The Menstural Cycle Flashcards
What are some of the factors involved in control of the menstrual cycle?
Gondatoprins- acting on the ovaru
Ovarian steriods- acting on the tissues of the reproductive tract
What are the features at the start of the menstural cycle?
There is no ovarian hormone production as little follicle devlepoment, there are low steriod and inhbin levels, and there is little inhibition of the hypothalmus or the anterior pituarity,
What are the effects of FSH in the early menstural cycle?
FSH binds to the granulosa cells, follicular development continues, the theca interna appears, and the follicle is now capable of oestrogen secretion and inhibin secretion also begins
What happens in the mid follicular phase?
There needs to be nomination of a dominant follicle, so follicular osetrogen is now at the concentration where it can exert postive feeback at the hypothalmus and anterior pituarity, gonadtorpin levels rise but LH only due to the presence of inhibin- meaning that there is selective ihibition of FSH production at the pituarity,
What happens in preparation for ovulation?
Circulating oestorgen and inhibin rise rapidlly, with oestrogen no longer dependant on FSH and there is a surge in LH production, and progesterone produciton begins as the granulosa cells become responsive to lH
What happens at ovulation?
Mesosis I completes and then Meosis II starts, and the mature oocyte is extruded through the capulse of the ovary
What are the affects of LH after ovualtion>
After ovulation the follicle is leutisined and therefore secretes oestrogen and progeseterone in large amounts, but LH is now suppressed due to negative feedback from the progesterone
What is the length of the leuteal phase?
14 days
What happens at the end of the mensutral cycle?
In the absence of a futher rise in LH, the corpus letueum regressed, and there is a dramatic fall in gondal hormones, which releives the negative feedback and allows everything to reset to the start
What happens if fertilisation occurs?
Synctiotrophoblast produces human chronoic gonadotropin, and this exerts a leutinising effect, and the maintaince of the corpus leuteum is vital to the success of gestatiom.
How does the phemonom of menstruation occur?
An endometiral event triggered by the loss of progesterone from the corpus letuem, and there is creation of endometrial ischmiam, and the promotion of endometrial sloughing
What are the roles of oestrogen in the follicular phase?
Fallopian tube function, thickening of the endometirum, growth and motility of the myometrium, thin alkaline cerivcal mucus, vaginal changes, changes in skin and hair metabloism
What are the roles of progesterone in the luteal phase?
Futher thickeing of the endometrium in a secretory form, and there is the thickeing of the myometrium but a reduction in the motility, thick acid cervical mucus, chnages in mammary tissue, and increased body temperature and metabolic and electryolte changes
What is the normal length of a menstruatl cycle and which part of the menstrual cycle is prone to variation?
The normal length is 21-35 days, and variations in the cycle are due to variations in the follicular phase
