Placenta - This is a temporary body that is formed during the grade of the embryonic development of mammals. Distinguish children's and maternal placenta. Children's placenta is formed by the aggregate of the Village of Allanto-Chorion. Maternal is represented by the sections of the mucous membrane of the uterus, with which these vile interact.

The placenta provides the supply of the embryo with nutrients (trophic function) and oxygen (respiratory), blood release of the embryo from carbon dioxide and unnecessary exchange products (excretory), the formation of hormones that support the normal course of pregnancy (endocrine), as well as the formation of a placental barrier (protective function) .

Anatomical classification of the compartment Considers the number and location of the villi on the surface of Allantochorion.

1. The diffuse placenta is expressed in pigs and horses (short, unbranched veins are uniformly located along the entire surface of the chorion).

2. Multiple, or quotional, placenta is characteristic of ruminant. Allantochorion Villina is located island - quotes.

3. The belt placenta in the predatory is a zone of cluster of villi, located in the form of a wide belt surrounding the fruit bubble.

4. At the discoal placenta of primates and rodents, the chorion vague zone has a disk form.

Histological classification of the compartment Consides the degree of interaction of Allantochorion Village with the structures of the mucous membrane of the uterus. Moreover, as the number of patches is descended, they become more branched in shape and deeper penetrate into the mucous membrane of the uterus, shortening the path of moving nutrients.

1. Epithelioral placenta is characteristic of pigs, horses. Chorion Vilony penetrate the uterine glands, without destroying the epithelial layer. During the birth valves, it is easy to put forward from the uterus glands, usually without bleeding, so this type of compound is also called the semi-flaccent.

2. The desphorial placenta is expressed in ruminants. Allanto-Horion Vilony is embedded in its own endometrial plate, in the area of \u200b\u200bits carunculus thickening.

3. The endothelioral placenta is characteristic of predatory animals. Vilki children's placenta come into contact with the endothelium of blood vessels.

4. The hemochorial placenta is found at primates. Pork chorion is immersed in lacuna-filled with blood and washed with maternal blood. However, the blood of the mother is not mixed with the blood of the fetus.

Question 13. Morphological classification and brief description of the main varieties of the epithelium.

The basis of the morphological classification of epithelial tissues is two traits:

1. The number of layers of epithelial cells;

2. Cell shape. At the same time, the species of multilayer epithelium takes into account only the form of the surface (cover) layer epithelocytes.

Single-layer epithelium, in addition, can be built from the same in shape and height of cells, then their kernels lie at one level - single-row epithelium, and from significantly different epitheliocytes.

In such cases, low cells of the nucleus will form a lower row, at the average over the magnitude of the epithelocytes - the next one, located above the first, and the highest one or two rows of nuclei, which ultimately one-layer fabric translates into a pseudo-layer form - multi-row epithelium.

The structure and features of the placenta.

Placenta.

The placentachelovka has a hemohorial type of structure - the presence of direct contact of maternal blood with chorion due to the disorders of the integrity of the seduction membrane with the opening of its vessels.

Development of the placenta.The main part of the placenta is chorion vile - derivatives of the trophoblast. In the early stages of ontogenesis, trophoblast forms protoplasmic grows consisting of cytotrofoblast cells - primary vile. Primary naval vessels do not have vessels, and the flow of nutrients and oxygen to the organism of the embryo from the surrounding maternal blood takes place according to the laws of osmosis and diffusion. By the end of the 2nd week of pregnancy, the junction tissue is growing into primary couples and secondary vigors are formed. Their foundation is connective tissue, and the outer cover is represented by the epithelium - trophoblast. Primary and secondary vapors are evenly distributed over the surface of the fetal egg.

The epithelium of secondary vapors consists of two layers:

a) cytotrofoblast (Langhance layer) - consists of rounded cell cells with light cytoplasm, cell kernels are large.

b) syncytia (symplast) - the borders of the cells are practically indistinguishable, the cytoplasm is dark, grainy, with brush border. The nucleus is relatively small sizes, spherical or oval shape.

Since the 3rd week of the development of the embryo, a very important process of developing the placenta begins, which consists in vascularization of the vice and turning them into tertiary, containing vessels. The formation of placenta vessels occurs both from the angioborests of the embryo and from the navel vessels growing from Allantois.

The vessels of Allanto are growing into secondary vile, as a result of which each secondary couple receives vascularization. The establishment of allantoid blood circulation ensures the intensive exchange between the organisms of the fetus and the mother.

In the early stages of the intrauterine development of chorion, the entire surface of the fetal egg evenly cover the entire surface. However, starting from the 2nd month of ontogenesis on a larger surface of the fetal eggs, parcels are atrophy, at the same time evils are developing facing the basal part of the decidual shell. So form smooth and branchy chorion.

Under the period of pregnancy, 5-6 weeks the thickness of the sycitiotrofoblast exceeds the thickness of the Langhanx layer, and, since the term of 9-10 weeks, the sycitiotropoblast gradually thinning and the number of nuclei in it increases. On the free surface of the sycitiotrofoblast addressed to the intervalized space, the long thin cytoplasmic grows (microvins) are well visible, which significantly increase the resorption surface of the placenta. At the beginning of the II trimester of pregnancy, there is an intensive transformation of the cytotrofoblast in sycyties, with the result that in many areas the Langhanes layer completely disappears.

At the end of pregnancy in the placenta, involutionary-dystrophic processes begin, which are sometimes called the aging of the placenta. Fibrin (fibrinoid), which is postponed mainly on the surface of the Vorsin begins to fall out of the blood circulating in the intervalistic space. The loss of this substance contributes to the processes of microtromotic formation and the death of individual sections of the epithelial cover of the Vorsin. Fibrinid-covered naval, largely turn off the active exchange between the organisms of the mother and the fetus.

There is a pronounced thinning of the placental membrane. Stroma Vorusin becomes more fibrous and homogeneous. There is some thickening of the endothelium of capillaries in the dystrophy sites are often postponed lime salts. All these changes are reflected on the features of the placenta.

However, along with the investments of the involution, the young Vorsin increases, which largely compensate the function of lost, but they only partially improve the function of the placenta as a whole. As a result, at the end of pregnancy, there is a decrease in the function of the placenta.

The structure of mature placenta. Macroscopically mature placenta very much resembles a thick soft pellet. The mass of the placenta is 500-600 g. The diameter is 15-18 cm, the thickness is 2-3 cm. The placenta has two surfaces:

a) Maternal - addressed to the wall of the uterus - the placenta has a grayish-red color and represents the remains of the basal part of the decidual shell.

b) the fruit - turned towards the fetus - covered with a brilliant amniotic shell, under which the vessels coming from the place of attachment attachment to the periphery of the placenta are suitable for chorion.

The main part of the fruit placenta is represented by numerous chorion navy, which are combined into pursuant formations - quotes, or slices - Basic structural and functional unit formed placenta. Their number reaches 15-20. Solutions of the placenta are formed as a result of the separation of chorion navy by partitions (septs), emanating from the basal plate. Each of these lobes is suitable for its large vessel.

Microscopic structure of mature vile. Distinguish two types of Vorsin.:

a) free - immersed in the intervalistic space of the decidual shell and "float" in maternal blood.

b) fixing (anchor) - attached to the basal decidual shell and ensure the fixation of the placenta to the wall of the uterus. In the third period of generics, the relationship of such a village with a decidual shell is disturbed and under the influence of the uterine reductions of the placenta is separated from the wall of the uterus.

With microscopic study of the structure of mature vapors, the following education is differentiated:

Sycytium, not having clear cell boundaries;

Layer (or residues) of the cytotrofoblast;

Strom of vile;

The endothelium of the capillary, in which the elements of the blood of the fetus are well noticeable.

Mastello placental blood circulation. Bloodstock and mothers and fetus are divided among themselves the following structural units of the chorion village:

Epithelial layer (syncytis, cytotrofoblast);

Strom of Vorsin;

Endothelium capillaries.

Bleeding in the uterus is carried out with the help of 150-200 maternal spiral arteries, which are opened in an extensive intervalic space. The walls of the arteries are deprived of the muscular layer, and the mouths are not able to shrink and expand. They have low blood flow vascular resistance. All these features of hemodynamics are of great importance in the implementation of the uninterrupted transport of arterial blood from the mother's body to the fetus. The flowing arterial blood ishes the chorion naval, while giving the fetal blood oxygen, the necessary nutrients, many hormones, vitamins, electrolytes and other chemicals, as well as the trace elements necessary to the fetus for its proper growth and development. Blood containing CO 2 and other products of the fetal metabolism is poured into the venous holes of the maternal veins, the total number of which exceeds 180. The blood flow in the intervalistic space at the end of pregnancy is quite intense and on average is 500-700 ml of blood per minute.

Features of blood circulation in the mother-placental-fruit system.Arterial vessels of the placenta after death from umbilicals are divided radially in accordance with the number of points of the placenta (quotients). As a result of the further branching of arterial vessels, a network of capillaries is formed in the final veins, the blood of which is assembled into the venous system, the veins in which arterial blood flows are assembled into larger venous trunks and fall into the vein of umbilical cord.

The blood circulation in the placenta is supported by cardiac abbreviations of mother and fetus. An important role in the stability of this blood circulation also belongs to the mechanisms of self-regulation of the royal and placental blood circulation.

The main features of the placenta. The placenta performs the following main functions: respiratory, excretory, trophic, protective and incultorial. It also performs the functions of antigension and immune sewn. Fruit shells and accumulating water play a major role in the implementation of these functions.

1. Respiratory function. Gas exchange in the placenta is carried out by penetrating oxygen to the fetus and removal from its body from 2. These processes are carried out according to the laws of simple diffusion. The placenta does not have the ability to accumulate oxygen and CO 2, so their transport occurs continuously. The exchange of gases in the placenta is similar to gas exchange in the lungs. A significant role in the removal of CO 2 from the body of the fetus is played by spindle water and paraplvent exchange.

2. Trophic function. Foot nutrition is carried out by transporting metabolic products through a placenta.

Proteins.The state of protein metabolism in the system of the mother-fruit is due to the protein composition of the mother's blood, the state of the protein-synthesizing the placenta system, the activity of enzymes, the level of hormones and a number of other factors. The content of amino acids in the blood of the fetus slightly exceeds their concentration in the blood of the mother.

Lipids.Transport of lipids (phospholipids, neutral fats, etc.) to the fetus is carried out after their preliminary enzymatic splitting in the placenta. Lipids penetrate the fetus in the form of triglycerides and fatty acids.

Glucose.It moves through the placenta according to the mechanism of light diffusion, so its concentration in the blood of the fetus may be higher than that of the mother. The fruit also uses glycogen liver glucose to form glucose. Glucose is the main nutrient for the fetus. It also owns a very important role in the processes of anaerobic glycolysis.

Water.Through the placenta to replenish the extracellular space and the volume of spindle water passes a large amount of water. Water accumulates in the uterus, fabrics and fetus organs, placenta and amniotect fluid. In physiological pregnancy, the amount of accumulating waters is increased daily by 30-40 ml. Water is necessary for the proper metabolism in the uterus, placenta and in the body of the fetus. Water transport can be carried out against a concentration gradient.

Electrolytes.. The exchange of electrolytes occurs transplascentary and through the amniotic fluid (paraploterno). Potassium, sodium, chlorides, bicarbonates freely penetrate the mother to the fetus and in the opposite direction. Calcium, phosphorus, iron and some other trace elements are able to deposit in the placenta.

Vitamins.Vitamin A and carotene deposited in the placenta in significant quantities. In the liver of the fetal, the carotene turns into vitamin A. Vitamins of the group in accumulate in the placenta and then binding to phosphoric acid, go to the fetus. The placenta contains a significant amount of vitamin C. At the fetus, this vitamin in excessive amounts accumulates in the liver and adrenal glands. The content of vitamin D in the placenta and its transport to the fetus depends on the content of vitamin in the blood of the mother. This vitamin regulates the exchange and transportation of calcium in the system of the mother. Vitamin E, as well as vitamin K, does not pass through the placenta.

3. Endocrine function. In the physiological course of pregnancy, there is a close relationship between the hormonal status of the parent organism, the placenta and the fruit. The placenta has the election capacity to endure maternal hormones. Hormones having a complex protein structure (somatotropin, thyrotropic hormone, ACTH, etc.), practically do not pass through the placenta. Penetration of oxytocin through a placental barrier prevents high activity in the placenta of the enzyme oxytocinase. Steroid hormones have the ability to switch through the placenta (estrogens, progesterone, androgens, gluco-corticoids). Thyroid hormones of the mother also penetrate the placenta, however, the thyroxine transplantary transition is carried out more slowly than triiodothyronine.

Along with the function on the transformation of maternal hormones, the placenta itself turns into a powerful endocrine body, which ensures the presence of optimal hormonal homeostasis both in the mother and the fetus.

One of the most important placental hormones of protein nature is placenta lactogen(Pl). By its structure, the PL is close to the hormone growth of adenogipophysis. The hormone is practically fully entered into maternal blood flow and is actively involved in carbohydrate and lipid metabolism. In the blood of a pregnant woman begins to be found very early - from the 5th week, and its concentration increases progressively, reaching a maximum at the end of the gestation. PL practically does not penetrate the fetus, and in the amniotic fluid contained in low concentrations. This hormone is given an important role in the diagnosis of placental insufficiency.

Another hormone of the placenta of protein origin is horionichi gonadotropin(XG). Hg in the blood of the mother is found in the early stages of pregnancy, the maximum concentrations of this hormone are marked at 8-10 weeks. Fruit goes to limited quantities. On the definition of the XG in the blood and the urine, hormonal pregnancy tests are based: immunological reaction, Ashheim reaction - Condeke, hormonal reaction on male frogs .

The placenta along with the pituitary of the mother and the fetus produces prolactin.The physiological role of placental prolactin is similar to such pl.

Estrogen(Estradiol, estrone, estriol) are produced by the placenta in an increasing quantity, while the highest concentrations of these hormones are observed before childbirth. About 90% of estrogen placenta are represented by estrine. It is reflected not only the features of the placenta, but also the state of the fetus.

An important place in the endocrine function of the placenta belongs to the synthesis progesterone. Products of this hormone begins with early time of pregnancy, however, during the first 3 months, the main role in the synthesis of progesterone belongs to the yellow body and only then this role takes on the placenta. From the placenta progesterone comes mainly in the blood flow of the mother and to a much lesser extent in the blood flow of the fetus.

The placenta produces glucocorticoid steroid cortisol.This hormone is also produced in the adrenalces of the fetus, therefore the concentration of cortisol in the mother's blood reflects the state of both the fetus and the placenta (fetoplazentar system).

4. Barrier feature of the placenta. The concept of "placental barrier" includes the following histological formations: syncytotrophoblast, cytotrofoblast, a layer of mesenchymal cells (strom of vigors) and the endothelium of the fruit capillary. It is characterized by the transition of various substances in two directions. The permeability of the placenta is inconsistent. In physiological pregnancy, the permeability of the placental barrier increases progressively up to the 32-35th week of pregnancy, and then somewhat decreases. This is due to the characteristics of the placenta structure at various times of pregnancy, as well as the needs of the fetus in certain chemical compounds. The limited barrier features of the placenta with respect to chemicals, randomly in the mother's body, are manifested in the fact that the toxic products of chemical production are relatively easily moving, most of the drugs, nicotine, alcohol, pesticides, causative agents, etc. Barrier features of the placenta are most fully manifested in physiological conditions, i.e. With the uncomplicated course of pregnancy. Under the influence of pathogenic factors (microorganisms and their toxins, the sensitization of the mother's body, the effect of alcohol, nicotine, drugs) the barrier function of the placenta is broken, and it becomes permeable even for such substances, which in conventional physiological conditions pass through it in limited quantities.

There are two surfaces of the placenta: fruit, fabricated to the fruit, and maternal, adjacent to the wall of the uterus. The fruit surface is covered with amnion - a smooth shiny shell of a grayish color, the cord is attached to the central part of it, from which the vessels radially diverge. The mother's surface of the dark brown placenta, divided by 15-20 poles - quotients, which are separated from each other by placenta partitions. From the umbilical arteries, the blood of the fetus enters the vessels of the vile (fruit capillaries), carbon dioxide from the blood of the fetus goes into maternal blood, and oxygen from maternal blood goes into fruit capillaries. The oxygen-enriched blood of the fetus from quotients is collected to the center of the placenta and then falls into the umbilical vein. Maternal and fruit blood is not mixed, there is a placental barrier between them. The structure of the placenta is finally formed by the end of the first trimester, but its structure changes as the needs of the growing kid change. From the 22nd to the 36th week of pregnancy there is an increase in the mass of the placenta, and by the 36th week it reaches full functional maturity. The normal placenta by the end of pregnancy has a diameter of 15-18 cm and a thickness of 2 to 4 cm. After childbirth (the placenta, together with the fetus shells - the last one is born within 15 minutes after the child appears) the placenta necessarily examines the doctor who has taken childbirth . First, it is very important to make sure that the placenta was born entirely (that is, there are no damage on its surface, and there is no reason to believe that the placenta pieces remained in the uterus cavity). Secondly, according to the state of the placenta, it is possible to judge the course of pregnancy (there was no detachment, infectious processes, etc.). There are three degrees of placenta maturity. Normally, up to 30 weeks of pregnancy should be determined by the zero degree of maturity of the placenta. The first degree is considered permissible from the 27th to 34th week. The second - from the 34th 39th. Since the 37th week, the third degree of maturity of the placenta may be determined. At the end of pregnancy, the so-called physiological aging of the placenta occurs, accompanied by a decrease in the area of \u200b\u200bits exchange surface, the appearance of sediments of salts. According to the ultrasound, the doctor determines the degree of maturity of the placenta, estimating its thickness and structure. Depending on the conformity of the period of pregnancy and the degree of maturity, the doctor chooses the tactics of pregnancy. This information also affects the tactics of the delivery.

The mature placenta is a disk-shaped structure with a diameter of 15-20 cm and a thickness of 2.5 - 3.5 cm. Its mass reaches 500-600 gr. The mother's surface of the placenta, which is facing the edge of the uterus, has a rough surface formed by the structures of the basal part of the decidual shell. The fruit surface of the placenta, which is addressed towards the fetus, is covered with an amniotic shell. The vessels are visible under it, which go from the site of attaching umbilical cord to the edge of the placenta. The structure of the fruit part of the placenta is represented by numerous chorion navy, which are combined into structural formations - quotes. Each quotary is formed by a trunkpit with ramifications containing the vessels of the fetus. The central part of the quotion is formed by the cavity, which is surrounded by a plurality of Vorsin. In a mature placenta there are from 30 to 50 quotes. Coteialon placenta is conventionally comparable to a tree, in which the support porsal I order is its barrel, naval and III of the order - large and small branches, intermediate vans - small branches, and terminal vapors - leaves. Cotionalons are separated from each other by partitions (septs) emanating from the basal plate.

Placenta functions

Its functions are multifaceted and aimed at preserving pregnancy and normal development of the fetus. A gas exchange is carried out through the placenta: oxygen penetrates the maternal blood to the fetus, and carbon dioxide is transported in the opposite direction. The respiratory function of the placenta is carried out by transmitting oxygen from maternal into fruit blood and carbon dioxide from fruit in maternal blood depending on the needs of the fetus. The fruit receives the nutrients through the placenta and get rid of products of its livelihoods. The placenta has immunist properties, that is, the antibodies (protective proteins) of the mother to the child, providing its protection, and at the same time delays the cells of the mother's immune system, which, penetrating the fruit and recognizing the alien object, could run the reaction of the fetus reaction, it plays The role of the gland of the internal secretion and the synthesis of hormones. Hormones placenta (chorionic gonadotropin, placental lactogen, progesterone, estrogens, etc.) provide a normal course of pregnancy, regulate the most important life functions of pregnant and fetus, participate in the development of the generic act. Especially high the activity of metabolic processes in the placenta in the third trimester of pregnancy.

In addition, the placenta performs a protective function. In it, with the help of enzymes, the destruction of the produced in the body of the mother and in the body of the fruit of harmful substances occurs. The barrier function of the placenta depends on its permeability. The degree and speed of the transition of substances through it are determined by various factors. Under a number of pregnancy complications, various diseases that are portable to pregnant, the placenta becomes more permeable for harmful substances than with normally flowing pregnancy. In this case, the risk of intrauterine pathology of the fetus is dramatically increasing, and the outcome of pregnancy and childbirth, the state of the fetus and the newborn depends on the degree and duration of the action of the damaging factor and on the preservation of the protective function of the placenta. With the normal development of pregnancy, there is a dependence between the growth of the fetus, its body weight and dimensions, thickness, the mass of the placenta. Up to 16 weeks of pregnancy, the development of the placenta is ahead of the growth rate of the fetus. In the event of death of the embryo (fetus), the growth of the growth and development of the chorion vice and the progression of involutionary-dystrophic processes occurs in the placenta. Having achieved the necessary maturity in 38-40 weeks of pregnancy, the processes of education of new vessels and vascular cease in the placenta.

The mother's body during pregnancy adapts to the fetus, which distinguishes the functional system of the mother - the fruit of the forms of the lives of two organisms known in the biology. The strict sequence of not only the development of organs and systems of the fetus, but also the adaptation processes for the pregnancy of the parent organism, which occurs in full compliance with the stages of intrauterine development.

For example, obtaining oxygen from the outside is provided by the hemodyne fictional functional system of a placenta - the fruit that is a subsystem of the general functional system is a fruit. It develops the first in the earlier ontogenesis. It simultaneously forms fetoplazater and uterine-placental blood circulation.

There are two blood flows in the placenta: 1) the flow of maternal blood due to mainly systemic hemodynamics of the mother; 2) Fetal blood flow, depending on the reactions of its cardiovascular system. The flow of maternal blood is shunted by the vascular channel of myometrium. At the end of pregnancy, the percentage of blood coming to the intervalized space ranges between 60 and 90. These fluctuations in blood flow depend mainly on the tone of myometrium. A paravascular network is developing around the arteries and veins, which is considered as a shunt capable of passing blood under conditions when the blood flow is difficult through the exchange part of the placenta. Fetoplazater and uterine-placental blood circulation are conjugate, the intensity of blood flow is the same. Depending on the changes in the state of the activity of the mother and the fetus, each of them occurs the redistribution of blood in such a way that the oxygenation of the fetus remains within the normal range.

It is peculiar to the development of the endocrine functional system Fruit of the placenta - mother, which is particularly clearly traced on the example of the estorol synthesis. The enzyme systems needed for the production of estrogen are distributed between the fruit (its adrenal glands and the liver), the placenta and adrenalities of the mother. The first stage in the biosynthesis of estrogen during pregnancy (hydro-xylation of the cholesterol molecule) occurs in the placenta. The resulting pregeronolone from the placenta enters the adrenal glands of the fetus, turning into dehydroepiyndrosterone (DEA). Dae comes with venous blood in a placenta, where aromatization is undergoing influenced by enzyme systems and turns into an estrone and estradiol. After the complex hormonal exchange between the organism of the mother and the fetus, they turn into estrogen (the main estrogen of the fetal-centurium complex).

As a result of the crushing of human's zygotes (complete asynchronous) and the formation of blastocysts, two types of blastomers are formed: dark(intracellular weight - embubline) I. light (trophoblast), there is a relationship between the parent organism with the embryo organism. At this stage, light blastomeres (trophoblast) play a big role, which provide two important processes: implantation - attachment and introduction of the embryo in the endometrium of the uterus; Placentating - the formation of a specialized integrated structure - placenta.

Subsequent processes of migration, formation and differentiation of germinal leaves, as well as the formation of axial organs in the embryos of mammals very similar to the nuclei of birds.

The process of forming some of the extraordinary shells in mammals and humans is closely related to the interaction of the embryo with the mother's organism.

Implantation. Chorion and placenta formation

The outer layer of mammalian blastocyters is gradually converted and has different names. At stage, blastocysts are called trophylast. After the formation of the hypovest and the mesoderm, it communicates with the ectoderma and is called trophoectrum. Then the extraordinary mesoderma is formed, which, together with the trophoblast, forms Chorion (who became extraordinary somatoplevia). Tropofoblast, and after and chorion, interact with the mucous membrane of the uterus, while the special complex structure is formed, called placentaAnd the process itself is placentating.

Many mammals, chorion is closely in contact with the mucous membrane of the uterus. However, some placental mammals choirion can be freely separated from the endometrium, because They do not grow together. In this case, the so-called contact (non-slip) placenta is formed. But some mammals, including a person, the placenta more specialized. At the same time, its fruit (from chorion) and the maternal (from the endometrium) parts are growing so that it is impossible to separate them from each other without causing a violation of the integrity of blood vessels and bleeding. In this case, after the birth of the fetus and the exit outside of the extraordinary shells in the form of a lie, most of the endometrium of the uterus turns along with the chorion. Unlike primitive contact placenta, such a type of placenta is called disappearing (decidual).

The attachment and further introduction of the embryo in the mucous membrane of the uterus is called implantation. This is promoted by the cells of the trophoblast, which destroy the mucous membrane lying under it.

The formation and development of the chorion Village in a person begins by the end of the second week. Prior to that, from the moment of implantation, Trofoblast continues to grow intensively. This stage was named previantly due to the presence of relatively shapeless cell mass of the trophoblast.

By the end of the second week, the formation of cell clusters, consisting only of epithelium without connecting stroma, and called primary vehicles begins in Trofoblast. They are very quickly differentiated and formed two layers:

1. Inner layer - cytotrofoblast - consisting of an ordered cell layer, each of which has clear boundaries.

2. Outer layer - symplastotrofoblast- uneven thickness structure having randomly located numerous kernels. Autoradiographic studies have shown that these nuclei have the origin of the cytotrofoblast. It can be assumed that the cytotrofoblast is a germinative center that supplies the simplastotrofublast as a nucleus and the cytoplasmic material.

This stage is primary Village - continues not long. At the beginning of the third week, after fertilization of the Mesoderma penetrates the primary patches and forms a very fragile and thin connective tissue basis. Such villins are called secondary. In the future, blood vessels and vile are rotated in the stroma of these villos, they are called tertiary. From now on, i.e. From the end of the third week, VILLINs are ready to perform their function absorption of nutrients and the elimination of metabolic products. Such a plan for the structure of the VILROWS is preserved over the entire period of embryonic development, although over time, the connective bowl and blood vessels become more developed, and regressive changes are observed in epithelial cover.

Contact with the maternal organism can be carried out in different ways and depends on the depth of immersion of the chorion villion into the uterine mucosa and on the degree of destruction of the mucous membrane. In this regard, the formation of several types of compounds differing in their structure. These differences relate to the number and types of cellular layers separating the blood of the mother of the fetus. This explains the name of the compound:

1. Epitheliochorial - Chorion's naps are closely adjacent to the epithelium of the uterus mucous membrane, while the destruction of the mucous membrane does not occur (sample, pigs, horses, camels, cetaceans).

2. Desphorial -chorion Vaults destroy the epithelium and are introduced into a connecting tissue under it (chewing).

3. Endothelioral -the chorion naps destroy the epithelium of the mucous membrane of the uterus, its connecting tissue and the wall of the vessels up to the endothelium (predators, laston-either).

4. Hemochorial - Chorion destroys not only the epithelium and the connective tissue of the mucous membrane of the uterus, but also completely the wall of its vessels, including endothelium (insectivore, bats, rodents, monkeys and man).

Placenta formation

The presence of the embryo causes a pronounced change in the endometrical of the uterus in the place where implantation occurred. Endometrial stroma cells around blastocysts are filled with glycogen and fat droplets. Similar change got the name reaction reaction. As a result, this reaction covers all the cells of stroma, spreading throughout the endometry. By the end of pregnancy (childbirth), endometrium containing these cells is brazed, and then it is formed again. This phenomenon of postpartum rejection and substitution and gave rise to the term dispassing, or degidual, applicable to endometrial during pregnancy. As the chorion grows, the part of the endometrium is stretched over it, covering it, and forms a layer, which is called capsular disappearing shell (Decidua Capsularis). Part of the endometrium, lining the walls of the uterus in other places, except the place of attachment of chorion, is called announcement with a spunky shell. The endometrium site, lying directly under the chorion called basal disappearing sheathwhich provides a trophy of the embryo, because It is here that intensively and abundantly occurs blood supply to the endometrium. On the third month, when, as a result of the growth of the embryo and the growing of amnion, the capsular and the clutch shells are tightly pressed together, the veins in this zone gradually disappear.

Thus, the Chorion, who was first all covered with Villas, to the fourth month, retains the veins only in the region of the basal decaying shell. The part of Chorion, which lost the villus under the capsular shell, is called smooth Chorion., and a part located in the region of the basal shell, where the villi is well developed, called branchy Chorion.. Thus, the branching chorion of the fetus and the basal dumping shell of the endometry of the uterus connecting and form a placenta, or a child seat.

After complete consolidation of chorion in the uterus, the implementation process slows down and simply follows the growth of the fetus. Chorion Villina acquire a more differentiated state. This is manifested in a more ordered structure of the symplastotrofoblast and cytotrofoblast. The mesenchymal base of the stroma of the Village turns into a loose fibrous connecting tissue. Here are large cells (Hofbauer cells), which are apparently primary macrophages. Gradually, the epithelial cover of Village becomes relatively thinner, because The introduction function that it performed becomes less important. The cytotrofoblast reaches its maximum development during the second month, and then loses its integrity. It seems that he, as it were, spent himself to build a symplastotrofoblast.

From the point of view of the functional value in embryogenesis, you can trace a certain dynamics of morphological changes in the structure of the trophoblast. Thus, the total development of the trophoblast reaches during the period of introduction in the endometrium of the uterus. Subsequently, there is a gradual reduction of the epithelial layers of villi, after they fulfilled their role. This leads to the thinning of the layer of tissue, through which the metabolism between the blood of the fetus and the blood of the maternal organism occurs. However, two circulatory systems never communicate, because separated by special placental barrierwhich includes the following structures: trophoblast; Basal membrane; Fabric stroma tubing fabric; Basal membrane vessel; Endothelial vessel liner.Through this barrier should be held in one direction the products of the fetus metabolism, and in the other - coming from the maternal substance necessary for breathing, growth, immunological protection of the fetus, etc.

From the mother's side, the blood enters into the intervalistic lacun space through the open ends of about 30 spiral arteries. This arterial blood is washes with a villus, forming flows in the form of small fountains, and then under less pressure, assembled at the bottom of the placental compartments (lacun) and flows through the uterine veins. The intervalic space occupied by blood is in a mature placenta about 150 ml and by the end of pregnancy this blood volume is replaced three times a minute.

On the part of the fetus, the blood enters the vessels of the Village according to the branches of the umbilical arteries. Despite the fact that anatomically, this blood is arterial, but physiologically equivalent to venous blood, i.e. Poor oxygen and contains a lot of 2 and metabolic products.

In the terminal branches, the Village is formed by a capillary network and it is here that the main placental exchange occurs. The blood enriched on 2 is then returned to the fetus through the drainage system of the umbilical vein.

The main features of the placenta are to transfer and synthesize various substances. The surface area through which the exchange is carried out, heavily increases both due to the branching of the chorion Village and due to the presence of a large number of microvones on the surface of the symplastotrofoblast.

Mothers to the fetus are transferred to the substance of several classes:

1. Legging substances (O 2, H 2 O, inorganic ions).

2. Low molecular weight organic substances (sugar, amino acids, lipids) - serve as a substance for anabolic processes in the body of the embryo. The transfer is carried out actively through the components of the placental barrier.

3. High molecular weight organic substances (proteins - hormones and enzymes, antibodies). Transfer is carried out by pinocytosis and diffusion.

The most important class of transportable macromolecules is maternal antibodies that protect the newborn baby from infectious influences until it becomes functioning its own immune system.

From the fetal side through the placenta, mainly CO 2, H 2 O, electrolytes, urea and other decay products, which are formed during the metabolism of the fetus.

The placenta synthesizes four hormones (synthesizes mainly symplastotrofoblast). Two protein hormones: chorionic gonadotropin and placental lactogen man.

The first hormone begins to be produced by trophoblast very early, before implantation. Its functions are to maintain the development of a yellow body and turning it into the yellow body of pregnancy. The presence of this hormone in the urine of a woman is the basis for many conventional pregnancy tests. The second hormone has been little studied, but it is believed that it possesses both somatic and prolactic actuat. It is often referred to as chorionic somatommotropin. Chemically, this hormone is similar to growth hormone, and functionally with prolactin. Two other hormones - steroid: progesterone and estrogen. The placenta also secretes another hormone - human chorionic thyrotropin.

Similar information.

Latin of the placenta means "pie". Placenta during pregnancy It really resembles a nosed cake, its diameter reaches an average of 20 cm, and the thickness is 2-3 cm.

How is the placenta forms? When a fruit egg is implanted, the trophoblast, embedded into the mucous membrane of the uterus and destroying the walls of the vessels, draws the nutrients necessary for the development of the egg.

Soon this simple mechanism ceases to satisfy the needs of a rapidly developing embryo. Then the maternal organism and the fruit egg create a small substation - placenta jointly. Trofoblast sends a lot of finest threads into the mucous membrane. For a few weeks, these threads thicken and form the so-called placental vehicles. You can imagine them in the form of a tree, the trunk of which is divided into the main branches, and those in turn are divided into branches minor. The latter are typical of a multitude of kidneys ending with tens of villi. There are from 15 to 33 large trunks, at the ends of which thousands of villings are formed by sequential division. The exchange between mother and child is carried out with their help.

Each vile at the level of the uterus is immersed in a small lake, filled with blood (this is the motherboard of the placenta). In the lake, the blood of the mother circulates, and in Vorki - the blood of a child delivered here with the help of umbilical cord.

So the blood of the mother and the child is found in the placenta, but never mixed, because the walls are separated by the walls, through which the mother exchange is a child. These walls are becoming thin during pregnancy, apparently in order to facilitate the exchange as the needs of the fetus grow.

This explanation may seem somewhat difficult, but it is necessary to understand the relationship between the blood of the mother and the child; The existence of the partition between them in the form of the walls of the Village shows that the blood of the mother does not penetrate directly into the blood of the child, as sometimes they think.

Main role placetes for pregnancy

Main role placetes for pregnancy In the fact that it is a genuine food plant. Through the shell of the villi, the blood of the fetus is saturated with oxygen. Placenta - real light fetus. Water easily passes through the placenta (3.5 l per 1 hour for 35 weeks), like most mineral salts. As for raw materials, i.e. nutrients, then it is more complicated with them. Carbohydrates, fats, proteins are easily passing, the remaining substances of the placenta must recycle before learning. That is why the placenta is called the plant, as soon as excess food occurs, it spares them. The plant is complemented by the warehouse from which the fetus gets products if necessary.

The second role of the placenta is that it is a barrier, delaying some elements, but transmitting others, that is, this is a kind of customs. The placenta performs such a protective function when it is necessary to block the path to some aggressive elements. So, most microbes cannot penetrate the placenta. But, unfortunately, there are also microbes that can overcome a placental barrier, for example, an intestinal wand or a pale spirochete (syphilis pathogen) passes through it, starting from the 19th week of pregnancy. Most of the viruses (due to their size) are easily passing through the placenta, which explains, for example, various disorders from the fetus caused by rubella (if contact with the patient was at the beginning of pregnancy).

Maternal antibodies also penetrate the placenta. These are substances that are generated to fight against infections. Most often, they are useful for the fetus: getting into his blood, the maternal anti-bodies protect it from the corresponding infectious diseases of approximately the first 6 months of life. Sometimes it is bad: in case your mother with a negative Rh-factor is pregnant with a child's positive rear factor. If it produces anti-convertible antibodies, then they, passing into the blood of the child, can destroy red blood cells.

Many medicines also overcome a placental barrier. And there is a positive side in this: one antibiotic will protect the child from toxoplasmosis, the other will fight against syphilis. But there is also a negative side: some medicines may have a harmful effect on the child.

Alcohol absorbed by the mother easily passes through the placenta, as well as drugs (especially morphine and its derivatives).

Thus, the placenta is generally a good safety barrier, but it is not always impenetrable.

The placenta produces hormones of two types

Filter, plant, warehouse; In addition, the placenta performs another important function - it produces two types of hormones; Some of them are characteristic of pregnancy - chorionic gonadotropin and lactogenic placental hormone. Chorionic Gonadotropin has already played a role in your pregnancy: after all, it was thanks to him that you learned about my pregnancy, since laboratory data is based on the content in the blood and the urine of this hormone. The content of chorionic gonadotropin is constantly increasing to the 10-12th week of pregnancy, then until the 4th month its amount decreases, and in the future it remains unchanged. The main role of chorionic gonadotropin is to maintain the activity of the yellow bodies of the ovaries necessary for the existence and prosperous flow of pregnancy.

The second placental hormone is lactogen - open relatively recently. Its role has not yet been fully studied, but it is already known that its presence is a good sign of the proper functioning of the placenta. These two hormones never penetrate the placenta to the child.

The placenta produces other hormones already known to you: Estrogens and progesterone. At the beginning of pregnancy, these hormones are highlighted with a yellow body. At the 7-8th week, the placenta takes the resettlement. It will produce these hormones in all increasing quantities before the end of pregnancy; By the time of birth in the urine of a pregnant woman contained 1000 times more estrogen than during menstruation. These hormones are needed to maintain pregnancy, for the growth and development of the fetus. Their content in blood and urine is a good sign of normal development of pregnancy.

The placenta performs the following main functions: respiratory, excretory, trophic, protective and incultorial. It also performs antigent and immune protection functions. Fruit shells and accumulate water play a major role in the implementation of these functions.

The transition through a placenta of chemical compounds is determined by various mechanisms: ultrafiltration, simple and light diffusion, active transport, pinocytosis, transformation of substances in chorion naval. The solubility of chemical compounds in lipids and the degree of ionization of their molecules are also important.

Processes ultrafiltration Depend on the magnitude of the molecular weight of the chemical. This mechanism takes place in cases where the molecular weight does not exceed 100. With a higher molecular weight, a hoped transplacental transition is observed, and with molecular weight 1000 and more chemical compounds are practically not passing through the placenta, so their transition from mother to the fetus is carried out using other mechanisms.

Process diffusion It is the transition of substances from the region of greater concentration into a lower concentration region. Such a mechanism is characteristic of transition of oxygen from the mother's body to the fetus and from 2 from the fetus into the mother's body. Lightweight diffusion differs from simple in that the equilibrium of concentrations of chemical compounds on both sides of the placental membrane is achieved much faster than this could be expected on the basis of the laws of simple diffusion. Such a mechanism is proved to transition from the mother to the fetus of glucose and some other chemicals.

Pinocytosis It is a type of transition of a substance through a placenta when the chorion vaults actively absorb the droplets of the maternal plasma together with those contained in them by those or other connections.

Along with these mechanisms of transplacental metabolism, great importance for the transition of chemicals from the mother of the mother to the fetus and in the opposite direction is solubility in lipids and the degree of ionization of the molecules of chemical agents. The placenta functions as a lipid barrier. This means that chemicals are well soluble in lipids, more actively switch through the placenta than poorly soluble. The role of ionization of the chemical compound molecules is that non-expocted and non-ionized substances go through the placenta more quickly.

The metabolic surface of the placenta and the thickness of the placental membrane is also essential for the exchange processes between the organisms of the mother and the fetus.

Despite the phenomena of the so-called physiological aging, the permeability of the placenta increases progressively until the 32-35th week of pregnancy. This is mainly due to an increase in the number of newly formed Vorsin, as well as the progressive thinning of the placental membrane itself (from 33-38 microns at the beginning of pregnancy up to 3-6 microns at the end of it).

The degree of transition of chemical compounds from the mother's body to the fetus depends not only on the peculiarities of the placenta permeability. A large role in this process belongs to the organism of the fetus itself, its ability to selectively accumulate precisely those agents that are currently especially necessary for him for growth and development. Thus, during the period of intense hematopoiesis, the need of the fetus in the hardware is increasing, which is necessary for the synthesis of hemoglobin. If the mother's body contains an insufficient amount of iron, then anemia arises from it. With intensive ossification of the skeleton bones, the need of the fetus in calcium and phosphorus increases, which causes an enhanced transplacent transition to their salts. During this period of pregnancy, the mother has particularly pronounced the processes of depletion of its body with these chemical compounds.

Respiratory function.Gas exchange in the placenta is carried out by penetrating oxygen to the fetus and removal from its body from 2. These processes are carried out according to the laws of simple diffusion. The placenta does not have the ability to accumulate oxygen and CO 2, so their transport occurs continuously. The exchange of gases in the placenta is similar to gas exchange in the lungs. A significant role in the removal of CO 2 from the body of the fetus is played by spindle water and paraplvent exchange.

Trophic function. Foot nutrition is carried out by transporting metabolic products through a placenta.

Proteins. The state of protein metabolism in the mother's system is due to many factors: the protein composition of the blood of the mother, the state of the protein-synthesizing system of the placenta, the activity of enzymes, the level of hormones and a number of other factors. The placenta has the ability to deamine and deamine amino acids, synthesize them from other predecessors. This determines the active transport of amino acids in the blood of the fetus. The content of amino acids in the blood of the fetus slightly exceeds their concentration in the blood of the mother. This indicates the active role of the placenta in the protein exchange between the organisms of the mother and the fetus. From amino acids, the fruit synthesizes its own proteins other than immunological terms from mothers proteins.

Lipids. Transport of lipids (phospholipids, neutral fats, etc.) to the fetus is carried out after their preliminary enzymatic splitting in the placenta. Lipids penetrate the fetus in the form of triglycerides and fatty acids. Lipids are mainly localized in the cytoplasm of the syncytosis of the chorion vault, thereby ensuring the permeability of the cell membranes of the placenta.

Glucose. It moves through the placenta according to the mechanism of light diffusion, so its concentration in the blood of the fetus may be higher than that of the mother. The fruit also uses glycogen liver glucose to form glucose. Glucose is the main nutrient for the fetus. It also owns a very important role in the processes of anaerobic glycolysis.

Water. Through the placenta to replenish the extracellular space and the volume of spindle water passes a large amount of water. Water accumulates in the uterus, fabrics and organs of the fetus, placenta and amniotic fluid. In physiological pregnancy, the amount of accumulating waters is increased daily by 30-40 ml. Water is necessary for the proper metabolism in the uterus, placenta and in the body of the fetus. Water transport can be carried out against a concentration gradient.

Electrolytes. The exchange of electrolytes occurs transplascentary and through the amniotic fluid (paraploterno). Potassium, sodium, chlorides, bicarbonates freely penetrate the mother to the fetus and in the opposite direction. Calcium, phosphorus, iron and some other trace elements are able to deposit in the placenta.

Vitamins. A very important role of the placenta plays in the exchange of vitamins. She is able to accumulate them and regulate their revenue to the fetus. Vitamin A and carotene deposited in the placenta in significant quantities. In the liver of the fetal, the carotene turns into vitamin A. Vitamins of the group in accumulate in the placenta and then binding to phosphoric acid, go to the fetus. The placenta contains a significant amount of vitamin C. At the fetus, this vitamin in excessive amounts accumulates in the liver and adrenal glands. The content of vitamin D in the placenta and its transport to the fetus depends on the content of vitamin in the blood of the mother. This vitamin regulates the exchange and transportation of calcium in the system of the mother. Vitamin E, as well as vitamin K, does not pass through the placenta. It should be borne in mind that synthetic preparations of vitamins E and K are moving through the placenta and found in the blood of the umbilical cord.

Enzymes. The placenta contains many enzymes involved in metabolism. It found respiratory enzymes (oxidases, catalase, degrogenase, etc.). In the tissues of the placenta, there is a succnatdehydrogenase, which is involved in the process of hydrogen transfer during anaerobic glycolize. The placenta is actively synthesized by a universal source of ATP energy.

From the enzymes that regulate carbohydrate exchange should be specified by amylase, lactase, carboxylase, etc. protein metabolism is adjustable using such enzymes as over- and appidiaphorazes. The placenta specific is the enzyme - thermostable alkaline phosphatase (TSHF). Based on the concentration of this enzyme in the blood of the mother, one can judge the function of the placenta during pregnancy. Another specific placenta is oxytocinase. The placenta contains a number of biologically active substances of the histamine histamine system, acetylcholine-cholinesterase, etc. The placenta is also rich in various coagulation factors and fibrinolysis.

Endocrine function. In the physiological course of pregnancy, there is a close relationship between the hormonal status of the parent organism, the placenta and the fruit. The placenta has the election capacity to endure maternal hormones. Thus, hormones having a complex protein structure (somatotropin, thyrotropic hormone, ACTH, etc.), practically do not pass through the placenta. Penetration of oxytocin through a placental barrier prevents high activity in the placenta of the enzyme oxytocinase. The transition of insulin from the mother's organism to the fetus, apparently, prevents its high molecular weight.

In contrast to this, steroid hormones have the ability to move through the placenta (estrogens, progesterone, androgens, glucocorticoids). Thyroid hormones of the mother also penetrate the placenta, however, the thyroxine transplantary transition is carried out more slowly than triiodothyronine.

Along with the function on the transformation of maternal hormones, the placenta itself turns into a powerful endocrine body, which ensures the presence of optimal hormonal homeostasis both in the mother and the fetus.

One of the most important placental hormones of protein nature is placenta lactogen (Pl). By its structure, the PL is close to the hormone growth of adenogipophysis. The hormone is practically fully entered into maternal blood flow and is actively involved in carbohydrate and lipid metabolism. In the blood of a pregnant woman begins to be found very early - from the 5th week, and its concentration increases progressively, reaching a maximum at the end of the gestation. PL practically does not penetrate the fetus, and in the amniotic fluid contained in low concentrations. This hormone is given an important role in the diagnosis of placental insufficiency.

Another hormone of the placenta of protein origin is chorionic gonadotropin (Xg). In terms of its structure and biological action, the XG is very similar to the luteinizing hormone of adenogipophism. During dissociation, two subunits (α and β) are formed. The most accurate feature of the placenta reflects β-xg. The mother's blood is found in the early stages of pregnancy, the maximum concentrations of this hormone are marked at 8-10 weeks of pregnancy. In the early periods of pregnancy, XG stimulates steroidogenesis in the yellow body of the ovary, in the second half - the synthesis of estrogen in the placenta. To the fetus xg goes into limited quantities. It is believed that the XG participates in the mechanisms of sex differentiation of the fetus. At the definition of the XG in the blood and the urine, hormonal pregnancy tests are based: the immunological reaction, the Ashheima Condeke reaction, the hormonal reaction on the males of frogs, etc.

The placenta along with the pituitary of the mother and the fetus produces prolactin.The physiological role of placental prolactin is similar to such pl.

In addition to protein hormones, the placenta synthesizes the genital steroid hormones (estrogens, progesterone, cortisol).

Estrogen (Estradiol, estrone, estriol) are produced by the placenta in an increasing quantity, while the highest concentrations of these hormones are observed before childbirth. About 90% of estrogen placenta are represented estrin. Its content is reflected not only by the features of the placenta, but also the state of the fetus. The fact is that the estrilla in the placenta is choking from the androgens of the fetal adrenal glands, therefore the concentration of estriol in the blood of the mother reflects the state of both the fetus and the placenta. These features of estriol products have formed the basis of the endocrine theory about the fetoplazentar system.

The progressive increase in concentration during pregnancy is also characterized estradiol. Many authors believe that this is this hormone belongs to be crucial in the preparation of the body of pregnant to childbirth.

An important place in the endocrine function of the placenta belongs to the synthesis progesterone. Products of this hormone begins with early time of pregnancy, however, during the first 3 months, the main role in the synthesis of progesterone belongs to the yellow body and only then this role takes on the placenta. From the placenta progesterone comes mainly in the blood flow of the mother and to a much lesser extent in the blood flow of the fetus.

The placenta produces glucocorticoid steroid cortisol.This hormone is also produced in the adrenal glands, therefore, the concentration of cortisol in the mother's blood reflects the state of both the fetus and the placenta (fetoplacementar system).

Until now, the question of the ACTG and TSH placenta products remain open.

Immune placenta system.

The placenta is a kind of immune barrier, separating two genetically alien organism (mother and fruit), therefore, with a physiologically occurring pregnancy, the immune conflict between the organisms of the mother and the fetus does not arise. The absence of an immunological conflict between the organisms of the mother and the fetus is due to the following mechanisms:

the absence or immaturity of the antigenic properties of the fetus;

the presence of an immune barrier between the mother and the fruit (placenta);

immunological features of the body of the mother during pregnancy.

Barrier feature of the placenta. The concept of "placental barrier" includes the following histological formations: syncytotrophoblast, cytotrofoblast, a layer of mesenchymal cells (strom of vigors) and the endothelium of the fruit capillary. The placental barrier to some extent can be likened by the blood-beer barrier, which regulates the penetration of various substances from the blood into the spinal fluid. However, in contrast to the hematorecephalic barrier, the electoral permeability of which is characterized by the transition of various substances in only one direction (blood  cerebrospinal fluid), the placental barrier regulates the transition of substances and in the opposite direction, i.e. From the fetus to the mother.

The transplacental transition of substances constantly in the blood of the mother and incidentally incurred in it is subject to different laws. The transition from the mother to the fetus of chemical compounds constantly present in the blood of the mother (oxygen, proteins, lipids, carbohydrates, vitamins, trace elements, etc.), is regulated by fairly accurate mechanisms, as a result of which some substances are contained in the blood of the mother in higher concentrations than In the blood of the fetus, and vice versa. In relation to substances, accidentally fell into the maternal organism (chemical production agents, drugs, etc.), the barrier features of the placenta are expressed significantly less.

The permeability of the placenta is inconsistent. In physiological pregnancy, the permeability of the placental barrier increases progressively up to the 32-35th week of pregnancy, and then somewhat decreases. This is due to the characteristics of the placenta structure at various times of pregnancy, as well as the needs of the fetus in certain chemical compounds.

The limited barrier features of the placenta with respect to chemicals, randomly in the mother's body, are manifested in the fact that the toxic products of chemical production are relatively easily moving, most of the drugs, nicotine, alcohol, pesticides, causative agents, etc. This creates a real danger to the adverse effects of these agents on the embryo and the fruit.

Barrier features of the placenta are most fully manifested in physiological conditions, i.e. With the uncomplicated course of pregnancy. Under the influence of pathogenic factors (microorganisms and their toxins, the sensitization of the body of the mother, the effect of alcohol, nicotine, drugs) the barrier function of the placenta is disturbed and it becomes permeable even for such substances that in conventional physiological conditions through it pass in limited quantities.

The content of the article:

Already in the earliest stages of pregnancy in the female organism, the formation of the system is "mother-placenta-fruit". This system is developing and actively operated until the end of the child's hatch period. The placenta, its essential element, is a complex body that plays a vital role in the formation and further development of the embryo. The form of the placenta is a round flat disk from the mother's side, which is connected by the vessels with the uterus wall, and from the fruit side with the fruit in the umbilical cord. During the normal placement of the placenta, it is located on the bottom of the uterus on the front or rear wall. At the same time, its lower edge is located on a distance of 7 cm or higher from the inner sewage.

Placenta functions

The main task of this authority is to maintain the normal course of pregnancy and ensure a full growth of the fetus. It performs several necessary functions, they include:

Protective;

Endocrine;

Respiratory function;

Power function;

Options feature.

The placenta is formed on the basis of decidual tissue, as well as the embryoblast and trophoblast. The main component in its structure is called a naval tree. Its formation of the placenta completes the 16th week of pregnancy.

By means of the placenta, the child is supplied with oxygen and all the necessary nutritional components, but the fruit blood is not mixed with the maternal due to the presence of protection (placental barrier), it has a big role in the formation of a conflict reserves between mother and fruit.

When pregnancy proceeds safely, then the increase in weight and the size of the placenta depends on the growth of the fetus. At first (up to about 4 months), the placenta growth rate is somewhat higher than the rate of embryo. If for some reason the embryo dies, it ceases to develop and the placenta. Instead, dystrophic changes are rapidly growing in it.

When everything is in order, the placenta approaches the maximum maturity at the later period (about 40 weeks or a little earlier), and only then the veins and blood vessels cease to be formed in it.

Mature placenta has a disco-shaped structure. Its thickness ranges from 2.5 to 3.5 cm, the diameter is on average equals approximately 20 cm. Weighs the organ usually not more than 600. The side of the placenta, facing the uterus of a pregnant woman, is called the maternal surface. The other side is directed towards the child, and therefore is called a fruit surface. Both sides differ somewhat in their structure. So, the mother surface is formed on the basis of the basal component of the decidual shell and is rough. The fruit surface is covered with a special layer - amniotic. Under it is well noticeable blood vessels directed from the edge of the placenta to the area where the umbilical cord is attached.

The structure of the fruit side is represented by quotes (vulnery associations). One such structure consists of a stem village that has branching, including the embryo vessels. Conditionally, the quotyon can be represented in the form of a tree. In it, the 2nd level (branches) and the next level (small branches) are departed from the main porce (or trunk), and the final villi can be compared with the leaves. When the placenta becomes mature, it has several dozen such formations in it (usually from 30 to 50). Each of the quotients is separated from those surrounding septa - with special partitions that come from the basal plate.

The chorial plate and the veils attached to it form an intervalic space (from the fruit). At the same time, with the mother's side, it limits the basal plate and the decidual shell from which the septa-partitions depart. Among the Village there are anchor, they are attached to the decidual shell. Thus, the placenta is connected to the wall of the uterus. The rest of the vigors (and much more of them) are freely immersed in intervalic space. There they are washes the blood of the mother.

The uterus of a pregnant woman is powered by ovarian, as well as from the uterine artery. The final branches of these vessels are called "spiral arteries". They are open to intervalic space. Due to this, constant flow of oxygen blood from the mother of the mother is maintained. Pressure in maternal arteries above the pressure of the intervalic space. That is why the blood from the mouths of these vessels goes to Vesinkam and, washing them, heads for the chorial plate. And from there by partitions, blood gets into maternal veins. It is important to note that the bleeding of the fetus and mothers are completely separated. And this means that the baby's blood will not be mixed with the maternal.

During the contact of the mother's blood with blood, various substances are exchanged (nutritional components, gases, metabolic products). Contact with the participation of a placental barrier. This barrier includes the epithelial layer of the villus, its stroma and the wall of the capillary (which is inside each villus). The fruit blood is moving through the capillaries, enriched with oxygen, and then enters large vessels leading to the cord vein. From this vein, it enters the growing fruit, gives him vital components, takes carbon dioxide and other metabolic products. Its outflow from the fetus occurs through the cord arteries. In the placenta, these vessels are separated according to the number of quotients. And in quotes, the vessels are branched on, the blood again enters the capillaries of the Village, where its enrichment of the components that the fetus are needed. That is, the cycle begins again.

So, through the placental barrier to the growing fetus, oxygen and nutrition (protein, fats, carbohydrates, enzymes, and vitamins, minerals) come to the growing fruit. At the same time, its metabolism products are derived from the fetus. Thus, the placenta performs its main tasks (respiration, power, separation function). Another important function of this body is to protect the fetus from the penetration of unwanted substances for it. This feature is implemented using a special natural mechanism - a placental barrier, which is characterized by selective permeability. In a situation where pregnancy develops without pathologies, its permeability continues to grow approximately until the term - 34 weeks of pregnancy. Then she begins to decrease.

But it should be borne in mind that the placental barrier will not be able to ensure complete protection of the fetus. There are substances that easily penetrate through it. First of all, we are talking about nicotine with alcohol. Many medical and chemicals are also dangerous. Even in the body of the fetus through the placenta, some types of pathogenic microorganisms can fall, which threatens the development of infection. The danger is aggravated by the fact that the influence of listed adverse factors reduces the protective ability of the placenta.

In the parent organism, the fruit is surrounded by aquatic shell - Amnion. This thin membrane covers the placenta (its fruit surface) and then goes to the umbilical cord. In the umbilical area, it connects with the skin of the child. Amnion is structurally associated with the placenta, contributes to the exchange of the arrogant fluid, participates in some metabolic processes and, moreover, has a function of protection.

The filler is attached to the placenta by means of a special organ - umbilical bodies. It has the appearance of the cord, and it has blood vessels (vein, two artery). Through a vein, the child is supplied with blood with oxygen. Giving oxygen, blood goes on the arteries in the placenta. All cord vessels are in a special substance having a cuxedentiary consistency. Call her "Study Vartonov". His task is to nourish the walls of the vessels, protect them from adverse effects and support the umbilical cord in an elastic state. Pupovina is attached usually in the central section of the placenta, but sometimes to the shell or side. The length of the organ (when the pregnancy is donoshen) reaches 50 cm.
The combination of fetal shells, placenta and umbilical cords are called "last". He comes out of the uterus after the child was born.

Translated from the Latin of the placenta means "cake" (however, it looks like it). Placenta is a unique organ. It exists only during pregnancy and serves two organisms at once - the parent organism and the body of the child. It is the future baby to know that the placenta is vital.

Placety features:

• supposes the fruit of oxygen (and removes spent carbon dioxide).
• delivers nutrients to the fetus (and removes the products of its livelihoods).
• protects the child from the immune system of the mother, which can take it for an alien object, as well as from adverse environmental factors.
• synthesizes hormones necessary for successful toaling pregnancy.

The placenta is formed by the 12th week of pregnancy, grows and develops with the child. The average dimensions of the placenta by the end of pregnancy - the diameter of about 15-18 centimeters and the weight of about 500-600 grams. But deviations are possible.

Deviations in the development of the placenta:

• - hypoplasia, or very small placenta. Most often, such a placenta is found in genetic pathologies of the fetus.
• - A giant or very large placenta is most likely formed in the presence of diabetes mellitus or infectious diseases in the future mother or rhesv conflict between mom and baby.
• - A very subtle placenta testifies to a chronic inflammatory process in a pregnant woman's uterus.

All significant deviations in the dimensions of the placenta are potentially dangerous, as they can lead to a shortage of nutrients, and, consequently, to the delay in the intrauterine development of the child.

Causes of deviations in developing placenta

Violations of the normal course of pregnancy lead to a slowdown, or, on the contrary, to the too fast ripening and aging of the placenta. The most common causes of deviations in the development of the placenta are in mothers, smoking and, excess or insufficient weight.

Due to the various diseases of the placenta, it can change its location. Ideally, it is attached to the upper uterus departments. However, due to inflammatory diseases in the uterine cavity, benign tumors, the presence in the past, the placenta may attached in the lower section, overlapping the outlet of the uterine cavity, which makes it difficult to make natural genera, and sometimes it makes it impossible (in which case it is applied cesarean section).

Injuries, blows in the abdomen, various chronic diseases of a pregnant woman (kidney disease, lungs or hearts) can lead to a detachment of the placenta, which is also very dangerous.

Any pathology of the placenta arises not from scratch, so every woman, even if she plans a child in a very distant future, it is necessary to relate to their health very carefully and responsibly.

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Placenta (Lat. Placenta, "Leping") - the embryonic organ in all females of placental mammals, allowing to carry out the transfer of material between the circulation systems of the fetus and the mother; The mammalian placenta is formed from the germinal shells of the fetus (naval, chorion, and the blade - allantois (AllanTois)), which are tightly adjacent to the wall of the uterus, form growth (patches), in the mucous membrane, and thus establish a close relationship between The germ and the mother's organism that serves to feed and breathing the embryo. Pupovina binds the embryo with the placenta. The placenta, together with the fetus shells (the so-called submission, the person comes out of the genital tract in 5-30 minutes (depending on the tactics of childbirth) after the child appears.

Placentation

The placenta is formed most often in the mucous membrane of the rear wall of the uterus from the endometrium and cytotrofoblast. Layers of the placenta (from the uterus to the fetus - histologically):

1. Decidua - transformed endometrium (with decidual cells rich glycogen),
2. Fibrinoid (layer of Lanthans),
3. Trophoblast, covering lacquers and inserting in the walls of the spiral arteries, preventing their reduction,
4. Lacuna filled with blood,
5. Syzitotropoblast (Snowy Symplast, Covering Cytotrofoblast),
6. Citotrofoblast (individual cells forming sycteiy and secreting BAV),
7. Strom (connective tissue containing vessels, Cashchenko-Hofbauer cells - macrophages),
8. Amnion (on the placenta more synthesizes the accumulate waters, unshaotable - adsorbates).

Between the fruit and mother part of the placenta - the basal decidual shell - are filled with the mother's blood of deepening. This part of the placenta is divided by decidual sects on 15-20 cups (quotes). Each quotary contains a major branch consisting of a navel blood vessels of the fetus, which is further branched in a plurality of chorion veins that form the surface of the quotylene (in the figure is indicated as Qillus). Thanks to the placental barrier, the blood flow of the mother and the fetus is not communicated to each other. Material exchange occurs with diffusion, osmosis or active transport. From the 4th week of pregnancy, when the heart of the child begins to fight, the fruit is supplied with oxygen and nutrients through the "placenta". Up to 12 weeks of pregnancy, this formation does not have a clear structure, up to 6 weeks. - Located around the whole fetal egg and is called chorion, "placentating" takes place in 10-12 weeks.

Where is and what does the placenta look like?

With a normally flowing pregnancy, the placenta is located in the region of the body of the uterus, developing most often in the mucous membrane of the rear wall. The location of the placenta does not affect the development of the fetus. The structure of the placenta is finally formed by the end of the trimester, but its structure changes as the needs of the growing baby change. From 22 to 36 weeks of pregnancy there is an increase in the mass of the placenta, and by 36 week it reaches full functional maturity. The normal placenta by the end of pregnancy has a diameter of 15-18 cm and a thickness of 2 to 4 cm.

Placenta functions

• Placenta gas exchange function The oxygen from the blood of the mother penetrates the blood of the fetus according to simple diffusion laws, carbon dioxide is transported in the opposite direction.
• Nutrient supplies Through the placenta, the fruit receives nutrients, the exchange products are received back, which is the excretory function of the placenta.
• Hormonal feature of the placenta The placenta plays the role of endocrine gland: chorionic gonadotropin is formed in it, supporting the functional activity of the placenta and stimulating the production of large quantities of progesterone with a yellow body; placental lactogen playing an important role in the maturation and development of the mammary glands during pregnancy and in their preparation for lactation; prolactin responsible for lactation; progesterone, stimulating endometrial growth and preventing new egg generation; Estrogens, which cause endometrial hypertrophy. In addition, the placenta is able to secrete testosterone, serotonin, relaxing and other hormones.
• Protective feature of the placenta The placenta has immunist properties - passes to the fetus of the mother's antibody, thereby providing immunological protection. Part of the antibodies pass through the placenta, providing protection of the fetus. The placenta plays the role of regulation and development of the immune system of the mother and fetus. At the same time, it warns the occurrence of the immune conflict between the organisms of the mother and the child - the immune cells of the mother, recognizing the alien object, could cause the fetus rejection. However, the placenta does not protect the fetus from some narcotic substances, drugs, alcohol, nicotine and viruses.

Placenta man

Human placenta - Placenta Discoidalis, Hemochorial Type Placenta: Maternal Blood Circulates around Thin Villages, containing fruit capillaries. In the domestic industry since the 30s developed by prof. V.P. Filatov and produced preparations of placenta extract and placenta suspension. The placenta preparations are actively used in pharmacology. From cord blood sometimes obtain stem cells stored in hemabanks. Stem cells theoretically may be later used by their owner for the treatment of heavy diseases, such as diabetes, stroke, autism, neurological and hematological diseases. In some countries, the placenta is offered to take home to, for example, make homeopathic medicines or bury it under the tree - this custom is common in various regions of the world. In addition, from the placenta, which is a valuable source of protein, vitamins and minerals, you can make nutritious dishes.

What do you want to know about the placenta doctors?

There are four degrees of placenta maturity. Normally, up to 30 weeks of pregnancy should be determined by the zero degree of maturity of the placenta. The first degree is considered permissible from 27 to 34 weeks. The second - from 34 to 39. Since 37 weeks, the third degree of maturity of the placenta may be determined. At the end of pregnancy, the so-called physiological aging of the placenta occurs, accompanied by a decrease in the area of \u200b\u200bits exchange surface, the appearance of sedimentation areas of salts. Place attachment place. Determined by ultrasound (on the location of the placenta with the uncomplicated course of pregnancy, see above). The thickness of the placenta, as already mentioned, is continuously growing up to 36-37 weeks of pregnancy (it ranges from 20 to 40 mm). It is then terminated, and in the future the thickness of the placenta is either decreased or remains at the same level. Why does the doctors know all these parameters characterizing the location and state of the placenta? The answer is simple: because the deviation from the norm at least one of them may indicate the unfavorable development of the embryo.

Placenta-related issues

Low attachment placenta. Low attachment of the placenta is a fairly common pathology: 15-20%. If the low location of the placenta is determined after 28 weeks of pregnancy, they talk about the prelationship of the placenta, since in this case the placenta is at least partially overlaps the urets. However, fortunately, only 5% is a low placenta location remains up to 32 weeks, and only in a third of these 5% of the placenta remains in this position by 37 week.

Prelation of placenta. If the placenta comes to the inner throat or overlaps it, they say about the preservation of the placenta (that is, the placenta is located ahead of the preserving part of the fetus). The prevention of the placenta is most often found in re-pregnant women, especially after previously transferred abortions and postpartum diseases. In addition, the prelationship of the placenta contributes to the tumor and anomalies of the development of the uterus, low implantation of a fetal egg. Determination on ultrasound placenta pregnancy in early pregnancy may not be confirmed in later. However, such a layout of the placenta can provoke bleeding and even premature labor, and therefore is considered one of the most serious types of obstetric pathology.

Placenta increment. Chorion's navy in the process of formation placenta "are introduced" into the mucous membrane of the uterus (endometrium). This is the most sheath that is rejected during menstrual bleeding - without any damage to the uterus and for the body as a whole. However, there are cases when the Vorsins germinate into the muscular layer, and sometimes in the entire thickness of the wall of the uterus. The increment of the placenta also contributes to its low location, because in the lower segment of the uterus of the chorion vile "deepen" in the muscular layer is much easier than in the upper departments.

Tight attachment of the placenta. In essence, the dense attachment of the placenta differs from the increment of a smaller depth of germination of the chorion vane into the wall of the uterus. Just like the increment of the placenta, the dense attachment often accompanies the prelation or low location of the placenta. Recognize the increment and tight attachment of the placenta (and distinguish them from each other), unfortunately, you can only in childbirth. With a dense attachment and increment of the placenta in the last period of the placenta, it is not separated spontaneously. With a dense attachment of the placenta, bleeding develops (due to the detachment of placenta sections); In case of increment, there is no bleeding bleeding. As a result of the increment or dense attachment of the placenta, it cannot be separated in the third period of birth. In the case of a dense attachment, it is resorted to the manual separation of the last - a doctor receiving childbirth introduces the hand into the uterus cavity and produces a separation of the placenta.

Placenta detachment. As noted above, the placenta detachment may accompany the first period of childbirth with a low placenta location or occur during pregnancy during the presence of the placenta. In addition, there are cases when a premature detachment of a normally located placenta occurs. It is a severe obstetric pathology observed in 1-3 of the thousands of pregnant women. Manifestations of detachment placenta depend on the surface of the detachment, the presence, magnitude and speed of bleeding, the reaction of the body of a woman on blood loss. Small detachants may not show themselves and find out after delivery when examining the last. If the placenta detachment is insignificant of its symptoms expressed weakly, as a whole, the fruit bubble in childbirth is revealed, which slows down or stops the placenta detachment. A pronounced clinical picture and increasing symptoms of internal bleeding - indications for Cesarean section (in rare cases, it is necessary to even resort to the removal of the uterus - if it is impregnated with blood and does not respond to attempts to stimulate its abbreviation). If, when detachanting the placenta, childbirth occur through natural generic paths, then a manual examination of the uterus.

Early ripening placenta. Depending on the pathology of pregnancy, the lack of function of the placenta with it is excessively manifested by a decrease in or an increase in the thickness of the placenta. So the "thin" placenta (less than 20 mm in the third pregnancy trimester) is characteristic of the late toxicosis, the threat of pregnancy interrupt, the hypotrophy of the fetus, while with hemolytic disease and diabetes mellitus on placental insufficiency testifies to the "thick" placenta (50 mm or more) . Thinking or thickening placenta indicates the need for medical measures and requires a re-ultrasound study.

Later maturation of the placenta. It is rarely observed, more often in pregnant women with diabetes, rezes conflict, as well as under congenital fetal developmental defects. The retention of the maturation of the placenta leads to the fact that the placenta, again, inadequately performs its functions. Often, the placenta leads to stillbirths and mental retardation of the fetus. Reducing the dimensions of the placenta. There are two groups of reasons leading to a decrease in the dimensions of the placenta. First, it may be a consequence of genetic disorders, which is often combined with the defects of the development of the fetus (for example, with Down syndrome). Secondly, the placenta can "not reach" in size due to the impact of various adverse factors (severe gestosis of the second half of pregnancy, arterial hypertension, atherosclerosis), resulting in a decrease in blood flow in placenta vessels and its premature ripening and aging. And in that and in another case, the "small" placenta does not cope with the duties of the supply of kid with oxygen and nutrients and delivering it from the exchange products.

Increase the size of the placenta. The placenta hyperplasia occurs when anemia conflict, a serious flow of anemia in pregnant, diabetes mellitus in pregnant, syphilis and other infectious lesions of the placenta during pregnancy (for example, with toxoplasmosis), etc. There is no particular sense to list all the reasons for increasing the size of the placenta, however it is necessary to keep in mind that when this state is detected, it is very important to establish the cause, since it determines the treatment. Therefore, it is not necessary to neglect the appointed physician studies - after all, the consequence of the hyperplasia of the placenta is the same placental insufficiency leading to the delay in the intrauterine development of the fetus.

What doctors to seek to examine the placenta:

What diseases are related to the placenta:

What tests and diagnostics need to be held for the placenta:

Echographic fetometry

Plocentography

Doppler Photo MPK and FPK

Cardiotokography

Cardiointervalography

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(+38 044) 206-20-00

If you have previously been performed any research, be sure to take their results for a consultation to the doctor. If the studies have not been fulfilled, we will do everything you need in our clinic or our colleagues in other clinics.

It is necessary to carefully approach your health as a whole. There are many diseases that at the beginning do not show themselves in our body, but in the end it turns out that, unfortunately, they are already treated too late. For this you just need several times a year take a survey from a doctorSo as not only to prevent terrible disease, but also maintain a healthy mind in the body and the body as a whole.

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Other anatomical terms per letter "P":

Esophagus

The chin

Spine

PUP (navel)

Penis

Prostate

Crotch

Liver

Parashydovoid glands

Pancreas

Bud

Medulla

Pleura

Peripheral nerves

Meat Labyrinth

Podolmal cavity

Oral cavity

Rectum

Plasma

Vertebrae

Lumbar vertebrae

Shoulder joint

Groin area

Shoulder

Brachial bone

Forearm

Finger

Peripheral nervous system

Parasympathetic nervous system

Sweat glage

Sex glands

Prostate

Ovarian appendage and near

Paraganglia

Right ventricle