Also called oogenesis, a ovulogenesis is the process in which the formation of eggs. This process begins before a woman is born, that is, during her embryonic development, around the third month of her intrauterine life.
At the beginning of the fetal stage, the oogonia (2n), precursor cells of female gametes, undergo mitosis, multiplying. After birth, around the third month of life, the oogonia they stop dividing, grow, duplicate their chromosomes and enter meiosis prophase I, when they are called the primary oocytes or oocytes I. You primary oocytes they remain that way until the woman reaches puberty. At birth, the girl already has her primary oocytes formed inside her ovaries, but more than half of them degenerate in a woman's lifetime.
Upon reaching puberty, the girl will have her first period, called menarche, and will have menstrual cycles that last approximately 28 days. In each menstrual cycle, one of the primary oocytes enters the maturation period, remembering that this process will be repeated until the arrival of the
menopause, which is when menstrual cycles definitively stop.During the maturation of the primary oocyte, division I of meiosis ends, forming cells of different sizes, one of which is large, called secondary oocyte or oocyte II (n); and the other small one, called polar body I or first polar globule, which degenerates shortly after its formation.
O secondary oocyte starts the second phase of meiosis, but stops at metaphase II, and then what we call ovulation, in which the secondary oocyte it will be released into the ovary and sent to the fallopian tube. That secondary oocyte that was released is called egg, and your meiosis will be complete only if there is fertilization of the egg fur sperm.
When the secondary oocyte (egg) is not fertilized, it degenerates 24 hours after being released. But when fertilization occurs by a sperm, the secondary oocyte ends the second division of meiosis, with the release of the second polar globule, also called polar body II. As well as the polar body I, Opolar body II also degenerates.
In addition to forming gametes, the ovulogenesis it is also associated with all the hormonal changes that prepare a woman's uterus for a possible pregnancy, and one of them is the thickening of the uterine wall to receive the embryo. If the egg is not fertilized by a sperm, the ovulogenesis does not complete, causing the uterine wall to desquamate, which we call menstruation. If there is fertilization of the egg, menstruation will not occur, and then a pregnancy.
by Paula Louredo
Graduated in Biology