Menstruation and Pregnancy Flashcards
(39 cards)
What is oestrogen followed by?
Progesterone (sequence of steroid action) - it cannot act without the production of oestrogen
What does the corpus luteum produce?
Oestrogen and progesterone - only responds to LH for a week then the corpus luteum changes and the 2 hormones decline (menstruation)
What is menstruation?
Shedding of superficial layer (functionalis) of endometrium.
Withdrawal of sex steroid support leads to:
vasoconstriction
-tissue hypoxia
-connective tissue breakdown
-fragmentation
What factors control blood loss locally?
Coagulation factors
What prevents menstruation?
Exogenous supply of steroid (e.g. contraceptive)
What is endometriosis?
Tissue escapes through the Fallopian tube instead of cervix and vagina. Associated with infertility
What is Eutopic endometrium?
Tissue in the right place
What is Ectopic endometrium?
Tissue in the wrong place
How does endometriosis arise?
Reflux menstruation - endometrial tissue fragments shed at menses passing through the fallopian tube, then becoming established in ectopic sites.
The lesions continue to cycle under hormonal control but are not lost at menstruation
Alternatively it may arise de novo from progenitor cells in ectopic tissues
How can endometriosis be treated?
Surgery can be used to remove lesions
Also treated with pain medication (NSAID).
Or by blocking pharmacologically the hormone cycle:
- Aromatase inhibitor - aromatase catalyses formation of oestrogens
- Combined oral steroid contraceptive
- Gonadotropin-releasing hormone (GnRH) modulators
When does pre-implantation take place?
Occurs as embryo moves down fallopian tube
What is the Blastocyst stage?
Embryonic stage in which implantation in the womb takes place - uterus has to be receptive (steroid hormones on endometrium create receptivity)
What happens when the embryo attaches to the surface cells of the endometrium?
Implants interstitially (under the surface) - then develops in the tissue environment for the rest of pregnancy
When is the receptive phase?
About 7 days after LH peak (36 hours before ovulation) the endometrium is receptive to an embryo. (days 7 - 10)
Less likely during the increasing days as steroid hormone levels are decreasing and leading towards menstruation
What is hCG?
Human chorionic gonadotrophin. (polypeptide hormone) - the compound that rescues the corpus luteum (after LH) - so progesterone continues to rise (as well as oestrogen)
What produces hCG?
The placenta produces hCG from the hatched blastocyst stage onwards
How is hCG used for pregnancy testing?
Found in maternal blood and urine soon after implantation
Once corpus luteum starts to degenerate can you reverse it?
NO - if hCG comes in too late - the receptive phase closes
What happens to hCG levels in pregnancy?
Levels peak at around week 8/9 then decline (not fully)
What regulates the rate of transport of the egg/embryo through the fallopian tube?
progesterone. It also:
- prepares the uterus to receive the implanting blastocyst
- sustains the uterine lining (endometrium) throughout pregnancy
- inhibits myometrial contractility – suppress contractions until the end of pregnancy
What is the luteoplacental endocrine switch?
At 7-9 weeks, the placenta takes over the production of oestrogen and progesterone from the corpus luteum (has a limited lifespan)
What produces steroid hormones in pregnancy?
Fetal-placental unit
Explain the steroid hormones during pregnancy when cholesterol is imported to the placenta.
Cholesterol is imported into the placenta, then converted to progesterone. The progesterone then goes to the fetus and is converted into androgens. The androgens then go back to placenta where they are converted to oestrogens which are released into maternal blood
When is pregnancy described as viable?
When heart pulsations can be visualised within gestation sac
Transvaginally: 5 weeks post LMP
Transabdominally: 6 weeks post LMP
(LMP = last menstrual period)
