2.2 - the menstrual cycle Flashcards
what is the reproductive cycle?
a series of physiological changes surrounding ovulation
what is the purpose of the first phase of the cycle?
ovaries, reproductive tract and other systems are prepared for ovulation, to maximise the chance of fertilisation
what is ovulation usually followed by? why?
followed by a phase of waiting as the conceptus is initially too small to signal its presence
what happens during the phase of waiting following ovulation (should fertilisation occur)?
waiting for a chemical signal from the developing placenta during which physiological changes occur in preparation for a potential pregnancy
what happens if there is no chemical signal from the developing placenta?
the cycle ends and a new menstrual cycle begins
what is the initial phase of a menstrual cycle known as?
follicular / proliferative phase
what is the waiting phase known as?
luteal / secretory phase
what are the events of each phase co-ordinated by?
gonadotrophins and gonadal steroids
when is the menstrual cycle deemed to begin?
on the first day of menstrual bleeding
physiologically the end of the previous cycle (bleed out uterus lining from previous cycle)
how long is the follicular phase?
12-14 days
how long is the luteal phase?
14 days
what is the early follicular phase characterised by?
relatively high titres of FSH + LH
low but rising titres of oestradiol, and very low titres of progesterone
what happens later in the follicular phase?
FSH falls
LH rises
oestrogen rises dramatically
what is the rise in oestrogen followed by?
LH surge + ovulation
what happens in early luteal phase?
FSH and LH levels are low,
with rising titres of oestradiol + progesterone
