Fertilization is the union of a woman’s egg with male sperm cell to create many – zygote – a new life opens.At the height of ejaculation, male penis into the vagina and poured the lead, together with his sperm. Overall, this is a milky seminal fluid contains about 300 million sperm. However, there are 99% of the volume (1-5 ml) of fluid from accessory glands, prostate glands, such as sperm. These provision in the main function of sperm motility, survival food supply to support acidic environment of the vagina.
FecondazioneDopo ejaculation, the many millions of sperm for fertilization begin a long journey in search of eggs, embedded in one of the two fallopian tubes (the tube connecting the ovary to the uterus). This trip pretty hard, so that sent the vast majority of the male gametes, even before a glimpse of the coveted goal. Among the first obstacles on this road, remember confined in the cervical mucus, uterus, the traps for a sustainable network less negative immature seed morphology. Saliva is less hostile to the days before ovulation and the horse that is convenient for the fertilization.
Sperm, mucus escapes to continue climbing to the uterus, followed by entry into the pipe. E calculated with the proportions right, the rate of the seeds will be the same, that the man who provided 55-hour kilometers. In fact, the very small size, their speed is relatively low, about 15 cm per hour (the uterus is about 6 – m 9 cm and 10 cm tubes).
Normally, fertilization occurs on the same day as the egg from the follicle (around the 14th day of the ovarian cycle of the canonical four-week release). Oocyte maturation, in fact, survived up to 24 hours after his release. However, stored sperm from a man who was four days in endometrial lights gradually from there to the tube. Fertilization usually takes place in its distal part, ie short term ovary.
During fertilization brings the game millions of sperm to fertilize an egg can only. The second fact is protected – even if only briefly – a layer of cells called the corona radiata. After passing the first hurdle, the sperm is a different, much harder glycoprotein barrier represented by the zona pellucida. To the seed enzymes nell acrosoma relatively high, limited bladder stab the top of their heads. This process, known as the acrosome reaction, so that digging a narrow channel, the sperm for fertilization. As already mentioned, it is only right, the first seeds oocyte completes the attack. The merger of the two cell membranes is very important because:
to complete, encouraged the distribution of the second meiotic oocyte.
Has been designed so that the nucleus of the egg and sperm fuse with his own;
Employment of a chemical reaction, called cortical reaction that prevents fertilization by other sperms (polyspermy occurs).
EU raises the grain of the new so-called zygote, 46 chromosomes, 23 of them inherited from the father, the sperm cell egg from which the mother of the 23 Zygote then faces a long list of mitotic division, which began again on his way to the uterus, which are hidden in a week. Continuation of embryonic development is described in this article: embryonic development of the embryo after fertilization. What we want to stress that sexual reproduction, as in humans and many other higher organisms, the new information network linking maternal and paternal chromosomes among the millions possible. It explains why the nature of each of us unique, reinforcing the gender, because it leads to the base of natural selection, organisms that suitable better with the drawing process as a particular environment. Such signs, due to inherent small random mutations are inherited, that is the true offspring through sexual fertilization.
SOURCE : http://healthcarecan.com/fertilization.html
0 comments: