Pregnancy – natural natural process. There is an opinion that there are no two identical pregnancies even at the same woman. Course of pregnancies, maybe, and a miscellaneous, and all of them here begin always and at all it is identical.
Instruction
1. Any pregnancy begins with maturing of reproductive cages: at women ova cyclically ripen, men have continuously spermatozoa. These processes are called an ovogenesis and a spermatogenesis respectively. Feature of gametes is existence in their kernel of vague set of chromosomes that leads to the fact that at merge of two such cages the zygote already with a usual set of chromosomes (46 chromosomes) is formed.
2. After maturing of gametes, conditions for a meeting of men's and female gametes, that is conceptions are necessary. Such conditions is directly sexual intercourse which apogee will be a men's ejaculation. After that the men's gametes supplied with special tails make the way on a genital tract of the woman to an ovum which waits for spermatozoa in one of two uterine tubes.
3. After merge of an ovum and one spermatozoon there is a sex determination of future child: it depends on existence in a spermatozoon of the chromosome which is responsible for a floor. If at merge the zygote with a set of chromosomes XX was formed, the girl will be born and if HU – the boy. At the same time ova always bear only the X chromosomes.
4. Further the ovum begins to share (process of crushing or formation of a mnogokletochnost), the blastocyst which slowly goes down on a uterine fallopian tube in a uterus is formed and for the seventh or tenth day it is attached to a wall of a uterus (implantation). This period is called preimplatatsionny. At the same time the uterus is also preparing for acceptance of the impregnated ovum: all that time which ripens a gamete in a female body on walls of a uterus accrues a special vystilka – endometrium which is ideal substrate for providing all necessary the new formed organism.
5. Pregnancy conditionally is divided into three stages – a trimester. In the first trimester lasting 12 weeks (embryonic period) there is an intensive formation and laying of all future bodies and parts of a body of a fruit (organogenesis) and also there is a formation of new body in mother's organism – placentae (afterbirth) which will feed and protect pregnancy, existing until exile of a fruit from a womb of mother (platsentation).
6. The formed germ on appearance does not remind the baby, only gradually, by the beginning of the fetal period (since the beginning of the 11th week), it will gain the lines similar to the newborn. For now the embryonic period lasts, the embryo will have branchiate arches, a tail, branchiate cracks, allantois.