Female Physiology Flashcards
What is the average length of menstrual cycle
28 days
What is the effect of moderate to low oestrogen levels on the HPG axis
Negative feedback on the HPG axis
What is the effect of high levels of oestrogen on the HPG axis
Positive feedback on the HPG axis
What is the effect of oestrogen in the presence of progesterone on the HPG axis
Negative feedback
What is the effect of inhibin at the HPG axis
Negative feedback on FSH from anterior pituitary only
Where is GnRH released from
Hypothalamus
What does GnRH stimulate the release of from where
FSH and LH from the anterior pituitary gland
Where do FSH and LH primarily act on
Ovaries
What causes ovulation
Surge in LH
What day roughly does ovulation occur
Day 14
Where does fertilisation occur
In the uterine tubes
what does the follicles develop into after ovulation
Corpus luteum
what is the function of the corpus luteum
Produces oestrogen and progesterone to maintain the endometrium for fertilisation and implantation
What happens to the corpus luteum in the absence of fertilisation
It spontaneously regresses
And there is a sig. fall in hormones
No more hormones to maintain the endometrium
Internal lining sheds
What happens to the corpus luteum if fertilisaiton does occur
The embryo produces bHCG exerting a luteal effect on the corpus luteum
Thus maintaining the corpus luteum
They reciprocally stimulate each other to keep producing hormones and maintaining the endometrium
What causes the surge in LH
Dominant follicle continuously producing oestrogen
Oestrogen levels eventually rise high enough
To exert positive feedback on the HPG axis
This is reflected in LH levels
Causing a surge in LH
What happens at the start of the follicular phase
There is little ovarian hormone production and the follicles begins to develop independently
What causes only one follicles to mature
As follicles mature oestrogen levels rise to moderate levels
This exerts negative feedback and FSH levels fall
This means only 1 follicles can survive (only enough FSH levels for one follicle)
What do the other follicles that do not survive form
Polar bodies
Which hormone dominates the follicular phase
Oestrogen
Which hormone dominates the luteal phase
progesterone
What marks the beginning of a new menstrual cycle
Menstruation
How long does menstruation last
Typically between 2-7 days
How much blood is lost in menstruation
10-80ml
