The birth of a child is a long-awaited event in the life of a family. Pregnancy of a woman is a crucial period of her life, when the he alth of her unborn baby is laid. Many factors influence its intrauterine development, but the most important is the normal functioning of the mother-placenta-child system. The placenta is a key link in this chain. A lot depends on its area, location and formation of structural units - cotyledons of the placenta. Violations in its formation threaten the he alth and even the life of the mother and child. About what cotyledon is, the structure of the placenta and the formation of a connection between the fetus and mother in the prenatal period of its development, this article.
Children's seat
From the beginning of zygote implantation, the mother-fetus system functions in the uterus. And the main component of this system is the placenta (from the Latin placenta - cake, pancake). This is a temporary complex organ, which is formed by derivatives of the embryoblast and trophoblast (zygote membranes). First of all, the functions of the placenta provide conditions forphysiological course of pregnancy and normal development of the embryo. All metabolic, hormonal and immune processes are provided by the mother's vascular system, which is closely intertwined in the structural components of the placenta - cotyledons. It is here that metabolism is ensured and the placental barrier is created.
In the normal course of pregnancy up to 16 weeks, the growth of the placenta outstrips the growth of the fetus. In the event of the death of the embryo, the growth of the placenta is inhibited, dystrophic phenomena begin to progress, which leads to termination of pregnancy. Having reached full maturity by 38 weeks of gestation, the placenta stops the growth of blood vessels, which also leads to the onset of labor, the end of pregnancy and placental rejection.
Structure of the placenta
The layers of the placenta are formed by two plates - chorionic and basal, and between them are the villi of the fetal chorion and the intervillous space. The maternal side of the placenta, which is adjacent to the walls of the uterus, has a rough surface and is formed by the decidua.
The side of the placenta facing the fetus is called the fetal side and is divided into autonomous segments. These lobules of the placenta are called cotyledons. The lacunae of cotyledon are filled with maternal blood, the volume of which is about 150 ml. Blood is exchanged every 3 minutes. This part is represented by numerous villi of the chorion (fetal membrane), which are combined into structural and functional units of the placenta - cotyledons. The total surface of the villi in one cotyledon is about 15square meters.
A mature placenta is a disc-shaped structure with a diameter of up to 20 centimeters and a weight of up to 600 grams. The thickness of the placenta is normal up to 3.5 centimeters.
How it all begins
Cotyledons of the placenta are formed in the following sequence. When the embryo enters the uterus on the 6-7th day, its membranes form a trophoplast, the function of which is to gain a foothold in the uterine mucosa and suppress the immune response of its rejection.
The implantation of the embryo is accompanied by the growth of primary villi, which branch out and form the villous membrane of the embryo - the chorion.
At 3-4 weeks of pregnancy, the blood vessels of the fetus grow into secondary villi that destroy the capillaries in the uterine wall. In the place of their destruction, blood lakes are formed - primary fossae, which subsequently become lacunae of cotyledons of the placenta.
The place where everything happens
The fetal part of the placenta is permeated with blood vessels that come from the umbilical cord of the fetus. They branch many times and reach the chorionic villi, which are combined into structural functional units of the placenta - cotyledons. They are formed by one stem villus, which branches into villi of the 2nd order. The central part of cotyledon (cotyledon) is formed by a cavity in which maternal blood is located and which is surrounded by many villi. Villi of the 2nd order also branch and form villi of the 3rd order. The structure of the cotyledon of the placenta is comparable to a tree, where the supportingthe villus is its trunk, and the terminal villi are its leaves. And the whole tree is immersed in a hole with mother's blood.
Cotyledons are separated from each other by septa - partitions of the basal plate. In the placenta, the total number of cotyledons ranges from 30-50.
Placental barrier
The exchange of blood gases, all nutrients, antibodies and hormones, metabolic products between maternal blood and fetal blood occurs in the cotyledons of the placenta at the time of contact of its villi with the mother's blood. The placental barrier is formed by the outer epithelial layer of the villus and the wall of the blood capillary. The latter is located inside the cotyledon villi of the placenta. The structure of this barrier provides selective permeability in both directions.
Due to the permeability of this barrier, the passage of gases and nutrients towards the fetus is easily carried out, and metabolic products are excreted back. But this barrier is easily overcome by some drugs, nicotine, alcohol, drugs, pesticides. And a number of infectious agents that have a negative impact on both the fetus and the placenta itself.
Functions of cotyledon
In addition to providing a hematoplacental barrier, these structural formations provide the following functions of the placenta:
- Gas exchange. Oxygen enters the blood of the fetus, and carbon dioxide is transported in the opposite direction due to the simple laws of diffusion.
- Nutrition and excretion. Water, electrolytes, vitamins, nutrients and minerals from maternal blooddiffuse into the blood of the fetus. In the opposite direction, metabolic products are transported - urea, creatinine.
- Regulation. The placenta secretes many hormones that regulate the course of pregnancy. For example, chorionic gonadotropin, progesterone, placental lactogen, prolactin. As well as testosterone, serotonin, relaxin.
- Protection. The immune properties of the placenta consist in passing antibodies from the mother's blood into the blood of the fetus. This is how primary innate immunity is formed.
Norm and pathology
Normally, the placenta is located in the anterior or posterior wall of the uterus. Its location is easily determined by ultrasound and serves as the basis for diagnosis for the course of pregnancy and its timing. The thickness of the baby's place grows up to 36-37 weeks, reaching sizes up to 4 centimeters, and then its growth stops, which is considered a mature placenta.
But sometimes the placenta is located elsewhere in the uterus:
- Low location. In this case, the placenta is located close to the uterine pharynx. For most women, this position is leveled off by later dates. Only in 5% of pregnant women, the location remains low by 32 weeks. This situation is dangerous with premature detachment of the placenta, and doctors decide on the method of delivery.
- Placenta previa is the position of the organ when it completely covers the internal os of the uterus. These conditions are fraught with uterine bleeding and abortion.
Other pathologies of the child's place
- Complete attachment of the placenta. This is a condition when the villi of the placenta not only adhere to the endometrium of the uterus, but also penetrate into the muscular layer of the uterus - the myometrium. It is safe for the fetus, but doctors have to manually remove the placenta during childbirth.
- A placental abruption is a partial or complete detachment of the placenta. It is considered a severe pathology of pregnancy, and patients are subject to urgent hospitalization. Occurs in 1-3 pregnant women out of a thousand.
Thin or thick
Inadequate function of the placenta can manifest itself with its early maturation in a decrease or increase in its thickness.
"Thin" placenta (hypoplasia) - up to 20 mm in the third trimester - is fraught with the threat of abortion, fetal malnutrition (developmental delay). The same consequences occur with a "thick" placenta (more than 5 centimeters).
In addition, there is a pathology associated with a decrease in the area of the placenta with its normal thickness. This may be the cause of genetic pathologies that often accompany fetal malformations (Down syndrome). In this case, a small child's place cannot cope with providing the fetus with all the nutrients and oxygen, which leads to its developmental delay.
Too big placenta is not good either. Its growth, as a rule, is often associated with various infections suffered by a pregnant woman. Placental proliferation often occurs with Rhesus conflict between mother and fetus. In this case, cotyledons are reborn and grow old. And we again have placental insufficiency and premature aging of the placenta(fading of its functions and growth).
Sometimes pathology manifests itself in the form of an additional cotyledon of the placenta. In this case, the lobule of the child's place is located separately and may remain in the uterus during childbirth. That is why after the release of the placenta in childbirth, it is carefully examined, weighed and measured. Normally, the placenta comes out within an hour after the baby is born.
Oncology can be here too
As in any organ of our body, malignant cell changes can also begin in the placenta. The most common chorioangioma is an abnormal growth of villi in one cotyledon. This tumor is benign and does not metastasize. Surgical intervention is usually not performed, since during labor the formation is removed from the mother's body along with the placenta.
The subject of close attention of the obstetrician
The condition of the placenta, its position and functions are the subject of close attention of the doctor. After all, the success of pregnancy and the he alth of the fetus largely depend on the child's place. The following methods are used to diagnose the condition of the placenta:
- Ultrasound examination makes it possible to assess the condition, location and development of the child's place.
- Laboratory studies will help determine the level of placental hormones and the activity of certain enzymes in the blood of a pregnant woman.
- Doppler will show the speed of blood flow in each of the vessels - uterus, umbilical cord, fetus.
Summarize
The placenta is a unique organwhich belongs to both the mother and the child. Its role in the development of the fetus is invaluable. It is in the cotyledons of the placenta that the main border barriers between the blood of the mother and the child are located. And any violation of the functioning of this system is fraught with very serious consequences.
