Egg and sperm combine

When a man and a woman have sexual intercourse, the man's sperm will naturally enter the woman's uterus and combine with the woman's egg. It should be said that as long as the bodies of both men and women are normal and no contraceptive measures are taken, then this combination is actually a fundamental condition for women to become pregnant. It can be said that only when the man's sperm and egg combine can new life be conceived.

Therefore, for those who are preparing to get pregnant and have children, it is actually very important to understand how the sperm and egg of a man combine. So how do the sperm and egg of a man combine? How can two individuals form an embryo?

1. During sexual intercourse, men discharge about 200 to 400 million sperm each time. After a man's sperm is ejaculated into a woman's vagina, most of the sperm is discharged from the vagina along with the semen. Because the cervical mucus is alkaline, it is conducive to sperm activity. A small number of sperm rely on the swinging of their tails to move forward and quickly swim to the cervical canal. The sperm releases protein lytic enzymes to dissolve the cervical mucus; the uterine contraction and fallopian tube peristalsis caused by sexual intercourse accelerate the movement of sperm; the peristalsis of the fallopian tube muscle layer, the swing of the mucosal cilia and the flow of the fallopian tube fluid secreted by the mucus cells lead to the movement of sperm from the uterine cavity to the ampulla of the fallopian tube.

2. At the final destination - the ampulla of the fallopian tube, it waits there to combine with the egg. It takes sperm only a few minutes to reach the fallopian tube from the vagina, at most 4 to 6 hours, and usually 1 to 1.5 hours. As sperms move forward, they are blocked by cervical mucus and swallowed by white blood cells in the uterine cavity. In the end, only dozens to one or two hundred sperms reach the fallopian tubes. Before sperm can fertilize the egg, it must be incubated in the female reproductive cavity for a period of time and undergo morphological, physiological, and biochemical changes before it becomes capable of fertilization. This process is called sperm capacitation.

3. After entering the female's vagina, the sperm immediately begin a long swim from the vagina to the entrance of the uterus. There, the mother secretes a sticky liquid that forms a net. When the egg flies out, the net is open, allowing the sperm to pass through easily. This net acts as a booster, helping the sperm to continue swimming upward. Except for about 24 hours after ovulation, this net is closed at all other times, preventing sperm from entering the uterus.

4. The number of sperm that successfully passes the "level" is about one thousandth during ejaculation. After that, they swim forward at a speed of 2 to 3 mm per minute. This seems so leisurely to humans, but the little sperms are already trying their best to "fly" forward as fast as possible. At this time, there are countless sperms lagging behind: some of them have run out of energy and stopped halfway; some of them have given up long ago due to lack of motivation; some are spinning in place; and some have gone in the wrong direction. The number of sperm that persisted and continued swimming to the end was less than 200.

5. The outer layer of the egg is protected by a transparent film, which makes it look like a beautiful planet suspended in the celestial body. At this time, the sperm, which has passed all kinds of obstacles, finally meets the egg, and the outer membrane of the egg becomes the first hurdle they need to overcome. At this time, the sperms drill their heads into the outer wall of the egg, and their tails keep flapping, while the egg slowly rotates counterclockwise with the movement of the sperm tails.

6. Sperm can survive in the female fallopian tube for 1-3 days, and the egg can survive for about 1 day. If sexual intercourse occurs within a few days before or after a woman's ovulation, the sperm and egg may meet in the ampulla of the fallopian tube. At this time, a group of sperm surround the egg. The capacitated sperm secrete acrosome enzymes from their heads to dissolve the corona radiata and zona pellucida around the egg, opening a path for the sperm to enter the egg. Ultimately, only one sperm enters the egg, while inhibiting the penetration of other sperm. At this point the sperm's head has already drilled in and we can also see its middle part and tail. It's like a constantly rotating drill, driven by the flapping of its tail and striving to enter the egg.

7. After the sperm completely enters the egg, through nuclear fusion, the 23 chromosomes from the father and the mother combine into 46 (23 pairs) chromosomes, and then form a new cell. This cell is called a fertilized egg or pregnant egg, and this process is called fertilization. This is the beginning of a new life. If the chromosomes of the fertilized egg are 46XX, it is a female, and if they are 46XY, it is a male.

8. The fertilized egg undergoes cell division 24 hours after fertilization. The fertilized egg absorbs nutrients and oxygen from the fluid secreted by the fallopian tube and continues to undergo cell division. At the same time, through the peristalsis of the fallopian tube, the fertilized egg gradually moves towards the uterine cavity and reaches the uterine cavity after 3-4 days.

9. 8 days after fertilization. The embryo has landed and is slightly embedded in the endometrium. At this point it divides and develops into several hundred cells. When it arrives at the uterine cavity 3-4 days later, it has developed into a solid cell mass with 12-16 cells, shaped like a mulberry, so it is called a morula, or santa embryo. The morula continues to divide in the uterine cavity, increasing in size and forming cavities and cell fluid. The fertilized egg at this time is called a blastocyst or blastocyst. About 6-8 days after fertilization, the zona pellucida of the blastocyst disappears and enters the endometrium. This process, that is, the implantation of the fertilized egg, is called implantation or implantation. This process takes about 4 to 5 days. The site where the fertilized egg implants is mostly on the posterior wall of the upper part of the uterine cavity, followed by the anterior wall, and occasionally on the side wall. You may feel some slight bleeding when the fertilized egg implants in your uterus. Six weeks after fertilization, the human figure is already vaguely visible. At this time, the embryo's heartbeat is 140-150 beats per minute, which is twice the mother's heartbeat.

10. After the blastocyst implants, its cells continue to differentiate and form three germ layers: ectoderm, mesoderm and endoderm, and accordingly develop into various tissues and organs of the fetus at different gestational weeks. The ectoderm is mainly differentiated into the nervous system, skin epidermis and hair; the mesoderm is mainly differentiated into muscles, bones, blood system, circulatory system and most of the urogenital system; the endoderm is mainly differentiated into epithelial tissue of the digestive system and respiratory system and related glands. 5-8 weeks after menstruation, the fertilized egg develops into an embryo, and then into a fetus after 9 weeks. Fetal appendages such as the placenta are formed partly from the differentiation of blastocyst cells and partly from the differentiation of maternal cells.

11. At this time, the fetus is four and a half months old. He moves his arms and puts his fingers to his lips, which can promote his response to sucking.

Now you know how the egg and sperm come together? It should be said that life is a very strange process, and this process is so beautiful. When the sperm and egg are dating, it actually indicates that a lovely life is about to come.