonsils develop. The third and fourth pairs of pharyngeal pockets give rise to the parathyroid and thymus glands. From the wall of the oral fossa (ie, due to the ectoderm) develop salivary glands, anterior pituitary gland, mucous membrane of the mouth and tongue The muscles of the tongue arise from the occipital myotomes.

Development of the pharyngeal region of the intestine in the human embryo. A - the initial section of the digestive tract of a 4-week-old embryo (front); B - development of derivatives of the pharyngeal pockets (cut); 1 - oral cavity; 2 - anlage of the thyroid gland; 3 - anlage of the trachea, 4 - anlage of the lungs; 5 - tabs of the parathyroid glands, 6 - tabs of the thymus gland (thymus), I-IV - pharyngeal pockets

Trunk intestine The embryo first presents a straight tube that starts behind the pharyngeal pockets and ends in the anus. The section of the tube that lies between the rudiment of the trachea and the diaphragm turns into esophagus. During 7-8 weeks of embryogenesis, the cells of the epithelium of the esophagus divide intensively, its lumen is almost completely closed. Later, it reappears due to the growth of the esophageal wall and partial cell death in its lumen. The growth of the esophagus in length occurs in parallel with the increase in the size of the lungs and heart in the chest cavity and the lowering of the diaphragm.

The part of the tube located behind the diaphragm expands, from which is formed stomach. In the early stages of development, the stomach is located almost vertically and is connected by the dorsal and ventral mesentery to the walls of the body. The expanding stomach rotates around the longitudinal axis so that its left side becomes anterior, the right - posterior, the longitudinal axis takes an almost transverse position. At the same time, its dorsal mesentery is pulled out and forms a cavity - an omental bursa.

At the end of 2 months of intrauterine development, the formation of the gastric mucosa begins. Folds, pits appear, and then the glands associated with them, from 3 months secretory cells begin to appear, but neither acid nor pepsin is released into the stomach cavity yet. Although cells acquire the ability to produce enzymes and hydrochloric acid even in the prenatal period, they begin to function actively only after birth.

The development of the digestive system in the human embryo. A-D - successive stages; 1 - pharynx; 2 - lung kidney; 3 - hepato-gastric ligament; 4 - dorsal mesentery; 5 - cloaca; 6 - allantoic stalk; 7 - yolk sac; 8 - liver contour; 9 - esophagus; 10 - gallbladder; 11 - small and 12 - cecum; 13 - mesentery; 14 - yolk stalk; 15 - mesentery of the colon; 16 - rectum; 17 - stomach; 18 - spleen; 19 - stuffing box bag; 20 - transverse colon; 21 - appendix; 22 - the ascending part of the colon; 23 - the descending part of the colon; 24 - hepatic ducts; 25 - sigmoid colon

The part of the intestinal tube of the fetus between the stomach and the anus turns into intestines. The border of the small and large intestine passes approximately near the place where the yolk stalk originates. By lengthening rapidly, the intestine bends, loses its middle position and forms loops. The small intestine coagulates spirally and forces the colon against the wall of the abdominal cavity. At the border between the small and large intestine, the rudiment of the cecum is outlined.

The ventral mesentery is preserved only on the stomach and duodenum. From the outgrowth of the intestine, penetrating between the sheets of its mesentery, the liver develops. The same outgrowth in the dorsal direction gives rise to the pancreas.

The pancreas develops in the form of a paired bookmark at the end of 1 month of intrauterine development. The ventral anlage arises from the hepatic outgrowth, and the dorsal - from the wall of the duodenum directly behind the stomach. As the anlages grow and the bowels are formed, both outgrowths approach, and later merge. In the adult state, in most people, the dorsal anlage of the gland loses its duct, and only 10% of this duct remains.

Development of the pancreas. A - the embryo is 4 weeks old; B - 5 weeks; B - 6 weeks; G - newborn; 1 - stomach; 2 - dorsal and 3 - ventral anlage of the pancreas; 4 - gallbladder; 5 - the rudiment of the liver; 6 - duodenum; 7 - bile and 8 - hepatic ducts; 9 - accessory duct, 10 - ventral duct and 11 - main pancreatic duct

The digestive system begins to form very early - already from the 7th-8th day of intrauterine development of the fetus, therefore, by the time of birth, it is already a fairly mature system. But, even in spite of this, the digestive system is adapted only for the assimilation of breast milk or special nutritional mixtures, and in no case is food consumed by an adult. In terms of its constituent parts, the digestive system of a child does not differ from that of an adult. It includes directly the gastrointestinal tract and the oral cavity, pharynx, esophagus, stomach entering into it, кишечник!} and digestive Specialized organs or a group of cells that synthesize and excrete substances are secrets. Depending on the place where the secretion is removed, there are endocrine glands (endocrine) that do not have special excretory ducts and secrete the substances they produce - hormones - directly into the blood or lymph, and exocrine glands (exocrine), which have excretory ducts through which the secret is excreted either on the surface of the body (sweat, lacrimal, milk), or in hollow organs (for example, in the gastrointestinal tract and genitourinary system).

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The wall of the organs of the gastrointestinal tract is formed by three components: the inner one - the mucous membrane. Spread. A thin membrane lining the inner surface of the hollow organs of animals and humans (for example, the stomach, ureters, paranasal sinuses, etc.) and moistened by the secretion of the glands.

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After birth, the baby feeds only on mother's milk or a mixture in the process of sucking due to the peculiarities of the structure of the oral cavity. The oral cavity of a child, compared to that of an adult, is very small, and most of it is occupied by the tongue. The tongue is relatively large, short, wide and thick.

The muscles of the cheeks and lips are very well developed, moreover, the presence of dense lumps of fat (fatty lumps of bisha) in the cheeks makes them look plump or even thick. On the gums, as well as on the cheeks, there are dense areas ^ resembling the appearance of rollers. It is thanks to this structure of the infant's oral cavity that the sucking process becomes possible.

The inner surface of the oral cavity is covered with a mucous membrane, which also has its own characteristics: it is very delicate, easily injured and richly supplied with blood vessels. Up to 3-4 months of age слюнные железы!} the child is not yet sufficiently developed, which causes some dryness of the mucous membrane, but after this age Selection. 1. Liberation of the human or animal body from the end products of metabolism (eg carbon dioxide, urea), excess water, or salts and organic matter. Comm., entered the body with food or formed in the body; necessary to maintain homeostasis; in humans, it is carried out through the kidneys, lungs, skin, digestion. tract. Syn .: excretion. 2. End products of metabolism, foreign substances and excess water, salts, etc., from which the body is released through the excretory system, for example, urine, feces, sweat, etc. Syn .: excretions.

"data-tipmaxwidth =" 500 "data-tiptheme =" tipthemeflatdarklight "data-tipdelayclose =" 1000 "data-tipeventout =" mouseout "data-tipmouseleave =" false "class =" jqeasytooltip jqeasytooltip20 "id =" jqeasytooltip20 "title =" (! LANG: Highlight">выделение!} saliva increases significantly, so much so that the child simply does not have time to swallow it, and it flows out.

The structural features of the esophagus in children are as follows: it is short, narrow and high.

The esophagus in a newborn begins at the level of the III-IV cervical vertebrae, by the age of 2 years it reaches the IV-V cervical vertebrae, and by the age of 12 it is at the level of the VI-VII vertebrae, that is, it has the same location as in adults. The length and width of the esophagus also increase with age, and if in an infant it is 10-12 cm, and the width is 5 cm, then by the age of 5 the esophagus is lengthened to 16 cm and expands to 1.5 cm. The esophagus is very well supplied with blood, but its muscle layer is poorly developed. The child's stomach also has its own characteristics. First of all, with age, the very location of the stomach changes. If in newborn children it is located horizontally, then by the age of 1-1.5 years, when the child begins to walk, it is located more vertically. Of course, the volume of the stomach also increases with age: from 30-35 ml at birth to 1000 ml by the age of 8. Mothers know very well that babies very often swallow air and regurgitate, but few people know that these processes are also due to the peculiarities of the structure of the stomach, or rather the place of transition of the esophagus to the stomach: the entrance to the stomach closes the muscular ridge, the excessive development of which does not allow food quickly enter the stomach and make regurgitation possible.

The inner mucous layer of the stomach is well supplied with blood, as it contains a huge number of blood vessels. The development of the muscle layer is inhibited, it remains underdeveloped for a long time. The glands of the stomach are underdeveloped, and their number is significantly inferior to the number of glands in an adult, which leads to a low content of gastric digestive juice in children of the first month of life and a decrease in its acidity. However, despite the small digestive activity, the gastric juice contains a sufficient amount of a substance that well breaks down the components of breast milk. However, by the age of 2, the child's stomach becomes, in its structural and physiological characteristics, practically the same as that of an adult.

Iron begins to grow most intensively during adolescence.

The pancreas is practically not divided into slices, however, by the age of 10-12, the borders become clearly visible.

The liver, like many other organs of newborns, is functionally immature, even though it is relatively large and protrudes from under the edge of the right costal arch by 1-2 cm.For example, in newborns, the liver is 4% from body weight, while in adults it is only 2%. I Like the pancreas, the liver acquires a lobular structure only by 1-2 years. By the age of 7, the lower edge of the liver is already at the level of the costal arch, and by the age of 8, its structure corresponds to that of an adult. The main role of the liver for the body is education. Also in the liver, most of the substances absorbed in the intestine are neutralized, nutrients are accumulated (Complex polysaccharide, the molecules of which are built from glucose residues. It is a rapidly mobilized energy reserve of living organisms, accumulates mainly in the liver and muscles. The splitting of glycogen - glycogenolysis - is carried out in several ways , and in the liver, a significant part of it is hydrolyzed to form free glucose, which enters the blood.

"data-tipmaxwidth =" 500 "data-tiptheme =" tipthemeflatdarklight "data-tipdelayclose =" 1000 "data-tipeventout =" mouseout "data-tipmouseleave =" false "class =" jqeasytooltip jqeasytooltip4 "id =" jqeasytooltip4 "title =" (! LANG: Glycogen">гликоген) и образуется !} желчь!}, which in turn is involved in the digestion of food. As the child grows up and a variety of foods are introduced into his diet, the amount of bile secreted gradually increases. The intestines are another component of the digestive system. The intestine is made up of the small intestine and the large intestine.

The main functions of the small intestine are the digestion of proteins, carbohydrates and, as well as the absorption of the substances necessary for the body obtained from them, but in children it remains immature for a long time, and therefore does not work well. In addition, the small intestine in children occupies a fickle

position, which is determined by the degree of its filling and relatively longer than that of an adult.

The large intestine also remains immature at birth. During the first 12-24 hours after birth, the child's intestines remain sterile, but after 4-5 days through the mouth, mouth; m. (many mouths, mouths, mouths). Biol. The entrance to the alimentary canal in women and humans

"data-tipmaxwidth =" 500 "data-tiptheme =" tipthemeflatdarklight "data-tipdelayclose =" 1000 "data-tipeventout =" mouseout "data-tipmouseleave =" false "class =" jqeasytooltip jqeasytooltip12 "id =" jqeasytooltip12 "title =" (! LANG: Mouth">рот , верхние дыхательные пути и прямую кишку в кишечник попадают различные !} The kingdom is microscopic. unicellular, aerobic and anaerobic organisms related to prokaryotes; have decomp. shape: rod-shaped (bacilli), spherical (cocci), spiral (spirochetes, spirilla, vibrios), star-shaped and annular; are motionless or can move with the help of flagella; some B. form disputes for waiting out unfavorable conditions; distributed everywhere - in water, air, soil

"data-tipmaxwidth =" 500 "data-tiptheme =" tipthemeflatdarklight "data-tipdelayclose =" 1000 "data-tipeventout =" mouseout "data-tipmouseleave =" false "class =" jqeasytooltip jqeasytooltip19 "id =" jqeasytooltip19 "title =" (! LANG: Bacteria">бактерии!} such as bifidum bacteria, lactobacilli and small amounts of E. coli. The colonization of the intestines with bacteria leads to improved food digestion and formation.

Common features of the intestine in infants and young children are its increased permeability, underdevelopment of the muscle layer and innervation, rich blood supply and increased vulnerability. Due to the fact that muscle cells in a child's body are poorly trained, food moves slowly through the gastrointestinal tract.

The frequency of bowel movements in a newborn child is equal to the frequency of feedings and is 6-7 times a day, in an infant - 4-5, in a child of the second half of life - 2-3 times a day. By the age of two, the frequency of bowel movements becomes the same as that of an adult: 1-2 times a day.