Menstrual cycle Flashcards
What is the purpose of the menstrual cycle?
generate oocyte
facilitate fertilisation
optimise endometrium for implantation
protect developing embryo
On what day does ovulation occur?
14
On what days does the follicular phase take place? (thinking about the cycle from the follicular perspective)
1-14
follicle generation takes place
On what days does the luteal phase take place?
thinking about the cycle from the follicular perspective
14-28
formation and degradation of corpus luteum takes place
What are days 1-5 of the menstrual cycle known as (from an endometrial perspective)?
Menstrual phase
What are days 5-14 of the menstrual cycle known as (from an endometrial perspective)?
Proliferative phase
What are days 14-28 of the menstrual cycle known as (from an endometrial perspective)?
secretory phase
What are the prominent hormones produced in follicular phase?
FSH - pituitary
oestrogen - ovary
What are the prominent hormones produced in luteal phase?
LH - pituitary
progesterone - ovary
What does HPO stand for?
hypothalamo-pituitary-ovarian
axis
What is the main oestrogen that is important during 1)reproduction, 2) pregnancy and 3) post menopause?
1) estradial (E2)
2) E3
3) E1
What are the different ways the cycle can be broken down in to phases?
From the follicular perspective: follicular phase (days 1-14) luteal phase (days 14-28)
From the endometrial perspective: menstrual phase (days 1-5) Proliferative phase (days 5-14) Secretory phase (days 14-28)
How is the menstrual cycle controlled?
Hypothalamo-pituitary-ovarian axis
What hormone, important to the menstrual cycle, is released by the hypothalamus?
GnRH
What hormones, important to the menstrual cycle, are released by the anterior pituitary?
FSH and LH
How does the GnRH effect the menstrual cycle?
stimulates anterior pituitary gland to produce FSH and LH
How do FSH and LH effect the menstrual cycle?
stimulate ovary to produce oestrogen
How does oestrogen effect the hypothalamus and the anterior pituitary gland? What is the exception to this?
negative feedback, causes reduced release of GnRH, FSH and LH
On day 14 (ovulation), very high levels of E2, which cause v. high levels of LH (triggering ovulation)
What is important about the way GnRH is released?
Hourly pulses - v. important
How is GnRh transported to pituitary?
hypophyseal portal blood system
What can cause alteration of GnRH secretion?
bereavement anxiety time zone day/night duty exercise weight loss/gain
What factors can alter the menstrual cycle?
bereavement anxiety time zone day/night duty exercise weight loss/gain
What hormone, important in reproduction (but especially birth), is produced in the posterior pituitary gland?
oxytocin
What cells in the anterior pituitary gland produce FSH and LH?
basophils
What does FSH do in the menstrual cycle?
Stimulates follicular activity - promotes estradiol (oestrogen) production from granulose cells
What does LH do in the menstrual cycle?
triggers release of egg from dominant follicle
promotes development of corpus luteum and production of progesterone
What happens when oestrogen levels peak on day 14/mid-cycle?
High E2 levels = surge in LH = ovulation
What happens to the follicle in the menstrual cycle?
develops and matures in ovary, released during ovulation,
becomes corpus luteum
degenerates if not fertilised
1) primordial follicle
2) primary/preantral follicle
3) secondary/antral follicle
4) preovulatory follicle
5) ovulation
What happens to the corpus luteum post-ovulation, if no fertilisation has taken place?
degenerates/fibroses to become corpus albicans
What is the endometrium?
Lining of uterus
What happens to the endometrium in the proliferative phase? What hormone causes this?
Endometrium thickens (by ovulation 2-3mm thick)
Increase stroll cells
Increased glands, blood cells
E2
Roughly how thick is the endometrium by ovulation?
2-3mm
What happens to endometrium in secretory phase? Which hormone is dominant?
Increased secretion
Increased lipid and glycogen
Increased blood supply
Endometrium 4-6mm thick
OPTIMAL CONDITIONS FOR IMPLANTATION OF FERTILISED EGG: STABLE, VASCULAR AND NUTRIENT-RICH
Progesterone
Roughly how thick is the endometrium during secretory phase?
4-6mm
What occurs in menstruation?
LH levels fall
Corpus lutes collapses
progesterone withdrawal = menstruation begins
vasodilation
necrotic outer layers of endometrium separate from uterus
separated tissue and blood initiate uterine contractions
expel contents
How does a follicle reach the fallopian tube?
released by ovary, collected by fallopian tube by chemotaxis
Where is mucus produced?
cervix - columnar glands
What is the consistency of cervical mucus around ovulation? How does this facilitate conception?
Stringy and runny (spinnbarkeit)
Facilitates sperm access during ovulation - the consistency changes after this, to prevent infection
What is the consistency of cervical mucus in the luteal phase? How does this facilitate pregnancy?
Tenacious and inelastic
prevents microbial ingress - protects developing embryo
critical to pregnancy - mucus plug
How can a malformed mucus plug effect pregnancy? What can cause this?
Can lead to miscarriage and pre-term birth
surgery or other problem that has damaged endothelial lining of cervix
Between what days are you at most risk of getting pregnant?
7-21
Actually a very wide period of time where risk of pregnancy is high.
RHYTHM METHOD OF CONTRACEPTION DOES NOT WORK
What does the combined oral contraceptive contain?
Estradiol
Progestogen (synthetic progesterone)
how does the COCP effect the menstrual cycle to prevent pregnancy?
Steady (but higher) levels of oestrogen and progesterone
inhibit GnRH/FSH/LH
prevent ovulation
thin endometrium
tenacious mucus
When is the worst time to forget to take pill?
at the beginning or end of 3 week cycle - extends time with no cover, therefore time for GnRH/FSH/LH levels to rise again
How are eggs collected in IVF?
Superovulation
How is super ovulation induced in IVF?
daily injections of recombinant FSH
