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Physiology of Reproduction

Genital anatomy. The genitals of men and women are divided into external and internal. The external genitals of a man include the penis (penis) and scrotum. The external genitals of a woman include large and small labia, clitoris, hymen. The internal genital organs of a man include the testicles, vas deferens, seminal vesicles, prostate gland (prostate) and urethra. The internal genital organs of a woman include the ovaries, the uterus (fallopian tubes), the uterus and the vagina.

Physiology of conception. In the male gonads, mobile cells are produced - sperm and male sex hormones. In the sperm, the head, neck, body and tail are distinguished. The length of the sperm is approximately 0.05 mm. Thanks to the tail, the sperm makes a movement around the longitudinal axis and against the flow of fluid. Sperm entering the woman’s vagina reach the uterine cavity after about 30-90 minutes.

The production of sperm and sex hormones begins with the onset of puberty and continues until old age. Sperm cells are found in the dense seminal fluid produced by the testes. Mixing with the secretion of the prostate and seminal vesicles, this fluid forms sperm. The amount of sperm, or ejaculate (i.e., the seed ejected at a time), is 2-8 ml. Semen has a complex composition. It contains hormones, amino acids, vitamins, mineral salts, etc. The sperm development process is 72 days and lasts continuously. In the sperm of a healthy man contains 50-200 million sperm. The speed of sperm movement is 3-4 mm in 1 min.

Sperm enter the uterus, then reach the ends of the fallopian tubes, where they meet with the egg, sometimes go into the abdominal cavity and fertilize the egg. Of the huge amount of sperm, a small part enters the uterus, since many sperm die under the influence of an acidic environment in the vagina. When the first sperm enters the egg, for the rest the egg shell becomes impassable, since the nucleus of only one sperm merges with the nucleus of the egg.

The egg is formed in the ovaries. Ovarian function is very complex. They form not only eggs, but also female sex hormones. Almost 100,000 eggs are laid in the ovaries. The egg is the largest cell in the human body. It has a round shape with a diameter of 0.2 mm. It cannot move independently. The first egg maturation occurs at the age of 12-13 years. Within a month, only one egg matures. Around an immature ovum, a cavity filled with fluid forms. This egg cavity is called a graaf bubble. When the egg matures, the graaf bubble bursts and the egg, along with the follicular fluid, is thrown into the abdominal cavity. This phenomenon is called ovulation.

Near the ovaries are the fallopian, or uterine, tubes that extend from the corners of the uterus. Their end, facing the abdominal cavity, looks like a funnel, lined from the inside with fringes, "flickering" towards the uterus. The egg enters the fringe and, thanks to their “flicker”, moves along the tubes towards the uterus.

The uterus is the muscular organ in which the fetus develops. It is located between the bladder in the front and the rectum in the back. The uterus has a pear-shaped shape, consists of a body and a neck. From the cervix, the vagina begins - the hollow muscle organ into which the penis is inserted during sexual intercourse and the seminal fluid is poured out.

Fertilization occurs at the very beginning of the fallopian tube or in the abdominal cavity, where the egg and sperm meet. A fertilized egg, having advanced through the fallopian tube through the fallopian tube into the uterine cavity, attaches there to the inner wall of the uterus, i.e. pregnancy comes. If a fertilized egg, due to the narrowing of the fallopian tube (which is most often due to inflammatory processes of the internal genital organs), remains in the fallopian tube, then an ectopic (tube) pregnancy occurs. In this case, the fetus cannot develop normally and surgical intervention is necessary.

A yellow body is formed in place of a bursting graaf bubble, which secretes a special substance such as a hormone that enters the bloodstream and affects the uterine mucosa: the uterine mucosa swells, becomes loose, and a large number of additional blood vessels develop in it. If fertilization has not occurred, then part of the uterine loose membrane exfoliates, blood vessels burst and menstruation begins (occurs from the moment of puberty every 21-28 days and lasts 3-4 days, sometimes longer). During menstruation, approximately 100-200 ml of blood is released from the vagina. Blood excretion is only an external manifestation of a complex process that repeats monthly in the female body. During menstruation, many women feel weakness, general malaise, headache, etc. These days, you should reduce physical activity, carefully observe the rules of personal hygiene of the external genital organs. It is forbidden to swim, go to the bath. It is preferable to take a shower.

A fertilized egg moves along the fallopian tube toward the uterus. After a three-day movement through the tube, the embryo (the fertilized egg called the zygote) undergoes the first division and then divides repeatedly; enters the uterine cavity and penetrates (implants) into the thickness of the uterine mucosa. This occurs approximately on the 5th day after fertilization.

Germ cells provide transmission of hereditary information. If the nuclei of all cells of the human body contain 46 chromosomes, i.e. 23 pairs, then germ cells contain 23 chromosomes. When the female and male germ cells merge, the fertilized egg again receives a complete set of chromosomes, consisting of 23 pairs, i.e. 46 chromosomes (half from father and half from mother). The combination of these chromosomes determines the sex of a person: XX - female cell, XY - male.

The physiology of pregnancy. In the process of fetal development, two periods are distinguished: embryonic (embryon - embryo), which lasts from the moment of fertilization to 8 weeks of pregnancy, and fetal (fetus - fetus), which lasts from 8 weeks of pregnancy to childbirth. In the embryonic period, the formation of the main organs and systems takes place, in the fetal period, their growth and development continues.

The fetus lives in conditions that ensure its development: its movements are limited, facilitated by swimming in a liquid, and all the energy goes to build its organs and systems.
In addition, receiving nutrients from the mother, he is in conditions of optimal temperature. For 9 months intrauterine life, the fetus turns into a complex human body. With a four-week embryo, ultrasound can clearly see the contractions of the heart, which indicates the presence of a formed circulatory system. At 8 weeks, the fetus has a body, head, rudiments of the limbs, eyes, nose and mouth, and the formation of genital organs begins. By the 12th week, the length of the fetus is 8-9 cm, weight 110-120 g, a noticeable difference in the structure of the external genitalia, the limbs make movements, the fingers and toes are visible. By the 16th week, the fetal length is 16 cm, body weight 120 g, the lungs, kidneys, and liver are well developed. From the 14th week, the fetus begins to move. But so far the mother does not feel these movements. She begins to feel them from 18-20 weeks of pregnancy. At 28 weeks, the fetal length is 35 cm, weight 1000-1200 g, the fetus is very active. A fetus born at this time is considered a newborn baby, not a miscarriage, but, as a rule, it is unviable. Over the past 12 weeks before giving birth, the fetus fully develops and by the 40th week (9 months) is ready for extrauterine life: its length is about 50 cm, weight is 3,200-3,400 g, the lungs are ripe for independent breathing. By the time of birth, the fetal head falls lower, the pregnant woman feels that it has become easier to breathe: both the fetus and mother are ready for childbirth.

Pregnancy lasts 280 days on average, or 10 obstetric months (obstetric month lasts 28 days, 10 obstetric months equals 40 weeks), counting from the first day of the last menstruation, i.e. about 9 calendar months. The entire pregnancy period is divided into three trimesters, three months each.

In connection with the development of the fetus, a significant restructuring of the body is observed in the pregnant body, which ensures the correct development of the fetus, prepares the mother's body for the upcoming birth and feeding. The body weight of a woman increases by the end of pregnancy by 10-12 kg, weekly weight gain in the second half of pregnancy is 300-350 g. Brown spots appear on the skin of the face, white line of the abdomen, nipples and paralosal circles. In addition, almost all women experience pregnancy scars that are localized on the skin of the abdomen, thighs, and mammary glands.

Significant hormonal changes occur in the body of a pregnant woman. The placenta produces a hormone new to the body - gonadotropin, placental lactogen, etc. The pituitary gland actively produces prolactin and lutropin, the thyroid gland in 35-40% of women increases in size with an increase in its function, the function of the parathyroid glands decreases, the activity of the adrenal cortex increases.

An increase in oxygen demand leads to increased lung activity, the chest is expanding. Since the cardiovascular system works more intensively, the pulse quickens, the vascular tone increases, and the mass of the heart muscle increases. Blood pressure during pregnancy is practically unchanged. In the middle of pregnancy, blood pressure may decrease in women with a slight high blood pressure before pregnancy, and in the last 2-3 months. pregnancy, as a rule, in such women, the pressure rises again, which complicates the course of pregnancy. Therefore, pregnant women regularly measure blood pressure.

The kidneys during pregnancy work with a heavy load, as they remove from the body metabolic products of not only the woman herself, but also the fetus. The amount of urine released depends on the amount of fluid you drink. A healthy woman during pregnancy secretes an average of 1,200-1,600 ml of urine per day. In the first and second trimesters of pregnancy, frequent urination appears, possibly the appearance of traces of protein and sugar in the urine. In some pregnant women, a change in the function of the digestive system occurs: taste sensations change, the acidity of the gastric juice decreases, constipation is noted, there may be heartburn. Changes in the musculoskeletal system are manifested by relaxation of the ligaments of the joints (under the influence of progesterone), a slight relaxation of the pubic bones, which is manifested by pain in the bosom, “duck gait”, sometimes back pain due to impaired posture.

Physiological birth. The estimated date of birth can be determined as follows: from the date of the first day of the last menstruation, 3 calendar months are counted back and 7 days are added.

Usually, before a birth, a pregnant woman has some symptoms - precursors of childbirth: prolapse of the uterine fundus, easier breathing, secretion of thick viscous mucus from the vagina, the appearance of irregular pulling pains in the lower abdomen and lumbosacral region. There are three periods of childbirth: the period of disclosure, the period of exile, the subsequent period. The onset of labor is the appearance of regular contractions after 10-12 minutes. Gradually, the intensity of contractions increases, pauses between contractions are reduced to 2-3 minutes, the duration of each fight reaches 60-80 s. The first period of labor ends with the full opening of the cervix. It lasts 12-16 hours in a primiparous woman and 6-10 hours in a multiparous. The fetal bladder normally bursts with an almost complete opening of the uterus. With the occurrence of regular contractions or in the case of premature discharge of water, a woman should be hospitalized in a maternity hospital. The period of exile begins from the moment of full disclosure of the external pharynx and ends with the birth of a child. The duration of the second period of labor is different, most often it is 30-60 minutes. During this period, the contractile activity of the uterus is most active. The subsequent period begins from the moment of the birth of the child and ends with the birth of the afterbirth (exfoliation of the placenta). The born placenta is carefully examined to verify the integrity of the placenta. The average duration of the third period is 10-15 minutes. Physiological blood loss is 200-250 ml.

Physiological postpartum period. The postpartum period begins with the expulsion of the placenta and lasts 6-8 weeks. On the 12th day after birth, the uterine fundus is at the level of the navel, the uterus is rapidly contracting in size and by the 10th day after birth, the fundus is at the level of the womb. The nature of the discharge from the uterus varies from bloody, serous-sucrose (from the 3rd .4th day) to light (by the 10th day after childbirth). Discharge from the uterus completely stops at the 5-6th week. Lactation begins on the 2-3rd day after birth. In the postpartum period, a woman is called a postpartum.
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Physiology of Reproduction

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