Obstetrics and Gynaecology Flashcards
Explain the menstrual hormonal axis?
- Hypothalmus secrets GnRH
- GnRH acts on anterior pituitary to secrete FSH
- FSH recruits ovarian follicles to grow
- Growing ovarian follicles secrete ostrogen and inhibin A –> negative feedback to inhibit FSH release
- One follicle becomes dominant follicle ( Graffian follicle) - remaining follicles decrease as FSH level decrease
- Ostreogen levels peak day before LH surge
- High levels of oestrogren create a postive feedback
- –> small release of FSH which induces large surge of LH
- LH Surge induces ovulation
- Corpus leutuem forms to produce progesterone –> inhibits effects of ostrogen
What does the corpus leutuem form from?
Remainder of the dominant follicle
What prevents continued LH surge during pregnancy?
Corpus leutuem producing progesterone
(Inhibits LH)
What are the phases of the menstrual cycle?
Which one may change in length, and which one is static?
Normal cycles: 21-35 days
Follicular phase: Accounts for most variability in length
Luteal phase: 14-15 days
How long is the follicular phase?
Day 1 of bleeding to LH surge
What produces ostrogen?
Granulosa cells of follicles
Ostrogen produced inhibits FSH via negative feedback
How is the Graafian follicle selected?
- Graafian follicle will have higher sensitivity FSH receptors
- Will produce more ostrogen than other follicles
- Suppresses FSH to other follicles, therefore suppresses their growth
Explain the endometrial changes on day 1 -4 of the menstrual cycle?
- Abscence of pregnancy leads to regression of the corpus leuteum (no LH to maintain it)
- Progesterone concentration decrease cause vasospam of spiral arteries
- Ischaemia and sloughing of endometrium
Explain the endometrial changes from day 4 -14?
- Growing follicles secrete oestrogen, stimulates growth and proliferation of endometrial lining
How do granulosa cells secrete oestrogen?
- Surrounding thecca cells have LH receptors - binding of LH secretes oestrogen precursor
- Granulosa cells ave FSH receptors - binding of FSH secrete aromatase
- Aromatase converts oestrogen precursor into oestrgoen
What is the histology of the endometrium during the follicular phase?
- Proliferation of endometrial epithelial cells (cells show high mitotic activity)
- Endometrial glands are straight, tubular, and lined by simple columnar epithelium.
- Stromal cells start to divide, enlarge, and accumulate glycogen.
- Uterine spiral arteries start to regenerate and extend two-thirds of the way into the endometrium.
How does the graafian follicle release the ova at day 14? And how does the follicle become the corpus leuteum?
Follicle ruptures releasing the ova following day 14 LH surge
Granulosa cells of the Graafian follicle secrete LH receptors
LH surge on day 14 transforms follicle into corpus leutuem
Thecca cells produce progesterone and granulosa cells produce Inhibin A - inhibits FSH production from pituitary
Why does the corpus leuteum regress if there is no pregnancy?
Corpus leuteum is requires trophic effect to maintain itself
It requires LH’s trophic effect for its growth - however LH is inhibited by progesterone
During pregnancy corpus leuteum requires Beta- HCG for it to maintain itself
What does the word trophic mean?
An endocrine needing the stimulation of another endocrine gland
How the release of GnRH change from before and after puberty?
Before puberty: GnRH release in steady manner
After: GnRH released in pusatile manner
What is the structure of a follicle cell?
Primary oocyte surrounded granulosa cells, with an outer layer of theca cells
How does the pituitary secrete LH on day 14?
Graafian follicle has been secrete oestrgen
Oestrogen levels peak a day 13 and sensitise pituitary to GnRH
Pulsatile GnRH acts as a postive feedback causing a lot of FSH and LH to be secreted on day 14
Explain what happens if fertilisation does not occur?
- Progesterone levels fall, as the corpus leuteum cannot be maintained
- Corpus leuteum becomes the corpus albicans (a white scar that doesn’t secrete homrone)
- Spiral arteries collapse in the endometrium and lining is sloughed off
What is primary dysmenorrhea?
Recurrent lower abdominal pain shortly before or during menstruation (in the absence of pathologic findings that could account for those symptoms)
What is the pathophysiological mechanism behind primary dysmenhorrhea?
increased endometrial prostaglandin (PGF2 alpha) production → vasoconstriction/ischemia and stronger, sustained uterine contractions
What are caused of secondary dysmenorrhea?
Endometriosis
Pelvic inflammatory disease (PID)
Intrauterine device (IUD)
Uterine leiomyoma
Adenomyosis
Psychological factors
What is primary amennorhea?
Abscence of periods at age of 15 or older
What is the aetiology of ammenorrhea?
Patients with normal puberty
Anatomical anomalies: (Uterine septum, hymenal atresia)
Competitive sports ( suppresses hypothalamus/pituitary)
Patients with growth delay and developmental delay
Hypogonadism (hypergonadotrophic gonadism or hypogonadotrophic gonadism)
Patients with virulisation
PCOS
Congenital adrenal hyperplasia
What is secondary amennorrhea?
Absence of menses for more than 3 months (in women with previously regular cycles) or 6 months (in women with previously irregular cycles)
