Terms: 1, 14, 28, corpus luteum, estradiol, follicular,GnRH, inhibitory, LH surge, luteal, ovulatory, progesterone,regresses, stimulatory
The ovarian cycle refers to the recurrent, cyclic changes inhormone secretion and follicle/oocyte development that occurroughly every 28 days in the 'typical' woman. The ovarian cycle canbroadly be divided into 3 sequential phases, the first, or_____________ phase which precedes or comes before release of theegg, the middle or ____________ phase during which the egg isactually released, and the final or _______________ phase whichcomes after the egg is released and lasts until the next cyclebegins.
Day 1 of the follicular phase marks the beginning of a newcycle. During the follicular phase, as the name implies, a 'cohort'or small group of follicles (i.e. the structures in the ovary inwhich the oocytes are maturing) begin to grow, develop and preparetheir oocytes for release in response to FSH stimulation from theanterior pituitary. These follicles are the main hormone-secretingstructures in the ovary and the main hormone they are secreting is____________. Early in the phase, when estrogen levels are low, theestrogen exerts ____________feedback control on thehypothalamic-pituitary axis and keep GnRH, LH and FSH levelsrelatively low. Eventually, a single follicle assumes dominance,outgrows and out develops the others, and begins to secrete largerand larger amounts of estrogen. When estrogen levels becomesufficiently high, estrogen's effect at the hypothalamus becomestransiently ______________, causing increases in GnRH secretionthat trigger a mid-cycle _______________.
Right around mid-cycle or around day _________ of the 'typical'__________ day long cycle, under the influence of high levels of LHproduced by the LH surge, the wall of the dominant follicle thinsand eventually ruptures, releasing the egg. This release of the eggis termed ovulation, hence the portion of the cycle immediatelypreceding and including ovulation is termed the ovulatory phase.Another effect of LH is that it luteinizes the follicle, producingchanges in the follicle cells that enable the granulosa cells tosecrete ____________ in addition to estratiol.
The final phase of the ovarian cycle, the luteal phase, beginsimmediately after ovulation and lasts until day 1 of the nextcycle. The luteal phase is characterize by the presence andfunctioning of a _____________. This is the name for the structurethat develops from the follicle after it has lost its egg. Theremainder of the follicle involutes or falls in upon itself,becomes highly vascularized and its luteinized' cells secrete highconcentrations of progesterone in addition to estradiol. Theprogesterone exerts an overriding inhibitory effect on hypothalamic__________ secretion at this time. In the absence of pregnancy, theCL will remain highly active for ~12 days before it __________, orbegins to die off and cease its hormone-secreting activities. CLregression causes a rapid drop in the concentrations of estrogenand progesterone secretion over the next 2 days that will result inshedding of the endometrial lining of the uterus and menstruation.Day 1 of menstruation coincides with and serves as the externalindicator that day _________ of a new ovarian cycle has begun.
