A scientist who described the blood supply to the fetus. Fetal circulation. The size of the fetus. Diagnosis of circulatory failures

It fluctuates according to the metabolic processes taking place in it. During pregnancy, its intensity in the uterus increases 20-40 times.
Implantation of a fertilized egg is accompanied by the expansion of the uterine vessels and the formation of lacunae, which contain maternal blood. Here, the mother's blood is exchanged with the blood of the fetus by the capillaries of the chorionic villi. There is a placental barrier between the blood of the mother and the fetus, which consists of the endothelium of the capillaries of the umbilical vessels and two layers of cells that form the walls of the chorionic villi. Its thickness is 2-6 microns, i.e. slightly larger than the thickness of the pulmonary membrane. The transition of compounds across the placental barrier occurs by diffusion and active transport. Ghazni, glucose, amino acids diffuse along the concentration gradient. However, in the blood of the fetus, many substances are contained in a higher concentration than in the mother's blood. These include Na +, K +, Ca2 +, vitamins Bb, Bb, Bl2, C. This indicates active transport. As a rule, the placental barrier is impermeable to compounds with a molecular weight of more than 1000. But there are exceptions to this rule. For example, thyroxin, vasopressin and some other substances that have a large molecular weight pass through the placenta.
By the end of pregnancy, up to 700-800 ml of blood passes through the vessels of the uterus in 1 minute, which is almost 2 times more than through the placenta from the side of the fetus. The permeability of the placental membrane for oxygen is lower than that of the lung. This is partly offset by the high affinity of fetal hemoglobin (HbF) in oxygen.
From the placenta, arterial blood enters the fetus by an odd vein in the umbilical cord. Part of it immediately enters the liver, which ensures the intensive development of this organ. Having passed the liver, the blood flows into the inferior vena cava, where, together with the rest of the arterial blood, it mixes with the venous, moving in the direction from the lower half of the body to the upper half into the right atrium, together with the mixed blood from the inferior vena cava, venous blood flows from the superior vena cava. From the right atrium, it goes to the left atrium through the foramen ovale and then to the left ventricle and aorta. The second part of the blood enters the right ventricle and pulmonary trunk, and since the vessels of the fetal lungs are narrowed, almost all of the blood from the right ventricle through the ductus arteriosus is also sent to the aorta.
However, in the right atrium, there is no complete mixing of blood coming from the inferior and superior vena cava. The more oxygenated blood of the inferior vena cava, due to the protrusion on the wall of the right atrium, enters mainly the left half of the heart. This blood from the aortic arch first enters the coronary vessels, brain and upper extremities. This ensures the development of these parts of the body during the prenatal period. The blood remaining, mixing with the less oxygenated blood of the ductus arteriosus, flows through the descending aorta to the organs of the lower half of the body and the placenta.
At the end of pregnancy, both ventricles function in parallel and pump up to 750 ml of blood in 1 minute, about 60% of this amount of blood enters the placenta, and 40% - to fetal tissues.
Cessation of placental circulation after birth significantly alters the baby's blood flow conditions. First, when the umbilical arteries are excluded from the circulatory system, the peripheral resistance of the vessels of the systemic circulation increases sharply. This leads to an increase in blood pressure from 60-70 mm Hg. Art. (8-9.3 kPa) at the end of pregnancy up to 85-90 mm Hg. Art. (11.3-12 kPa) after birth. Secondly, with the onset of pulmonary respiration, the hydrostatic resistance of the vessels of the pulmonary circulation decreases almost 5 times and the blood flow through them sharply increases. Third, the cessation of blood flow from the placenta leads to a decrease in the volume and pressure of blood in the right atrium, while the sharply increased blood flow through the pulmonary veins leads to an increase in pressure in the left atrium. Due to the pressure gradient that occurs between the atria, the oval valve closes. By the end of the second month after birth, this hole grows.
Immediately after birth, due to an increase in pressure in the aorta and a decrease in pressure in the pulmonary artery, some of the blood flows through the ductus arteriosus against the flow that went during the prenatal period (from the aorta to the pulmonary artery). But soon, due to the contraction of the smooth muscles of the strait, the blood flow through it decreases, and after 1-8 days it almost completely stops. The main reason for the contraction of smooth muscles is an increase in the oxygen tension in the aortic blood now coming from the lungs. But if the Raoi level decreases, then the ductus arteriosus may reopen. The spasm of the strait is accompanied by ischemia of the wall itself, which leads to the development of connective tissue in it and anatomical closure of the duct. This usually happens in 2-5 months.
The regulation of blood flow during the prenatal period is still imperfect. Although vessels are well innervated from the 4th month and reflexogenic zones appear early, their reflexes are still weak. In the fetus, myogenic and humoral mechanisms of regulation are more pronounced. The vascular tone depends mainly on the automatism of muscle cells, their response to pressure and hormonal and metabolic factors. The tension of oxygen in the blood also affects the tone of the vessels: with a decrease in the level of Rao, the tone of the vessels of some organs weakens, with an increase, on the contrary, it increases. At. hypoxia, the heart rate increases, the vessels of skeletal muscles and skin are narrowed, blood flow through the umbilical vessels increases. Norepinephrine and vasopressin increase the movement of blood across the placenta, while angiotensin II decreases it.
After birth, the blood circulation regulation system is gradually improved. This process is completed only towards the end of puberty. In babies under the age of 7-8 months, the depressor reflex from the baroreceptors of the carotid sinus and aortic zones is not yet expressed. Reflex mechanisms of blood flow regulation are more actively formed during the formation of the child's motor system. First, at about the end of the first year of life, reflexes are formed from chemoreceptors, and then, gradually, from baroreceptors. The renin-angiotensin-aldosterone system is involved in the regulation of blood circulation in newborns.

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

After about two weeks, after conception, the fetal cardiovascular system is formed, and from that time on, he needs a constant influx 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 be constantly monitored by a doctor.

How does the formation of the unborn child take place?

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 in the womb
0 - 14 days	After the penetration of the fertilized egg into the uterus, the stage of fetal formation, called the yolk period, takes place in 14 days. During these days, the cardiovascular system of the unborn child is being formed. The embryo of the child is the yolk sac that delivers the necessary nutrients to the embryo through the newly formed vessels.
21 - 30 days	After 21 days, the formed circle of the embryo's blood circulation begins to function. In the period from 21 to 30 days, the start of blood synthesis in the liver of the embryo takes place, here hematopoietic cells begin to form. This developmental stage lasts until the fourth week of embryo development. Together with this, the heart of the embryo develops, and the development of the heart begins from the primary circle of blood circulation. And twenty-two days later, the first heartbeat of the embryo begins. The nervous system does not yet control him. The size of the heart at this stage is tiny and is the approximate size of a poppy seed, but the pulse is already there.
1 month	The formation of the heart tube occurs at about 30-40 days of pregnancy, as a result of which the ventricle and atrium develop. The embryo's heart is now able to circulate.
9 week	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, valves is formed.
4 month	At the beginning of 4 months, the bone marrow is formed, which takes over the function of forming erythrocytes and lymphocytes, as well as other blood cells. In parallel with it, the synthesis of blood in the spleen begins. From the beginning of the fourth month, the formed 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.
22 week	Full formation of the heart occurs from the twentieth to twenty-second weeks of pregnancy.

What is especially the circulation of blood in the embryo?

Connects the embryo to the mother by a channel through which nutrients are supplied, called the umbilical. This canal contains one vein and two arteries. Venous blood fills the artery as it passes through the umbilical ring.

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

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

Absolutely the entire 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 uniqueness of the circulation of the child's blood, the following should also be highlighted:

• Lung function rests entirely on the placenta;
• First, blood comes out of the superior vena cava, and only then fills the rest of the heart;
• If the embryo does not have respiration, then the small capillaries of the lungs create pressure on the movement of blood, which in the artery of the lung is unchanged, and in the aorta it falls in comparison with it;
• Moving from the left ventricle and artery, the volume of blood ejection by the heart is formed, and it is 220 ml / kg / min.

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

What is fetal circulation?

The name fetal circulation is also associated with placental circulation.

It also contains its own characteristics:

• Absolutely all organs of the embryo are necessary for life (brain, liver and heart) and feed on blood. It is supplied from the superior aorta and is more oxygenated 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 with the help of the opening separating the aorta and the artery of the lung;
• 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, there is a contraction of the right and left ventricles;
• The right ventricle produces two-thirds more blood flow than total ejection. At this time, the system stores a large load pressure;
• With such blood circulation, the same pressure is maintained in the artery and aorta, which is usually 70/45 mm Hg;
• The right atrium differs in greater pressure than the left.

Fast speed is a normal indicator of fetal circulation.

Why is blood circulation unique after birth?

In a fully-fledged full-term baby, after he is born, a number of physiological changes in the body take place, during which his vascular system begins to function independently. After cutting and bandaging the edging of the navel, 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 small circle of circulation by almost 5 times. As a consequence, there is no need for a ductus arteriosus.

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

From the first breath, changes begin, leading to the formation of a full-fledged human body, overgrowth of the oval window occurs, bypass vessels are blocked, coming to a full-fledged system of functioning.

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 the abnormalities in the development of the fetus.

It is imperative to examine the additional circle of blood circulation, since its violation can lead to serious complications, miscarriages and fetal death.

Doctors share three forms according to which disorders of fetal blood circulation are divided:

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

The scheme of action of blood circulation is reduced to "mother - placenta - fetus". This system helps to remove substances that remain after metabolic processes, and to saturate the fetus's body with oxygen and nutrients.

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

Diagnosis of circulatory failures

Determination of problems with blood flow, and any damage to the unborn child, occurs using ultrasound (ultrasound), or Doppler (one of the types of ultrasound diagnostics that helps to 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 circulatory disorders.

Among them:

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

When performing dopplerometry, 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 the embryo, placental insufficiency appears. This is because the placenta is the main supplier of oxygen and nutrients for the embryo, and unites the two main systems of the immediate future mother and fetus.

Any deviations in the mother's body lead to a failure of the embryo's blood circulation.

Doctors always diagnose the degree of blood circulation disorder. In the case of a diagnosis of the 3rd degree, urgent measures are taken in the form of therapy or surgery. According to statistics, about 25% of pregnant women are exposed to pathology of the placenta.

The mother's blood, rich in nutrients and oxygen, travels through the umbilical vein to the fetus. Having passed the umbilical ring, the umbilical vein gives off branches to the liver and portal vein and then, in the form of the so-called Arancian duct, 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 the larger venous trunks and, in the form of hepatic veins, flow into the inferior vena cava.

Thus, arterial blood entering the fetus from the umbilical vein mixes with the venous blood of the inferior vena cava and enters the right atrium, where the superior vena cava flows, carrying venous blood from the upper half of the body. Between the mouths of the superior and inferior vena cava there is a valve, due to which the mixed blood from the inferior vena cava is directed to the oval opening located in the septum between the atria, and through it to the left atrium, and from here to 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, through the botal duct connecting the pulmonary artery and the aorta, enters directly into the aorta. Thus, blood enters the aorta in two ways: partly through the foramen ovale into the left atrium and the left ventricle, and partly through the right ventricle and botallic duct. The vessels departing from the aorta nourish all organs and tissues, and the upper half of the body receives blood richer in oxygen. After giving oxygen and absorbing carbon dioxide, blood from the fetus enters the placenta through the umbilical arteries ( rice. 1). Fig 1. Scheme of blood circulation in the fetus: 1 - umbilical arteries; 2 - umbilical vein: 3 - arantia duct; 4 - aorta; 5 - the lower part of the vein; 6 - botall 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 circulation is the shutdown of the pulmonary circulation, since the lungs do not breathe, and the presence of embryonic blood pathways - the foramen ovale, Batall and Arantia ducts.

During childbirth, with contractions of the uterus, partial separation of the placenta from the uterine wall begins, resulting in a placental fetal circulation is violated. In the blood of the fetus, the amount of oxygen decreases and the content of carbon dioxide increases - the phase of oxygen starvation begins. With the correct course of childbirth, at the time of the birth of the child, due to irritation of the respiratory center, the first breath of the child occurs. For the onset of respiration, the reaction to a lower ambient temperature compared to intrauterine temperature and to the touch of hands on the body of the child is also important.

After the birth of a child, his direct connection with the mother's body ceases. To get enough oxygen, the newborn needs to breathe vigorously. An indicator of sufficient breathing is a loud cry, as it occurs with increased 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, a loud cry should be achieved by various skin irritations or artificial respiration. If the child breathes only 8-10 times a minute and does not cry, he cannot be transferred to the nursery.

With the first breath of the child, the lungs are straightened, the pulmonary vessels expand. Due to the suction action of the lungs, blood from the right ventricle begins to flow into the lungs, bypassing the botallic duct. Oxygenated blood flows from the lungs through the pulmonary vein into the left atrium, then into the left ventricle. The flow of blood from the right atrium to the left one stops - the foramen ovale gradually overgrows, deserts the arantia and botal ducts and the remains of the umbilical vessels, which gradually turn into connective tissue ligaments. With the birth of a child, the pulmonary circulation begins to function, extrauterine circulation is established ( rice. 2). Rice. 2. Circulation diagram of a newborn. 1 - umbilical arteries; 2 - umbilical vein; 3 - arantia duct; 4 - aorta; 5 - inferior vena cava; 6 - botall duct; 7 - right atrium; 8 - left atrium; 9 - pulmonary artery; 10 - left ventricle; 11 - right ventricle; 12 - superior vena cava

The cardiovascular system guarantees the preservation of the vitality of all organs of the human body. Its correct development in the prenatal period is the key to good health in the future. Fetal blood circulation, the scheme and description of the distribution of blood flows in its body, understanding of the features of this process are important for understanding the nature of pathological conditions that occur in newborns and in the later life of children and adults.

Fetal circulation: diagram and description

The primary circulatory system, which is usually ready for use by the end of the fifth week of pregnancy, is called the vitelline system and consists of arteries and veins called the umbilical-mesenteric. This system is rudimentary and decreases in importance during development.

Placental circulation is what provides the fetus with gas exchange and nutrition during pregnancy. It begins to function even before the formation of all elements of the cardiovascular system - by the beginning of the fourth week.

Blood flow path

• From the umbilical vein. In the placenta, in the area of ​​the chorionic villi, the mother's blood, rich in oxygen and other useful substances, circulates. Passing through the capillaries, it enters the main vessel for the fetus - the umbilical vein, which directs the blood flow to the liver. On this path, a significant part of the blood flows through the ductus venosus (arantia) into the inferior vena cava. The portal vein, which is poorly developed in the fetus, joins the umbilical vein to the gate of the liver.
• After the liver. Blood returns through the hepatic vein system to the inferior cavity, mixing with the flow coming from the venous duct. Then it passes into the right atrium, where the upper vena cava, which has collected blood from the upper body, flows in.
• In the right atrium. Full mixing of the streams does not occur, due to the structural features of the fetal heart. Of the total amount of blood in the superior vena cava, most of it passes into the cavity of the right ventricle and is expelled into the pulmonary artery. The flow from the inferior cavity rushes through the right to the left atrium, passing through a wide oval window.
• From the pulmonary artery. Part of the blood enters the lungs, which do not function in the fetus and resist the flow of blood, then flows into the left atrium. The rest of the blood through the ductus arteriosus (botalls) enters the descending aorta and is further distributed in the lower body.
• From the left atrium. A portion of blood (more oxygenated) from the inferior vena cava is combined with a small portion of venous blood from the lungs, and through the ascending aorta is thrown out to the brain, the vessels that feed the heart and the upper half of the body. Part of the blood flows into the descending aorta, mixing with the flow going through the Botallus duct.
• From the descending aorta. The blood deprived of oxygen through the umbilical arteries flows back to the villi of the placenta.

The fetal circulation is thus closed. Thanks to the placental circulation and the structural features of the fetal heart, it receives all the nutrients and oxygen necessary for full development.

Features of the fetal circulation

Such a device of placental blood circulation implies such a work and structure of the heart in order to ensure the exchange of gases in the body of the fetus, despite the fact that its lungs do not function.

• The anatomy of the heart and blood vessels is such that metabolic products and carbon dioxide generated in the tissues are removed by the shortest route - to the placenta from the aorta through the umbilical arteries.
• Blood partially circulates in the fetus in the pulmonary circulation, without undergoing any changes.
• The main amount of blood is in the systemic circulation, due to the presence of an oval window that opens the communication of the left and right chambers of the heart and the existence of the arterial and venous ducts. As a result, both ventricles are predominantly occupied with filling the aorta.
• The fetus receives a mixture of venous and arterial blood, while the most oxygenated portions go to the liver, which is responsible for hematopoiesis and the upper half of the body.
• In the pulmonary artery and in the aorta, blood pressure is recorded equally low.

After birth

The first breath that a newborn takes causes his lungs to expand, and blood from the right ventricle begins to flow into the lungs, as the resistance in their vessels decreases. At the same time, the arterial duct becomes empty and gradually closes (obliterated).

The flow of blood from the lungs after the first breath leads to an increase in pressure in it, and the flow of blood from right to left through the oval window stops, and it also overgrows.

The heart switches to the "adult mode" of functioning, and no longer needs the end sections of the umbilical arteries, the ductus venosus, the umbilical vein. They are reduced.

Fetal circulatory disorders

Often, fetal circulatory disorders begin with a pathology in the mother's body, affecting the state of the placenta. Doctors note that placental insufficiency is now observed in a quarter of pregnant women. With insufficient attention to herself, the expectant mother may not even notice threatening symptoms. It is dangerous that in this case the fetus may suffer from a deficiency of oxygen and other useful and vital elements. This threatens with developmental delay, premature birth, and other dangerous complications.

What leads to pathology of the placenta:

• Diseases of the thyroid gland, arterial hypertension, diabetes mellitus, heart defects.
• Anemia is moderate, severe.
• Polyhydramnios, multiple pregnancies.
• Late toxicosis (preeclampsia).
• Obstetric, gynecological pathology: previous arbitrary and medical abortions, malformations, uterine fibroids).
• Complications of the current pregnancy.
• Blood clotting disorder.
• Urogenital infection.
• Depletion of the maternal body as a consequence of lack of nutrition, weakening of the immune system, increased stress, smoking, alcoholism.

A woman should pay attention to

• frequency of fetal movements - change in activity;
• the size of the abdomen - whether it meets the deadline;
• Pathological bloody discharge.

Placental insufficiency is diagnosed by ultrasound with Doppler. In the normal course of pregnancy, it is done at 20 weeks, with pathology - from 16-18 weeks.

As the term increases in the normal course of pregnancy, the possibilities of the placenta decrease, and the fetus develops its own mechanisms for maintaining adequate vital functions. Therefore, by the time of childbirth, he is already ready to experience significant changes in the respiratory and circulatory system, which allow breathing through his lungs.

Fetal circulation is rather complex and has a number of distinctive features. From the first days of maturation of the embryo, a bond is established between the mother and the child. Subsequently, nutrients begin to circulate in both organisms separately.

What are the features of fetal blood circulation? How is communication between organisms formed? Answers to these and not only questions can be found below.

short info

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

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

All the most essential nutrients pass through the internal system from the female body to the fetus. This process is carried out thanks to a system of interacting capillaries. Excellent circulatory characteristics of the fetus are observed in the early stages of intrauterine development.

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

The bundle vein, getting into the body of the fetus, begins to divide into two main branches. The first branch is the arantia of the ducts, which ensures the transfer of purified arterial blood to the lowest genital vein. As a result, arterial and venous blood mixes, the blood becomes tangled. On the other branch, arterial blood flows through the portal vein system, which flows into the liver of the fetus itself. There is a complete cleansing of toxins. Only after undergoing complete cleansing, the blood begins 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 that are located in the atrial 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 entered the left ventricle in full, it begins to move through the aorta in the direction of the systemic circulation. As a result, the following scheme is obtained: the mixed blood mass begins to move towards the organs and tissues of the fetus. During the movement, an endless flow of blood is provided, which can only be provided by the batholov strait. It provides continuous blood flow through an already formed pulmonary trunk that 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 cavity 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.