The egg is surrounded by a sticky mass of cells that mature in the hours before ovulation and attaches to the surface of the ovary. One end of each fallopian tube is connected to the uterus, while the other end looks a bit like a funnel, closer to the ovary, and is open. The seam at the entrance is covered with protrusions called fimbriae. Healthy fallopian tube muscles are strong and can bend toward the ovary. The sticky material on the outside of the egg makes it easier for the fimbriae to enter the fallopian tube. The egg stays at the funnel-shaped end of the fallopian tube for 1 to 2 days. This is where sperm often arrives, and the fertilization process is completed here. The exact length of time an egg can survive outside the follicle is still unknown, but experimental studies show thatfertilization is usually completed within 24 or 36 hours after ovulation.
Normal ovulation is crucial to pregnancy, but it is not the only condition. Sperm must have the ability to swim in order to reach the location of the egg and fertilize it, and the embryo can enter the uterus and implant in the uterus.
The large amount of estradiol secreted by the dominant follicle before ovulation prepares the cervix for the smooth passage of sperm. If the mucus secreted by the cervix is abnormal, sperm cannot pass through. As estradiol levels in the body increase, the opening of the cervix relaxes and widens. This allows large amounts of sperm to quickly leave the vagina, enter the uterus, and then travel to the fallopian tubes.
So-called reproductive mucus has many functions. Normally, acidic secretions from a woman\’s vagina can kill sperm within a few hours, while the mucus protects the sperm\’s survival. The mucus secreted by the cervix also provides a home for some sperm before entering the uterus and fallopian tubes, where they can wait for a day or two. Why do some sperm enter the uterus faster than others? This question is still a mystery.
If the mucus-secreting glands of the cervix cannot work properly, or the estrogen level in the body does not reach the required value, the amount of mucus secreted will be reduced. During each menstrual cycle, mucus is secreted for a short period of time, usually about 7 days.
The main task of progesterone is to prepare the uterine wall to receive the embryo. In addition, within a few days after ovulation, progesterone also causes the cervix to tighten, making the mucus thicker and more sticky to prevent sperm from entering. It is estimated that 5% to 10% of infertility cases are caused by abnormal cervical function.
When cervical mucus is in normal conditionDuring sexual intercourse, normal, active sperm will quickly reach the fallopian tube. At this time, if an egg appears, a sperm will pass through the protective body of the egg (i.e. egg membrane), and the egg membrane will undergo chemical changes to prevent other sperm from entering. Conversely, if more than one sperm\’s chromosomes combine with those of the egg, genetic confusion can occur.
Mature sperm has 23 chromosomes, and the egg initially has 46 chromosomes. After stimulation by luteinizing hormone, half of the chromosomes leave the egg cell. The egg contains an X chromosome, and the sperm contains either an X or a Y chromosome, which is the sex chromosome. After the egg is fertilized, the 23 chromosomes (X or Y) of the sperm combine with the 23 chromosomes of the egg, so a fertilized egg has 46 complete and normal chromosomes. In this process, the embryo possesses the same amount of genetic material from both parents. If the incoming sperm carries a Y chromosome, the egg will develop into a male embryo, because the Y chromosome provides all the information for the development of male sex characteristics. If the sperm carries an X chromosome, the embryo will be female.
After the genetic material of the sperm and egg is added, the egg develops into an embryo and begins to break down. For aging eggs, the gene replication mechanism may be abnormal, genetic disorders may occur, and the embryo will stop developing.
The embryo, which can only be seen under a microscope, is transported from the fallopian tube toward the uterus, \”escorted\” all the way by hair-like cilia. If cilia are missing, or the number of cilia is too small, the embryo will not move forward, so the embryo may implant on the fallopian tube wall, leading to fallopian tube pregnancy or ectopic pregnancy. If the fallopian tube is infected or damaged by surgery or other injuries, the embryo cannot pass smoothly, eventually leading to fallopian tube pregnancy or the death of the embryo due to lack of adequate nutritional support.
If all of the above goes well, the endometrium is now ready to grow the embryo. The large amounts of estradiol and progesterone secreted by the corpus luteum thicken the endometrium and make it soft and elastic. It also generates new blood vessels to provide nutrients for the implanted embryo. The embryo can only achieve its own adhesion by getting rid of the egg membrane. This process is vividly called incubation.
After hatching, most of the embryos settle down in a corner of the lining of the uterus, where they merge with the tiny vascular disc a few days later. The outermost chorion of the cell group begins to secrete human chorionic gonadotropin. Human chorionic gonadotropin can be found in the blood on the 10th day after ovulation. However, the presence of human chorionic gonadotropin does not mean that the embryo has entered the uterus or fallopian tube.
This article is provided by Baidu Reading and is excerpted from \”The Clear \”Conception\” Plan\” Author: Sun Jianqiu and Xie Yingbiao