What is a placenta, when is it formed and what functions does it perform?

The placenta is an amazing organ that is essential to pregnancy. It grows inside the uterus and provides the developing baby with life support. Although it’s widely known, not everyone is aware of how crucial it is to the health and development of the unborn child.

The placenta, which forms early in pregnancy, makes sure the fetus gets oxygen and nutrients from the mother’s bloodstream. Additionally, it eliminates waste products, serving as a filter to shield the infant from dangerous materials. A baby couldn’t develop and flourish inside the womb without it.

The placenta not only provides nutrition for the unborn child but also secretes vital hormones that support a pregnancy’s continued health. It is delivered after the baby and continues to support it until the baby is born, at which point it is discarded.

Characteristics

One unique organ of the embryo is the placenta. It is normal for other mammals as well as for humans. Without the chorion, the placenta’s appearance in the female body is inconceivable. After the fertilized egg is inserted into a specific uterine wall, it starts to form. Then, a particular structure known as the chorion emerges all around it. The membranes of the organ then start to change and become placental tissue.

Scientists have established that the chorion first appears in the body of a pregnant woman within 7-12 days from the moment of fertilization. It takes some time to transform into the placenta. On average, it is several weeks. The first formed placental tissue appears only at the beginning of the second trimester of pregnancy. The placenta did not acquire its name by chance. 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 birth of the placenta also occurs. This feature contributed to the fact that the placenta was called the afterbirth 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 does resemble a cake. Often, doctors also call the placenta "the baby"s place". This term is often used even in medical literature.

Structure

Pregnant women’s placentas have a varied structure. Actually, this is a special organ that needs to carry out a wide range of tasks. Any disruptions to the placenta’s structure have the potential to cause pathologies, which can be extremely dangerous. The normal course of the fetus’s intrauterine development is disrupted by the existence of defects in the structure of placental tissue.

Villi are unique projections of the placenta that are responsible for its dependable attachment to the uterine walls. They serve as a dependable means of fixing placental tissue to the uterine wall. The interaction between the endometrium, placenta, and small embryo is also determined by this characteristic.

The umbilical cord, a unique organ situated between the placenta and the fetus, serves as the biological link between the baby and its mother. This special bond will last right up until the baby is born. The umbilical chord is only cut subsequent to the baby’s birth, signifying the birth of a new individual.

Important blood vessels – arteries and veins – pass through the umbilical cord. On the outside, they are surrounded by a special substance – "Wharton"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 of various negative environmental factors. During a normal pregnancy, the placenta remains in the woman"s body throughout the pregnancy. Its birth occurs after the birth of the baby. On average, the placenta is born 10-60 minutes after the birth of the child. The difference in this time interval in different births depends on many factors. All the tissue of the placenta can be conditionally divided into 2 parts – maternal and fetal. The first is adjacent directly to the uterine wall, and the second – to the fetus. Each part of the placenta has a number of unique anatomical features.

Maternal part

The decidual membrane, or more specifically, its basal portion, serves as the foundation for the formation of this region of the placenta. The unique density and structure of the placenta’s maternal portion are determined by this characteristic. This region of placental tissue has a fairly rough surface. Blood flow between the mother and the fetus is kept apart by unique partitions found in the placenta. At this point, the placental barrier prevents the mother’s and the fetus’s blood from mixing. Particular "exchange" starts to happen a little later. Osmosis and diffusion are the active processes that cause this to happen.

Fetal part

A unique layer of amniotic fluid covers this portion of the placenta. Such a structure is required in order for the uterine cavity to subsequently form a unique aqueous environment, where the baby will "live" for several months during its intrauterine development.

On the fetal side of the placenta there is a special chorionic formation, which ends with numerous villi. These villi participate in the formation of an important element – the intervillous space. Some of the villi are called anchor villi, since they are tightly fixed to the uterine wall, providing reliable fixation. The remaining outgrowths are directed into the intervillous space, which is filled with blood from the inside. Decidual septa (partitions) divide the surface of the placental tissue into several separate parts – cotyledons. They can be called structural-anatomical units of the placenta. The number of cotyledons changes as the placenta matures. When it finally matures, the total number of such structural-anatomical formations is several dozen.

Cotyledon

The placenta’s main component has an appearance similar to a bowl. The umbilical blood vessel has a large branch that splits into multiple smaller branches in each structural-anatomical unit of placental tissue. This structure enables the placenta to perform one of its most vital functions, which is to supply the fetus’s body with blood that contains all the nutrients it needs for growth and development. Every section of the placental tissue receives blood flow from the vast blood network covering the cotyledon. This helps to guarantee that the body of the developing baby and the placenta both receive an unbroken supply of blood.

How blood supply is ensured?

This is a crucial question because the placenta cannot function properly without constant blood flow. The ovarian and uterine arteries supply the uterus, where the fetus grows, with nourishment. These are referred to by physicians as spiral vessels. The intervillous space contains the branches of the uterine and ovarian arteries.

It is significant to remember that the intervillous space and the spiral vessels have different pressures. Nutrient provision and gas exchange depend on this characteristic. The blood from the arteries is able to enter the villi, clean them, and then proceed to the chorionic plate thanks to the pressure differential. Then it gets into the veins of the mother.

This aspect of blood flow guarantees a specific level of placental tissue permeability. It is thought that with every day that passes during pregnancy, the capacity to absorb different nutrients and oxygen progressively grows. The placenta’s permeability reaches its peak between weeks 32 and 34. After that, it starts to progressively drop.

Weight

The placenta’s size varies almost continuously during pregnancy. Therefore, the average birth weight of a healthy placenta is between 0.5 and 0.6 kg. Its diameter ranges from 16 to 20 cm most of the time. There can be variations in the placenta’s thickness. This primarily depends on the traits of each individual as well as the presence or absence of pathologies in the organ’s development. The placenta gets thicker every day that a pregnancy progresses.

Physicians think that this increase only stops between weeks 36 and 37 of pregnancy. Normal placenta thickness after birth is between two and four centimeters.

Type

Human placental tissue has a number of features that distinguish it from the placenta of other mammals. The human placenta belongs to the hemochorial type. This type of placental tissue is characterized by the ability of maternal blood to circulate around the villi, which contain fetal capillaries. This structure of the placenta has interested many scientists. Already at the beginning of the 20th century, Soviet scientists conducted a number of scientific studies and made interesting developments based on the properties of placental tissue. Thus, Professor V. P. Filatov developed special pharmaceuticals that contain placenta extract or suspension in their chemical composition. Currently, science has made great progress. 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. Storing stem cells requires certain conditions and responsible adherence to a number of strict sanitary and hygienic rules.

Scientists held the long-held belief that the human placenta is a sterile organ. Many scientific studies, however, have refuted this. There are microorganisms found in even a healthy placenta after childbirth, many of which are found in a pregnant woman’s mouth.

When and how it is formed?

The placenta’s formation is a complicated biological process. After fertilization, the chorion first emerges 7–12 days later, and it takes several weeks for it to develop into the placenta. Although the placenta begins to actively form between weeks 15 and 16 of pregnancy, there may be variations in the organ’s final development time. Therefore, blood vessels in the placental tissue don’t start to actively function until 20 weeks into the pregnancy.

The posterior wall of the uterus is where the placenta typically forms. The endometrium (the inner lining of the uterine wall) and a unique embryonic formation called cytotrophoblast participate in the formation of placental tissue.

• Decidua – the first layer in the direction from the uterus to the embryo. In essence, it is a modified 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 contractions.
• Numerous lacunae, that are filled with blood.

• Multinuclear symplast, lining the cytotrophoblast (syncytiotrophoblast).
• Cytotrophoblast layer. Is a layer of arranged cells that form a syncytium and produce the formation of certain hormone-like substances.
• Stroma. 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. Necessary for the formation of a special aqueous environment in which the intrauterine development of the baby will occur.

The basal decidua of the placenta is a crucial structural component. It functions as a sort of partition separating the placenta’s maternal and fetal sections. Maternal blood can be found inside a number of depressions near the basal decidua.

Functions

A crucial role for the placenta is played during pregnancy. This organ is responsible for a wide range of functions. The barrier or protective function is among the most crucial of them. The hematoplacental barrier is formed in part by the placenta. Making sure the fetus’s intrauterine development is not interfered with is essential.

The hematoplacental barrier involves the following anatomical units:

• the cellular layer of the endometrium (the inner wall of the uterus);
• the basement membrane;
• loose pericapillary connective tissue;
• the basement membrane of the trophoblast;
• the cellular layers of the cytotrophoblast;
• the syncytiotrophoblast.

The placenta’s vital functions cannot be performed by the hematoplacental barrier without such an intricate structure. It can be harmful to violate the histological structure. The placental tissue just won’t be able to function properly in such a circumstance.

Participation in gas exchange

The fetus "gets rid" of carbon dioxide and receives oxygen through the blood vessels, which are abundant in the placental tissue.

This occurs as a result of regular, basic diffusion. The baby’s body is receiving oxygen at the same time that carbon dioxide exhaust is being released. This unusual "cellular respiration" continues for the duration of pregnancy. The development of this special mechanism is brought about by the fetus’s relatively late lung formation.

A fetus does not breathe for itself while it is inside its mother. It won’t breathe for the first time until after birth. Such cellular gas exchange takes place to make up for this condition.

Provision of nutrition

The baby cannot eat on its own even though its mouth and digestive system have formed by a certain point in pregnancy. Through the blood vessels, the baby’s body gets all the nutrients it needs for birth. The mother’s arteries allow proteins, fats, and carbohydrates to enter the baby’s body. The infant also gets water, vitamins, and microelements in this manner.

This aspect of fetal nutrition elucidates the significance of a pregnant woman’s diet. The expectant mother needs to pay close attention to what she eats during the day to ensure that the fetus develops fully in the uterus.

It is crucial that a pregnant woman’s diet consist primarily of high-quality sources of protein and fresh fruits and vegetables.

Excretion of unnecessary metabolic products

The fetus’s kidneys and excretory system develop relatively late in life. The placenta protects them even though they haven’t fully developed yet. Unnecessary metabolites processed by the child’s body are eliminated through the placental tissue. In this way, the body of the fetus "gets rid" of extra urea, creatinine, and other chemicals. Transport, both active and passive, is used in this process.

Synthesis of hormones

Among the most significant roles played by the placenta is probably its hormonal function. Because placental tissue contributes to the creation of physiologically active substances, it is even an organ of internal secretion during pregnancy.

Chorionic gonadotropin, the most significant pregnancy hormone, is one of them. It is essential to the typical progression of pregnancy. This hormone promotes the production of progesterone in a pregnant woman’s body and ensures the placenta functions as it should. In order to promote endometrial growth and temporarily halt the maturation of new follicles in the ovaries, it is required during pregnancy.

Placental lactogen is also formed with the placenta’s assistance. In order to get the mammary glands ready for the impending changes—lactation—this hormone is required. Prolactin, another hormone required for pregnancy, is created under the placenta’s influence. The mammary glands of the expectant mother must also be ready for the impending lactation.

Researchers have discovered that placental tissue is capable of synthesizing a number of other hormones, including relaxin, serotonin, and testosterone. Placental tissue is involved in the production of hormone-like substances that are essential for the healthy progression and development of pregnancy, in addition to the active synthesis of hormones.

Protection of the fetus

There are various categories into which the placenta’s function can be placed. It may thus be both immune and mechanical. Throughout the fetus’s intrauterine development, each of them is crucial.

The term "mechanics of fetal protection" refers to shielding the developing child’s body from outside influences. The structure of placental tissue is extremely delicate. It is situated close to the developing foetus. The placenta seems to "soften" the blow in a variety of injuries. This lessens the possibility of harm that could endanger the developing fetus.

The placenta’s role in supplying the baby’s body with maternal antibodies is part of its immune-protective function. The fetus gains immunity from these unique substances during its whole intrauterine life in the mother’s womb.

Immunoglobulins are antibodies that are transferred from the mother’s blood to the developing child’s body. Some of them enter the baby’s body through the placenta with ease. As a result, the placenta shields the unborn child from several viral and bacterial infections.

Preventing an immunological conflict between the mother and the fetus is another benefit of the entry of maternal antibodies. In this instance, the fetus is not viewed by the mother’s body as an alien genetic object. Throughout pregnancy, this characteristic aids in preventing the fetus from being rejected from the uterus.

Additionally, the unique function of syncytium—a unique component of placental tissue—should be mentioned. Many hazardous substances that can cross the placenta from the mother to the fetus are absorbed through it. As a result, the placenta shields the developing child’s body from harmful drugs, toxins, and other substances.

It is crucial to keep in mind that this kind of penetration selectivity may be unique to each person. Dangerous substances are retained if the placenta’s histological structure is normal. Toxins and poisons can easily enter the child’s body if it is disturbed, harming it beyond repair. For this reason, expectant mothers are advised by doctors to give up all harmful habits while they are pregnant.

When a fetus is still developing, smoking, drinking alcohol, and using drugs can all lead to the development of serious illnesses. Preventing their development is far simpler than trying to manage the pathologies that have developed subsequently.

The expectant mother’s lifestyle plays a critical role in the placenta’s development and regular operation.

As the baby’s lifeline, the placenta is an essential organ that develops early in pregnancy, typically by the end of the first trimester. It serves as a conduit between the developing child and the mother’s uterus, removing waste materials and supplying nutrients and oxygen. Furthermore, by bolstering the baby’s immune system and serving as a barrier against dangerous substances, the placenta provides protection.

Migration

One crucial clinical indicator is the placenta’s initial position within the uterus. Pregnancy even varies in length based on where it occurs.

Placental tissue is typically adhered to either the anterior or posterior wall of the uterus. It is only very infrequently attached to one of the side walls. Placental tissue implantation is linked to the location of the fertilized egg’s implantation and starts in the first trimester of pregnancy.

Typically, the fertilized egg is attached near the uterine fundus. Good blood flow is present here, which is essential for the fetus’s complete intrauterine development during the pregnancy. This circumstance does not, however, always arise.

Cases involving the implantation of a fertilized egg in the lower uterus are documented in obstetric practice. This is prior to a plethora of distinct reasons. The fertilized egg in this instance may descend nearly to the base of the internal cervical os, where it joins the uterine wall.

The placenta is located lower the lower the implantation occurs. Physicians refer to the expansion of placental tissue in the internal cervical os presentation area as os presentation. This dangerous pathology can even lead to the development of dangerous complications during pregnancy, making it much worse.

The placental tissue’s original location may vary. This usually happens when the placenta affixed itself to the uterine anterior wall. Migration is the process of shifting the placental tissue’s original location. In this instance, the placenta typically moves from the bottom to the top. Therefore, even if the placental tissue’s low position was identified during the first half of pregnancy, it is still subject to change.

Placental migration usually proceeds very slowly, taking six to ten weeks. Usually, it is finished by the middle of the third trimester of pregnancy.

The placenta, which is found on the uterine back wall, hardly moves at all. There is very little chance that placental tissue will shift in this orientation. This is made possible in large part by specific uterine structural characteristics.

Norm

A healthy placenta is essential to a pregnancy’s typical progression. This particular organ of pregnancy gradually develops. The placenta is nearly always changing from the time it forms in the female body until childbirth.

By using ultrasound examinations, medical professionals can evaluate the placenta’s anatomical characteristics and spot different developmental abnormalities. This requires the expectant mother to have multiple ultrasounds throughout her pregnancy.

Specialists can see the placental tissue fairly clearly with the aid of contemporary technology. An ultrasound examination allows the doctor to view the placenta’s structure, any diffuse changes that may be present, and any developing pathologies.

The placenta’s maturity is a critical clinical indicator that obstetricians and gynecologists must assess during pregnancy. Every stage of pregnancy brings about changes. This is a typical occurrence. Assessing whether the placenta matures in accordance with a particular stage of pregnancy is crucial.

Consequently, experts differentiate between multiple possibilities regarding placental tissue maturity:

• Zero (0). Characterizes the normal structure of the placenta up to approximately 30 weeks of pregnancy. The placenta of such maturity has a fairly smooth and even surface.
• First (1). Characteristic of a healthy placenta at a period of 30 to 34 weeks of pregnancy. With the 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 relief, specific striations appear on it, as well as small furrows.
• Third (3). Is the norm for a normal full-term pregnancy. A placenta with such a degree of maturity has quite pronounced large waves on its surface that reach the basal layer. Also, on the outer surface of the placental tissue, merging spots of irregular shape appear – salt deposits.

Doctors can better understand the impending birth by assessing the placenta’s level of maturity. Placental tissue can sometimes mature too quickly. A number of hazardous complications follow from this. In this instance, experts should assess the pregnancy management strategies.

Question	Answer
What is the placenta?	The placenta is an organ that develops during pregnancy. It connects the mother"s blood supply to the baby"s, allowing nutrients and oxygen to reach the baby.
When is the placenta formed?	The placenta begins to form shortly after the fertilized egg attaches to the uterine wall, usually around the third week of pregnancy.
What functions does the placenta perform?	The placenta provides oxygen and nutrients to the baby, removes waste, and also helps protect the baby by filtering harmful substances.

The placenta, which develops early in pregnancy to supply the developing baby with food and oxygen, is an integral component of the pregnancy. It’s an amazing organ that begins to develop in the second week following conception and is vital to the mother-child bond during pregnancy.

In addition to providing essential nutrients, the placenta serves as a filter, shielding the unborn child from some dangerous substances while permitting essential antibodies to flow through. It is in charge of eliminating waste from the infant’s blood and making sure the child has all the nutrients necessary for a robust and healthy growth.

Pregnant parents can better appreciate the amazing processes at work during pregnancy by having a basic understanding of the placenta. It is a vital part of a healthy pregnancy because it is a transient but strong organ that maintains and supports life.

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