During the embryonic and fetal periods in higher vertebrates, 3 circulatory systems are formed: vitelline, placental and pulmonary.

In the initial stages of development, following the separation of the umbilical vesicle, yolk circulation occurs, which consists of the appearance of arterial and venous vessels that entwine the wall of the yolk vesicle and gather into larger trunks in the area of ​​the umbilical ring. This circulation is of great importance in oviparous animals. In mammals it is poorly developed and is formed almost simultaneously with the placental circulation.

The latter performs the functions of the pulmonary circulation of adult individuals, since in the embryo the pulmonary circulation does not function. Placental circulation is characterized by the following anatomical features: the left and right halves of the heart are not separate, but are connected by an oval opening located between the atria; a membranous valve is attached to the edges of this opening, pressing into the cavity of the left atrium. The pulmonary artery is connected by a large anastomosis to the aorta, as a result of which the bulk of the blood from the right ventricle enters the aorta. Little blood flows into nonfunctional lungs. Two umbilical arteries are separated from the aorta, they run along the side walls of the bladder, penetrate through the umbilical canal, participating in the formation of the umbilical cord. Located between the allantois and chorion, the branches of the umbilical arteries approach the fetal part of the placenta and form a dense arterial network there, inserting their terminal branches into each villi. The arterioles of the villi pass into venules, the latter, gathering into larger trunks, forming the umbilical vein. The umbilical vein, as part of the umbilical cord, passes into the abdominal cavity and goes to the liver, where it flows into the portal vein. Ruminants and carnivores have an additional ductus venosus connecting the umbilical vein to the caudal cava. Peculiarities of fetal blood circulation: fetal blood is always poorer in oxygen than maternal blood, since oxygen is captured by fetal red blood cells only in the placental villi; the umbilical vein carries oxygenated blood; in the liver, the blood of the umbilical vein mixes with the venous blood of the portal vein; through the foramen ovale, blood from the right atrium penetrates into the left, mixes with venous blood from the pulmonary vein and enters the right ventricle; Blood entering the right ventricle is driven by its contraction from the pulmonary artery through the ductus botalli into the aorta. As a result of this mixing, the systemic blood contains little oxygen and the umbilical arteries carry “venous” blood.

During childbirth, when the umbilical cord is compressed or breaks, the fetus reflexively inhales, at the same time the valve of the oval opening closes, thus the right and left atria are isolated. After birth, the fetal provisional vessels turn into ligaments.

The growth of the embryo and fetus is extremely rapid, so it needs intensive nutrition. In many vertebrates, the fetus is fed by the yolk of the egg. In organisms at a higher stage of development, the nutrition of the fetus is partially provided by the yolk of the cell, but mainly as a result of the plastic material of the maternal body due to the placental connection between the pod and the mother. The higher the organization of the animal, the less role in the nutrition of the embryo the reserves of plastic material stored in the egg cell have. The circulatory systems of the mother and fetus are closely connected.

In the first days, the embryo develops due to the reserves of the cytoplasm of the egg. This explains the fact that during intensive fragmentation in the morula stage, the size of the embryo does not change. After the disappearance of the transparent shell, it begins to grow rapidly, drawing plastic material from the mother’s body. With the penetration of the embryo into the uterus, the trophoblast absorbs nutrients from the embryopeat (“royal jelly”). Embryotorf is the secretion of the uterine mucosa. Soon, a network of blood vessels in the yolk circulation develops; it extracts nutritional material from the yolk sac and distributes it to all elements of the embryo. In domestic animals, the yolk circulation cannot provide the fetus with nutrients; this role is played by the placental circulation. For the fetus, the placenta replaces the activity of a number of organs involved in metabolism in an adult animal. The functions of the placenta are carried out not only through osmosis and diffusion, but also through complex biochemical transformations of substances.

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, 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 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

For the embryo, blood circulation is the most important function, because it is through it that the fetus is saturated with nutrients.

Approximately two weeks after conception, the fetal cardiovascular system is formed, and from now on it needs a constant supply of nutrients.

You also need to carefully monitor the health of the expectant mother, because frequent illnesses will lead to abnormalities in the development of the embryo. That is why during pregnancy, it is recommended to constantly see a doctor.

How is the unborn child formed?

The formation of the unborn child occurs in stages, at each of which a system or organ develops.

The table below shows the stages of development of the unborn child:

Pregnancy period	Processes occurring in the womb
0 – 14 days	After the fertilized egg penetrates the uterus, a stage of fetal formation occurs within 14 days, called the yolk period. During these days, the cardiovascular system of the unborn child is formed. The embryo of a child is a yolk sac, which delivers the necessary nutrients to the embryo through the newly formed vessels.
21 – 30 days	After 21 days, the formed circulation of the embryo begins to function. In the period from 21 to 30 days, blood synthesis begins in the liver of the embryo, and here hematopoietic cells begin to form. This stage of development lasts until the fourth week of embryonic development. Along with this, the heart of the embryo develops, and the development of the heart begins with the primary circle of blood circulation. And twenty-two days later the first cardiac contraction of the embryo begins. The nervous system does not yet control it. The size of the heart at this stage is tiny and is about the size of a poppy seed, but there is already a pulse.
1 month	The formation of the heart tube occurs approximately on the 30-40th day of pregnancy, as a result of which the ventricle and atrium develop. The fetal heart is now capable of circulation.
Week 9	From the beginning of the ninth week of fetal development, blood circulation begins to work, with the help of which the vessels of the embryo join the placenta. A new level of supply of nutrients to the embryo occurs through the formed connection. By the ninth week, a heart with 4 chambers, main vessels, and valves is formed.
4 month	At the beginning of the 4th month, bone marrow is formed, which takes over the function of forming red blood cells and lymphocytes, as well as other blood cells. In parallel with it, blood synthesis begins in the spleen. From the beginning of the fourth month, the resulting blood circulation is replaced by the placental one. Now the placenta is responsible for all important functions and blood circulation for the healthy development of the fetus.
Week 22	Complete heart formation occurs between the twentieth and twenty-second weeks of pregnancy.

What is special about blood circulation in an embryo?

The embryo is connected to the mother by a channel through which nutrients are supplied, called the umbilical canal. This canal contains one vein and two arteries. Venous blood fills the artery, passing through the umbilical ring.

Entering the placenta, it is enriched with the necessary nutrients for the fetus, oxygen saturation occurs, after which it goes back to the embryo. All this happens inside the umbilical vein, which flows into the liver and divides inside it into 2 more branches. This blood is called arterial blood.

One of the branches in the liver enters the area of ​​the inferior vena cava, while the second branches from it and is divided into small vessels. This is how the vena cava becomes saturated with blood, where it mixes with blood that comes from other parts of the body.

Absolutely all blood flow moves to the right atrium. The hole located at the bottom of the vena cava allows blood to flow into the left side of the formed heart.

In addition to the listed unique features of a child’s blood circulation, the following should also be highlighted:

• The function of the lungs lies entirely with the placenta;
• First, the blood comes out of the superior vena cava, and only then fills the rest of the heart;
• If the embryo does not breathe, then the small capillaries of the lungs create pressure on the movement of blood, which in the artery of the lung is constant, but in the aorta decreases in comparison with it;
• Moving from the left ventricle and artery, the volume of blood ejected by the heart is formed and is 220 ml/kg/min.

When the blood circulates in the embryo, only 65% ​​is saturated in the placenta, the remaining 35% is concentrated in the organs and tissues of the unborn child.

What is fetal circulation?

The name fetal circulation of blood is also inherent in placental circulation of blood.

It also contains its own features:

• Absolutely all organs of the embryo are necessary for life (brain, liver and heart) and are fed with blood. It comes from the upper aorta, which is richer in oxygen than the rest of the body;
• There is a connection between the right and left halves of the heart. This connection occurs through large vessels. There are only two of them. One of them is responsible for blood circulation, using the oval window, in the septum between the atria. And the second vessel produces circulation through the opening separating the aorta and the pulmonary artery;
• It is due to these two vessels that the time of movement of the blood flow along the large circle of circulation is longer than in the small circle;
• At the same time, contraction of the right and left ventricles occurs;
• The right ventricle produces two-thirds more blood flow than the total output. During this time, the system stores high load pressure;
• With such blood circulation, the same pressure is maintained in the artery and aorta, which is usually 70/45 mmHg;
• The right atrium has higher pressure than the left.

Fast speed is a normal indicator of fetal circulation.

What is unique about blood circulation after birth?

In a full-term baby, after it is born, a number of physiological changes in the body occur, during which its vascular system begins to function independently. After cutting and ligating the navel cord, the exchange between mother and child stops.

In a newborn, the lungs themselves begin to function, and the working alveoli reduce the pressure in the pulmonary circulation by almost 5 times. As a result, there is no need for the ductus arteriosus.

When blood circulation through the lungs is started, substances are released that promote vasodilation. Blood pressure rises and becomes higher than in the artery of the lung.

From the first breath, changes begin that lead to the formation of a full-fledged human body, the oval window becomes overgrown, the bypass vessels are blocked, leading to a full-fledged functioning system.

Fetal circulatory abnormalities

To prevent any disturbances in the development of the unborn child, a pregnant girl should be constantly monitored by a qualified doctor. Because pathological processes in the body of the expectant mother affect deviations in the development of the fetus.

It is extremely necessary to examine the additional circulation, since its disruption can lead to serious complications, miscarriages and fetal death.

Doctors distinguish three forms into which fetal blood circulation disorders are divided:

• Placental (PN). It is a clinical syndrome in which structural and functional changes in the placenta occur, which affects the condition and normal development of the fetus;
• Fetoplacental (FPN). It is the most common complication of pregnancy;
• Uteroplacental.

The scheme of blood circulation is reduced to “mother – placenta – fetus”. This system helps remove substances that remain after metabolic processes and saturate the fetal body with oxygen and nutrients.

It also protects against viral infections, bacteria, and disease provocateurs entering the fetal system. Failure of blood circulation will lead to pathological changes in the embryo.

Diagnosis of circulatory problems

Problems with blood flow and any damage to the unborn child are determined using ultrasound (ultrasound) or Doppler (one of the types of ultrasound diagnostics that helps determine the intensity of blood circulation in the vessels of the uterus and umbilical cord).

When the examination takes place, the data is displayed on the monitor and the doctor monitors the manifestation of factors that may indicate a circulatory disorder.

Among them:

• Thinner placenta;
• The presence of diseases of infectious origin;
• Assessment of the state of amniotic fluid.

When performing Doppler measurements, the doctor can diagnose three stages of circulatory failure:

An ultrasound examination is a safe examination method for expectant mothers at any stage of pregnancy. Additionally, blood tests of the expectant mother may be prescribed.

Consequences of circulatory failure

In the event of a failure in the unified system of blood functioning from the mother to the placenta and embryo, placental insufficiency appears. This happens because the placenta is the main supplier of oxygen and nutrients to the embryo, and unites two main systems directly - the expectant mother and the fetus.

Any deviations in the mother’s body lead to disruptions in the blood circulation of the embryo.

Doctors always diagnose the degree of blood circulation disorder. If stage 3 is diagnosed, urgent measures are taken in the form of therapy or surgery.

According to statistics, about 25% of pregnant women experience placental pathology.

The formation of circulatory function, significantly different from the hemodynamics of an adult, is an important stage in the formation of the fetus. Through blood circulation, the child is saturated with nutrients. Disruption of the normal pattern of blood movement through the vascular system leads to the appearance of various anomalies in the intrauterine development of the embryo. How does fetal blood circulation occur? How dangerous is its violation for a child? Can this be prevented?

How does an embryo form?

Fetal development occurs in stages. At each stage of this process, which consists of 6 main stages and lasts about 22 weeks from the moment of conception, the formation of some internal organ or system occurs. Below is a general description of the intrauterine development of a child.	Fetal development stage	Gestational age
1	Intrauterine processes	First 2 weeks
2	Formation of the cardiovascular system, supplying the fetus with necessary substances through the formed vessels.	The launch of the formed circulatory system and the process of hematopoiesis, the synthesis of blood in the liver, the development of the heart and the primary circulatory system.
3	31–40 days	Formation of the heart tube, ventricle, atrium.
4	Week 9	Starting the blood circulation process, forming a heart with four chambers, main vessels and valves.
5	4 month	Formation of bone marrow, synthesis of blood in the spleen, replacement of the formed blood circulation with placental one.
6	Week 20–22	Final formation of the heart.

Features of blood circulation in the fetus

The anatomy of a child involves a connection with the mother through the umbilical canal, through which the components necessary for life are supplied to him. It consists of a vein and two arteries, which are filled with venous blood passing through the umbilical ring.

When it enters the placenta, it is enriched with nutrients necessary for the full development of the fetus, saturated with oxygen, and then returned to the embryo. This process occurs in the umbilical vein, which flows into the liver and branches in two. One of the branches “flows” into the inferior vena cava, the other forms microvessels.

In the vena cava, blood saturated with everything necessary merges with that coming from other parts of the body. All blood flow moves towards the right atrium. The hole in the lower part of the vena cava directs blood to the left region of the formed heart. In addition, the fetal blood flow has the following features:

• the placenta performs the functions of the lungs;
• blood fills the heart after leaving the superior vena cava;
• in the absence of breathing, the microcapillaries of the lungs exert pressure on the movement of blood, which is constant in the artery of the lung, and decreases in relation to it in the aorta;
• the amount of blood ejected by the heart when moving from the left ventricle and artery per minute is 220 ml/kg;
• 65% of the blood circulating in the embryo is saturated in the placenta, the rest is concentrated in its organs and tissues.

What is fetal circulation?

Fetal blood circulation is characterized by high speed. It has the following specifics:

• presence of placental circulation;
• dysfunction of the pulmonary circulation;
• blood flow into the systemic circulation, bypassing the small one, through two right-left shunts;
• the predominance of the minute volume of the systemic circulation over this amount obtained through the small closed vascular pathway;
• nutrition of embryonic organs with mixed blood;
• maintaining pressure in the artery and aorta within a constant value of 70/45 mm Hg. Art.

Abnormalities in the fetal circulatory system

To prevent abnormalities in fetal hemodynamics, it is recommended to undergo regular examinations. The activity of pathogenic agents in the female body can provoke placental insufficiency.

The “mother-placenta-fetus” blood circulation pattern protects the baby from the influence of pathogens. The failure of this process will provoke a disruption in the development of the embryo.

The table provides information about the types of this phenomenon.

Classification of blood flow disorders		Description
By bookmarking dates	Primary	Occurs before 16 weeks of gestation. The formation and functioning of the placenta is negatively affected by inflammatory processes in a woman’s body, problems with the thyroid gland, and infections. Incomplete implantation of the embryo by the end of the 12th week of pregnancy inhibits the formation of uteroplacental blood flow.
	Secondary	The already formed placenta is damaged.
With the flow	Acute	Failure of the gas exchange function of the placenta. Blood flow is disrupted by a heart attack, premature separation of the placenta from the walls of the uterus, and blockage of the blood vessels of the placenta.
	Chronic	They often have a secondary genesis.
According to severity	Compensated	Minor symptoms of the pathological process at an early stage lead to slight tension, activation of defense mechanisms and the ability to adapt to changes.
	Subcompensated	The negative impact leads to overexertion, which reduces the compensatory capabilities of blood flow. Prolonged oxygen starvation and lack of nutrients cause a delay in the child’s development and incoordination of blood movement.
	Decompensated	The compensatory capabilities of blood flow are reduced due to increased tension.

Diagnosis of circulatory disorders

In the early stages of blood flow disturbances, the clinical picture is insignificant. Making a diagnosis in this case begins with an analysis of the patient’s complaints, collection of anamnesis and physical examination. After this, she is prescribed additional procedures. The table reflects information about the manipulations used to diagnose abnormalities in the blood flow of the embryo.

Diagnostic methods	Types of diagnostic procedures	Purpose of the event
Laboratory	Blood analysis	Analysis of alkaline phosphatase and oxytocin concentrations.
	Analysis of urine	Estradiol level determination
Instrumental	Sonographic photometry	Determination and comparison of embryo sizes with normal values
	Placentography	Identification of the place of attachment, size and shape of the placenta.
	Echocardiographic functional study of the state of the fetoplacental complex	Assessment of tone, respiratory, motor and cardiac function.
	Dopplerography	Determination of the nature of blood circulation between the placenta and the child by hemodynamics in the arteries of the umbilical cord, the aorta of the embryo, and the arteries of the uterus.
	Cardiotocography	Tracking changes in heart rate under the influence of various external and internal stimuli.

Consequences of circulatory pathologies

This pathological phenomenon can cause:

• spontaneous termination of gestation;
• lack of oxygen (intrauterine hypoxia);
• congenital heart defects;
• increasing the likelihood of prenatal or perinatal death of the child;
• premature detachment or aging of the placenta;
• gestosis;
• internal lesions;
• external deformities.

Treatment of pathology

Therapy in this case depends on the etiology and implies an integrated approach:

• To normalize blood circulation, Hofitol, Pentoxipharm or Actovegin are used;
• Curantil is used to increase vascular permeability;
• Drotaverine or No-Shpa is prescribed to dilate blood vessels;
• to reduce the tone of the uterus and improve blood flow, drip administration of magnesium and oral administration of Magnesium B6 are indicated;
• Vitamins E and C contribute to the achievement of an antioxidant effect.

Prevention of blood flow disorders during pregnancy

To prevent this problem, a pregnant woman needs to:

• eat well;
• maintain a drinking regime (in the absence of water-salt imbalance);
• control body weight;
• do not allow pressure to increase;
• visit a gynecologist regularly;
• promptly eliminate identified pathologies.

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 for understanding 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 enters the right ventricle through the tricuspid valve, from where it enters the lungs through the pulmonary trunk (= pulmonary artery).

Scheme: vena cava? right atrium? ? right ventricle? [pulmonary valve] ? 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 ejected 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 complicated, 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 diagram
(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 systemic 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 organ of all that receives pure 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 extend from the aorta above the level of the confluence of the 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 of the umbilical arteries also become overgrown. 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. There are congenital heart defects in 1% of newborns. Most often registered:

• defect(non-closure) 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.