4 Stages of Menstrual Cycle & Ovulation | Biology Blog

                                      Menstruation cycle

Every month females in their life passes through their reproductive cycle. In this cycle, the female prepares itself for a possible pregnancy if the pregnancy not happens then the body aborts all its preparation done for pregnancy and starts again for a possible pregnancy. Generally, this cycle starts when a female attains it’s s puberty stage called Menarche. After a particular age i.e., 40-50 this cycle stops and known as Menopause.           

Duration - generally the duration of this cycle is ideally 28 days but in some cases, its duration extends from 28 to 32.

                                         

Phases -  This cycle completed in four phases -

•       Menstrual Phase
•        Pre - Ovulatory Phase
•         Ovulatory Phase
•          Post-Ovulatory Phase

•  Menustartion Phases -   During days 1-5, a low level of female sex hormone in the body causes the endometrium to disintegrate and its blood vessels to rupture. On day one of the cycle, a flow of blood and tissues, known as the menses, passes out of the vagina during menstruation, also called the menstrual period.
  
  
• Pre- Ovulatory Phase - After the four to five days this phase begins. During this phase, due to the release of some GnRH hormone further and further, the anterior pituitary gland secretes some FSH  to stimulate the development or growth of follicle which mature to form Graffian Follicle. The theca interna also starts to develop. This is called the follicular phase of the ovary.   This follicle starts secreting estrogen hormone, this hormone responsible for the further proliferation of the endometrium.
  
  
• Ovulatory Phase -   The estrogen level increases further and further up to the end of the 10th day, after this,  estrogen hormone give negative feedback to the anterior pituitary to stop secreting further hormone consequences of this is continuously falling in FSH level and also rising of  LH hormone. This rising of LH  concentration in blood is known as  LH surge.  Now LH surge induces rupturing of graffian follicle and releasing of an ovum (Ovulation )on the 14th day of the menstruation cycle.

• Post Ovulatory Phase -   After releasing ovum or secondary oocyte, the graffian follicle starts to degenerate and forms a new structure known as  Corpus Leuteum.  Inside this corpus lutetium a yellow color liquid is formed due to presence lutein pigment. In case of absence of pregnancy, this luteum degenerate after the 14th day of the cycle, and after degenerating this is known as Corpus Albicans( white color liquid) is formed.  Corpus leuteum stimulates due to LH hormone and secrete progesterone and estrogen hormone and now this hormone facilitating the development of the endometrium and endometrium activity for receiving the embryo and its implantation.            Progesterone inhibits the contraction of the uterus so that pregnancy could be maintained. If pregnancy happens then corpus leuteum persist and secretes progesterone hormone. Due to this reason, Progesterone is also known as Pregnancy Hormone.

                          

Menopause -Menopause, is the period in the human life in which the human ovarian and uterine cycle ceases. It has occurred between the age of 45 and 55. The ovaries are no longer secrets estrogen and progesterone. At the onset of menopause, the uterine cycle becomes irregular, but as long as menstruation occurs, it is still possible for women to conceive. Therefore, a woman is usually not considered to have completed menopause until there has been no menstruation for years .

                

Related Links  -

•   Menstruation cycle in Hindi

• Female Reproductive System