The egg is the cell produced by one of the ovaries of a woman every month and is able to develop into a new organism if it is fertilized by a sperm. The egg consists of a nucleus present in the middle that carries the genetic material and contributes to determining the inherited characteristics. Of the embryo, and surrounding this nucleus the plasma fluid that works to supply the egg with the nutrients needed for its growth, and it is worth noting that the eggs are preserved in follicles of the ovary, and the eggs mature in the follicles in response to the follicle-stimulating hormone . (FSH) produced by the pituitary gland and released in response to luteinizing hormone, or luteinizing hormone (LH), which is produced by the pituitary gland.Also, in a process called ovulation, or ovulation. 
A man releases about a hundred million sperm in every ejaculation, and although an egg needs one sperm to fertilize, the sperm journeyTo the intended organ in the female is an arduous journey during which many sperms die, and that is why the man releases millions of sperms, and the sperm that can penetrate the thick egg shell is the one that fertilizes the egg, and it is worth noting that the natural concentration of male sperm It should be equal to or more than 15 million sperm per milliliter, while the normal volume of semen should be approximately 2 to 6 milliliters per ejaculation, while the normal movement of sperm when taking a sample Of the semen, about 32% of the sperms in it must be able to move forward an hour after ejaculation, and it is also important that the morphology of the sperms is normal, through which the shape, size, and appearance are examined sperm. 
Fertilization of the egg
In order for an egg to be fertilized , the following processes must be completed: 
In order for the egg fertilization to take place, the sperm must be able to push itself and advance in the environment of the vagina and the cervix , and also the sperm must be able to change its shape to penetrate the membrane of the egg, and it is important to be The hormonal environment in the woman's body is ready to receive sperm, and that depends on the timing of the menstrual cycle and the level of hormones at the time, and the best time for fertilization to occur is the time of ovulation, as the mucus secreted in the cervix becomes thinner and less acidic, and this enables the sperm to stay as long as possible for life, And when the sperm can reach the uterusThe contractions of the uterus connect them to the fallopian tube, and in this channel fertilization takes place, and it is worth noting that sperm can survive for up to five days in the female reproductive system. 
The egg travels to the fallopian tube
The movement of the egg begins since the occurrence of ovulation, which is the process of releasing the egg from the ovarian follicle, and cilia at the end of the fallopian tube help to capture the egg, and muscle contractions in the fallopian tube help to move the egg through it, and the process of moving the egg through the tube takes about thirty hours, It is worth mentioning that there are many disorders can be exposed women and affect the function of this channel , which hinders the fertilization of the egg, and examples of these disorders pelvic infections and disease Alantbaz endometriosis . 
The process of fertilization of the egg
The egg can be fertilized by the sperm after ovulation, approximately 12 to 24 hours after the process of ovulation, and in fact fertilization occurs precisely at the point where the ampulla meets the isthmus in the fallopian tube , and it should be noted that the egg spends what It is approximately thirty hours at this point before fertilization occurs, and it is worth noting that only one sperm penetrates the egg due to a transparent membrane that surrounds the egg and contains sperm receptors that make the membrane impermeable after it has been penetrated by The first sperm, and during the process of fertilization and the transfer of the egg in the parts of the fallopian tube, the uterus preparesTo receive the fertilized egg to be implanted in its wall, and for the egg transfer process to succeed through the channel towards the uterus, the fallopian tubes must be healthy Because having any problems in the ducts increases the risk of a woman having an ectopic pregnancy . 
Infertility and risk factors
There are many factors that increase the likelihood that both men and women will become infertile, and among these factors are the following: 
- Age: the fertility of women and men decreases with increasing age. For women, the quality and number of eggs that they produce decreases after reaching the age of thirty-five, and fertility decreases after they reach the age of forty years.
- Weight: Obesity reduces fertility of men and women alike, and severe thinness, especially for women who suffer from eating disorders, reduces fertility.
- Smoking: reduces smoking chances of pregnancy, and reduces the chance to respond to infertility treatments, women smokers are more susceptible to abortion, as well as smoking increases the vulnerability of erection problems in men and reduces the number of sperm.
- Alcohol: Drinking alcohol affects the chances of conception, increases the chances of giving birth to a child with birth defects, reduces the number of sperms and affects their motility.
- ↑ "Ovum" , www.britannica.com , Retrieved 2-12-2017. Edited.
- ↑ "Sperm FAQ" , www.webmd.com , Retrieved 2-12-2017. Edited.
- ^ A b T w "Conception: How To It the Works" , Www.ucsfhealth.org , Retrieved 2-12-2017. Edited.
- ↑ "Infertility" , www.mayoclinic.org , Retrieved 3-12-2017. Edited.