During pregnancy, the external genitalia become swollen, moist and take a cyanotic color. The vaginal mucosa becomes juicy, hyperemic, its folding is more pronounced. Vaginal discharge increases due to increased secretion of cervical and vestibular glands. In the cervix, the amount of connective tissue and, to a lesser extent, the muscle elements gradually increases. The neck becomes dense, its vascularization is intensified.
The uterus undergoes the greatest changes. Its dimensions during the period of pregnancy increases to 37-38 cm in length and 25-26 cm in diameter (the length of the unfermented uterus is 7-8 cm, the diameter of 4-5 cm), and the weight increases to 1000-1200 g (the weight of the not pregnant uterus is 50-70 g). The uterus loses its pear-shaped form and first becomes asymmetric through the nidation of the fetal egg in one of its corners. Later this asymmetry is equalized and from the second half of pregnancy the uterus acquires the correct ovoid form. Antibiotics of the uterus, increasing in the first week of pregnancy, later disappears. The consistency of it during pregnancy also changes. The uterus becomes soft, especially in the area of the isthmus.
In myometrium, there are significant structural changes that adapt the muscle fibers to the size of the fetal egg. They are manifested in hypertrophy and hyperplasia of myocytes, which are caused by the endocrine action of the pituitary gland, ovaries and placenta. The synthesis in the muscles of the uterus of actinomiosin constantly increases, and at the end of pregnancy neogenesis of smooth muscle cells from elastic fibers increases, which is of great importance in increasing the contractile activity of the myometrium.
At the same time, the connective tissue elements are also subject to change. Elastic fibers in the body and the bottom of the uterus thicken considerably, but remain thin in the isthmic department. Therefore, by the end of pregnancy, the lower segment retains the ability to stretch.
The capacity of the bloodstream of the uterus increases: arterial and venous vessels sharply expand, their thin branches grow and thicken, the formation of new vessels increases; uterine vessels sinuous at the beginning of pregnancy, in the third trimester straighten. The volume of blood circulation in them differs constancy even with functional changes in the blood filling of other organs, is enhanced by the influence of the hormones of the yellow body, acetylcholine and the limited vasopressor influence of the antidiuretic hormone on the uterine vessels.
The ligamentous apparatus of the internal genital organs increases, which allows the uterus to develop normal generic activity. Pipes straighten and thicken. Ovaries during pregnancy increase, ovulation ceases. On one of the ovaries is the yellow body of pregnancy.
As it grows, the uterus leaves the pelvic cavity in the abdominal cavity, reaching the ninth month of pregnancy of the xiphoid process of the sternum.
Mammary glands during pregnancy are prepared for lactation. The iron lobes increase in volume and grow in quantity. The vasculature of the mammary glands grows, the subcutaneous veins widen. Epithelial tissues in ferruginous lobes increase, lipid inclusions appear in their protoplasm. By squeezing out in the first weeks of pregnancy, you can get a few drops of colostrum from the gland .
Such changes in the mammary glands during pregnancy are exacerbated by the influence of sex hormones and prolactin. Estrogens stimulate the growth of the secreting mammary gland tissue and its hypervascularization, progesterone promotes the growth of the excretory ducts, and prolactin causes the secretion of milk.