Fetal circulation. Fetal nutrition

This article is the first part of a series about the heart and blood circulation. Today's material is useful not only for general development, but also to understand what heart defects there are. For a better presentation, there are many drawings, half of them with animation.

Diagram of blood flow in the heart AFTER birth

Deoxygenated blood from the whole body is collected in the right atrium through the superior and inferior vena cava (upper - from the upper half of the body, along the lower - from the lower). From the right atrium venous blood through tricuspid valve enters the right ventricle, from where it enters the lungs through the pulmonary trunk (= pulmonary artery).

Scheme: vena cava? right atrium? ? right ventricle? [valve pulmonary artery] ? pulmonary artery.

Structure of the adult heart(picture from www.ebio.ru).

Arterial blood from the lungs through 4 pulmonary veins (2 from each lung) it is collected in the left atrium, from where through the bicuspid ( mitral) the valve enters the left ventricle and is then released through the aortic valve into the aorta.

Scheme: pulmonary veins? left atrium? [mitral valve] ? left ventricle? [aortic valve] ? aorta.

Pattern of blood flow in the heart after birth(animation).
Superior vena cava - superior vena cava.
Right atrium - right atrium.
Inferior vena cava - inferior vena cava.
Right ventricle - right ventricle.
Left ventricle - left ventricle.
Left atrium - left atrium.
Pulmonary artery - pulmonary artery.
Ductus arteriosus - ductus arteriosus.
Pulmonary vein - pulmonary vein.

Diagram of blood flow in the heart BEFORE birth

For adults, everything is simple - after birth, the blood flows are separated from each other and do not mix. In the fetus, blood circulation is much more difficult, which is due to the presence of the placenta, non-functioning lungs and gastrointestinal tract. The fruit has 3 features:

• open foramen ovale(foramen ovale, “forAmen ovale”),
• open ductus arteriosus(ductus arteriosus, ductus arteriosus)
• and open ductus venosus(ductus venosus, “ductus venosus”).

The foramen ovale connects the right and left atria, the ductus arteriosus connects the pulmonary artery and aorta, and the ductus venosus connects the umbilical vein and the inferior vena cava.

Consider the blood flow in the fetus.

Fetal circulation pattern
(explanations in the text).

Oxygen-enriched arterial blood from the placenta flows through the umbilical vein, which runs in the umbilical cord, to the liver. Before entering the liver, the blood flow is divided, and a significant part of it bypasses the liver along ductus venosus, present only in the fetus, and goes into the inferior vena cava directly to the heart. Blood from the liver itself through the hepatic veins also enters the inferior vena cava. Thus, before flowing into the right atrium, the inferior vena cava receives mixed (venous-arterial) blood from the lower half of the body and the placenta.

Through the inferior vena cava, mixed blood enters the right atrium, from where 2/3 of the blood passes through the open foramen ovale enter the left atrium, left ventricle, aorta and big circle blood circulation

Oval hole And ductus arteriosus in the fetus.

Movement of blood through the foramen ovale(animation).

Movement of blood through the ductus arteriosus(animation).

1/3 of the mixed blood entering the inferior vena cava is mixed with all purely venous blood from the superior vena cava, which collects blood from the upper half of the fetal body. Next, from the right atrium, this flow is directed to the right ventricle and then to the pulmonary artery. But the lungs of the fetus do not work, so only 10% of this blood enters the lungs, and the remaining 90% through ductus arteriosus are discharged (shunted) into the aorta, worsening its oxygen saturation. 2 umbilical arteries depart from the abdominal aorta, which in the umbilical cord go to the placenta for gas exchange, and a new circle of blood circulation begins.

Liver the fetus is the only one of all organs that receives a clean arterial blood from the umbilical vein. Thanks to the “preferential” blood supply and nutrition, by the time of birth the liver has time to grow to such an extent that it takes up 2/3 of the abdominal cavity and in relative terms weighs 1.5-2 times more than an adult.

Arteries to the head and upper body arise from the aorta above the level of its confluence ductus arteriosus, so the blood flowing to the head is better oxygenated than, for example, the blood flowing to the legs. Like the liver, a newborn's head is also unusually large and takes up 1/4 of the entire body length(in an adult - 1/7). Brain newborn is 12 - 13% body weight(in adults 2.5%). Probably, young children should be unusually smart, but we cannot guess this due to a 5-fold decrease in brain mass. 😉

Changes in blood circulation after birth

When a newborn takes his first breath, he the lungs expand, vascular resistance in them drops sharply, and blood begins to flow into the lungs instead of the arterial duct, which first becomes empty and then becomes overgrown (scientifically speaking, it becomes obliterated).

After the first inspiration, the pressure in the left atrium increases due to increased blood flow, and the foramen ovale stops functioning and overgrown. The ductus venosus, umbilical vein and terminal sections also become overgrown umbilical arteries. Blood circulation becomes the same as in adults.

Heart defects

Congenital

Because heart development is quite complex, this process can be disrupted during pregnancy by smoking, drinking alcohol or taking certain medications. Congenital defects there are hearts in 1% of newborns. Most often registered:

• defect(non-fusion) of the interatrial or interventricular septum: 15-20 %,
• incorrect location ( transposition) aorta and pulmonary trunk - 10-15%,
• tetralogy of Fallot- 8-13% (narrowing of the pulmonary artery + malposition of the aorta + ventricular septal defect + enlargement of the right ventricle),
• coarctation(narrowing) of the aorta - 7.5%
• patent ductus arteriosus - 7 %.

Purchased

Acquired heart defects occur in 80% of cases due to rheumatism(as they now say, acute rheumatic fever). Acute rheumatic fever occurs 2-5 weeks after a streptococcal throat infection ( sore throat, pharyngitis). Since streptococci are similar in antigenic composition to the body's own cells, the resulting antibodies trigger damage and inflammation in the circulatory system, which ultimately leads to the formation of heart defects. In 50% of cases the mitral valve is affected(if you remember, it is also called bicuspid and is located between the left atrium and the ventricle).

Acquired heart defects are:

1. isolated (2 main types):
   • valve stenosis(narrowing of the lumen)
   • valve insufficiency(incomplete closure, resulting in reverse blood flow during contraction)
2. combined (stenosis and insufficiency of one valve),
3. combined (any damage to different valves).

It is worth noting that sometimes combined defects are called combined, and vice versa, because There are no clear definitions here.

The fetal circulation occurs through the placenta, which receives 60% of the combined ventricular output, and after birth most of it is sent to the lungs.

Fetal circulatory system

When studying fetal circulation, several anatomical and physiological factors should be noted.

The normal adult circulation consists of a series of circuits of blood flow through the right heart, lungs, left heart, systemic circulation, and back to the right heart. The fetal circulation is a parallel system with cardiac output from the right and left ventricles directed to different vessels. For example, the right ventricle, which accounts for about 65% of combined output, pumps blood through the pulmonary artery, ductus arteriosus, and descending aorta. Only a small part of its output passes through the pulmonary circulation. The left ventricle supplies blood primarily to tissues supplied by the aortic arch (for example, the brain). The fetal circulation is a parallel circuit characterized by channels (ductus venosus, foramen ovale, ductus arteriosus) that provides the flow of more highly oxygenated blood to the upper half of the body and brain, less highly oxygenated blood to the lower half of the body, and low oxygenated blood to the non-functioning lungs.

The umbilical vein, carrying oxygenated blood (oxygen saturation reaches 80%) from the placenta to the fetal body, penetrates the portal system. Part of the umbilical-portal blood passes through the microcirculation of the liver, where oxygen is released. From there, the blood flows through the hepatic veins into the inferior vena cava. In the fetal circulation, most of the blood bypasses the liver through the ductus venosus, which directly enters the inferior vena cava, which also receives unsaturated (25%) venous blood from the lower half of the body. The blood that reaches the heart through the inferior vena cava is approximately 70% oxygenated (maximally highly oxygenated blood). About one-third of the blood returning to the heart from the inferior vena cava flows primarily through the right atrium, mixing with blood from the superior vena cava, then through the foramen ovale into the left atrium, where it mixes with the relatively small volume of venous blood from the lungs. Blood flows from the left atrium into the left ventricle, then into the ascending aorta.

From proximal part The aorta, which carries the most oxygenated blood (65%) from the heart, branches off to supply blood to the brain and upper half of the body. Most of the blood returning through the inferior vena cava enters the right atrium, where it mixes with unsaturated blood returning through the superior vena cava (25% oxygen saturation). Blood from the right ventricle (oxygen saturation - 55%) enters the aorta through the ductus arteriosus. The descending aorta supplies the lower half of the body with blood that is less oxygenated (about 60%) than the blood coming to the brain and upper half of the body.

The role of the ductus arteriosus should be especially noted. Blood in the fetal circulation from the right ventricle enters the pulmonary trunk, most of which, due to high vascular resistance, bypasses the lungs through the ductus arteriosus and enters the descending aorta. Although the descending aorta gives branches to the lower half of the fetal body, the bulk of the blood from it flows to the umbilical arteries, which carry oxygen-free blood to the placenta.

Oxygen exchange in the fetal circulation

Unlike the lungs, which require a small amount of oxygen, a statistically significant proportion of the oxygen obtained from the mother’s blood during childbirth is consumed by the placental tissue. The degree of functional shunting of placental blood passing through the exchange centers is approximately ten times higher than in the lungs. The main reason for functional shunting is likely to be a mismatch between maternal and fetal blood flow in the metabolic centers, which serve as examples of ventilation-perfusion inequalities similar to those in the lungs.

Uteroplacental circulation promotes gas exchange during fetal circulation. Oxygen, carbon dioxide and inert gases cross the placenta by simple diffusion. The degree of transfer is proportional to the difference in gas pressure and inversely proportional to the diffusion distance between maternal and fetal blood. The placenta does not serve as a significant barrier to the exchange of respiratory gases until it separates (placental abruption) or becomes edematous (severe hydrops fetalis).

The figure shows the anatomical distribution of uterine and umbilical blood flow and oxygen transfer across the placenta. The maternal shunt accounts for 20% of the uterine blood flow and includes a portion of the blood diverted to the myoendometrium. The fetal shunt supplies blood to the placenta and fetal membranes and accounts for 19% of the umbilical blood flow. Maternal-fetal pressure gradients of oxygen and carbon dioxide are calculated in accordance with the parameters of gas tension in the uterine and umbilical arteries and vein. The umbilical vein of the fetus, like the pulmonary vein of the adult, carries the most oxygen-rich blood. The oxygen pressure in her is about 28 mm Hg, which is lower than in adults. Relatively low fetal stress is required for intrauterine survival, since high pressure oxygen initiates physiological adaptations (eg, closure of the ductus arteriosus and dilation of the pulmonary vessels) that normally occur in the newborn but have adverse effects in fetal life.

While not involved in gas exchange, fetal respiratory movements are involved in lung development and respiratory regulation. Fetal respiration differs from adult respiration in that in the fetus it is episodic, sensitive to glucose concentrations, and inhibited by hypoxia. Due to sensitivity to acute lack of oxygen, fetal breathing clinical practice used as an indicator of the complete oxygenation of the fetus.

Hemoglobin dissociation curves in the fetus and mother

Most of the oxygen in the fetal circulation is carried by red blood cell hemoglobin. The maximum amount of oxygen carried by 1 g of hemoglobin at 100% saturation is 1.37 ml. The volumetric velocity of hemoglobin movement depends on the degree of blood supply and hemoglobin concentration. Uterine blood flow by the end of pregnancy is 700-1200 ml/min, with about 75-88% of it occurring in the intervillous space. Umbilical blood flow is 350-500 ml/min, and more than 50% there's blood coming out to the placenta.

The oxygen capacity of the blood is determined by the concentration of hemoglobin. It is expressed in milliliters of oxygen per 100 ml of blood. Towards the end of pregnancy, the hemoglobin concentration in the fetus is about 180 g/l, and the oxygen capacity is 20-22 ml/dl. The oxygen capacity of the mother's blood, proportional to the hemoglobin concentration, is lower than that of the fetus.

The affinity of hemoglobin for oxygen, expressed as the percentage of saturation at the available oxygen tension, depends on chemical conditions. In the fetal circulation, oxygen binding by hemoglobin under standard conditions (carbon dioxide pressure, pH and temperature) is much higher than in non-pregnant adults. In contrast, the affinity of hemoglobin for oxygen in the mother is lower under these conditions: with a pressure of the latter of 26.5 mm Hg. (in the fetus - 20 mm Hg) 50% of hemoglobin is saturated with oxygen.

Higher fetal temperature and lower pH in vivo shift the oxygen dissociation curve to the right, and more low temperature mothers and higher pH shift the curve to the left. As a result, the oxygen dissociation curves for fetal and maternal blood are not as different at the placental transition site. The maternal venous oxygen saturation is probably 73% and its pressure is about 36 mmHg. The corresponding values ​​for umbilical vein blood are approximately 63% and 28 mmHg. As the only source of oxygen for the fetus, blood in the umbilical vein has higher oxygen saturation and pressure than fetal blood. When the oxygen pressure in the arterial blood of the fetus is low, its oxygenation is supported by increased blood flow in the tissues caused by an increase in cardiac output. Along with lower oxygen saturation of hemoglobin in the blood, this leads to its normal delivery to the fetal organs.

The decrease in the affinity of hemoglobin for oxygen caused by a decrease in pH is referred to as the Bohr effect. Due to the special situation in the placenta double effect Boron facilitates the transfer of oxygen from mother to fetus. When carbon dioxide and related acids are transferred from the fetus to the mother, the concomitant increase in fetal pH increases the affinity of fetal red blood cells to capture oxygen. The concomitant decrease in maternal blood pH reduces oxygen affinity and promotes the unloading of oxygen from her red blood cells.

Changes in the anatomy of the cardiovascular system after birth

After birth, the following changes occur in the fetal circulation and cardiovascular system.

• Termination of placental circulation with rupture and further obliteration of the umbilical vessels.
• Closure of the ductus venosus.
• Closure of the foramen ovale.
• Gradual narrowing and subsequent obliteration of the ductus arteriosus.
• Dilation of pulmonary vessels and formation of pulmonary circulation.

Termination umbilical circulation, closure of vascular shunts and the formation of pulmonary circulation lead to the fact that the newborn’s circulatory system turns from parallel to the maternal one into a closed and completely independent one.

Everything necessary for the intrauterine growth and development of the baby comes to him directly with the mother’s blood from the placenta, where the communication of 2 circulatory systems occurs - mother and baby. Blood circulation through the placenta begins around the end of 2 months of fetal life. At the same time, fetal blood circulation has its own characteristics.

What are the features of blood circulation in the fetus?

So arterial blood, carrying oxygen to the baby, comes to him directly from the placenta through the umbilical vein. This vein is composed of umbilical cord, together with 2 umbilical arteries, carries blood to the fetus from the placenta.

Then, in the fetal body, the umbilical vein is divided into 2 branches: the ductus venosus (Arantius), which delivers arterial blood directly to the inferior vena cava, where it is mixed; along the second branch, the mother’s blood flows through the portal vein system directly to the fetal liver, where it is cleared of toxic substances.

As a result, during the placental circulation of the fetus, mixed blood from the inferior vena cava enters the baby’s right atrium, and purely venous blood from the superior one. From the right atrium, only a small part of the blood enters the right ventricle, which goes to the pulmonary circulation through the pulmonary trunk. It is she who supplies the lung tissue, because The baby's lungs do not function in the womb.

Having examined the blood circulation pattern of the fetus, it is necessary to mention the presence in it of some functional formations that are normally absent in a born baby.

So in the septum located between the atria, there is a hole - the oval window. Through it, mixed blood, bypassing the small circle, enters directly into the left atrium, from where it flows into the left ventricle. The blood flow is then directed to the aorta, into the systemic circle. Thus, there is a communication between 2 circles of the fetal blood circulation.

Also in the fetal circulatory system there is such functional education, like a battle canal. It connects the pulmonary trunk with the aortic arch, and adds a certain portion of mixed blood to it. In other words, the batal duct, together with the oval window, relieves the pulmonary circulation, directing blood directly to the large circle.

From the moment a child takes his first breath, from his birth, the pulmonary circulation begins to function. After the umbilical cord is tied, the circulatory system of the fetus and mother ceases to exist. In this case, placental blood circulation is completely suspended and the umbilical vein is empty. It leads to sharp decline pressure in the cavity of the right atrium and its increase in the left, because This is where the blood from the small circle is directed. As a result, due to such a pressure difference, the valve oval window slams shut on its own. If this does not happen, then the baby is diagnosed with a congenital defect, because mixing of venous and arterial blood occurs, As a result, tissues and organs receive mixed blood.

As for the Batalov and Arantius ducts, which existed during the intrauterine blood circulation of the fetus, they spontaneously, literally by the end of the first month of the baby’s life, become overgrown. As a result, in a baby, like in an adult, 2 circles of blood circulation begin to function. However, despite this, the baby still has some characteristics circulatory system, which is associated with the functioning of individual organs and systems. That's why the cardiovascular system babies are one of the first to be examined by ultrasound after birth.

The blood circulation of the fetus is arranged in such a way that the needs of its development are fully met. by the time the child is born undergoes certain changes. With the first breath, the newborn experiences a rush of blood to the lungs and a normal type of blood circulation appears, different from intrauterine circulation.

The process of formation of the fetal heart begins in the second week of pregnancy, and its formation is completed in the second month of intrauterine development. During this period, it acquires all the features of a four-chambered heart. Along with the formation of the heart, the vascular system and blood circulation of the fetus develop. It receives oxygen and nutrients from its mother. Therefore, there are certain features of the blood supply to the unborn child.

How does blood circulation occur in the fetus?

Oxygenated blood comes from the placenta through the umbilical vein. In this case, approximately half of the blood is discharged from the umbilical cord through the venous network of the fetus. The discharged blood bypasses the vascular system of the fetal liver and enters the inferior vena cava. The rest of the blood enters the liver through Then it rushes through the veins of the liver into the inferior vena cava.

As a result of these circulatory features, the blood in the inferior vena cava is mixed. The oxygen content in it is greater than in the blood returning from the atrium (right). This is a very important aspect, since both blood flows in the right atrium are separated, which means they have different paths.

The blood supply to the fetus due to the separation of blood flow directions has following features: his brain and myocardium are supplied with blood from high content oxygen. And less oxygenated blood enters the placenta through the descending aorta and umbilical arteries for oxygen saturation.

The blood entering the right atrium (more of it) from the inferior vena cava through the foramen ovale is directed to the left atrium. Oxygen-rich blood is discharged thanks to the lower edge of the septum secundum. This septum is called the “Eustachian valve”. It is located above the opening leading into the right atrium from the inferior vena cava.

Next, the process of mixing the incoming blood with a small amount of insufficiently oxygenated blood occurs, returning through the fetus to the left atrium. From the left atrium, blood moves into the left ventricle and is then ejected into the ascending aorta. And from the aorta, the oxygen-rich blood flow is distributed in three directions:

1. B to carry out myocardial perfusion. This is approximately 9% of the blood ejected from the left ventricle.

2. Into the brain and upper sections torso. The amount of such blood is about 62%. It enters through the carotid and subclavian arteries.

This way the blood circulation of the fetus occurs. Its proper intrauterine development depends on many factors: the heredity of the expectant mother, her lifestyle, nutrition, etc.

Fruit size

In parallel with the process, its size increases. It grows every hour, every day. Before reaching twenty-one weeks of pregnancy, the fetus is measured from the parietal part to the sacrum. After this period, measurements are taken from head to toe. Knowing the size of the fetus, a woman can monitor how timely it develops.

The development of the child depends, among other things, on the weight gain of the expectant mother. Therefore, it is necessary to strictly follow the diet recommended by your doctor. In addition, you need to perform a set of special physical exercises. Compliance by the expectant mother with all the instructions of specialists will help the fetus develop in accordance with the deadlines.

The portal vein is also subject to significant interindividual variability. In newborns, its initial section lies at the level of the XII thoracic, I (usually) or II lumbar vertebrae, behind the head of the pancreas. The number of vein sources ranges from 2 to 5, they can be: upper, lower

mesenteric, splenic, left gastric, ileocolic veins. More often it is formed by the fusion of two veins - the splenic and superior mesenteric. Of the tributaries of the portal vein, the most consistently distinguishing

There are gastroduodenal ones (2-3 in number). The veins of the gallbladder (1-2) flow into the portal vein or into its right branch.

The main trunk of the portal vein is usually cylindrical in shape, in some cases its initial and final sections are expanded. Its length varies from 18 to 22 mm, diameter (in the initial part) - from 3 to 5 mm. Its division into right and left branches occurs at the porta hepatis at an angle of 160-180° (sometimes the trunk splits into 3 and 4 branches). The portal vein develops quickly after birth and at 4 months its structure is final.

Porto-caval anastomoses in newborns are diverse and are defined throughout the retroperitoneal space (where the vein lies only in its initial section) in the form of subtle communications between: 1) the left testicular (ovarian), veins of the left renal capsule and inferior mesenteric; 2) left renal and splenic; 3) left lower adrenal, left testicular (ovarian) and splenic; 4) veins of the right renal capsule, right testicular (ovarian) and superior mesenteric with its tributaries; 5) veins of the right renal capsule and veins duodenum.

FEATURES OF FETAL BLOOD CIRCULATION

Oxygen and nutrients are delivered to the fetus from the mother's blood using the placenta - placental circulation. It's happening

in the following way. Arterial blood enriched with oxygen and nutrients flows from the mother's placenta into the umbilical vein, which

enters the fetal body in the navel area and goes up to the liver, lying in its left longitudinal groove. At the level of the portal of the liver, v.umbilicalis is divided into two branches, of which one immediately flows into the portal vein, and the other, called the ductus venosus (duct of Arantius), runs along the lower surface of the liver to its posterior edge, where it flows into the trunk of the inferior vena cava.

The fact that one of the branches of the umbilical vein delivers pure arterial blood to the liver through the portal vein determines the relatively large size of the liver; the latter circumstance is related to the necessary

For developing organism hematopoietic function of the liver, which predominates in the fetus and decreases after birth. After passing through the liver, the blood flows through the hepatic veins into the inferior vena cava.

Thus, all the blood from v.umbilicalis either directly (through the ductus venosus) or indirectly (through the liver) enters the inferior vena cava, where it is mixed with venous blood flowing through the vena cava inferior from the lower half of the fetal body. Mixed (arterial and venous) blood flows through the inferior vena cava into the right atrium. From the right atrium it is directed by the valve of the inferior vena cava, valvula venae cavae inferioris, through the foramen ovale (located in the atrial septum) into the left atrium. From the left atrium, mixed blood enters the left ventricle, then into the aorta, bypassing the not yet functioning pulmonary circulation.

In addition to the inferior vena cava, the superior vena cava and the venous (coronary) sinus of the heart flow into the right atrium. Venous blood entering

V the superior vena cava from the upper half of the body, then enters the right ventricle, and from the latter into the pulmonary trunk. However, due to the fact that the lungs do not yet function as a respiratory organ, only a small part of the blood enters the lung parenchyma and from there through the pulmonary veins into the left atrium. Most of the blood from the pulmonary trunk passes through the ductus arteriosus

V the descending aorta and from there to the viscera and lower extremities. Thus, despite the fact that in general mixed blood flows through the vessels of the fetus (with the exception of the v.umbilicalis and ductus venosus before it flows into the inferior vena cava), its quality below the junction of the ductus arteriosus deteriorates significantly. Consequently, the upper body (head) receives blood richer in oxygen and nutrients. The lower half of the body is nourished worse than the upper half and lags behind in its development. This explains the relatively small size of the pelvis and lower limbs newborn

Blood flows from the fetus to the placenta of the maternal body through two umbilical arteries, which arise from the internal iliac arteries.

The act of birth represents a leap in the development of the organism, during which fundamental qualitative changes in vital processes occur. The developing fetus moves from one environment (the uterine cavity with its relative constant conditions) to another (the outside world with its changing conditions), as a result of which the metabolism of substances previously received through the blood radically changes; food enters digestive tract, and oxygen begins to come not from the mother’s blood, but from the outside air due to the inclusion of the respiratory organs. All this is reflected in blood circulation.

At birth, there is a sharp transition from the placental circulation to the pulmonary circulation. When you inhale for the first time and stretch the lungs with air, the pulmonary vessels greatly expand and fill with blood. Then the ductus arteriosus collapses and during the first 8-10 days it becomes obliterated, turning into a liga-

mentum arteriosum. The physiological mechanism of its closure is not entirely clear at present. It is believed that at the moment of the first breaths, the pressure at the two ends of the duct equalizes, blood flow through it stops, and physiological separation occurs between the pulmonary artery and the aorta. The process of obliteration is complex and is associated with changes occurring in its wall. The inner surface of the duct becomes loosened, then the walls gradually thicken due to the intensive proliferation of connective tissue. By the second week of life, its inner surface is covered with a large number of unevenly spaced folds.

In newborns, the ductus arteriosus arises from the pulmonary trunk at the site of its bifurcation or from the upper surface of the left branch (93%), extremely rarely from the right. It usually flows into the lower edge of the aortic arch, opposite the base of the left subclavian artery or slightly distal from it. The duct is projected along the left sternal line in the second intercostal space and is almost entirely located extrapericardially, with the exception of a small area adjacent to the pulmonary artery. In half of the cases, the pericardium forms a volvulus here, surrounding the duct in the form of a sleeve. At the level of the aortic arch, in close proximity to the duct, the left phrenic and vagus nerves pass. From below, the left duct and aortic arch go around recurrent nerve. The posterior surface of the duct is in contact with the left main bronchus, from which it is separated by a layer of loose tissue and mediastinal lymph nodes.

The shape of the duct is often cylindrical, less often conical. It may have kinks and be twisted around its axis. The length of the canal ranges from 1 to 16 mm (usually 6-9 mm), width - from 2 to 7 mm (usually 3-6 mm). There are two types of ducts: long and narrow, short and wide (Fig. 13). The former overgrow faster, the latter more often remain open. At birth, the diameter of the lumen of the ductus arteriosus is equal to, and sometimes greater than, the lumen of the pulmonary vessels. The opening on the side of the aorta, as a rule, is narrower than on the side of the pulmonary artery, and is covered by a valve-shaped valve.

Rice. 13. Differences in the ductus arteriosus.

a – long narrow; b – short wide.

Umbilical vessels, aa.umbilicales and v.umbilicalis, undergo significant changes during the neonatal period due to the loss of their function. IN last years interest in these vessels has increased due to their use for insertion contrast agent into the portal vein system (direct extraperitoneal portohepatography and splenoportography) and the aorta (aortography and probing of the aorta). Through these vessels, exchange blood transfusions and the administration of medicinal substances are also carried out for the purpose of resuscitation of infants in the first

hours and days after birth.

Umbilical arteries- the largest branches of the internal iliac. Adjacent to the side wall of the bladder, they follow in the preperitoneal tissue and reach the umbilical ring, in the area of ​​which the v.umbilicalis joins them, and then all three vessels become part of the umbilical cord. Along the anterior abdominal wall, the umbilical arteries are intimately fused with the parietal peritoneum, which must be taken into account when isolating the vessels. Close relationship between blood vessels and back surface of the abdominal wall is noted from the level of the inguinal ligaments or slightly above them, while the pelvic sections of the vessels are well mobile. From each umbilical artery branches go to bladder, rectum and anterior abdominal wall. Thus, aa.umbilicales, in addition to their function in the placental circulation, take part in the supply of these pelvic organs. In the first three days of a child’s life, the lumen of the aa.umbilicales is open throughout its entire length (diameter ranges from 3 to 5 mm) and contains blood cells. The shape of the artery gradually changes to a cone-shaped due to the functional closure of its distal section. The vessel wall differs from other arteries in the development of its elastic framework and the richness of muscle elements. After birth, the distal sections of the aa.umbilicales (between the umbilical ring and the superior vesical

artery) undergo obliteration. This process begins from the first day and ends in different periods: more often from 4 weeks to 3 months, less often it drags on up to 9 months and even 5 years; sometimes arteries long years remain open. The initial sections of the umbilical arteries function in the postnatal period and take part in the blood supply to the bladder,

rectum and anterior abdominal wall.

Umbilical vein - in a newborn relatively large vessel, is projected along the midline of the abdomen, the length of the intra-abdominal section ranges from 7 to 8 cm, and the diameter – from 4 to 6.5 mm. The vein in this section does not contain valves, while along the umbilical cord, semilunar valves were found in the vessel (A.I. Petrov). From the umbilical ring the vein goes to the liver, where in the area of ​​the umbilical notch it flows into left branch v.portae (98%) or extremely rarely into its main trunk (2%). The intra-abdominal section of the vein, in turn, is divided into extra- and intraperitoneal parts, the extra-peritoneal part lies between the transverse fascia and the peritoneum. After 3 weeks of a child’s life, the vein may be located in the so-called “umbilical canal”, limited in front by the white line of the abdomen, and behind by the umbilical fascia. The peritoneum of the anterior abdominal wall forms a funnel-shaped depression at the site of the transition of the extraperitoneal part of the vein to the intraperitoneal one. The vein, passing through this depression, is covered with peritoneum on all sides. The serous cover does not adhere tightly to the initial sections of the vessel (over 0.5-0.8 cm) and, if necessary, can be easily separated from its wall. Towards the end of the newborn period, due to a decrease in the relative size of the liver (especially its left lobe), the direction of the umbilical vein changes; it deviates from the midline of the abdomen by 0.5-1 cm to the right (G.E.Ostroverkhov, A.D.-Nikolsky).

After birth, due to the cessation of blood flow through the vein, its wall collapses and functional closure of the lumen occurs. Starting from the 10th day

within 1-1.5 months, the distal portion of the vessel over 0.4-2 cm is subject to obliteration. In this regard, he accepts characteristic shape– narrow at the umbilical ring and gradually widening as it approaches the liver. The obliterated part is represented by connective tissue cords (one to three). Throughout the rest of the vein, there is a lumen (“residual channel”) with a diameter of 0.6 to 1.4 mm. Tributary veins provide

V her central department blood flow in a centripetal direction, which prevents its fusion. The largest tributary is the Burov vein (one of the first described porto-caval anastomoses), formed from the confluence of the sources of both inferior epigastric veins and the vein of urachus. Paraumbilical veins accompanying round ligament liver, also often fall into v.umbilicalis. If no tributaries flow into the umbilical vein, which is very rare, then it becomes completely overgrown. Rarely observed complete non-closure of v.umbilicalis is combined with congenital portal hypertension. Anastomo-

call of the umbilical vein high blood pressure in the portal vein system they play the role of natural porto-caval shunts. Due to them, the portal vein system is also connected to the veins of the anterior abdominal wall.

The flow of blood from the right atrium to the left through the foramen ovale stops immediately after birth, since the left atrium is filled with blood coming here from the lungs, and the difference in blood pressure between the right and left atria is equalized. Closure of the foramen ovale occurs much later than obliteration of the ductus arteriosus, and often the hole persists during the first year of life, and in 1/3 of cases throughout life.

ANOMALIES OF BLOOD VESSEL DEVELOPMENT. The most common developmental anomalies occur in derivatives of the branchial (aortic) arches, although small arteries of the trunk and limbs often have a diverse structure and different topography options. If the 4th right and left branchial arches and the roots of the dorsal aortas are preserved, the formation of an aortic ring, covering the esophagus and trachea, is possible. There is a developmental anomaly in which the right subclavian artery departs from the aortic arch more caudally than all other branches of the aortic arch.

Anomalies in the development of the aortic arch are expressed in the fact that it is not the left 4th aortic arch that reaches development, but the right one and the root of the dorsal aorta.

Developmental anomalies are also disturbances in the pulmonary circulatory system, when the pulmonary veins flow into the superior vena cava, into the left brachiocephalic or azygos vein, and not into the left atrium. Structural anomalies are also found in the superior vena cava. The anterior cardinal veins sometimes develop into independent venous trunks, forming two superior vena cava. Developmental anomalies also occur in the inferior vena cava system. The wide communication through the medial sinus of the posterior cardinal and subcardinal veins at the level of the kidneys contributes to the development various anomalies in the topography of the inferior vena cava and its anastomoses.

L I M F A T I C H E S S I S T E M A

Lymphatic system during the neonatal period it is already formed and represented by the same structural links as in an adult. These include: 1 – lymphatic capillaries; 2 – intraorgan and extraorgan lymphatic vessels; 3 – lymphatic trunks; 4 – lymph nodes; 5 – main lymphatic ducts.

Each link of the lymphatic system has specific functional and anatomical differences, depending on age and individual characteristics body. In general, the lymphatic system at any age has common functional tasks and structural principles. Nevertheless

Children are characterized by a relatively high degree of expression of lymphatic structures; their differentiation and formative processes continue until the age of 12-15, which is associated with the formation of barrier filtration and immune forces of the body.

Lymphatic capillaries in newborns and children, including adolescence, they have a relatively larger diameter than in people of mature age, the contours of the capillaries are even, the walls are smooth. The networks they form are denser, finely looped, with a characteristic multilayer structure. Thus, the intraorgan lymphatic system small intestine in a newborn it is represented by developed networks in the mucous, submucosal, muscular and serous layers. Each of them is distinguished by a finely looped structure, a relatively large diameter of the capillaries that form it and numerous connections with the lymphatic vessels of adjacent layers (D.A. Zhdanov).

The tunica mucosa of the colon contains a network lymphatic capillaries, numerous outgrowths of which form a superficial network of the mucous membrane. From the vessels of the submucosal and partly mucous layers dense finely looped networks are formed around lymphatic follicles, located in large numbers in the area of ​​the iliocecal angle (their number decreases towards the right flexure of the colon). The network of capillaries in the longitudinal layer of the muscularis propria is less dense than in the circular layer. The serous membrane also has a single-layer network of lymphatic capillaries (E.P. Malysheva).

With age, the diameter of the lymphatic capillaries becomes smaller, they are narrower, some of the capillaries turn into lymphatic vessels. After 35-40 years, signs of age-related involution are found in the lymphatic bed. Contours of lymphatic capillaries and starting from them lymphatic vessels become uneven lymphatic networks open loops, protrusions, and swelling of the capillary walls appear. In elderly and senile age, the phenomena of reduction of lymphatic capillaries are more clearly expressed.

Lymphatic vessels in newborns and children of the first years of life they have a characteristic clear-shaped pattern due to the presence of constrictions (narrowings) in the area of ​​the valves, which are not yet fully formed. In parenchymal organs, lymphatic vessels are characterized by a multi-tiered arrangement. Thus, the lymphatic vessels in the parenchyma of the pancreas in a newborn form a three-tiered network: intralobular, interlobular and around the main duct. They are connected to each other by a large number of connections, as well as to the surface network, in the thickness of the peritoneal layer covering the organ. The efferent vessels of the head and processus uncinatus in the thickness of the upper, lower and posterior pancreatic-duodenal ligaments, where they reach the nodes of the duodenum and then the nodes along

inner semicircle duodenum. Characteristic is the direct flow of efferent vessels into the lymph nodes of the second stage: mid-mesenteric, hepatic (behind the pyloric part of the stomach), and sometimes into more distant ones (para-arterial, renal). The vessels of the body and tail end in nodes along the edges of the gland, the gate of the spleen, etc. (L.S. Bespalova).

In children's and adolescence lymphatic vessels are connected to each other by numerous transverse and obliquely oriented anastomoses, as a result of which lymphatic plexuses are formed around arteries, veins, and gland ducts. The valve apparatus of the lymphatic vessels reaches its full maturity by 13-15 years.

Signs of reduction of lymphatic vessels are detected at the age of 40-50 years, their contours become uneven, protrusions of the walls appear in places, the number of anastomoses between lymphatic vessels decreases, especially between superficial and deep. Some vessels become empty altogether. In elderly and senile people, the walls of the lymphatic vessels thicken, their lumen decreases.

The lymph nodes begin to develop in the embryonic period from 5-6 weeks from the mesenchyme near the developing plexuses of blood and lymphatic vessels. Many processes of the structural formation of lymph nodes occur during the period of intrauterine development of the fetus and are completed by the time of birth, others continue after birth. Starting from the 19th week, in individual lymph nodes you can see the emerging border between the cortex and medulla; lymphoid nodules in the lymph nodes also begin to form in the prenatal period and, basically, this process is completed by the time of birth. Light centers in lymphoid nodules appear shortly before and shortly after birth. Bookmarks of lymph nodes in various areas bodies are formed during various periods of intrauterine development up to birth, as well as during the neonatal period and in the first years of a child’s life. The main age-related formative processes in the lymph nodes end by 10-12 years.

Just like in an adult, in newborns, lymph nodes are concentrated in certain areas of the body, you can also distinguish superficial and deep lymph nodes, visceral and parietal, depending on the location of the inguinal, lumbar, axillary, parotid and all other clusters of lymph nodes, distinguished in an adult body. Typically, lymph nodes are located next to blood vessels. However, a feature of the newborn period is that the variation in the number of regional lymph nodes is insignificant than in adults, which probably means complex age-related and individual changes in the processes of formation and reduction of nodes during a person’s life. For example, in newborns the total number of mesenteric lympha-

phatic nodes range from 80 to 90 (T.G. Krasovsky), and in adults - from 66 to 404 nodes (M.R. Sapin).

With age, changes are observed in the involuting lymph nodes. Already in adolescence, the number of lymph nodes decreases lymphoid tissue, adipose and connective tissue grows in the stroma and parenchyma of the nodes. With age, the number of lymph nodes in regional groups also decreases. Many nodes are not large sizes are completely replaced by connective and adipose tissue and cease to exist as organs of the immune system. Nearby lymph nodes can grow together and form larger segmental or ribbon-shaped nodes.

Thoracic lymphatic duct in newborns and children it is correspondingly smaller in size than in adults, its wall is thin. The thoracic duct begins in newborns at various levels: from XI thoracic to II lumbar vertebra. The ductal cistern is not pronounced and intensively increases in the first weeks of life, which, according to D.A. Zhdanov, is associated with the acceleration of lymph circulation caused by food intake and active function musculoskeletal system. The length of the duct ranges from 6 to 8 cm. The differences in the wall thickness of the initial and final sections are insignificant. Elastic fibers in the subendothelial layer are well defined (N.V. Lukashuk). The number of valves in the vessel is variable. More often they occur along the entire length, less often - only in places of “compression” of the duct neighboring organs(at the diaphragm, between the spine, aorta and esophagus). D.thoracicus is usually represented by a single trunk, less often there is an additional vessel (d.hemithoracicus), and in isolated cases several short trunks that do not communicate with each other. The position of the thoracic part of the duct is variable. It can be adjacent to the middle of the esophagus or to its right edge, less often it is located between the esophagus and the aorta. From level V thoracic vertebra the duct deviates to the left, on the II-III vertebrae it departs from the esophagus (M.N. Umovist).

The thoracic lymphatic duct reaches its maximum development in mature age. In old and senile age in the wall of the thoracic duct with some atrophy smooth muscle connective tissue grows.

ABOUT R G A N Y C R O V E T C E R E N I

AND I M M U N N OY SYSTEMS

The hematopoietic organ in humans is Bone marrow. Blood cells develop in the bone marrow due to the proliferation of stem cells. Organs immune system provide protection to the body (they

immunity) from genetically foreign cells and substances coming from outside or formed in the body. These include: bone marrow, thymus(see "Glands internal secretion"), tonsils, lymphoid nodules located in the walls of the hollow organs of the digestive and respiratory systems, lymph nodes (see “Lymphatic system”) and spleen.

BONE MARROW

The bone marrow is both an organ of hematopoiesis and the immune system. In the embryonic period (from the 19th day to the beginning of the 4th month of intrauterine life), hematopoiesis occurs in the blood islands of the yolk sac. From the 6th week of intrauterine development, hematopoiesis is observed in the liver, and from the 3rd month - in the spleen and continues in these organs until the birth of the child.

Bone marrow begins to form in the embryo in the bones at the 2nd month, and from the 12th week blood vessels, around which reticular tissue appears, the first islands of hematopoiesis are formed. From this time on, the bone marrow begins to function as a hematopoietic organ.

During the period of intrauterine development, only red bone marrow is present in the bones of the embryo; starting from the 20th week, its mass rapidly increases, and the bone marrow spreads towards the epiphyses of the bones. Subsequently, the bone crossbars in the diaphysis of the tubular bones are resorbed, and a bone marrow cavity filled with bone marrow is formed in them.

In a newborn, red bone marrow occupies all the bone marrow cavities. In the 1st year of a child’s life, fat cells begin to appear in the bone marrow, and by the age of 20-25, yellow bone marrow is formed, which completely fills the marrow cavities of the diaphysis of long tubular bones.

MIN DA LIN Y

Tonsils - lingual and pharyngeal (unpaired), palatine and tubal (paired), located in the region of the root of the tongue, pharynx and nasal pharynx, respectively. In general, this complex of six tonsils is called the lymphoepithelial ring of the pharynx (Pirogov-Waldeyer ring), which performs a protective, barrier function against the passage of food and air.

Lingual tonsil appears in fetuses at 6-7 months of intrauterine development in the form of diffuse accumulations of lymphoid tissue in the lateral sections

root of the tongue. At 8-9 months, lymphoid tissue forms denser clusters - lymphoid nodules, the number of which increases noticeably by the time of birth. Soon after birth (in the 1st month of life), reproduction centers appear in the lymphoid nodules, the size of which is about 1 mm. Subsequently, the number of lymphoid nodules increases up to adolescence. In infants, there are an average of 66 nodules in the lingual tonsil, in the period of first childhood - 85, and in adolescence - 90, the size of the nodules increases to 2-4 mm. Breeding centers are less common.

The lingual tonsil reaches its largest size by the age of 14 - 20 years; its length and width are 18 - 25 mm (L.V. Zaretsky). In old age, the amount of lymphoid tissue in the lingual tonsil is small; connective tissue grows in it.

Palatine tonsils are formed in fetuses of 12-14 weeks in the form of thickening of the mesenchyme under the epithelium of the second pharyngeal pouch. A 5-month-old fetus has an accumulation of lymphoid tissue up to 2-3 mm in size. By the time of birth, the amount of lymphoid tissue increases, individual lymphoid nodules appear, but without reproduction centers, which form after birth. The largest number of lymphoid nodules is observed in childhood and adolescence.

In a newborn, the palatine tonsils are relatively large in size, clearly visible, since they are little covered by the anterior arches; the lacunae of the tonsils are poorly developed. During the first year of a child’s life, the size of the tonsils doubles (up to 15 mm in length and 12 mm in width), and by the age of 8-13 they are at their largest and remain this way until about 30 years. Their greatest length (13-28 mm) is in 8-30 year olds, and their greatest width (14-22 mm) is in 8-16 years old.

Age-related involution of lymphoid tissue in the palatine tonsils occurs after 25-30 years. Along with a decrease in the mass of lymphoid tissue in the organ, there is a proliferation of connective tissue, which is already clearly noticeable at 17-24 years of age.

Tubal tonsils begin to develop at 7-8 months of fetal life in the thickness of the mucous membrane, around the pharyngeal opening auditory tube. Initially, separate accumulations of future lymphoid tissue appear, from which

V Subsequently, the tubal tonsil is formed.

U In a newborn, the tubal tonsil is quite well defined (its length 7-7.5 mm), it is located next to the opening of the Eustachian tube, cranial from soft palate and it can be removed with a rubber catheter through the nasal cavity. Lymphoid nodules and reproductive centers in the tubal tonsils appear in the 1st year of a child’s life, and they are at their greatest development