Ovulation Cycle
The ovulation cycle refers to the menstrual cycle. It symbolizes the fertility of a woman. This cycle starts at the beginning of the teenage years mostly. The ovulation cycle is under the control of the endocrine system. It is necessary for reproductions. It is counted from the first day of menstrual bleeding and is divided into three stages.
Stage I
The first stage of ovulation cycle is the follicular phase. It is also known as the proliferative phase since the uterus proliferates due to the release of estrogen. In the follicular phase the body secretes estrogen. Estrogen thickens the wall of the uterus. The hormone follicle stimulating hormone is secreted during the first few days of the cycle, this hormone stimulates the ovarian follicles. These follicles are present in females since birth. During the years before the menses, these follicles are in a fierce competition with each other for complete domination. Due to the effect of certain hormones only one of the ovarian follicles will be allowed to dominate and grow to maturity. This follicle is known as the graffian or tertiary follicle. This follicle forms the ovum. As the follicle grows, they secrete increased amount of estrogen. The estrogen initiates the formation of the layer called endometrium in the uterus. This hormone also stimulates the production of the cervical mucous in the cervix.
Stage II
The second stage of the ovulation cycle is the ovulation phase. During this phase, the hormone LH is released around the twelfth day and it keeps on increasing in the system for the next forty eight hours. This hormone takes the egg to maturity. It also causes the weakening of the follicle walls in the ovary. This results in the egg being released by the matured follicle. The egg is then known as the secondary oocyte. The secondary oocyte matures into an ootid and then matures into an ovum. The mature ovum nears a diameter of 0.2mm. The ovary that the ovum ends up in is purely by chance, there is no fix co ordinate system navigating the ovum into the ovaries. Sometimes two ovums are released and thus both ovaries are then filled by an ovum. If in that case both ovaries are matured the result would be fraternal twins. Once the egg leaves the ovary it is taken by fimbria (present at the end of fallopian tube) into the fallopian tube. If the egg is not fertilized in a day the egg will disintegrate and dissolve into the fallopian tube.
Stage III
The third phase is the Luteal phase. It is also known as the secretory phase. In this phase a major role is played by the corpus luteum. This is a solid body formed by the fallopian tube when an egg is released from it. This body continues to grow after the egg is ejected. It is this body that forms progesterone. Progesterone prepares the uterus for an implantation of a zygote. It also causes the woman’s body temperature to rise. After ovulation, the FSH and LH cause the remaining fallopian tube to disintegrate and become a part of the corpus luteum. With increased progesterone level there is increased estrogen level too. The hormones produced by corpus luteum block the production of FSH and LH. These hormones are needed by the corpus luteum to maintain itself. Once the progesterone level falls, the corpus luteum breaks down and menstruation is triggered.