During pregnancy, unique anatomical formations and even new organs appear in the female body. One of them is the placenta. Without it, it is impossible to imagine the development of a baby in the womb. This article will tell you about what the placenta is, how it is formed and what functions it performs.
Characteristic
The placenta is a special embryonic organ. It is typical not only for humans, but also for other mammals. The appearance of the placenta in the female body cannot be imagined without the chorion.
Its formation begins to occur after a fertilized egg is implanted to a specific wall of the uterus. Subsequently, a specific formation appears around it, which can be called a chorion. Its membranes later begin to transform and transform into placental tissue.
Scientists have found that for the first time chorion appears in the body of a pregnant woman within 7-12 days from the moment of fertilization. It takes some time to transform to the placenta. On average, it is several weeks. For the first time, the formed placental tissue appears only by the beginning of the second trimester of pregnancy.
The placenta acquired its name for a reason. This specific organ, formed only during pregnancy, has been known to doctors since ancient times. Agree that it is not difficult to notice it. During childbirth, after the birth of the child, the placenta is born. This feature contributed to the fact that the placenta was called the placenta for a long time. It should be noted that this name has survived to this day.
From Latin, the term "placenta" is translated as "cake". This name almost completely characterizes the appearance of the placenta. It really looks like a cake. Doctors often refer to the placenta as a “baby's place”. This term is often used even in the medical literature.
Structure
The placenta of pregnant women has a heterogeneous structure. In fact, it is a unique organ that must perform a huge variety of different functions. Any disturbances in the structure of the placenta can be very dangerous due to the development of pathologies. The presence of defects in the structure of the placental tissue causes a disruption in the course of the normal intrauterine development of the fetus.
For reliable attachment to the walls of the uterus, the placenta has special outgrowths - villi. Through them, there is a reliable fixation of the placental tissue to the wall of the uterus. This feature also determines the interaction between the small embryo, placenta and endometrium.
The umbilical cord is located between the placenta and the fetus - this is a special organ that, in fact, connects the baby with his mother at a biological level. This unique bond will last until the very birth. Only after the birth of the baby is the umbilical cord cut, which means the birth of a new person.
The umbilical cord contains important blood vessels - arteries and veins. Outside, they are surrounded by a special substance - "Warton's jelly". It has an interesting texture that resembles jelly. The main purpose of this substance is to reliably protect the blood vessels of the umbilical cord from the effects on them of various negative environmental factors.
In the normal course of pregnancy, the placenta remains in the female body throughout pregnancy. Her birth occurs after the birth of a baby. On average, the placenta is born 10-60 minutes after the baby is born. The difference in this time interval in different genera depends on many factors.
All tissue of the placenta can be conditionally divided into 2 parts - maternal and fetal. The first is directly adjacent to the uterine wall, and the second to the fetus. Each part of the placenta has a number of unique anatomical features.
Mother part
This area of the placenta is formed largely on the basis of the decidua, or rather, its basal part. This feature determines the special density and structure of the maternal part of the placenta. The surface of this area of the placental tissue is rather rough.
The presence of special septa, which are present in the placenta, ensures the separation of maternal and fetal blood flow. The placental barrier prevents maternal and fetal blood from mixing at this stage. The specific "exchange" begins to occur somewhat later. This is due to the actively proceeding process of osmosis and diffusion.
Fruit part
This part of the placenta is covered with a special amniotic layer. Such a structure is necessary so that a special water environment is subsequently formed in the uterine cavity, in which the baby will "live" for several months of its intrauterine development.
On the fetal side of the placenta, there is a special chorionic formation, which ends in numerous villi. These villi are involved in the formation of an important element - the intervillous space.
Some of the villi are called anchoring, as they are tightly fixed to the uterine wall, providing a secure fixation. The rest of the outgrowths are directed to the intervillous space, which is filled with blood from the inside.
Decidual septa (septa) divide the surface of the placental tissue into several separate parts - cotyledons. They can be called the structural and anatomical units of the placenta.
The number of cotyledons changes as the placenta matures. When it finally matures, the total number of such structural and anatomical formations is several dozen.
Cotyledon
The main component of the placenta resembles a bowl in appearance. Each structural and anatomical unit of placental tissue has a large branch of the umbilical blood vessel, which branches into several small branches.
This structure provides a very important function of the placenta - the blood supply to the fetus's body with all the necessary substances for its growth and development. The plentiful circulatory system that covers the cotyledon provides blood flow to each individual site of the placental tissue. This helps to ensure uninterrupted blood flow not only to the placenta itself, but also to the body of an actively developing baby.
How is the blood supply ensured?
This question is very important, since the functioning of the placenta is impossible without uninterrupted blood flow. The uterus, in which the baby develops, is nourished through the ovarian and uterine arteries. It is their doctors who call it spiral vessels. The branches of the ovarian and uterine arteries are located in the intervillous space.
It is important to note that there is a pressure difference between the spiral vessels and the intervillous space. Such a feature is necessary in order for gas exchange and supply of nutrients to occur. The difference in pressure contributes to the fact that the blood from the arteries penetrates to the villi, washes them and then moves to the chorionic plate. Then it enters the maternal veins.
This feature of blood flow provides a certain permeability of the placental tissue. It is believed that the ability to penetrate various nutrients and oxygen gradually increases with each subsequent day of pregnancy. By 32-34 weeks, the placenta permeability is maximal. Then it begins to gradually decrease.
The weight
During pregnancy, the size of the placenta is almost constantly changing. So, for childbirth, a healthy placenta weighs on average about 0.5-0.6 kg. Its diameter in most cases is from 16 to 20 cm.
The thickness of the placenta may vary. This largely depends on individual characteristics, as well as on whether there are any pathologies of the formation of this organ. With each subsequent day of pregnancy, the thickness of the placenta increases.
Doctors believe that such an increase ends only at 36-37 weeks of pregnancy. On average, after delivery, the thickness of the normal placenta is approximately 2-4 cm.
A type
Human placental tissue has a number of features that distinguish it from the placenta of other mammals. The human placenta is of the hemochorial type. This type of placental tissue is characterized by the possibility of maternal blood circulation around the villi, in which the fetal capillaries are located.
This structure of the placenta has interested many scientists. Already at the beginning of the 20th century, Soviet scientists carried out a number of scientific studies and made interesting developments based on the properties of placental tissue. So, Professor V.P. Filatov has developed special pharmaceutical preparations that contain in their chemical composition an extract or suspension of the placenta.
Science has advanced a lot now. Scientists have learned to actively work with the placenta. Stem cells are isolated from it, which have a number of important functions. There are even cord blood banks where they are stored. The storage of stem cells requires certain conditions and the responsible observance of a number of strict sanitary and hygienic rules.
For many years, scientists believed that the human hemochorial placenta was a sterile organ. However, numerous scientific studies have rejected this. Even in a healthy placenta after childbirth, some microorganisms are found, many of which live in the oral cavity of a pregnant woman.
When and how is it formed?
Placenta formation is a complex biological process. For the first time, the chorion appears within 7-12 days from the moment of fertilization; it takes several weeks for its transformation into the placenta. The active formation of the placenta is observed at 15-16 weeks of pregnancy, but the term for the final development of an organ may vary. So, only at the 20th week of pregnancy, blood vessels begin to actively function in the placental tissue.
In most cases, the placenta forms in the back of the uterus. Placental tissue is formed with the participation of a special embryonic formation - cytotrophoblast and directly the endometrium itself (the inner lining of the uterine wall).
The final histological structure of the placenta became known to doctors relatively recently - in the era of microscopic studies. In the placental tissue, scientists distinguish several sequentially located layers:
- Decidua - the first layer in the direction from the uterus to the embryo. In fact, it is an altered endometrium.
- Lanthans layer (Rohr's fibrinoid).
- Trophoblast. This layer covers the lacunae and grows into the walls of the spiral arteries, which prevents their active contraction.
- Numerous lacunaethat are filled with blood.
- Multicore symplastlining cytotrophoblast (syncytiotrophoblast).
- Cytotrophoblast layer... It is a layer of located cells that form syncytium and produce the formation of certain hormone-like substances.
- Stroma... It is a connective tissue in which blood supply vessels pass. Also in this layer are very important cellular elements - Kashchenko-Hofbauer cells, which are macrophages and provide local immunity.
- Amnion. Participates in the subsequent formation of amniotic fluid. It is necessary for the formation of a special aquatic environment in which the intrauterine development of the baby will take place.
A very important structural element of the placenta is its basal decidua. It is a kind of barrier between the maternal and fetal part of the placenta. In the area of the basal decidua there are numerous depressions, inside of which maternal blood is present.
Functions
The placenta plays a very important role during pregnancy. The number of functions performed by this body is quite large. One of the most important of these is the protective or barrier function. The placenta is involved in the formation of the hematoplacental barrier. It is necessary so that the intrauterine development of the fetus is not disturbed.
The following anatomical units are involved in the participation of the hematoplacental barrier:
- the cell layer of the endometrium (the inner wall of the uterus);
- basement membrane;
- loose pericapillary connective tissue;
- basement membrane of trophoblast;
- cytotrophoblast cell layers;
- syncytiotrophoblast.
Such a complex structure is necessary in order for the blood-placental barrier to provide important functions of the placenta. Violation of the histological structure can be dangerous. In such a situation, the placental tissue simply cannot fully function.
Participation in gas exchange
Through the blood vessels, which are in large quantities in the placental tissue, the fetus receives oxygen, and also "gets rid" of carbon dioxide.
This happens through the usual simple diffusion. At the same time, oxygen penetrates into the body of an actively growing baby, and waste carbon dioxide is released. This kind of "cellular respiration" occurs throughout the entire period of pregnancy. This unique mechanism develops due to the fact that the lungs of the fetus are formed quite late.
A child in the womb does not breathe on its own. He will take his first breath only after birth. In order to compensate for this condition, such cellular gas exchange occurs.
Providing food
Despite the fact that the baby has a mouth, as well as the organs of the digestive system, by a certain period of pregnancy, he still cannot take food on his own. All the nutrients that a child's body needs for its birth, it receives through the blood vessels. Proteins, fats and carbohydrates enter the baby's body through the arteries of his mother. In the same way, the baby receives water, vitamins and minerals.
This feature of fetal nutrition clearly explains why the diet of a pregnant woman is very important. For the full intrauterine development of the fetus, the expectant mother should carefully monitor what food she consumes during the day.
It is very important that fresh fruits and vegetables, as well as quality sources of protein, are regularly present in the diet of a pregnant woman.
Highlighting unnecessary exchange products
The kidneys and excretory system of the fetus begin to function quite late. While they are not yet well formed, the placenta comes to the rescue. Through the placental tissue, the unnecessary metabolites, spent by the child's body, are removed. Thus, the fetus's body "gets rid" of excess urea, creatinine and other substances. This process takes place through active and passive transport.
Synthesis of hormones
The hormonal function of the placenta is perhaps one of the most important. During pregnancy, the placental tissue is even an organ of internal secretion, as it participates in the formation of biologically active substances.
One of them is the most important hormone of pregnancy - chorionic gonadotropin. It is essential for the normal course of pregnancy.This hormone ensures the correct functioning of the placenta, and also stimulates the formation of progesterone in the body of a pregnant woman. It is necessary during pregnancy in order to stimulate the growth of the endometrium and temporarily stop the maturation of new follicles in the ovaries.
Placental lactogen is also formed under the participation of the placenta. This hormone is necessary in order to prepare the mammary glands for the upcoming changes - lactation. Under the influence of the placenta, the formation of another hormone necessary during pregnancy occurs - prolactin. It is also necessary in order to prepare the mammary glands of the expectant mother for the upcoming lactation.
Scientists have found that placental tissue can synthesize some other hormones - testosterone, relaxin, serotonin, and others. In addition to the active synthesis of hormones, placental tissue is also involved in the formation of hormone-like substances that are necessary for the normal course and development of pregnancy.
Fetal protection
This function of the placenta can be divided into several types. So, it can be mechanical and immune. Each of them is very important during the period of intrauterine development of the fetus.
Mechanical protection of the fetus implies the protection of the child's body from any environmental influences. The placental tissue is a very delicate structure. It is located in the immediate vicinity of the fetus. With various injuries, the placenta, as it were, "softens" the blow. This helps to reduce the risk of harm to the fetus.
The immune protective function of the placenta is that the placenta is involved in providing the child's body with maternal antibodies. These special substances ensure the immunity of the fetus throughout its intrauterine life in the mother's womb.
Antibodies that enter the baby's body from his mother through the blood are immunoglobulins. Some of them easily penetrate the placenta, getting into the child's body. Thus, the placenta helps to protect the baby from a number of bacterial and viral infections.
The ingestion of maternal antibodies also helps to prevent an immunological conflict between the mother and the fetus. In this case, the maternal organism does not perceive the fetus as an alien genetic object. This feature helps to prevent the rejection of the fetus from the uterine cavity throughout pregnancy.
It should be noted about the special role of syncytium - a special element of placental tissue. It is involved in the absorption of a number of hazardous chemicals that can cross the placenta from mother to fetus. Thus, the placenta, as it were, protects the baby's body from the penetration of dangerous drugs, toxic and other dangerous drugs into it.
It is important to remember that this selectivity of penetration can be individual. If the histological structure of the placenta is normal, then hazardous substances are retained. If it is violated, then toxins and poisons can easily penetrate into the child's body, causing irreparable harm to it. That is why doctors recommend that expectant mothers give up all bad habits during pregnancy.
Smoking and drinking alcohol, as well as drugs, can cause the development of dangerous diseases in an actively developing fetus. Preventing their development is much easier than trying to cope with the pathologies that have arisen in the future.
Leading a healthy lifestyle by the expectant mother is of great importance in the formation and normal functioning of the placenta.
Migration
The initial position of the placenta in the uterine cavity is a very important clinical indicator. Even the course of pregnancy depends on how it will be located.
Usually, placental tissue is attached to the back or front of the uterus. It is extremely rare that it is attached only to one of the side walls. The laying of the placental tissue begins in the first trimester of pregnancy and is associated with the site of implantation of a fertilized egg.
Normally, a fertilized egg is attached to the fundus of the uterus. In this zone, there is good blood flow, which is necessary for the full intrauterine development of the fetus throughout pregnancy. However, this situation does not always develop.
In obstetric practice, cases are recorded when the implantation of a fertilized egg occurs in the lower parts of the uterus. This is preceded by a huge variety of reasons. In this case, the fertilized egg can descend almost to the base of the internal uterine pharynx, where it attaches to the uterine wall.
The lower the implantation occurs, the lower the placenta is. The accretion of placental tissue on the area of the internal uterine pharynx is called presentation by doctors. This dangerous pathology significantly worsens the course of pregnancy and can even cause the development of dangerous complications.
The original location of the placental tissue may change. This occurs most often when the placenta is attached to the anterior wall of the uterus. The process of changing the initial localization of placental tissue is called migration. The displacement of the placenta in this case, as a rule, occurs from the bottom up. Thus, if a low position of the placental tissue was detected in the first half of pregnancy, then it may still change.
Usually the process of migration of the placenta proceeds rather slowly - within 6-10 weeks. It ends completely, as a rule, only by the middle of the 3rd trimester of pregnancy.
The placenta, located on the back wall of the uterus, practically does not migrate. The probability of displacement of placental tissue in this position is extremely small. This is largely facilitated by certain structural features of the uterus.
Norm
A healthy placenta is an important part of a healthy pregnancy. The development of this unique organ of pregnancy occurs gradually. From the moment of formation in the female body until delivery, the placenta is almost constantly changing.
Doctors can evaluate the anatomical properties of the placenta, as well as identify various anomalies in its development by performing ultrasound examinations. To do this, the expectant mother must undergo several ultrasounds throughout the pregnancy.
With the help of modern devices, specialists can get a fairly clear visualization of the placental tissue. During an ultrasound examination, the doctor can see the structure of the placenta, the presence of any diffuse changes in it, as well as emerging pathologies.
A very important clinical indicator, which is necessarily determined by obstetricians-gynecologists during pregnancy, is the maturity of the placenta. At each stage of pregnancy, it changes. It's quite normal. In this case, it is important to assess the correspondence of the maturity of the placenta to a certain period of pregnancy.
So, experts identify several options for the maturity of the placental tissue:
- Zero (0). Characterizes the normal structure of the placenta until approximately 30 weeks of gestation. The placenta of this maturity has a fairly smooth and even surface.
- First (1)... It is characteristic of a healthy placenta between 30 and 34 weeks of gestation. At maturity of the first degree, specific inclusions appear on the placenta.
- Second (2). It is formed normally after 34 weeks of pregnancy. Such placental tissue already looks more prominent, specific striation appears on it, as well as small grooves.
- Third (3). It is the norm for normal full-term pregnancy. The placenta, which has such a degree of maturity, has rather pronounced large waves on its surface, which reach the basal layer. Also, on the outer surface of the placental tissue, spots merging with each other appear, having an irregular shape - salt deposits.
Determining the degree of maturity of the placenta allows doctors to orientate themselves in the timing of the upcoming birth. In some cases, the placental tissue matures too quickly. This leads to the development of a number of dangerous complications. In this case, the tactics of pregnancy must be reviewed by specialists.
Pathology
Unfortunately, abnormalities in the development and formation of the placenta are quite common in obstetric practice. Such conditions significantly worsen the prognosis of the course of pregnancy. The arising defects in the structure of the placenta contribute to the deterioration of blood flow, which is necessary for the full intrauterine development of the baby.
Currently, quite a few different pathologies of the placenta are known. One of the most dangerous of them is the strong growth of placental tissue to the uterine wall. It would seem that the stronger the placenta “grows” into the endometrium, the more reliable the fixation should be, but in fact this is not entirely true.
Strong accretion of the placenta to the uterine wall is dangerous for the development of problems with its separation during childbirth. In such a situation, the birth of the child, as a rule, proceeds normally, and the birth of the placenta is delayed. Such a clinical situation can be dangerous by the development of massive uterine bleeding.
Also, the long-term presence of the placenta in the uterine cavity is a threat to the development of infection of the reproductive organs.
With a strong increment of placental tissue to the wall of the uterus, surgical gynecological intervention is required. In this situation, doctors purposefully separate the placenta from the uterine walls.
Quite often, scars form on the uterus. This usually happens when various surgical operations have been carried out on it - cesarean section, excision of damaged tissues, and others. A strong proliferation of connective tissue leads to scarring.
The ingrowth of the placenta into a scar on the uterus is a rather dangerous pathology. In this case, dangerous complications can arise during natural childbirth. In order to avoid them, doctors quite often have to resort to performing surgical obstetrics - cesarean section.
Strong prolapse of the placenta to the level of the internal uterine pharynx is dangerous by the development of its presentation. This pathology worsens the prognosis of gestation. With placenta previa, the threat of developing dangerous infectious diseases and premature birth is quite high. In order to preserve and prolong pregnancy as much as possible, the expectant mother must strictly follow the recommendations made for her by doctors.
Placental abruption is another dangerous pathology that occurs in obstetric practice. It is characterized by detachment of placental tissue due to certain reasons from the walls of the uterus. In this case, bleeding usually develops. If placental abruption occurs over a fairly large area, then this situation is extremely dangerous for the life of the fetus. Massive detachment of placental tissue, accompanied by the occurrence of functional disorders in the child's body, may be an indication for an emergency caesarean section.
Another dangerous pathology is placental edema. A wide variety of reasons can lead to the development of this condition, including bacterial and viral infections. Prolonged edema of the placenta can lead to the development of placental insufficiency, fetal hypoxia, and also provoke premature birth. When this pathology is detected, doctors carry out complex treatment.
The placenta contains quite a few blood vessels. The surrounding placental tissue is rather loose and delicate. Strong mechanical stress can contribute to the appearance of small microdamages and even ruptures in it. As a rule, clinically, such minor injuries do not appear for a long time.
If the breaks in the placental tissue are quite significant, then this will contribute to the disruption of its functioning. In this case, the general condition of the fetus may also be disturbed. Violation of the blood supply can affect the increased heart rate of the baby, as well as the increase in oxygen deficiency in his blood.
It is possible to detect defects and small hemorrhages in the placenta only with the help of modern ultrasound examinations. Minor injuries, as a rule, are determined already retrospectively - after childbirth during a visual examination of the placenta.
Structural changes can also be determined with the help of a histological examination, which is performed after childbirth. For this examination, the afterbirth is sent to a special laboratory, where it is studied.
For what the placenta is, see the next video by Larisa Sviridova.
