What are the 3 main phases in the menstrual cycle?
1 Answer
In fact, there are 4 phases of human female menstrual cycle which happens one after another but as you have mentioned
- Follicular phase or proliferative phase
- Luteal or secretory phase
- Menstrual phase
(One being skipped i.e ovulation phase)
Explanation:
Follicular Phase or Proliferative phase:
- Anterior lobe of pituitary gland releases
#FSH# (follicle stimulating hormone) at the start of puberty. - This hormone stimulates the development of several primary follicles.
- Only one of these follicles continue to grow with its primary oocyte.
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The remaining follicles break down by degenerative process called follicle atresia.
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FSH stimulates the ovary to produce estrogen hormone.
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Estrogen stimulates the endometrium(tissue lining inner wall of uterus) and vascularizes it.
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High level of estrogen inhibits the secretion of FSH from pituitary gland.
{Decrease of FSH and increase of estrogen stimulates the pituitary gland to secrete luteinising hormone
Luteal phase or Secretory Phase:
- The follicle cells ruptured in follicle atresia form a special structure called corpus luteum. It is a yellowish grandular structure.
- Corpus luteum starts secreting progesterone.
- Progesterone further develops the endometrium and make it receptive for the implantation of zygote. Now if the fertilization occurs then the implantation of zygote take place . And if it does not occur then last phase of female reproductive cycle starts i.e mensturation.
Menstural Phase:
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In this phase, corpus luteum starts degenerating and thus secretion if progesterone is also reduced.
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Now endometrium has no supporting effect of progesterone. Consequently endometrium starts to breakdown.
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This starts the discharge of cell debris and blood through vagina which is known as menstruation.
Hope it helps...