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IBDP Biology- Hormones for menstrual cycle

Topic 6- Hormones associated with the menstrual cycle

· IBDP BIOLOGY,IB,menstrual cycle

How do hormones contribute towards the female menstrual cycle? Well, in this IBDP Biology Blog post, we will explore in detail the main hormones that are responsible for it and the different phases that it takes to complete one whole cycle!

Menstrual cycle hormones 

  • Pituitary hormones 

(FSH and LH) released from anterior pituitary gland; acts on the ovaries to develop follicles

  • Ovarian hormones

 (oestrogen and progesterone) released from the ovaries; act on the uterus to prepare of pregnancy

FSH: stimulates follicular growth in ovaries, stimulates oestrogen secretion from develping follicles

LH: surge causes ovulation, results in the formation of corpus luteum

Oestrogen: thickens uterine lining (endometrium), inhibits FSH and LH for most of cycle, stimulates FSH and LH release pre-ovulation

Progesterone: thickens uterine lining (endometrium), Inhibits FSH and LH 

Menstrual cycle phases

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1. Follicular Phase: 

  • FSH secreted from AP; growth of ovarian follicles
  • Dominant follicle produces oestrogen inhibiting FSH secretion (negative feedback)
  • Oestrogen acts on the uterus to stimulate thickening of endometrial

2. Ovulation

  • Day 12: oestrogen stimulates AP to secrete hormones (positive feedback)
  • Large surge of LH and less FSH
  • LH cause dominate follicles to rupture and release egg 

3. Luteal Phase

  • Ruptured follicle develops into a slowly degenerating corpus luteum
  • This secretes high levels of progesterone and lowers levels of oestrogen
  • Oestrogen and progesterone act on uterus to thicken endometrial lining (preparing for preg); these two inhibit secretion of FSH and LH preventing follicles from developing

4. Menstruation

  • If fertilisation occurs, the developing embryo will implant in endometrium and release hormones to sustain corpus luteum
  • If fertilisation doesnt occur, the corpus luteum degenerates; oestrogen and progesteron levels drop; endometrial layer shed into menstrual blood; oestrogen and progesterone levels low to inhibit the anterior pituitary and cycle begins again 

That's all for the menstrual cycle!

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References:

  • https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.nagwa.com%2Fen%2Flessons%2F607135742101%2F&psig=AOvVaw0ozEuJNtUQr6BstiJAKkeH&ust=1626348072569000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCNjDk4S54vECFQAAAAAdAAAAABAa

Drafted by Venetia (Biology)

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