Where is the umbilical vein located in the fetus. Fetal circulation and its changes after birth

FETAL BLOOD CIRCULATION

The blood circulation of the fetus is otherwise called placental circulation: in the placenta, an exchange of substances occurs between the blood of the fetus and the maternal blood (in this case, the blood of the mother and the fetus does not mix). In the placenta, placenta, begins with its roots umbilical vein, v. umbilicalis, through which arterial blood oxidized in the placenta is directed to the fetus. Following as part of the umbilical cord (umbilical cord), funiculus umbilicalis, to the fetus, the umbilical vein enters through the umbilical ring, anulus umbilicalis, into the abdominal cavity, goes to the liver, where part of the blood through venous duct, Arantiev (ductus venosus) reset to inferior vena cava v. cava inferior, where it mixes with venous blood ( 1 mix ), and the other part of the blood passes through the liver and through the hepatic veins also flows into the inferior vena cava ( 2 mixing ). Blood through the inferior vena cava enters the right atrium, where its main mass, through the valve of the inferior vena cava, valvula venae cavae inferioris, passes through oval hole, foramen ovale, interatrial septum into the left atrium. From here it follows into the left ventricle, and then into the aorta, through the branches of which it is directed primarily to the heart, neck, head and upper limbs. In the right atrium, except for the inferior vena cava, v. cava inferior, brings venous blood to the superior vena cava, v. cava superior, and coronary sinus of the heart, sinus coronarius cordis. Venous blood entering the right atrium from the last two vessels is sent, together with a small amount of mixed blood, from the inferior vena cava into the right ventricle, and from there into the pulmonary trunk, truncus pulmonalis. The arch of the aorta, below the place where the left subclavian artery departs from it, flows into ductus arteriosus, ductus arteriosus (Botallov duct), through which blood from the latter flows into the aorta. From the pulmonary trunk, blood flows through the pulmonary arteries into the lungs, and its excess through the arterial duct, ductus arteriosus, is sent to the descending aorta. Thus, below the confluence of the ductus arteriosus, the aorta contains mixed blood ( 3 mixing ), entering it from the left ventricle, rich in arterial blood, and blood from the ductus arteriosus with a high content of venous blood. Through the branches of the thoracic and abdominal aorta, this mixed blood is directed to the walls and organs of the thoracic and abdominal cavities, pelvis and lower extremities. Part of the said blood follows two paths - right and left - umbilical arteries, aa. umbilicales dextra et sinistra , which, located on both sides of the bladder, exit the abdominal cavity through the umbilical ring and, as part of the umbilical cord, funiculus umbilicalis, reach the placenta. In the placenta, the fetal blood receives nutrients, releases carbon dioxide and, enriched with oxygen, is again sent through the umbilical vein to the fetus. After birth, when the pulmonary circulation begins to function and the umbilical cord is ligated, a gradual desolation of the umbilical vein, venous and arterial ducts and distal parts of the umbilical arteries occurs; all these formations become obliterated and form ligaments.

Umbilical vein, v. umbilicalis , forms round ligament of the liver, lig. teres hepatis; ductus venosus - venous ligament lig. venosum; ductus arteriosus, ductus arteriosus - ligament arteriosus lig. arteriosum and from both umbilical arteries, aa. umbilicales , cords are formed, medial umbilical ligaments, lig g . umbilicalia medialia , which are located on the inner surface of the anterior abdominal wall. Overgrown also foramen ovale, foramen ovale , which turns into fossa ovalis, fossa ovalis , and the valve of the inferior vena cava, valvula v. cavae inferioris, which has lost its functional significance after birth, forms a small fold stretched from the mouth of the inferior vena cava towards the fossa ovale.

Fig. 113. Fetal circulation

1 - placenta; 2 - umbilical vein (v. umbilicalis); 3 - portal vein (v. portae); 4 - ductus venosus (ductus venosus); 5 - hepatic veins (vv. hepaticae); 6 - oval hole (foramen ovale); 7 - ductus arteriosus (ductus arteriosus); 8 - umbilical arteries (aa. umbilicales)

Umbilical cord, or umbilical cord (funiculus umbilicalis), occurs when the ventral wall of the embryo closes and its body separates from the amnion and yolk sac. In this process, already described in previous chapters, the umbilical duct, the allantois outlet (urachus), the vessels formed in the allantois mesoderm (umbilical vessels), and the mesoderm of the embryonic trunk are compressed into an increasingly thinner cord, the surface of which is finally covered ectodermal epithelium of the amnion.

Thus, umbilical cord appears, cord connecting the placenta to the ventral wall of the fetal body; The umbilical cord contains umbilical cord vessels, which provide a connection between the fetal blood circulation and the capillary network of the placenta (chorion).

Umbilical duct and the urinary tract of the fetus in the second month of pregnancy becomes obliterated and then completely disappears, and therefore not a trace of them remains in the developed umbilical cord. In a similar way, at an early stage, the reverse development of the umbilical-mesenteric vessels occurs - the yolk vessels (vasa omphalomesenterica), which were first located in the area of ​​the yolk sac. Finally, the remainder of the yolk sac (vesicula umbilicalis) also disappears, which first remains for some time between the chorion in the area where the umbilical cord attaches to the placenta, and then also disappears.

Full-term human fetal umbilical cord It is a cord, 40-50 cm long with a diameter of approximately 1.5 cm. It lies between the inner (fetal) side of the placenta and the ventral wall of the fetal body. The surface of the umbilical cord is covered with the ectodermal epithelium of the amnion, which in the placenta imperceptibly passes into the amniotic ectoderm covering the inner surface of the placenta, and towards the fetus passes directly into the skin (epidermis) of the surface of the fetus or, rather, the newborn.

Place of attachment umbilical cord towards the ventral wall of the fetal body it has a ring-shaped shape (umbilicus, umbilicus). The basis of the umbilical cord stroma is formed by embryonic jelly-like tissue containing a relatively small number of cells, some fibrils and a significant amount of gelatinous ground substance (Wharton's jelly). Rudiments of the umbilical duct and urinary tract of the embryo in the full-term umbilical cord are usually absent.

In the stroma of the umbilical cord umbilical vessels pass through, namely one umbilical vein, initially laid in pairs, and two umbilical arteries. The umbilical vein (vena umbilicalis) carries oxygenated fetal blood from the capillary network of the chorionic villi of the placenta into the fetal body, while the two umbilical arteries drain oxygen-deprived blood into the placenta. At the site of attachment of the umbilical cord to the placenta, the umbilical vessels first branch in the chorionic membrane into fairly large branches that are visible through the amniotic membrane of the placenta.
Smaller branches of these branches then pass into the chorionic villi, forming a capillary network in them.

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We all have one place on our body that reminds us that we once lived in the womb and were completely dependent on it - this is the navel.

What is the function of a baby's umbilical cord?

The umbilical cord is the connection between a woman and a child. The umbilical cord supplies nutrients to the fetus and also produces waste products. The mother's umbilical cord is connected to the placenta and the baby's umbilical ring. It forms in the second week of pregnancy. The umbilical cord is important to the baby's life, but it can also pose a threat to the fetus.

Structure of the umbilical cord

The umbilical cord consists of several arteries, two veins and three vessels. Sometimes it happens that one vessel is missing in the umbilical cord; usually this does not interfere with the normal development of the fetus. If such a defect is detected in the umbilical cord, it is necessary to examine the child to see if his kidneys are functioning normally. Since such a defect can lead to kidney failure, or the absence of one kidney. The umbilical cord does not connect directly to the baby. On the way from mother to child, all nutrients pass through the umbilical cord through the placenta, which prevents mixing of the blood of mother and child.
As the umbilical cord arteries develop, they twist around the vein in a spiral.

When the umbilical cord vessels develop too quickly, tangles appear on the vessels. With varicose veins, false nodular expansions occur. Such nodes do not obstruct blood flow.

In addition to false ones, there are also worn nodes that occur during the movement of the fetus in the womb and during childbirth; they also do not pose a danger to the fetus. Only in the early stages of pregnancy, a tightened knot can cause disruption of blood flow in the umbilical cord.

Why can the umbilical cord become a threat to the baby?

Umbilical cord entanglement

At the end of pregnancy, the umbilical cord is usually about 60 cm long - this is its normal length. If the umbilical cord reaches 40 cm by the end of pregnancy, it can be considered short, and more than 70 cm - long. An umbilical cord that is too long can wrap around the baby's body or throat, putting the baby's life at risk. As a result of the baby being entangled in the umbilical cord, childbirth can be seriously difficult. This can also lead to perinatal hypoxia (lack of oxygen in the baby). However, having blood vessels wrapped around the neck does not mean that your baby will be harmed. If doctors notice that the baby is entwined with the umbilical cord, they will closely monitor the fetal reaction and its development. Many children are born with the umbilical cord entwined and are completely healthy.

Also, due to the fact that the baby is entwined with the umbilical cord and constantly pulls on it, premature placental abruption can occur. If doctors discover this complication, an urgent caesarean section is necessary to save the child’s life.

How is the umbilical cord cut?

After the baby is born, the umbilical cord must be cut. Doctors do this using clamps and a surgical scalpel. The umbilical cord must be cut at exactly the right moment. If it is cut off too quickly, oxygenated blood will not have time to return from the placenta to the baby’s vascular system. This can lead to a decrease in the level of hemoglobin and iron in the baby's blood. To determine a newborn's blood type and Rh factor, doctors take blood from the umbilical vein.
Typically, the umbilical cord is tied 2 cm above the baby's abdomen, and cut 1 cm above the ligation site.

A small part of the umbilical cord remains in place of the newborn's navel; after about a month, it dries out and falls off. And the small dimple, our navel, remains as a memory of the connection with our mother.

Glossy surface, spirally twisted, its length during full-term pregnancy is usually 50-60 cm, diameter at the umbilical ring is 1.5-2 cm. More often, P. is attached in the center of the placenta (central attachment), less often eccentrically (lateral attachment) or at the edge of the placenta (marginal attachment). The umbilical cord contains two umbilical arteries and one umbilical artery, along which nerve fibers are located. The vessels and P. are surrounded by a gelatinous substance -. On the outside, P. is covered with amnion (see Membrane). In P., nodular thickenings (false nodes) are observed, their occurrence is caused by thickening of the arteries, varicose veins, and accumulations of Wharton's jelly.

II Umbilical cord

1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary of Medical Terms. - M.: Soviet Encyclopedia. - 1982-1984.

Synonyms:

See what “Umbilical Cord” is in other dictionaries:

UMBILICAL CORD- (funiculus umbilicalis), syn. The umbilical cord is a cord that connects the fetal navel with the placenta and contains vessels that serve the purpose of nutrition and respiration of the intrauterine fetus (umbilical vessels 2 arteries and 1 vein), as well as remnants... ... Great Medical Encyclopedia

UMBRICAL CORD, a long thick cord that connects the developing EMBRYO to the PLACENTA. The umbilical cord contains two large arteries and one vein. During childbirth, the umbilical cord is clamped and separated from the placenta. Part of it remaining on the child’s belly dries out and... ... Scientific and technical encyclopedic dictionary

UMBRICAL CORD, s, female. A dense cord connecting the fetal body to the placenta and serving as a channel for its nutrition. | adj. umbilical cord, oh, oh. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 … Ozhegov's Explanatory Dictionary

Umbilical cord, cord, connection Dictionary of Russian synonyms. umbilical cord noun, number of synonyms: 5 omphaloneurons (2) ... Synonym dictionary

In humans and placental mammals, it connects the fetus with the placenta. The umbilical cord contains 2 umbilical arteries and an umbilical vein... Big Encyclopedic Dictionary

UMBILICAL CORD, umbilical cord, female. (anat.). A veiny tube connecting the embryo of mammals (and humans) to the uterus and serving as a channel for transferring nutrition to the embryo from the mother’s body. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 … Ushakov's Explanatory Dictionary

Umbilical cord (funiculus umbilicalis), a cord that connects the fetus to the placenta and, through it, to the mother’s body in all placental animals and humans. Consists mainly made of connective tissue with a gelatinous consistency (the so-called Wharton’s jelly), in a swarm... ... Biological encyclopedic dictionary

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The fetus receives the nutrients and oxygen necessary for life from the mother through the vessels children's place, or placenta.

The placenta is connected to the fetus by the umbilical cord, which contains two umbilical arteries(branches of the internal iliac arteries of the fetus) and umbilical vein. These vessels pass from the cord into the fetus through an opening in its anterior abdominal wall (umbilical ring). Through the arteries, venous blood is delivered from the fetus to the placenta, where it is enriched with nutrients, oxygen and becomes arterial. After this, the blood returns to the fetus through the umbilical vein, which approaches its liver and divides into two branches. One of them flows directly into the inferior vena cava (ductus venosus). The other branch passes into the portal of the liver and divides into capillaries in its tissue.

Rice. 2.17 Fetal circulation

From here, the blood drains through the hepatic veins into the inferior vena cava, where it mixes with venous blood from the lower part of the body and enters the right atrium. The opening of the inferior vena cava is located opposite the foramen ovale in the interatrial septum (Fig. 2.17). Therefore, most of the blood from the inferior vena cava enters the left atrium, and from there into the left ventricle. In addition, the pulsating flow of blood from the placenta coming through the umbilical vein can temporarily block the flow of blood through the portal vein. Under these conditions, predominantly oxygenated blood will enter the heart. In between, venous blood enters the heart through the superior and inferior vena cava.

As previously described, most of the venous blood from the right atrium enters the right ventricle and then into the pulmonary artery. A small volume of blood goes to the lungs, but most of it through the ductus arteriosus enters the descending aorta after the arteries to the head and upper extremities depart from it and disperses through the systemic circulation, connected through the umbilical arteries to the placenta.

Thus, both ventricles pump blood into the systemic circulation, so their walls have almost equal thickness. Purely arterial blood flows in the fetus only in the umbilical vein and ductus venosus. Mixed blood circulates in all other vessels of the fetus, but the head and upper torso, especially in the first half of intrauterine development, receive blood from the inferior vena cava, which is less mixed than the rest of the body. This promotes better and more intensive brain development.

Changes in blood circulation after birth

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At birth, placental circulation is interrupted and pulmonary respiration begins. The enrichment of blood with oxygen occurs in the lungs. Compression of the umbilical vessels leads to a decrease in the amount of oxygen and an increase in the amount of carbon dioxide in the circulating blood. Irritation of receptors in the walls of blood vessels and neurons of the respiratory center causes a reflex inhalation. With the first breath of a newborn, the lungs expand and all the blood from the right half of the heart passes through the pulmonary artery into the pulmonary circulation, bypassing the ductus arteriosus and foramen ovale. As a result, the duct becomes empty, the smooth muscle cells in its wall contract and after some time overgrow, remaining in the form of an arterial ligament. The oval opening is obscured by a fold of the endocardium, which soon grows to its edges, causing the opening to turn into an oval fossa.

From birth, venous blood circulates in the right half of the heart, and only arterial blood circulates in the left. The vessels of the umbilical cord become empty, the umbilical vein turns into the round ligament of the liver, the umbilical arteries into the lateral umbilical ligaments running along the inner surface of the abdominal wall to the navel.

Age-related changes in the structure of the circulatory system

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The heart of children in the first year of life is spherical, the walls of the ventricles vary little in thickness. The atria are large, with the right one being larger than the left. The mouths of the vessels flowing into them are wide. In the fetus and newborn, the heart is located almost across the chest. Only at the end of the first year of life, due to the child’s transition to a vertical body position and the lowering of the diaphragm, the heart assumes an oblique position. In the first two years, the heart grows vigorously, with the right ventricle lagging behind the left. An increase in the volume of the ventricles leads to a relative decrease in the size of the atria and their appendages. From 7 to 12 years of age, heart growth slows down and lags behind body growth. During this period, careful medical monitoring of the development of schoolchildren is especially important, aimed at preventing heart overload (hard physical work, excessive interest in sports, etc.). During puberty (at 14–15 years), the heart grows rapidly again.

The development of blood vessels is associated with body growth and the formation of organs. For example, the more intensely muscles function, the faster the diameter of their arteries increases. The walls of large arteries form faster, and the number of layers of elastic tissue in them increases most noticeably. At the same time, the propagation of the pulse wave through the arterial vessels is stabilized. In children, more intense blood flow is observed in the brain than in adults. Blood flow changes little during exercise; these changes are different in children of different ages. Using the rheoencephalography method, it was found that in right-handed people, during exercise, the blood flow of the left hemisphere increases more intensely than the right.

Slow enlargement of the heart continues after 30 years. Individual fluctuations in the size and weight of the heart may be due to the nature of the profession. With old age, in the walls of the aorta and other large arteries and veins, the number of elastic and muscular elements decreases, connective tissue grows, the inner lining thickens, and seals form in it - atherosclerotic plaques. As a result, the elasticity of the blood vessels noticeably decreases, and the blood supply to the tissues deteriorates.