PLACENTA

From Big Medical Encyclopedia

PLACENTA (Latin. placenta, from grech, plakus flat cake; synonym afterbirth) — the provisional body which is formed during pregnancy and providing communication of a fruit with an organism of mother.

The comparative anatomy

At various mammal P. differs in a form and an arrangement, and also the relation vorsin chorion to a mucous membrane of a uterus. According to Grosser's classification distinguish four types P.: epitheliochorial, connective tissue and fleecy, 'endoteliokhorpal-ny, haemo chorial.

Epiteliokhornalny (diffusion) P., napr, at a horse, has the simplest structure — chorion only adjoins to an epithelium of a mucous membrane of a uterus, without destroying it, the decidua is not formed, vorsina of chorion are located in crypts of a mucous membrane of a uterus. The power supply of a fruit in this case is embriotrof — the secret allocated by glands of a uterus.

The connective tissue and fleecy P. characteristic of ruminants consists of separate segments (kotiledon); vorsina of chorion are implemented into a stroma of a mucous membrane of a uterus (sindesmokhorl-and flax I am P.), destroying its cover epithelium.

Endoteliochorial P. meets at carnivorous, it has the form of the coupling or a belt (zone P.). Vorsina of chorion P. of this type destroy an epithelium of a mucous membrane of a uterus, its stroma and walls of vessels (except for an endothelium of the last).

Haemo chorial (diskoidalny) P. is the most perfect type P., at Krom chorion destroys all elements of a mucous membrane. As a result of destruction of vessels, including and their endothelium, a vorsina of chorion are shipped in blood of mother. Increase in a contact surface of a trophoblast with blood is reached by development of a labyrinth of channels (labyrinth haemo chorial P. of rodents) or the educations which are difficult branching vorsin chorion, floating in maternal blood (vorsinkovy haemo chorial P. of monkeys and the person).

Development of a placenta

Fig. 21. Microdrug of a mucous membrane of a uterus with the implanted oospore: 1 — an oospore, 2 — the mucous membrane of a uterus surrounding it with growths of a trophoblast; coloring hematoxylin-eosine; X 200. Fig. 22. Microdrug vorsin chorion on the 10th week of pregnancy: vorsina of chorion are covered outside with a sincytium, from within — cytotrophoblastomas; coloring hematoxylin-eosine; X200. Fig. 23. Microdrug of a placenta with compensatory and adaptive changes: trailer vorsina of chorion with numerous syncytial small knots (are specified by shooters): coloring by acridic orange; X200.

Implantation of a blastocyste is done in an endometria preferential on the centerline of a back wall of a uterus on 6 — the 7th day after fertilization of an ovum. In the first 2 weeks after implantation trophoblast (see) expands and destroys a mucous membrane of a uterus (tsvetn. fig. 21). Due to enzymatic activity of a trophoblast there is a dissolution of surrounding maternal fabric. The expanding symplast of a trophoblast forms primary vorsina. By the end of the 2nd week the trophoblast creates a chorial epithelium which with the extraembryonic mesenchyma spreading it forms chorion.

Primary vorsina are turned into cavities — the lacunas formed on site disintegration of vessels and connecting tissue of a mucous membrane of a uterus. Set of these lacunas forms intervillous space, a cut is filled with blood of mother from vessels of a decidua. Fibrillation at the same time does not happen since it is interfered by a sincytium vorsin (see. Germ ).

Along with primary vorsina on the surface of chorion turned to a muscular coat of a uterus, there are larger and branched secondary vorsina in which structure the chorial epithelium and a mesenchyma take part. Development secondary vorsin goes in parallel with development of an allantois and vessels. Final branchings of the last are presented by the capillary network which is the mezenkhimny cornerstone vorsinony Vascularization vorsin begins with the 3rd week and comes to an end by IV—V month of pregnancy. Primary vorsina disappear, secondary strenuously develop, and to 9 — two parts of chorion — form 12th week of pregnancy fleecy, or branchy (cliorion frondosum), and smooth (chorion laeve) chorion. Fleecy chorion with the site of amnion covering it makes germinal or fetal part P. Fleecy chorion establishes close connection with a deep part of a spongy layer of a mucous membrane of a uterus (a basal deciduous cover) which makes maternal, or uterine, part P. (pars uterina).

By 2,5 — 3 months of pregnancy of P. takes the typical diskoidalny form.

The fleecy chorion forming the main part P. is presented by a thick soyedinntelnotkanny plate (a chorial plate) and fibers departing from it. In chorion branches of vessels on which the blood of a fruit which is carrying out placental blood circulation circulates are concluded. It is treelike the branching vorsina of chorion are shipped in the lacunas filled with the maternal blood arriving from spiral gyrose arteries of maternal part P. Outflow of blood happens through the veins which are randomly located between arteries. Thus, the big circle of blood circulation of the pregnant woman joins uteroplacental blood circulation.

Fig. 1. Microdrug of a placenta on early phases of formation (9 — the 12th weeks of pregnancy): 1 — anchor vorsina, 2 — tyazh of cytotrophoblasts, 3 — a decidua; coloring hematoxylin-eosine; X 120.

Vorsina of chorion have complex structure, a cut changes with increase in duration of gestation. The surface layer vorsin is formed by a chorial (trophoblastic) epithelium, a stroma — friable fibrous not properly executed connecting fabric which in the basis vorsin proceeds in connecting fabric of a chorial plate. At early stages of development the chorial epithelium is presented by a deep cellular layer — a tsitotrofo-blast (Langkhans's layer) and superficial — a syntrophoblast (tsvetn. fig. 22). Cells of a tsitotrofo-blast (trophoblastocytes) have the cubic or polygonal form, in them pictures of a karyokinesis or amitotic division are often noted. The syntrophoblast is formed by cell fusion of a tsitotrofo-blast in multinuclear structures. Earlier considered that by V—VI month of pregnancy the cover vorsin consists only of a syntrophoblast (fig. 1). On modern representations by places of a cell of a tsitotro-foblast remain, being a reserve for completion of a syntrophoblast. At the same time sites of the last can disappear and be replaced with the canalized fibrin, or fibrinoid.

Vorsina of chorion, growing into a decidua, are called anchor, fixing. Distal departments of these vorsin consist from tyazhy a tsitotrofo-blast (fig. 1). P.'s growth results from intensive branching vorsin chorion between its plates. From the fruit surface covered with amnion, P. is limited to a chorial plate with the kotiledona departing from it, and with maternal — a basal plate and placental partitions (septa). In a soyedinrkhtel-notkanny basis of a chorial plate funic vessels are distributed (arteries and veins). The compact layer of decidua basalis together with tyazha of a cytotrophoblast forms a basal plate. In the intervillous space located between these plates blood of mother circulates.

On modern representations everyone kotiledon (has the form of a drum with it is central the located cavity) is connected to a chorial plate by means of a trunk vorsin, to Krom there go the artery and a vein. Sharing dichotomizing, it forms branches vorsin and the vessels passing in them. The last give rise to branches vorsin and to vessels of the III order, to-rye and attach kotiledon to septa of a basal plate. In the second trimester of pregnancy in kotiledona growth vorsin continues, the quantity trailer rezorbtsionny vorsinony Idea of the kotiledena especially increases as to the main structurally functional unit of P. it is supplemented with a concept about the so-called pla-tsentena — the functional link of P. deprived of exact anatomic borders.

Anatomy and histology

Fig. 2. Diffraction pattern of a sintsitpotrofoblast of a trailer vorsina of a placenta: 1 — microvillis on a surface of a sincytium of a trailer vorsina, 2 — intervillous space, 3 — vacuoles, 4 — mitochondrions; X 32240.

Mature P. has an appearance of a disk (see fig. to St. Afterbirth period ) with a diameter from 17 to 20 cm, 2 — 4 cm thick it is also powerful (weighing) 500 — 600 g. The relation of weight of P. to the weight of a fruit (placental and fruit coefficient — PPK) normal makes 1/5 — 1/7. To a fruit (fetal) surface of P. it is attached umbilical cord (see) with the vessels dispersing from it. The wall of arteries of a chorial plate and trunk vorsin consists of a hypertrophied circular muscular layer. Vienna differs only in the smaller thickness of a muscular layer. In the trunk vorsena there are 2 — 4 blood vessels sometimes sclerosed or completely obliterated. Trailer vorsina (diameter them fluctuates from 40 to 120 microns) contain only a capillary network. The syntrophoblast covering vorsina in places forms the reniform outgrowths rich with kernels (syncytial shoots, syncytial small knots). It has a brush border which is constructed of microvillis (fig. 2), contains lipids, RNA and is characterized by high activity of enzymes. The cytotrophoblast located out of vorsin is called a peripheral trophoblast. At early stages of pregnancy a stroma trailer vorsin friable, contains the main substance, argyrophil fibers, capillaries and fibroblasts among which find cells of Kashchenko — of Hofbauer — a large cell of preferential rounded shape with foamy cytoplasm. Consider that Kashchenko's cells — Hofbauera transfer the substances participating in exchange processes; they have communication with an extravascular hemogenesis in a mesenchyma of chorion. It is not excluded, however, that these cells are macrophages (see). From IV month of pregnancy number of cells of Kashchenko — Hofbauera decreases.

In P. unstructured homogeneous substance — fibrinoid always meets. Fibrinoid (Nitabukh's layer) appears on border of maternal fabric and a cytotrophoblast. For the III—IV month of pregnancy fibrinoid is laid for surfaces of a trophoblast of the basal plate turned into intervillous space (Rohrs's layer). In the second half of pregnancy fibrinoid is laid for surfaces of the trophoblast located under a chorial plate (a fibrinoid layer of Langkhans).

Fig. 3. Diffraction pattern of a sintsitiokapillyarny membrane of a placenta: 1, 5 — vacuoles, 2 — a basal membrane of a trophoblast, 3 — the main substance of connecting fabric, 4 — an endothelial cell, 6 — mitochondrions, 7 — a gleam of a capillary; X37400.

By electronic microscopic examinations it is established that the maternal blood stream is separated from plodovo go by a sintsitiokapnllyarny membrane (fig. 3). According to most of researchers, the main outflow of maternal blood comes from P. through a regional sine. Blood supply of fruit part P. is carried out at the expense of two funic arteries and one funic vein. In a placenta intra-fleecy and paravascular capillary networks are described. The intra fleecy capillary network in P.'s kotiledona comes into close contact with a sincytium (a sintsitiokapillyarny membrane). The paravascular capillary network in the basis of segments connects arterioles and venules and forms network of the small arteriolovenulyarny anastomosis in turn connected with an intra fleecy capillary network.

The physiology

P. carries out a metabolism between mother and a fruit, performing functions of gas exchange, trophic, endocrine, secretory and protective, has antigenic and immunogene properties. The item not only combines, but also divides genetically heterogeneous organisms of mother and a fruit, preventing emergence immunol, the conflict.

Gas exchange between blood of mother and a fruit happens by diffusion through an endothelium of capillaries, a layer of cells of Langkhans and the syntrophoblast vorsinony It is made on all surface vorsin which area, according to various data, makes from 6,5 to 14,9 sq.m. Thus, the area of a boundary surface vorsin P. defining conditions of gas exchange of a fruit on 1 kg of its weight, more than in 3V2 of time surpasses the surface area of air cells falling on 1 kg of weight of the adult. Besides, perhaps compensatory increase in a respiratory surface of P. at some diseases of mother, napr, heart diseases, a hypertension, etc. In the course of gas exchange, oxygen passes to a fruit since its content in blood of a fruit is lower, than in blood of mother. According to it there is a transition of carbon dioxide gas from an organism of a fruit in blood of mother. The item has ability to regulate process of transition of oxygen (and other gases) in blood of a fruit at high content it in blood of mother. At substantial increase of the oxygen content in blood of mother, napr, at an inhalation anesthesia (nitrous oxide in mix with oxygen), concentration of oxygen, as well as nitrous oxide in blood of a fruit increases in much smaller degree that is explained by features of the placental byaryer promoting preservation of a homeostasis of internal environment of a fruit.

Trophic function. Transport of proteins, carbohydrates, fats from blood of mother in blood of a fruit is carried out as a result of complex processes of zymolysis and synthesis of nutrients according to requirements of the developing fruit. The item contains the enzymes (proteases, a deaminase, an arginase, mono - and a diaminok-sidaza, an alkaline phosphatase, etc.) splitting and synthesizing proteins. In it the specific thermostable isoenzyme of an alkaline phosphatase which content in blood of the pregnant woman characterizes degree of functional activity of P. Sintsitiotrofoblast and a cytotrophoblast is formed contain a large amount of RNA that indicates activity in P. of process of protein synthesis. In P. glutamatde-hydrogenase, a glutamine-ketoksilovaya the transaminase and other enzymes necessary for preservation of constant set of amino acids of a fruit are found (see. Nitrogen metabolism ).

In P. processes of carbohydrate metabolism what existence in it of a significant amount of enzymes (a diastase, invertases, esterases, lactases, carboxymanholes, glyukozo-6-fosfatdegidrogenazy, etc.), and also the steroid hormones influencing carbohydrate metabolism testifies to intensively proceed, in particular. The glycogen is located in decidual cells, Langkhans's cells, in a stroma vorsin and walls of blood vessels. From IV month of pregnancy the maintenance of a glycogen in P. gradually decreases since by this moment in carbohydrate metabolism the liver of a fruit begins to play an important role.

In cytoplasm of cells of a syntrophoblast lipids, fiziol which role is estimated ambiguously are found. Believe that lipids take part in the synthesis of hormones which is made in a syntrophoblast. However their high content in P. and availability of lipolytic enzymes is pointed to an active metabolism of lipids and neutral fats in the Item. The lipids which are formed owing to splitting of the phospholipids (arriving from blood of mother) get through P. the same as products of zymolysis of neutral fats.

Activity of oxidation-reduction enzymes P. is especially high in the first trimester of pregnancy. The epithelium vorsin chorion contains a large number OVER - and NADF-diaphorases, glyukozo-6-fos-fatdegidrogenazy, succinatedehydrogenases, malate dehydrogenases, cytochrome oxydases, etc.

P. contain calcium, iron, phosphorus, also copper, zinc, manganese, cobalt and other microelements are found. These substances arrive from blood of mother, are deposited with P. and used according to requirements of the growing fruit. Contents phosphorus increases in P. in process of fetation. Believe that microelements are used not only on direct requirements of a fruit, but also participate in implementation of hormonal function

of P. P. contains a significant amount of vitamins (And, B1, B2, B6, C, D, E). Vitamins come from blood of mother to P., are deposited in it and then come to an organism of a fruit. It is established that P. is capable not only to deposit vitamins, but also to regulate process transition& them in an organism of a fruit. Process of accumulation of polyneuramins P. is influenced by food of mother and degree of a saturation vitamins of its blood.

In P. blood-coagulation factors and a fibrinolysis, but biol are found, the role them is found insufficiently out. P. contains thromboplastin which amount is especially considerable in early durations of gestation and decreases in process of its development. The item contains also fibrino-and fib-rinogenolitichesky enzymes, to-rye in interaction with other factors interfere with a blood coagulation, circulating in intervillous space of the Item. Blood-coagulation factors promote the termination of bleeding from vessels placental platform (see) later births of a fruit and afterbirth (see).

Endocrine function. The placenta is a hemaden in which processes of synthesis, secretion and transformation of hormones are carried out. The hormones produced in P. cause development of the adaptive changes in an organism of the pregnant woman necessary for growth and fetation, preparation of function of a lactation, implementation of the act of childbirth. The item produces a chorionic gonadotrophin and chorionic somatomam-motropina, progesterone and estrogen. There are data on allocation from a placenta of AKTG, thyritropic hormone, oxytocin, vasopressin, cortisol and other hormones, however their synthesis in P. is not proved. In a placenta also significant amount of a histamine and acetylcholine is revealed.

Hormones P. are synthesized in an epithelium vorsin — a syntrophoblast and a cytotrophoblast. There are data indicating that the syntrophoblast synthesizes and emits steroid hormones (estrogen and progesterone), and in a cytotrophoblast the chorionic gonadotrophin is formed. Excretion chorionic gonadotrophin (see) begins with the first weeks of pregnancy and reaches the most high level in 10 — 12 weeks. In the subsequent there is a gradual decrease in maintenance of a chorionic gonadotrophin (to its small rise on 230 — the 240th days of pregnancy). Thus, the maximum level of excretion of a chorionic gonadotrophin corresponds to a phase of functional activity of a yellow body of pregnancy (see. Yellow body ) and to process of formation of the Item. Decrease in synthesis and allocation of a chorionic gonadotrophin connect with action of an anti-gonadotropic factor. The chorionic gonadotrophin disappears from blood by the end of the first week of a puerperal period.

Chorionic lactosomatotropic hormone (see) it is synthesized in P.'s syntrophoblast and has lactogenic, luteotropic and somatotropic activity. Connect with effect of chorionic lactosomatotropic hormone fiziol, changes in carbohydrate, proteinaceous and a lipometabolism, the pregnancies happening in the second half; believe that it regulates adaptation changes of exchange processes in an organism of mother and a fruit.

With development of pregnancy synthesis increases in P. progesterone (see) and according to it its content in blood of mother increases. Progesterone influences development fiziol. the processes promoting the favorable course of pregnancy. Under the influence of this hormone there is a secretory transformation of an endometria (see. Menstrual cycle ); it interferes with rejection of a decidua, stimulates proliferative processes in mammary glands, slows down sokratitelny activity of the pregnant woman uterus (see).

In early durations of gestation is oestrogenic (see) are formed in ovaries, is later the main source of their education the Item is. The fermental systems providing synthesis and metabolism of estrogen are distributed between P. and a fruit that formed the basis for emergence of the concept about fetoplacental system. In P. are formed of the cholesterol which is contained in blood of mother pregnenolon and progesterone, to-rye come to blood of mother and a fruit. In a liver of mother there is a metabolism of progesterone, and apprx. 20% it is allocated with urine as pregnandiol. In adrenal glands and a liver of a fruit progesterone turns into neutral steroids (hl. obr. in degidroepiandrosteron), to-rye come with blood of a fruit to P. and are transformed through androstendion and testosterone to estrone and oestradiol. A considerable part of a degidroepiandrosteron is exposed in P. to a hydroxylation and is a source of formation of estriol.

In process of development of pregnancy, especially in its second half, synthesis of estrogen increases in P. According to it the content of estrogen in blood and their excretion with urine increases. At the end of pregnancy the content of estrone and oestradiol in urine increases in 100, estriol and — by 1000 times (in comparison with excretion up to pregnancy). Estrogen has significant effect on processes of growth, defines a current important biochemical, the processes proceeding in myometriums and an endometria of a pregnant uterus and other metabolic processes in an organism. There are data on a role of estrogen in approach of childbirth and regulation of patrimonial activity.

Antigenic and immunogene properties of a placenta. All cellular and fabric elements which are P.'s part, having a germinal and maternal origin (a trophoblast, decidual cells, erythrocytes, leukocytes, hormones) are potential antigens. In P. define species-specific, group, fabric and organ, hundred-diospetsifichesky antigens and histocompatibility antigens (reaction of transplant immunity, responsible for induction). Fabric P. and fetal membranes have differentiated group (on AVO-system) antigenic specificity: in a decidua contain And - and B-factors of blood of mother, in amnion — group antibodies of blood of a fruit, and fabric of chorion does not contain the antigenic substances defined in amnion and in blood of the child. The fact that fabrics of amnion and chorion, despite uniform — germinal — an origin, are qualitatively various in the antigenic relation has no explanation so far, however in this distinction the sense is put obvious biol; immunol, «inertness» of fruit (fetalis) part P. concerning a maternal organism is the important factor of mutual defense of mother and a fruit protecting them from development of immunoconflict reactions (see. Immunology of an embryogenesis , Incompatibility immunological ).

A placental barrier — set morfol, and the functional features defining P.'s ability to regulate process of penetration of various substances of blood of mother to a fruit and in the opposite direction. Morfol, substrate of a placental barrier are an epithelial cover vorsin and an endothelium of the capillaries which are located in vorsina. The syntrophoblast and a cytotrophoblast have high activity concerning a resorption, zymolysis and synthesis of many connections. High biol, activity of the specified P.'s layers considerably defines also property of permeability. The factors causing P.'s permeability are the state and functional activity of membranes of a syntrophoblast and cellular components (a cytotrophoblast, an endothelium of capillaries). An essential role is played by activity of kernels, mitochondrions, lysosomes, a cytoplasmic reticulum and other ultrastructures of cells of the Item.

The processes which are made in P. define transition to a fruit from mother of all substances necessary for its development, and removal from its organism of products of metabolism. The item brakes or transition of a number of substances from mother to a fruit, and also from a fruit in blood of the pregnant woman detains. On the basis of these data the concept about the barrier function P. promoting protection of a fruit against penetration of unnecessary or harmful substances is put forward (see. Barrier functions ). According to L. S. Stern, the placental barrier in the functional relation is similar with blood-brain barrier (see). However selectivity of a blood-brain barrier is carried out in the direction blood — cerebrospinal liquid, and the placental barrier regulates transition of substances from blood of mother to a fruit and in the opposite direction. The placental barrier significantly differs from hematoencephalic in what participates in a metabolism of two organisms having considerable independence.

Protective function P. is limited to certain limits. So, transition from mother to a fruit of the proteins, fats, carbohydrates, vitamins, electrolytes, oxygen and other substances which are constantly contained in blood of mother is regulated by the mechanisms which arose in P. in process filo-and ontogenesis. In relation to the substances entered from the outside or which are accidentally getting to blood of mother (the toxicants which are formed at some diseases, medicines, alcohol, nicotine various chemical agents, etc.), barrier functions P. are expressed to a lesser extent or are absent. It is established that through P. drugs, alcohol, nicotine, mercury, arsenic, potassium cyanide, hemolitic poisons and many other toxicants get. The item limits, but does not interfere with penetration to a fruit practically of all pharmaceuticals — antibiotics, streptocides, barbiturates, salicylates, analgetics, glucosides, hormones, etc. Transition to a fruit of viruses and microbes — activators inf is proved. diseases.

P.'s permeability changes during pregnancy according to the increasing requirements of the developing fruit. There are P. given about increase in permeability by the end of pregnancy. It is connected with changes in structure of boundary membranes, including with disappearance of a cytotrophoblast and gradual thinning of a syntrophoblast vorsin the Item. Changes of permeability are connected also with features fiziol, the processes inherent in the different periods of development of P. and a fruit. P.'s permeability in the second half of pregnancy increases not to all substances entered into an organism of mother. E.g., permeability of sodium bromide, calcium, sodium, thyroxine, Oxacillinum and some other substances is higher not at the end, and at the beginning of pregnancy. Apparently, the increased or limited receipt to a fruit of a number of chemical elements depends not only on permeability of a placental barrier, but also on extent of development of the major systems of a fruit regulating his requirements and processes of a homeostasis. Originally believed that penetration of various substances from mother to a fruit and in the opposite direction happens at the expense of physical. - chemical processes of osmosis and diffusion. However such mechanism is proved only for a small amount of substances (oxygen, carbonic acid, narcotic gaseous connections, etc.). As for the majority of other organic and inorganic matters, their transplacental transition is regulated, apparently, by more difficult mechanisms. Permeability of a placental barrier was also connected about a pier. weight of substances. So, substances about a pier. weighing up to 600 rather easily get through P.; for the substances having a pier. weight higher than 1000, P. is almost impenetrable. However nek-ry substances with high a pier. the weight (thyroxine, vasopressin) rather quickly get through a placental barrier.

Transition of chemical connections through P. depends also on extent of ionization of their molecules; not dissociated and not ionized substances pass through P. quickly, and ionized — hardly. Transplacental transition of chemical substances is provided thanks to their solubility in lipids. It is explained with affinity of chemical connections with high lipidic solubility and the cellular membranes consisting generally of lipoproteids.

At action patol, the factors causing changes in P., barrier function P. is broken. Disturbances of barrier function P. arise at dystrophic processes, inflammatory reaction and other changes in P. Otmecheno disturbance of permeability of II. at effect of toxicants, alcohol, ionizing radiation, at a hyperthermia, a hypoxia, etc. Dysfunction of a placental barrier at diseases of pregnant women is possible, to-rye cause disorders of placental blood circulation, a hypoxia, intoxication and others patol, processes. At the same time possibility of compensatory changes is established (a hyperplasia of capillaries and increase in quantity vorsin, etc.).

Artificial placenta — various type the devices replacing gas exchange function of natural P. capable to support life activity of the fruit isolated from a maternal organism. Artificial P. is applied in an experiment for the purpose of studying of metabolism of a fruit without those changes, to-rye are connected with transplacental transfer of substances, their placental synthesis and utilization. It can be used for maintenance of life activity of the mature or unripe newborn at heavy asphyxia or insolvency of pulmonary function before recovery at it of ability to independent pulmonary exchange. Now the first test pieces of artificial P. are developed for experiments.

Methods of a research

In obstetric practice are applied the methods of a research promoting recognition of the place of an attachment and features of development of P., and also some of its functions. These methods are applied only in the presence of the corresponding indications, taking into account safety to mother and a fruit. So, the ultrasonic platsentografiya allows to study process of formation of P., to establish its localization, the sizes (see. Ultrasonic diagnosis ). The radio isotope platsentografiya is applied in need of specification of the place of an attachment of P. before carrying out diagnostic amniocentesis (see). Small (indicator) doses of radioactive drugs are for this purpose used, to-rye do not get (or almost do not get) through P. to a fruit, have short half-life and are quickly brought out of an organism (see. Platsentografiya ).

Methods of a research of the hormones produced by P. apply to recognition it funkts, activities.

In early durations of gestation diagnostic value has determination of level of excretion of a chorionic gonadotrophin (the menacing abortion, not developing pregnancy, an extrauterine pregnancy), and also the level of progesterone in blood and pregnandiol in urine. Detection of the contents of these hormones (especially progesterone) does not lose diagnostic value and in late durations of gestation, napr, at pe renashivaniya of pregnancy. In obstetric practice methods of determination of content of estrogen in blood and their excretion with urine are widely used. Especially the size of excretion of estriol characterizing functional activity of P. and a condition of a fruit is important. Considerable decrease in excretion of estriol (9 — 10 mg a day are lower) indicates an aggravation of symptoms of a fruit and functional insufficiency of the Item. Results of a research of estriol on - help the choice of an optimum method of delivery. About change of endocrine function P. judge by extent of decrease in excretion (or contents in blood) the hormones synthesized in the Item. For examination funkts, P.'s activities resort to definition of activity of a thermostable alkaline phosphatase which is synthesized in the Item.

Are applied to studying of structure and functions P., and also the changes arising under the influence of various pathogenic factors, as a rule in an experiment, macroscopic, microscopic (light and a submicroscopy), histochemical, tsitol., immunol., biochemical, and rentgenol, methods of a research, methods of perfusion, an angiography and reconstruction are used, artificial P. Primenyayutsya's models are created pilot studies of P. of the animals having haemo chorial type P.

Pathological anatomy

Changes of proteinaceous, lipidic, carbohydrate and mineral exchanges in P. mostly are not dystrophic, but gistofiziolo-gichesky, i.e. with allocation in intervillous space of some products of exchange of a fruit, endocrine function P.

Gidropicheskaya P.'s dystrophy is shown by the fabrics P. connected with a producing and removal of amniotic waters, transport and transfer of nutrients from mother to a fruit in the form of hypostasis of fabric. At antenatal death of a fruit owing to a perenashpvaniye of pregnancy, a diabetes mellitus, an infection, an inflammation, late toxicoses of pregnant women, etc. in a stroma vorsin the plentiful adjournment of acid glikozaminoglikan leading to decrease in permeability of the Item is found.

Horn dystrophy (see. Proteinaceous dystrophy ) it is observed in any department of a fruit part of amnion, but most often near the place of an attachment of an umbilical cord. It is preceded by a metaplasia of a single-row cubic and cylindrical epithelium of amnion in multilayer flat. Small sites of a metaplasia of an epithelium with horn dystrophy have an appearance of plaques of white or gray color with a diameter from 1 to 2 mm, call them an amniotic fleshy outgrowth.

Very seldom, in the absence of amniotic waters, knotty amnion (amnion nodosum) — grayish-yellow color small knots on the surfaces of amnion with a diameter up to 1 — 2 mm consisting of horn scales and amorphous acidophilic masses meets. Emergence of knotty amnion is usually combined with malformations of urinogenital bodies of a fruit.

Hyalinosis (see) stromas vorsin a chorial plate arises in connection with plasmatic treatment, emergence of fibrinoid with the subsequent necrotic changes and inflammatory leukocytic, infiltration (a fibrinoid necrosis), formation of acidophilic proteinaceous masses — a hyalin. The hyalinosis of cytoplasm of a sincytium with pycnosis of kernels most often is found at late toxicoses of pregnant women, especially at an eclampsia.

P.'s ischemia can be diffusion and focal. Diffusion ischemia of P. is characterized by all P.'s blanching and is an indicator of the general anemization of a fruit. Focal ischemia does not extend to a chorial plate. Microscopically ischemia is expressed by fall of capillaries, preferential trailer vorsinony

Fig. 4. Macrodrug of a placenta (cross section): the arrow specified a white heart attack; coloring hematoxylin-eosine; x 16.

P.'s heart attacks — focal necrotic changes vorsin — most often arise owing to disturbances in system of maternal blood circulation of P. Razlichayut red and white heart attacks of the Item. The red heart attack has dark red color, vague borders, its basis borders on maternal part P. Microscopically sharply expressed expansion and a krovenapolneniye of capillaries vorsin, hemorrhage in intervillous spaces, initial signs of necrotic changes of a syntrophoblast are found. The red heart attack needs microscopically to be differentiated with an intraplatsentarny hematoma and a focal hyperemia vorsinony the White heart attack, according to most of researchers. develops on site a red heart attack. This roundish or irregular shape dense formation of white or whitish-yellow color to dia. 1 — 3 cm, accurately delimited from surrounding fabric P. (fig. 4). The central area of a white heart attack is presented by nekrotizirovanny vorsina of chorion, to-rye are surrounded with the blood which turned in intervillous space. Its peripheral zone consists from avascular sclerosed vorsin, immured in fibrinoid. In a circle of a white heart attack on a surface vorsin syncytial small knots are found.

The centers of calcification meet in maternal part P., in a syntrophoblast, a stroma vorsin often at the normal full-term pregnancy; at premature pregnancy they are observed less often, at postmature — is more often. Occasionally calcification extends to all segment of P., to all its maternal part. Adjournment of salts of calcium in P. can be promoted by late toxicoses of pregnancy, fibrinferments of intervillous space and heart attacks of the Item. The centers of a necrosis with the subsequent adjournment of salts of calcium in them arise at normally current pregnancy in P. and fetal membranes, striking preferential a decidua, and also at syphilis, tuberculosis, listeriosis, toxoplasmosis, a brucellosis, a cytomegaly, chicken pox, at local circulatory disturbances.

Compensatory and adaptive processes are shown in a compensatory hyperplasia of capillaries (a compensatory angiomatosis, hyper vascularization vorsin), compensatory increase in quantity vorsin, education of young people (young) vorsin, the early durations of gestation reminding vorsina, increase in quantity of syncytial small knots with signs of proliferative activity (tsvetn. fig. 23).

Postmortem changes arise in P. owing to the termination of fruit blood circulation. In cases of stay of the dead of a fruit in a uterus during weeks and more P. becomes thin, on its maternal surface adjournment of fibrin is visible. Due to the termination of fruit blood circulation fall of capillaries in trailer vorsina, death of their endothelium is observed. Sometimes proliferation of an endothelium and an obliteration of large vessels is found. However nek-ry researchers consider an obliteration of large vessels of P. as the reason of antenatal death of a fruit. In the first days after death of a fruit of a stromal cell vorsin and a sincytium do not change. In differential diagnosis of an inflammation and postmortem changes consider existence of leukocytic infiltration in a chorial plate and a fibrinoid layer of Langkhans where leukocytes after death of a fruit get from intervillous space.

Pathology

Distinguish anomalies of an arrangement of P. (see. Placental presentation ) and its attachments (see. Increment of a placenta ). A heavy complication for mother and a fruit is premature amotio of normally located P. (see. Premature placental detachment ).

Malformations — changes of size, a form, localization and an attachment of the Item. They can arise at implantation of a blastocyste in cases of underdevelopment of an endometria, generally at its defective blood supply or in an infantile uterus. P.'s hypoplasia (the weight less than 400 g, diameter less than 16 cm and PPK lower than 0,13) can be combined with a hypoplasia of a fruit. Sometimes P.'s hypoplasia, apparently, promotes a heavy pre-natal hypoxia of a fruit or secondary asphyxia of the newborn (see. Asphyxia of a fruit and newborn ). Often P.'s hypoplasia is combined with malformations of a fruit (see. Malformations ) or umbilical cords, napr, an aplasia of one of her arteries, the shell attachment, an absolute korotkost, etc. (see. Pupovina ). At P.'s hyperplasia (the weight of 800 g and more, diameter more than 20 — 30 cm) additional shares, two-share P., a regional and shell attachment of an umbilical cord are more often observed. Significant increase in weight of P. can be caused actually by a hyperplasia (a large fruit, polycarpous pregnancy, a chronic hypoxia of a fruit), long venous stagnation of blood of a fruit, hypostasis (most often as a result of a hemolitic disease), P.'s hemangioma, etc.

Fig. 5. Macrodrug of a placenta (placenta marginata): the arrow specified a ring from which interior fetal membranes depart.

Such malformations of P. as placenta marginata (fig. 5) and placenta circumvallata surrounded with a whitish ring from which interior fetal membranes depart are known. The ring in placenta circumvallata acts over a fruit surface of P. in the form of the roller. Histologically this ring consists of deposits of fibrin between which nekrotizirovanny vorsina and decidual cells are located. Filmy P. (placenta membranacea) has an appearance thin-walled, 3 — 5 mm thick, the bag occupying the most part of an inner surface of a uterus. Zone P. (placenta zonaria) has the form of a belt 4 wide — in cm, places reaching 20 — 23 cm, passing on an inner surface of a uterus, or a form of a horseshoe. These malformations of P. have harmful effect on a fruit.

Two-share P. (placenta bidis-coidalis, placenta bipartita), trekhdo the left P. (placenta tripartita), P with additional segments (placenta succenturiata) essential a vliya a niya do not render on a fruit, however in case of a delay in a uterus of an additional segment bleeding in a puerperal period is observed uterine'. Fenestrated P. (placenta fenestrata) contains various size the sites deprived vorsin of chorion that, however, does not exert impact on the course of pregnancy. The listed malformations are diagnosed after the birth of a placenta.

Pathology of a placenta at diseases and morbid conditions of mother and a fruit. Inflammatory process P. (placentitis) can have an infectious origin or to be aseptic, napr, under the influence of meconium, change of pH of amniotic waters, etc. The most frequent is the ascending way of infection of P. via the channel of a neck of uterus in an amniotic cavity. Hematogenous infection comes from blood of mother through spiral arteries of a decidua of P., but perhaps hematogenous defeat of P. from a fruit at pre-natal sepsis. Also P.'s infection with the descending way — from the inflammatory center in an abdominal cavity through a uterine tube, and also the mixed way of infection is observed. In P. the exudative inflammation, preferential seroznognoyny character is more often observed; purulent fusion of fabrics is observed seldom. The fibrinous and serous and hemorrhagic inflammation of P., apparently, is possible at some viral infections, in particular at flu and a parainfluenza. Morphologically the inflammation is more often shown by leukocytic infiltration of fabrics of an afterbirth.

Fig. 6. The scheme of a microscopic structure of a placenta and localization in it inflammatory processes: I \a chorial plate, II — intervillous space from vorsina, III — a basal plate; 1 — the vasculitis, 2 — subchorial intervillezit, 3 — a placental horio-amnionitis, 4 — central intervillezit, 5 — a basal deciduitis, 6 — basal intervillezit, 7 — villezit.

On localization of inflammatory process in P. (fig. 6) distinguish: subchorial intervillezit — plentiful accumulation of leukocytes and fibrin under a chorial plate, central intervillezit (in a distance from chorial and basal plates) and basal intervillezit — the inflammation which is localized on a basal plate. Besides, it can be noted a pitchfork-luzit — leukocytic infiltration in a stroma vorsin; a basal deciduitis — an inflammation of a basal plate; a septal deciduitis — an inflammation in septa; placental horioamnionit — an inflammation of a chorial plate and its vessels.

P.'s tuberculosis meets seldom. It is observed at acute miliary tuberculosis (see) at mother also strikes a basal plate.

The centers can be productive or necrotic - exudative. The epithelium vorsin nekrotizirutsya, their stroma for the second time is surprised, the centers of a caseous necrosis, hillocks with huge multinucleate cells of Pirogov — Langkhansa appear. Along with specific changes are found also nonspecific — blood clots of intervillous space, hemorrhage in a decidua, proliferation of a stroma, its fibrosis, etc.

Syphilis (see) it is transmitted from mother to a fruit through P., at this P. changes not always. At the inborn hypostasis caused by syphilis, P. is increased, pale color, is thickened, brittle; its kotiledona large, clearly are separated from each other. PPK can reach 0,3 — 0,5. Morfol, changes are not specific. Large and edematous vorsina (on the periphery with the increased number of cells of Kashchenko are characteristic — Hofbauera) with a fibrozi-rovanny stroma, especially around vessels, to-rye are sclerosed, sometimes thrombosed. The productive endarteritis, in trunk vorsina quite often obliterating is often observed.

At listeriosis (see) in intervillous space the fibrin penetrated by leukocytes is found. In the vorsina adjoining to it deprived by places of a chorial epithelium leukocytic and histiocytic infiltrates, the centers of a necrosis meet. In single vorsina the endarteritis and a periarteritis sometimes are found. In the centers of a necrosis and an inflammation listeriya, sometimes fagotsitirovanny stromal cells come to light. The basal plate also can be involved in process. Sometimes preferential chorial plate is surprised.

At toxoplasmosis (see) can be observed, but not always, P.'s changes in the form of dystrophy of a trophoblast with existence in it, in maternal part P. of willows vorsina toksoplazm. Sometimes in vorsina plasmocytes, and also the centers of a necrosis near which pseudo-cysts toksoplazm are located are found.

Nonspecific and specific inflammatory processes in P. can lead to infection of a fruit or to development of pre-natal hypotrophies (see), chronic hypoxias (see) and other pathology fruit (see).

At defects hearts (see) the most expressed changes in P. are observed at a decompensation of cordial activity, especially at active rheumatic process. These changes are characterized by reduction of weight, a rezorbtsionny surface, the largest size and P.'s perimeter; are observed intensive collagenization trailer vorsin and extensive deposits of fibrinoid on their surfaces, increase in quantity of syncytial small knots with symptoms of dystrophy.

Processes of proliferation of a chorial epithelium are expressed poorly.

Decrease in functional activity of P. is demonstrated falloff of content of RNA in cytoplasm of a sincytium, by decrease in maintenance of a glycogen, accumulation of acid glikozaminoglikan in fibrous structures vorsin, increase in lipids in a chorial plate and a stroma vorsinony

At late toxicoses of pregnant women (see) functional disturbances of blood circulation in decidua basalis which are shown originally in vasospasms, staza of blood further lead to changes of a wall of vessels (fibrinoid dystrophy and a sclerosis), formation of blood clots and the centers of a necrosis — heart attacks owing to what the volume of the functioning fabric P. decreases. The focal congestive hyperemia and irregularity of thickness of separate shares of P., places narrowing of intervillous spaces and underdevelopment of vessels vorsin, P., testimonial of a delay of maturing, reduction of PPK, weight and sizes, a rezorbtsionny surface of P. are noted; massive deposits of fibrinoid in the field of a chorial plate and adjacent to it vorsin, collagenization vorsin and accumulation in them of acid glikozaminoglikan, dystrophy of a chorial epithelium, decrease of the activity of some oxidation-reduction enzymes are observed. Degree of manifestation of the given changes (they prevail in the central departments of P.) depends not so much on a look and weight of toxicosis how many from duration of a disease: at the long course of toxicosis macro - and microscopic changes of P. are the most considerable. Along with the last in other sites P. (it is preferential in its peripheral departments) the compensatory and adaptive reactions providing necessary conditions for fetation at disturbance of circulator adaptation are observed. Similar patol, changes are found in P. at the raised ABP and hron, a glomerulonephritis. There are, however, instructions and on nek-ry distinctions. So, e.g., changes in maternal part P are characteristic of hypertensia more expressed morfol.

At an edematous form of an eritroblastoz (see. Hemolitic disease of newborns ) P.'s weight can reach 2000 — 2600, and PPK sostavlyaet0,5 — 1. The placenta is thickened, increased, edematous, easily torn; quite often in it the small centers of a necrosis and calcification are found. Vorsina are sharply increased, with hypostasis of a stroma which quite often contains a large number of connective tissue elements (a giperpdasticheeky stroma) and Kashchenko's cells — Hofbauera. Under a sincytium Langkhans's cells sometimes remain. Capillaries are not enough, sinusoids and sintsitiokapillyarny membranes are not formed. The specified structural changes meet at sharply expressed delay of maturing vorsinony Vessels an unripe endothelium contain nuclear erythrocytes (an intraka-iillyarny erythrogenesis). The centers of a hemopoiesis are observed in a stroma vorsin and especially in subchorial area. If the Rhesus factor conflict does not lead to developing of a disease of the newborn, then the weight and the size P. do not differ from weight and mature P.'s size at uncomplicated pregnancy.

At a diabetes mellitus of pregnant women (see. diabetes mellitus ) defects of development of capillary system P. are observed; at the same time along with normal vaskulyarizovanny vorsina trailer vorsina which capillaries are small, narrow are found and are localized in their center.

In P. which is located over an intramural leiomyoma of a uterus with the central growth find atrophic changes, in the fringe region of P. the increased amount of fibrinoid comes to light.

P.'s defeats at toxicoses of pregnant women, heart diseases, an eritro-blastoza, a diabetes mellitus, a leiomyoma of a uterus are secondary and are distinguished after P. Klinicheski's birth they can be shown by change of weight of a fruit, hron, a hypoxia, etc.

Cysts of a placenta can be true and false. True cysts meet only in a chorial plate. Adventitious cysts have no epithelial vystilka, are formed owing to a softening and fluidifying of heart attacks of P., fibrin in intervillous space, fabric of partitions (small septal cysts). The last meet at late toxicoses of pregnant women, a diabetes mellitus more often, a Rhesus factor conflict and are quite often combined with hypostasis vorsinony

Tumours in a placenta meet rather seldom. From benign tumors P.'s hemangiomas are known (see. Hemangioma ), angiofibromas (see), angiomyxomas and teratomas (see). The hemangioma (chorion angioma) is most often observed. At superficial macroscopic survey of P. it can not be found because of the small sizes. Large hemangiomas (more than 5 cm in the diameter) usually meet in the presence big P., is powerful St. 800 g, is more often single, but can be and multiple. Benign tumors of a placenta usually a wedge, do not matter and are diagnosed only after the birth of the Item.

Malignant primary tumors of P. (except for a horionepitelioma), and also metastatic tumors are observed very seldom. Metastasises in P. can arise in the presence of a malignant tumor at mother or at a fruit. In certain cases, napr, at a melanoma and sarcoma, transition of tumor cells through P. from mother to a fruit is possible.



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V. I. Bodyazhina (mt. issl., physical.), B. I. Zheleznov (An., stalemate. An., pathology), S. A. Nadirashvili (artificial placenta).

Яндекс.Метрика