chapter 28 lecture eight is on hormonal regulation the female reproductive cycle has two separate cycles within it it includes both the ovarian cycle in which the oocyte is produced as well as the uterine cycle that prepares the uterus for implantation of the fertilized eggs hormones a complex series of hormonal changes regulates these two cycles and as well as cyclical changes that occur in the breast and in the cervix the ovarian cycle as i said is changes in the ovary and the uterine cycle prepares the endometrium and if implantation doesn't occur then the stratum functionalis is shed it starts with gonadotropin releasing hormone that's secreted by the hypothalamus that stimulates the release of follicle stimulating hormone and luteinizing hormone just like we saw in the male reproductive system here though follicle stimulating hormone is going to initiate the growth of the follicles and that's pretty easy to remember because that's what it's saying it does the follicles themselves secrete estrogen and estrogen helps to maintain the reproductive organs luteinizing hormone is what stimulates ovulation it also promotes the formation of the corpus luteum remember there's the corpus following ovulation there's the corpus hemorrhagicum or the bloody body and then the corpus luteum or the yellow body and that is going to secrete estrogens progesterone relaxin and in heaven until fertilization takes place in which case the growing embryo the placenta is going to start secreting the hormones to help maintain the pregnancy if fertilization doesn't occur then the corpus luteum degenerates into scar tissue and stops secreting the estrogens and progesterone and menstruation occurs so progesterone helps to get the uterus ready for implantation it also works in the mammary glands relaxin facilitates implantation in the relaxed uterus and relaxin also helps storing labor it helps to cause the pubic symphysis to spread a bit uh the joint there inhibin inhibits the secretion follicle stimulating hormone if you're pregnant already you don't want to get pregnant while you're pregnant so inhibit prevents follicle stimulating hormone from causing new follicles to develop while pregnancy is ongoing there are we talked about estrogen as though we're just one hormone but there's actually at least six different ones and three that are found in significant quantities are beta estradiol estrone and estriol so here we have the gonadotropin releasing hormone stimulating follicle stimulating hormone luteinizing hormone from the anterior pituitary from the gonadotrophes so the follicle stimulating hormone is going to work on um helping the follicles to grow and also um helping the follicles secrete estrogens and inhibits the luteinizing hormone stimulates ovulation and also development of the corpus luteum estrogens are important because they like testosterone increase protein anabolism they also like testosterone are going to help with the development the maintenance the female secondary sexual characteristics uh they help to lower blood cholesterol and many times women find that they aren't women aren't as susceptible to developing heart disease until after they go through menopause when their estrogen levels decline moderate levels of estrogens also inhibit release of gonadotropin releasing hormone follicle stimulating hormone and luteinizing hormone progesterone progesterone works with estrogens to get the endometrium ready for implantation the mammary glands discrete milk and also inhibits release of gonadotropin releasing hormone and luteinizing hormone relaxin is going to inhibit contraction of uterine smooth muscle and make it easier for the fertilization plant in the tissue and during labor it increases the flexibility the pubic symphysis also is involved in dilation of the cervix inhibin is going to inhibit release follicle stimulating hormone so here you can see at the top we have the ovarian cycle the bottom the menstrual cycle so here we have the primordial follicles that develop into the primary follicles and then every month we're going to have some follicles that are going to start to develop these are going to then produce the estrogens when they mature you have a graffian follicle and then ovulation occurs and we have the corpus hemorrhagicum which becomes the corpus luteum that secretes progesterone and estrogens a fertilization doesn't occur and this doesn't get a feedback signal from the embryo then it degenerates into scar tissue and that's the corpus albicans as far as the menstrual cycle is concerned at the same time the menstrual cycle always starts with the first day of the menstrual period so as the tissue is sloughing off and here we have those spiral arteries and they're leaking blood um we get back down to uh where there it's mainly the stratum basalis just a little bit of functionalism above it then we go into the preovulatory phase where it proliferates and the tissue grows in preparation of implantation and about the time of ovulation it's almost it has almost achieved the growth of the tissue that it eventually will then there's the secretory phase that or the post-ovulatory phase and if implantation doesn't occur then menstruation happens and the tissues shed and the process happens again estrogens as i said are important for secondary sex characteristics for muscle protein anabolism strong bones lower blood cholesterol and progesterone works with them um i talked about relaxing and inhibin and here you can see the um patterns of these different hormones during the cycle so most women have a 28-day menstrual cycle and so this is starting with the process of menstruation and then as it's building up ovulation happens when there's a peak in the luteinizing hormone and luteinizing hormone then declines so it only has one peak estrogens have two peaks they peak right around the time of ovulation and then again um prior to the process of menstruation it's the declining levels of progesterone that actually cause menstruation to happen and some women who don't have problem conceiving that have a hard time maintaining the pregnancy quite often it's they've low progesterone levels and if the progesterone levels are too low then that endometrial tissue slops off and with it the implanted embryo