Normal pregnancy

Pregnancy is a physiological process in which of the fertilized egg in the woman's body is developing fetus.
The conception and development of the ovum. Conception is called the moment of fertilization with sperm Mature egg cells. In most cases, fertilization occurs immediately after vyhozhdeniya egg from the ovary cells, usually in ampullar fallopian tube. In the fertilization process, the sperm enter through the transparent membrane of the egg cell, which is possible because they secrete the enzyme - hyaluronidase, increasing permeability of fabrics. In the cytoplasm of the egg cell is embedded usually a single sperm. To meet it head on the surface ooplasma formed "perceiving bump". The head of the sperm separates from the tail, quickly moving closer and merges with moving towards the core of the egg, forming one common core of crushing fertilized eggs - a zygote. With the introduction of the first ball crushing begins the process of embryonic development (see Embryo). During fertilization of two egg cells are formed dayzetia twins. The result is atypical crushing egg cells appear identical twins.
In the process of breaking the egg thanks mainly peristaltic contractions of the uterine tube is pushed her to the uterus and there is implanted (Fig. 1).

Fig. 1. Implantation of human eggs (Peters): 1 - the epithelium of the mucous membrane of the uterus (in the place of implementation of eggs is not); 2 - hole gland;
3 - "fibrinous mushroom; 4 - a place of introduction of eggs; 5 - egg; 6 - embryo; 7 - muscle; 8 - gland; 9 - capillaries in circumference eggs; 10 - mesoblast; 11 - ectoplasm (trophoblast), the beginning of formation of fibers; 12 - stroma mucous the membrane of the uterus.

Implantation (the process of vaccination fertilized eggs) is due to the melting subject of the mucous membrane of the uterus enzymes trophoblast (outer layer of cells of morula), providing a nutrient medium for the fetus.
The melting of the mucous membrane of the uterus violated integrity into the capillaries; the gushing blood as it forms the blood pool, washing outgrowths of trophoblast. Formed on the implementation of the ovum defect in the beginning is closed by a fibrin clot ("fibrinous mushroom"), then the edge of the mucous membrane, adjacent to have penetrated to its thickness egg, grow, covering him in the form of capsules.
In the implantation process, trophoblast eggs comes into contact with thickened and loosened the endometrium, which is the decidual metamorphosis and after the implantation of the egg sharper reveals the division of functional layer on two layers. First - compact - converted into the lumen of the uterine cavity and consists of decidual cells, rich in protoplasm and glycogen, the second - a spongy, located more deeply, addressed to the muscle layer of the uterus and is composed of connective tissue cells. In the spongy layer of cancer sharply exaggerated, stretched, megjelenitese space propisyvayutsya blood vessels. The thickness of the mucous membrane of the uterus, called now decidual (decidua - falling away), in General, up to 1 cm (before pregnancy - 1 - 2 mm).
In fertilized egg differentiate two cell complex: ectoplasm associated with trophoblast, and endoblast, located more centrally. Later they become hollow: accablante formed cavity of the amnion, surrounded by cells of ectodermal, antabuse - primary intestinal cavity and the cavity of the yolk bubble lined with cells endoderm. The partition between the two cavities is the embryo of the future embryo - embryoblast (Fig. 2).

Fig. 2. The scheme of formation of a cavity of a blastula (blastocyst), the umbilical cord and fetal membranes: I - the formation of cavities amnion and yolk bladder; II-the transformation of the morula in the blastula and education primary CVS; III and IV - education umbilical cord and fetal membranes (early and late stage); 1 - cavity amnion; 2 - cavity yolk bubble; 3 - abdominal foot, 4 and 5 - ecto - and entuziasty (cavity yolk bubble) bubbles; 6-primary fibers; 7 - abdominal leg with the allantois, 8 - foot yolk bubble; 9 - chorionic villi; 10 - primary intestinal cavity; and germ; 12 - amnion; 13 - primary intestine; 14 - Rorion; 15 - intestine; 16 - allantois; 17 - yolk bubble; 18 - the umbilical cord; 19 - yolk turn.

Between the two layers embryoblast - ecto - and antiblastoma - produced third - mesoderm.
The power of the ovum initially provided by trophoblasts: allocated to them enzymes melt adjacent cells decidual shell (see), and he absorbed nutrients. On 18-20 th day after fertilization, the diameter of eggs is about 20 mm
Cells of the outer layer of the trophoblast, merging into a solid protoplasmatic mass with a large number of cores, form syncytium. Internal trophoblast layer (layer Langhans) consists of separate, well-marked cylindrical cells. Syncytium, growing, forming processes - primary NAP, which later included the cells of the inner layer; covered with villi serous membrane of the egg is called primary chorion (chorion primitivum).
The Bud of the Bud and the adjacent cavity amnion and yolk bubble surrounded metallisticheskoy cloth, associated peripherals eggs only the so-called abdominal leg. On the 3rd week of embryonic development in the back of primary intestinal cavity appears ledge with richly developed vascular network, communicating directly with the aorta of the embryo,the allantois. Rapidly growing, it extends and reaches primary chorion. Branches of the vessels of the allantois together with the surrounding connective tissue elements penetrate the primary NAP, and primary chorion becomes true (chorion verum), able to perceive the nutrients from the surrounding maternal tissues and deliver them to the fetus.
The cavity of the amnion gradually filled amniotic fluid (liquor amnii); increasing its number amnion approaching the inner surface of the serous membrane and comes into contact with it. By the end, pregnancy amnion is a thin avascular translucent membrane covered with a cylindrical or cubic epithelium, intimately, but loosely connected to the chorion. Abdominal leg with the remnants of the yolk bladder, allantois and the prisoners therein vessels turns into the umbilical cord, or umbilical cord (funiculus umbilicalis). The umbilical cord is attached to the fetus (umbilicus) and the chorion. The chorionic villi, previously evenly cover the entire periphery of the egg, for the most part atrophy; this part of the chorion is smooth (chorion laeve). On a small space in the area of the former abdominal legs NAP powerfully proliferate, forming branching chorion (chorion frondosum), which is the fruit part of the placenta. From this moment occurs placental blood circulation system, developing and continued throughout pregnancy.
In decidual the lining of the uterus (decidua) there are following parts: located between the egg and the muscle layer of the uterus decidua basalis (old name decidua serotina - belated)covering an egg on top decidua capsularis (old name decidua reflexa) and lining the uterus that is not occupied by the fertilized egg, decidua parietalis (decidua vera, s. decidua uterina). With the development and growth of the ovum decidua capsularis and decidua parietalis merge (4-th month. pregnancy). Decidua basalis hypertrophies, it develops a large number of blood vessels, which form a dense network, making this part of the decidual shell acquires cavernous character. It penetrate numerous chorionic villi, their syncytium melts connective tissue decidua basalis, corrodes the walls of the capillaries, the blood from flowing into majorsince space. The chorionic villi are immersed in maternal blood (Fig. 3). Decidua basalis and branchy the chorion in the late 3rd or early 4th months. pregnancy into the placenta (see).

Fig. 3. Diagram of blood flow in the placenta: 1 - umbilical artery; 2 - umbilical vein; 3 - majorsince space; 4 - fibers; 5 - maternal vessels; 6 - the remainder cavity yolk bubble; 7 - the uterine musculature.

The fruit is connected with the placenta, umbilical cord. Her blood vessels - two arteries and one Vienna - embedded in Vartanova Studeny, component of the connective tissue framework of the umbilical cord, covered outside the amnion. Attach the cord to the placenta may be Central, eccentric (side), regional or shell. Placenta with the umbilical cord and membranes is the last.
The fruit with the umbilical cord floats in amniotic, or amniotic, liquid, which is the product of secretory activity of epithelial amnion mixed with waste products of the fetus, especially urine. Amniotic fluid contains protein, salt (especially a lot of sodium chloride), urea, oil, extractive substances, some hormones, vitamins and enzymes. Towards the end of pregnancy, the amount of amniotic fluid is 0.5-1.5 l They prevent the formation of growths between the skin of the fetus and the amnion, allow the fruit to make active movements necessary for its proper development, make them less noticeable for pregnant protect the umbilical cord and the placenta from the pressure from parts of the fetus, protect the fetus from bumps and bruises from the outside, affect, Clearspace fruit on the disclosure of uterine throat during childbirth. During pregnancy, the fetus grows and develops; by the end of the 10th obstetric months. pregnancy its length is up to 50-52 cm, weight 3000-3500 g (see the Fruit).