Terms: 1, 14, 28, corpus luteum, estradiol, follicular, GnRH, inhibitory, LH sur
ID: 62727 • Letter: T
Question
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 in hormone secretion and follicle/oocyte development that occur roughly every 28 days in the 'typical' woman. The ovarian cycle can broadly be divided into 3 sequential phases, the first, or _____________ phase which precedes or comes before release of the egg, the middle or ____________ phase during which the egg is actually released, and the final or _______________ phase which comes after the egg is released and lasts until the next cycle begins.
Day 1 of the follicular phase marks the beginning of a new cycle. During the follicular phase, as the name implies, a 'cohort' or small group of follicles (i.e. the structures in the ovary in which the oocytes are maturing) begin to grow, develop and prepare their oocytes for release in response to FSH stimulation from the anterior pituitary. These follicles are the main hormone-secreting structures in the ovary and the main hormone they are secreting is ____________. Early in the phase, when estrogen levels are low, the estrogen exerts ____________feedback control on the hypothalamic-pituitary axis and keep GnRH, LH and FSH levels relatively low. Eventually, a single follicle assumes dominance, outgrows and out develops the others, and begins to secrete larger and larger amounts of estrogen. When estrogen levels become sufficiently high, estrogen's effect at the hypothalamus becomes transiently ______________, causing increases in GnRH secretion that trigger a mid-cycle _______________.
Right around mid-cycle or around day _________ of the 'typical' __________ day long cycle, under the influence of high levels of LH produced by the LH surge, the wall of the dominant follicle thins and eventually ruptures, releasing the egg. This release of the egg is termed ovulation, hence the portion of the cycle immediately preceding and including ovulation is termed the ovulatory phase. Another effect of LH is that it luteinizes the follicle, producing changes in the follicle cells that enable the granulosa cells to secrete ____________ in addition to estratiol.
The final phase of the ovarian cycle, the luteal phase, begins immediately after ovulation and lasts until day 1 of the next cycle. The luteal phase is characterize by the presence and functioning of a _____________. This is the name for the structure that develops from the follicle after it has lost its egg. The remainder of the follicle involutes or falls in upon itself, becomes highly vascularized and its luteinized' cells secrete high concentrations of progesterone in addition to estradiol. The progesterone exerts an overriding inhibitory effect on hypothalamic __________ secretion at this time. In the absence of pregnancy, the CL will remain highly active for ~12 days before it __________, or begins to die off and cease its hormone-secreting activities. CL regression causes a rapid drop in the concentrations of estrogen and progesterone secretion over the next 2 days that will result in shedding of the endometrial lining of the uterus and menstruation. Day 1 of menstruation coincides with and serves as the external indicator that day _________ of a new ovarian cycle has begun.
Explanation / Answer
The ovarian cycle refers to the recurrent, cyclic changes in hormone secretion and follicle/oocyte development that occur roughly every 28 days in the 'typical' woman. The ovarian cycle can broadly be divided into 3 sequential phases, the first, or Follicular_ phase which precedes or comes before release of the egg, the middle or _Ovulatory_ phase during which the egg is actually released, and the final or _Leutal phase which comes after the egg is released and lasts until the next cycle begins.
Day 1 of the follicular phase marks the beginning of a new cycle. During the follicular phase, as the name implies, a 'cohort' or small group of follicles (i.e. the structures in the ovary in which the oocytes are maturing) begin to grow, develop and prepare their oocytes for release in response to FSH stimulation from the anterior pituitary. These follicles are the main hormone-secreting structures in the ovary and the main hormone they are secreting is Estradiol_. Early in the phase, when estrogen levels are low, the estrogen exerts Stimulatory__feedback control on the hypothalamic-pituitary axis and keep GnRH, LH and FSH levels relatively low. Eventually, a single follicle assumes dominance, outgrows and out develops the others, and begins to secrete larger and larger amounts of estrogen. When estrogen levels become sufficiently high, estrogen's effect at the hypothalamus becomes transiently _Inhibitory_, causing increases in GnRH secretion that trigger a mid-cycle __ LH Surge __.
Right around mid-cycle or around day 14 of the 'typical' _1__ day long cycle, under the influence of high levels of LH produced by the LH surge, the wall of the dominant follicle thins and eventually ruptures, releasing the egg. This release of the egg is termed ovulation, hence the portion of the cycle immediately preceding and including ovulation is termed the ovulatory phase. Another effect of LH is that it luteinizes the follicle, producing changes in the follicle cells that enable the granulosa cells to secrete _Progesterone_ in addition to estratiol.
The final phase of the ovarian cycle, the luteal phase, begins immediately after ovulation and lasts until day 1 of the next cycle. The luteal phase is characterize by the presence and functioning of a corpus luteum. This is the name for the structure that develops from the follicle after it has lost its egg. The remainder of the follicle involutes or falls in upon itself, becomes highly vascularized and its luteinized' cells secrete high concentrations of progesterone in addition to estradiol. The progesterone exerts an overriding inhibitory effect on hypothalamic _GnRH_ secretion at this time. In the absence of pregnancy, the CL will remain highly active for ~12 days before it _Reresses_, or begins to die off and cease its hormone-secreting activities. CL regression causes a rapid drop in the concentrations of estrogen and progesterone secretion over the next 2 days that will result in shedding of the endometrial lining of the uterus and menstruation. Day 1 of menstruation coincides with and serves as the external indicator that day 28 of a new ovarian cycle has begun.
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