BISC 307L 1st Edition Lecture 21 Current Lecture Endocrine Events of Ovarian and Menstrual Cycles o o o o o First row and third row show changes in important hormones in ovarian cycle 1 28 days Second row and fourth row are pictures of what the follicle look like Hormonal changes Two halves 1 Follicular Phase first 14 days dominated by events going on in the follicle day 1 onset of menstruation Estrogen In first few days levels of estrogen are falling because its been coming from the corpus luteum and now that is degenerating stops falling and begins to increase because the follicle is growing positive feedback secreting more estrogen In particular there are 6 10 follicles that move on to this second phase at the time when the hormone levels are appropriate but usually only one follicle are ovulating in humans one grows more than the others in rare cases two ovulate fraternal twins ovulation injures the follicle so the dip in estrodiol is due to ovulation as corpus luteum secretes estrogen is increases and progesterone also increases only secreted by the corpus luteum corpus luteum has fixed lifespan unless it has support regresses after 10 days as corpus luteum regresses then levels of estrogen and progesterone fall Inhibin secreted by granulosa cells so it has the same progression as estrogen Menarchy is the beginning of reproductive cycling in girls Menarchy menopause 2 Luteal phase dominated by the corpus luteum Menopause The supply of follicles become reduced not enough competent follicles left to do this not secreting estrogen and progesterone because the tissues needed are not there lack of negative feedback suppression of gonadotropins are high Estrogen supports secondary sex characteristics so this is lost Hormone replacement therapy can reduce these changes risk of cancer Bottom part endometrium Sensitive to estrogen and progesterone so it will grow and differentiate in response to those hormones At end levels of progesterone and estrogen are falling and the endometrium has grown thick but now the levels of these gonadotropins are falling so the endometrium starts to degenerating by necrosis murdered since vascularized by blood vessels that like to vasoconstrict and this is stimulated by prostaglandins tissue then dies prevented by estrogen and progesterone Prostaglandins go down as tissue dies and vasoconstriction relaxes menstruationbleeding Prostaglandins also causes menstrual cramps myometrial tissue constricting This whole thing lasts 3 5 days first 5 days Proliferative phase o Follows menstrual phase o In response to the rising levels of estrogen the endometrium doubles in thickness and there are more glands which secrete glycogen rich mucus uterine milk energy source for the zygote should fertilization occur after fertilization before implantation o Cervical mucus plug changes consistency so that it is less viscous and sticky and more watery and its pH becomes less acidic for sperm to enter designed to get you pregnant Secretory phase o Endometrium growth slows but gland and vascularization increases o Meanwhile the high levels of estrogen are producing other changes in the breasts and mammary tissue grows o Pigmentation of nipple gets darker o If pregnancy occurs these changes will continue in preparation for lactation o If not then the changes will go back to the way it was Endometriosis o Affects 5 10 of women o The occurrence of endometrial tissue in abnormal and ectopic locations other abdominal pelvis locations like on the ovary or on the outside of the uterus o These changes in hormones that cause the growth of endometrium affects these places too o Associated with pain which ranges from mild to very severe why not clear causes pressure on other organs and pain nerves can also attract sensory nerves if large enough o Tends to be worse during the times when the hormone levels are high and the endometrium is growing o Cause isn t known genetic most likely o How this happens Retrograde menstruation endometrium lines oviducts and fallopian tubes and when the lumen of the uterus fills with this debris it normally goes out the vagina but sometimes it may squirt out the oviduct and end up in the abdomen o Occurs in most women but usually the immune system will kill this tissue but in some this does not happen o Theory that this did not happen in ancestors because women did not live that long o Associated with a certain type of cancer o Cigarette smoking decreases risk lowers estrogen and progesterone levels Fertilization and Implantation o o Fertilization Occurs in the outer third of the oviduct called the ampulla The cilia take up the egg into the oviduct where it is fertilized How long can the oocyte live without being fertilized 12 24 hours Sperm can last about 4 6 days in the oviduct Means that the period of potential fertilization is about 6 days before ovulation and 1 day after Sperm After ejaculation which occurs in the vagina The sperm appear in the oviduct about 30 minute after being expelled into the vagina prostaglandins in the semen stimulate smooth muscle contraction and relaxation of the muscle that pinches the opening of the cervix so the sperm can make it through and get sloshed around and are spread in the lumen of the uterus and the oviducts and enough get into the upper third of the oviduct at least 1000 The viability of the sperm and their concentration has to be high because they have to make it all that way Changes in sperm 1 Capacitation o Sperm in semen is not capable of fertilizing anything so it acquires the ability to fertilize triggered by something in the uterus o Become more motile o Acrosome becomes primed for release 2 Activation o Chemicals on the surface of the granulosa cells trigger activation when the sperm get close to the egg o They start burrowing and being active and aggressive o Make it so that the sperm plasma membrane can bind to corresponding receptors on the egg oocyte o Important that only one sperm penetrates the egg otherwise its called polyspermy o What prevents polyspermy Depolarization 1 Fast block that spreads from one side to the other 2 Fertilization membrane granules on the outer cortex of the egg are secreted around the space and swell and push the granulosa cells out of the way and therefore the rest of the sperm are pushed out of the way Days 2 4 After fertilization starts dividing and form morula All stays in the oviduct Delay between fertilization and release into the uterus is necessary for