2.2 Flashcards
Describe the duration of the menstrual cycle. Why is their variation?
21-35 days
Variation in length of follicular phase.
What are the three phases of the menstrual ccle
Follicular
Preovuatory
Luteal
Describe the follicular phase. How long?
Preparation of the gamete (ovarian cycle).
Preparation of the endometrium (uterine cycle).
Stimulate development of a follicle in the ovary.
Uterus prepared for sped transport and implantation.
12-14 days long.
Describe the pre-ovulatory phase
LH surge stimulates ovulation
Brief period of fertility (36 hours)
Formation of corpus luteum
Describe the luteal phase.
How long?
LH maintains the corpus luteum in th eovary
Waiting to see if there is a pregnancy.
14 days.
Give the changes occurring in the repro tract in the follicular phase due to rising oestrogen.
Fallopian tube
- Stimulates secretion and muscular contraction and growth of motile cilia.
Myometrium:
- Stimualtes growth and motility
Endometrium
- Increased thickness
- Secretes watery fluid conductive to sperm
Stimulates secretion of cervical mucus
Vaginal epithlium proliferates
Mildly anabolic
Give the effects of progesterone on oestrogen primed cells in the luteal phase.
Fallopian tube:
Reduced motility, secretion and cilia activity.
Myometrium:
Further thickening
Redcued motility
Endometrium:
Stimulates further thickening
Increased secretion
Spiral arteries develop
Cervical mucus
Thickening and acidification
Inhibits sperm transport
Mildly catabolic
Raised body temp
What happens following the sudden fall in progesterone and oestrogen in the luteal phase.
Secretory epithelium of endometrium collapse.
Apoptotic cell death
Dead tissue sheds as menstrual bleed
Spiral arteries contract to reduce bleeding.
Give the hormonal changes in the early follicular phase.
Relatively high FSH/LH
Low but rising oestrogen
Very low progesterone
Give the hormonal changes in the late follicular phase.
FSH falls
LH rises
Oestrogen levels rise dramatically.
Give the hormonal changes during ovulation.
Rise in oestrogen is followed by LH surge.
Give the hormonal changes in the early luteal phase.
FSH and LH low
Rising oestrogen and progesterone.
Give the hormonal changes in the late luteal phase.
FSH and LH low
Oestrogen and progesterone are high with progesterone higher.
Give the hormonal changes at the end of the luteal phase.
Progesterone then oestrogen falls.
Menstruation begins.
Draw a graph of the endometrial and hormonal changes through the menstrual cycle.
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When is the menstrual cycle deemed to begin?
First day of menstrual bleeding, through this is physiologically the end of the previous cycle.
What are the hormone levels at the beginning of the cycle?
Oe, Pro, In low
GnRH secretion is released from inhibition.
LH and FSH rise.
FSH more so as released from selective inhibition by inhibin.
What are the actions of gonaotrophins in the follicular phase?
FSH binds to granulosa cells
Follicular development continues.
Theca intern appears.
Follicle now capable of oestrogen secretion.
Oestrogen and inhbin secretion rises.
FSH secretion is selectively inhibited by inhibit.
Rising oestrogen leads to GnRH stimulation and hence LH secretion.
LH continues to stimulate follicular development.
What happens 12-14 days into the cycle?
Oestrogen and ihibin rise rapidly.
Oestrogen production no longer dependent on FSH.
Positive feedback of oestrogen stimulates LH surge.
This produces ovulation.
Describe ovulation
Oestrogen falls dramatically.
Corpus luteum forms
Pogesterone production begins
Granulosa cells become unresponsive to LH
Meiosis I completes and Meiosis II starts.
Mature oocyte extruded.
What happens after ovulation?
LH promotes oestrogen and progesteron secretion from the corpus luteum in large quantities.
Inhibin is still produced.
LH is now suppressed because of negative feedback and presence of progesterone.
As corpus luteum grows, more steroids are produced.
Rising oestrogen does not cause LH/GnRH surge due to rising progesterone.
Waiting phase.
What happens if there is no pregnancy after the luteal phase? How long after luteal phase?
14 days Corpus luteum regresses spontaneously. P and O levels fall Triggers menstrual bleed. Relieves inhibition of GnRH, FSH and LH, triggering development of new follicles.
What happens after the luteal phase if there is a pregnancy?
hCG released by placenta prevents corpus luteum regression:
Continues to secrete O and P
Supports early weeks of pregnancy. (After 12, placenta takes over)
Maintains the suppression of ovarian cycle.
How long does it take from ovulation to menses?
14 days
