Question

The female ovarian cycle is divided into two stages. What are they called and what is occurring during each stage?

Answer 1

Female ovarian cycle undergoes formation and development of the ovarian follicles throughout ,consists of two stages- follicular phase and luteal phase.

Follicular phase - In this stage the follicular go through maturation stages, and enters into the phase of releasing egg .The secretion of follicle stimulating hormones (FSH) from the anterior pituitary stimulates the formation of Graafian follicles .FSH tend to trigger the proliferation of granulosa cells in follicles and LH receptors on the surface of the granulosa cells. Thus, causes secretion of estrogen hormone.Increased amount of the estrogen stimulates the GnRH to release the LH hormones and triggers the angrodrogen release from the thecal cells ,it causes the proliferation differentiation and secretion of follicular thecal cells and helps in elevation of expression of the LH receptor displaying on granulosa cells. Therefore, increase level of estrogen causes growth of endometrium, myometrium lining of the uterus and also helps in increasing progesterone receptors. This is followed by the estrogen surge and LH surge continues to the ovulation process.During LH surge ,first meiotic division of oocytes completes and promotes the luteinization of the thecal and granulosa cells.

Luteal phase- It is the final phase of ovarian cycle . In this phase anterior pituitary gland releases FSH and LH acts on the dominant ovarain follicles and forms the corpus luteum, once corpus luteum is produced ,starts secreting progesterone.Increased progesterone acts to adrenals and triggers the estrogen secretion .,suppresses the release of FSH and LH from the pituitary. In certain time , FSH nad LH secretion decreases ,causes the corpus luteum to regress.Thus , secretion of progesterone also fall causes menstruation to begin.Bit when fertilization occurs, the outer layer of blastocyst (syncytiotrophoblast) produces human chorionic gonadotrophin (hCG) functions similarly like lH and mainatins the growth of corpus luteum and corpus luteum continue to produce progesterone in order to maintain the new pregnancy.