Female reproduction Flashcards
What are the components of the HPG axis?
Hypothalamus
Anterior pituitary gland
Gonads (Ovaries or testes)
What hormones are produced by the ovaries?
Oestrogen
Progesterone
What are the 3 main forms of oestrogen?
Oestrone - Menopause
Oestrodiol - Reproductive
Oestriol - Pregnancy
What affect does oestrogen and progesterone have on the hypothalamus and anterior pituitary?
They can both stimulate or inhibit hormone production from them, forming the axis
How is GnRH released from the hypothalamus in females?
From neurones in a pulsatile manner
The frequency of pulses then corresponds to the hormones produced by the pituitary
How does GnRH pulse frequency affect pituitary secretion?
Increased frequency ⇒ Increased LH levels
Decreased frequency ⇒ Increased FSH
How does oestrogen increase GnRH pulsatility?
Oestrogen increases pulsatility,
How does progesterone affect GnRH pulsatility?
Progesterone decreases pulsatility
How do oestrogen and progesterone affect GnRH pulsatility, when GnRH neurones do not contain their receptors?
They interact with receptor on kisspeptin hormones, which then go on the activate the neurones
How long is the average menstrual cycle?
28 days
What are the 2 main phases of the menstrual cycle?
- Follicular (Proliferative) Phase
- Luteal (Secretory) phase
Which of the 2 menstrual stages is most variable in length?
Follicular, lasting 14 days, but varying by around 7 days either side
Describe the changes in hormones during the follicular phase of the menstrual cycle
- GnRH stimulates LH and FSH release
- Follicular phase causes increase of FSH
- FSH stimulates oestrogen release from ovarian follicles
- Oestrogen causes decrease of FSH
- Oestrogen also stimulates LH surge
- LH surge leads to ovulation
On what day of the menstrual cycle is ovulation?
14 days
Describe the changes in hormones during the luteal phase of the menstrual cycle
- LH surge also leads to corpus luteum formation
- This produces progesterone
- Progesterone decreases LH
- Lack of pregnancy causes cessation of progesterone release from corpus luteum, causing period
How long does bleeding usually last in the menstrual cycle?
<7 days