Oxygen and nutrients delivered to the fetus from the mother's blood using the placenta - placental circulation. It happens as follows. Arterial blood enriched with oxygen and nutrients flows from the mother’s placenta into the umbilical vein, which enters the fetal body at the navel 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 ductus venosus, flows 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 associated with the hematopoietic function of the liver, which is necessary for the developing organism, 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 or directly ( via 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 The inferior vena cava flows 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 still non-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 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 ductus arteriosus passes into 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 v. umbilicalis and ductus venosus before its confluence with the inferior vena cava), its quality below the confluence 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 extremities of the newborn.

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 relatively constant conditions: temperature, humidity, etc.) to another (the outside world with its changing conditions), as a result of which metabolism, as well as methods of feeding and breathing, radically change. Instead of the nutrients previously received through the blood, food enters the digestive tract, where it undergoes digestion and absorption, and oxygen begins to come not from the mother’s blood, but from the outside air due to the inclusion of the respiratory system. All this is reflected in blood circulation.

At birth there is a sharp transition from placental circulation to the pulmonary. 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 to 10 days is obliterated, turning into ligamentum arteriosum.

>The umbilical arteries overgrow during the first 2 - 3 days of life, the umbilical vein - somewhat later (6 - 7 days). 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. The described changes were confirmed by living studies using X-rays.

Educational video anatomy of blood circulation in the fetus

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 of the 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 the developing organism, the function of liver hematopoiesis, 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 extremities of the 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 relatively constant conditions) to another (the outside world with its changing conditions), as a result of which the metabolism previously received through the blood radically changes, food enters the digestive tract, and oxygen begins to flow 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 recurrent nerve bends around the duct and aortic arch. 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 recent years, interest in these vessels has increased due to their use for introducing a contrast agent into the portal vein system (direct extraperitoneal portohepatography and splenoportography) and the aorta (aortography and aortic sounding). 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. The close relationship of the vessels to the posterior 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 there are branches to the 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 the arteries remain open for many years. 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.

The umbilical vein is a relatively large vessel in a newborn, 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 the left branch of the 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, it takes on a 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 in its central section, blood flows 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. The paraumbilical veins accompanying the round ligament of the liver also often flow into the 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-

At elevated pressure in the portal vein system, umbilical vein veins 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 arises 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 of 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

During the neonatal period, the lymphatic system is already formed and is represented by the same structural units 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 the age and individual characteristics of the 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 of the small intestine in a newborn 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 of lymphatic capillaries, the numerous outgrowths of which form the superficial network of the mucous membrane. From the vessels of the submucosal and partly mucosal layers, dense finely looped networks are formed around the lymphatic follicles, located in large numbers in the area of ​​the iliocecal angle (their number decreases towards the right bend 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 contains 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. The contours of the lymphatic capillaries and the lymphatic vessels starting from them become uneven, open loops, protrusions, and swellings of the capillary walls appear in the lymphatic networks. 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 childhood 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. Lymph node anlages in various areas of the body are formed during various periods of intrauterine development up to birth, as well as during the newborn 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; superficial and deep lymph nodes, visceral and parietal, can also be distinguished; depending on the location, inguinal, lumbar, axillary, parotid and all other clusters of lymph nodes are 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 amount of lymphoid tissue in the lymph nodes decreases, 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 small nodes 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. In newborns, the thoracic duct begins at various levels: from the XI thoracic to the 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 the active function of the 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 where the duct is “compressed” by neighboring organs (near 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 the level of the V thoracic vertebra, the duct deviates to the left, at the II-III vertebrae it departs from the esophagus (M.N. Umovist).

The thoracic lymphatic duct reaches its maximum development in adulthood. In old age and senility, connective tissue grows in the wall of the thoracic duct with some atrophy of smooth muscles.

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 the bone marrow. Blood cells develop in the bone marrow due to the proliferation of stem cells. The organs of the 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 gland (see “Endocrine glands”), 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.

The bone marrow of the embryo begins to form in the bones at the 2nd month, and from the 12th week blood vessels are formed in the bone marrow, around which reticular tissue appears, and 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 until 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 of the 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 to the soft palate and can be reached 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

Blood circulation in a single functional system mother-placenta-fetus is the leading factor ensuring the normal course of pregnancy, growth and development of the fetus.

From the end of the 2nd month of life, the fetus has its own blood circulation.

The flow of oxygenated blood from the placenta through the umbilical vein on the surface of the liver is distributed in two directions: one enters the portal vein, bringing with it 50% of all blood, the other, continuing the umbilical vein in the form of the duct of Arantius, flows into the inferior vena cava, where placental blood mixes with venous blood coming from the pelvic organs, liver, intestines and lower extremities. The blood flowing through the vena cava into the right atrium is divided into two channels.

The bulk of the blood (60%) from the inferior vena cava, due to the presence of a valve-shaped fold in the right atrium (Eustachian valve), enters through the oval window into the left atrium, left ventricle and aorta. The remaining blood from the inferior vena cava and blood from the superior vena cava flows through the right atrium into the right ventricle and further into the pulmonary trunk. This blood is sent through the pulmonary artery to the non-functioning lungs and the ductus arteriosus, entering the descending aorta below the origin of the vessels that supply blood to the brain.

Rice. 1. Diagram of fetal blood circulation before birth. 1 - left common carotid artery; 2 - left subclavian artery; 3 - ductus arteriosus; 4 - left pulmonary artery; 5 - left pulmonary veins; 6 - two-leaf valve; 7 - blood flow to the aortic opening from the left ventricle; 8 - blood flow to the opening of the pulmonary trunk from the right ventricle; 9 - celiac trunk; 10 - superior mesenteric artery; 11 - adrenal gland; 12 - kidney; 13 - left renal artery; 14 - dorsal aorta; 15 - inferior mesenteric artery; 16 - common iliac artery; 17 - external iliac artery; 18 - internal iliac artery; 19 - superior cystic artery; 20 - bladder; 21 - umbilical artery; 22 - urinary duct; 23 - navel; 24 - umbilical vein; 25 - sphincter; 26 - venous duct in the liver; 27 - hepatic vein; 28 - opening of the inferior vena cava; 29 - compensatory blood flow through the foramen ovale; 30 - superior vena cava; 31 - left brachiocephalic vein; 32 - right subclavian vein; 33 - right internal jugular vein; 34 - brachiocephalic trunk; 35 - portal vein; 36 - right renal vein; 37 - inferior vena cava; 38 - intestine

The flow of oxygenated blood from the placenta through the umbilical vein on the surface of the liver is distributed in two directions: one enters the portal vein, bringing with it 50% of all blood, the other, continuing the umbilical vein in the form of the duct of Arantius, flows into the inferior vena cava, where placental blood mixes with venous blood coming from the pelvic organs, liver, intestines and lower extremities. The blood flowing through the vena cava into the right atrium is divided into two channels. The bulk of the blood (60%) from the inferior vena cava, due to the presence of a valve-shaped fold in the right atrium (Eustachian valve), enters through the oval window into the left atrium, left ventricle and aorta. The remaining blood from the inferior vena cava and blood from the superior vena cava flows through the right atrium into the right ventricle and further into the pulmonary trunk. This blood is sent through the pulmonary artery to the non-functioning lungs and the ductus arteriosus, entering the descending aorta below the origin of the vessels that supply blood to the brain.

Thus, fetal circulation is characterized by:

Both ventricles contract and pump blood into the great vessels more parallel and simultaneously;

The right ventricle pumps approximately 2/3 of the total cardiac output;

The right ventricle pumps blood against a relatively greater loading pressure;

Pulmonary blood flow is reduced, accounting for approximately 7% of cardiac output (3.5% for each lung, respectively);

Functioning of hemodynamically significant shunts:

Blood flow through the ductus arteriosus, from right to left, accounts for 60% of total cardiac output;

The functioning of the right-left shunt, due to the higher resistance of the pulmonary artery relative to the aorta, despite the same pressure values ​​(70/45 mm Hg);

The pressure in the right atrium slightly exceeds the pressure in the left atrium;

Placental blood is 70% oxygenated and has an oxygen pressure of 28-30 mmHg;

Minor changes in the properties of blood are observed in the left atrium, so oxygen saturation is 65%, i.e., slightly exceeding in the right atrium - 55%. Oxygen pressure in the left atrium is 26 mm Hg, in contrast to the pressure in the right atrium - 16-18 mm Hg;

Oxygen pressure in the brain and myocardium is relatively higher;

Placental blood flow is divided into two streams:

Flow through the ductus venosus;

Flow through the liver, predominant in the left lobe;

Placental blood flow is characterized by a higher speed and low resistance of the vascular bed; this blood flow is responsible for the exchange of oxygen for carbon dioxide and serves to deliver nutrients to the fetus. Thus, the placenta is an active metabolic organ;

The lungs are a whole organ, oxygen is extracted in them, and after birth a change in metabolic functions occurs. Lungs in late gestation secrete intraalveolar fluid and produce surfactant;

There is a decrease in blood flow through the narrowing of the aorta;

Blood enters the right ventricle and pulmonary artery through the superior vena cava and coronary sinus.
Morphometric and hemodynamic parameters of the fetal heart

Fetal echocardiography allows for an objective assessment of the morphometric and hemodynamic parameters of the fetal heart.

In the physiology of the fetal blood circulation during the transition from intrauterine to postnatal life, much remains unclear. Features of fetal hemodynamics in the second half of uncomplicated pregnancy give reason to say that changes after birth are not only an abrupt restructuring of the functions performed by various parts of the heart. The identified features indicate the presence of systematic preparation of hemodynamics in the fetus for restructuring in extrauterine life, in which the left ventricle begins to prevail.

The blood circulation of the fetus is quite complex and has a number of distinctive features. From the first days of embryo maturation, a connection is established between mother and child. Subsequently, nutrients begin to circulate in both organisms separately.

What features of fetal blood circulation can be identified? How is communication between organisms formed? Answers to these and more questions can be found below.

brief information

During the first trimester of pregnancy, special regulation may occur in blood circulation processes. Basically, humoral mechanisms dominate over neural ones. Over time, the fetus begins to ripen and the blood circulation of the fetus undergoes a number of changes. Separately, it can be noted that increased growth of the sympathetic and parasympathetic nervous systems begins.

If atropine is periodically administered to a pregnant woman, it will change the heart rate of the fetus, not the woman. This process may indicate the beginning of cardiac regulation.

All the most necessary nutrients are supplied through the internal system from the female body to the fetus. This process is carried out thanks to a system of interacting capillaries. Excellent characteristics of fetal blood circulation are observed in the initial stages of intrauterine development.

Placental blood circulation is activated during the 1st trimester (2-3 months). Purified maternal blood begins to flow into the fetus through the umbilical vein. It refers to the umbilical cord, which in addition to the umbilical wreath has 2 more umbilical arteries. They just transfer blood from the fetus in the placental membrane.

The fascicular vein, entering the fetal body, begins to divide into two main branches. The first branch is the Arantian duct, which provides the transfer of purified arterial blood to the lowest pudendal vein. As a result, arterial and venous blood mixes and the blood becomes confused. The other branch carries arterial blood through the portal vein system, which drains into the liver of the fetus itself. There there is a complete cleansing of toxins. Only after complete cleansing does the blood begin to move into the inferior vena cava.

As a result, a mixture of venous and arterial blood begins to flow into the right atrium through the inferior vena cava. Then a small proportion of “pulmonary” blood enters the right ventricle through the right atrium. “Pulmonary” blood passes through the pulmonary circulation, the purpose of which is to constantly provide nutrients to the lung tissues, since at this stage they are not yet fully formed.

The predominant mass of mixed blood begins to flow through special openings located in the interatrial septum. The septum looks like a small oval, and the blood moves around the small circle straight into the left atrium. From there it begins its active movement into the left ventricle.

After the blood has fully entered the left ventricle, it begins to move through the aorta in the direction of the systemic circulation. The result is the following scheme: the mixed blood mass begins to move towards the organs and tissues of the fetus. During the movement, an endless flow of blood is ensured, which can only be provided by the Bathol Strait. It ensures continuous blood flow through the already formed pulmonary trunk, which exits the right ventricle.

The direct outflow of blood from the fetus begins in the direction of the 2 umbilical arteries. They extend from the abdominal aorta in a hollow direction towards the placenta. During this movement, carbon dioxide and other waste products are released through the placental system. The blood takes on a different state and becomes arterial. In the future, this cycle continues, and the body can fully function.

The mother's blood, rich in nutrients and oxygen, flows through the umbilical vein to the fetus. After passing the umbilical ring, the umbilical vein gives off branches to the liver and portal vein and then, in the form of the so-called duct of Arantius, flows into the inferior vena cava, which carries venous blood from the lower half of the body. The hepatic branches pass through the liver, merge into larger venous trunks and, in the form of hepatic veins, flow into the inferior vena cava.

Thus, arterial blood entering the fetal body from the umbilical vein is mixed with venous blood from the inferior vena cava and enters the right atrium, where the superior vena cava, carrying venous blood from the upper half of the body, flows. Between the mouths of the superior and inferior vena cava there is a valve, thanks to which mixed blood from the inferior vena cava is directed to the foramen ovale, located in the septum between the atria, and through it into the left atrium, and from here into the left ventricle.

The blood of the superior vena cava from the right atrium enters the right ventricle and from here into the pulmonary artery, but due to the fact that the lungs and pulmonary vessels of the non-breathing fetus are in a collapsed state, the blood, bypassing the pulmonary circulation, enters through the ductus arteriosus connecting the pulmonary artery and the aorta. directly into the aorta. Thus, blood enters the aorta in two ways: partly through the foramen ovale into the left atrium and left ventricle, and partly through the right ventricle and the ductus botalli. The vessels extending from the aorta nourish all organs and tissues, with the upper half of the body receiving blood richer in oxygen. Having given off oxygen and absorbed carbon dioxide, blood from the fetus enters the placenta through the umbilical arteries ( rice. 1). Fig 1. Diagram of blood circulation in the fetus: 1 - umbilical arteries; 2 - umbilical vein: 3 - duct of Arantius; 4 - aorta; 5 - lower vein; 6 - botal duct; 7 - right atrium; 8 - left atrium; 9 - pulmonary artery: 10 - left ventricle; 11 - right ventricle; 12 - superior vena cava; 13 - blood flow through the foramen ovale. So, the main distinguishing feature of intrauterine blood circulation is the shutdown of the pulmonary circulation, since the lungs do not breathe, and the presence of embryonic circulatory tracts - the foramen ovale, the Batallus and Arantius ducts.

During labor, contractions of the uterus begin to partially separate the placenta from the uterine wall, resulting in placental fetal circulation is violated. The amount of oxygen in the fetal blood decreases and the carbon dioxide content increases - a phase of oxygen starvation begins. With the correct course of labor, at the moment of birth of the child, due to irritation of the respiratory center, the child’s first breath occurs. For the occurrence of breathing, the reaction to a lower ambient temperature compared to intrauterine temperature and to the touch of hands on the child’s body is also important.

After the birth of a child, its direct connection with the mother’s body ceases. To get enough oxygen, the newborn must breathe vigorously. An indicator of sufficient breathing is a loud cry, as it occurs with forceful exhalation.

The absence of a loud cry indicates that the child’s lungs are poorly expanded and his breathing is not deep. In such cases, through various skin irritations or artificial respiration, a loud cry should be achieved. If a child breathes only 8-10 times per minute and does not cry, he cannot be transferred to the nursery.

With the baby's first breath, the lungs expand and the pulmonary vessels dilate. Thanks to the suction action of the lungs, blood from the right ventricle begins to flow into the lungs, bypassing the ductus botallis. Oxygen-enriched blood flows from the lungs through the pulmonary vein to the left atrium, then to the left ventricle. The flow of blood from the right atrium to the left stops - the foramen ovale gradually becomes overgrown, the Arantius and Botalli ducts and the remains of the umbilical vessels become empty, which gradually turn into connective tissue ligaments. With the birth of a child, his pulmonary circulation begins to function, and extrauterine circulation is established ( rice. 2). Rice. 2. Blood circulation pattern in a newborn. 1 - umbilical arteries; 2 - umbilical vein; 3 - Arantsian duct; 4 - aorta; 5 - inferior vena cava; 6 - botal duct; 7 - right atrium; 8 - left atrium; 9 - pulmonary artery; 10 - left ventricle; 11 - right ventricle; 12 - superior vena cava