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How does LH and FSH cycle throughout the first year of life
- The levels are both high during development and then fall prior to birth
- In the first six months of the babies life the levels go up again, and then fall until puberty
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What are the levels of FSH and LH following puberty
They have monthly surges and then consistently high levels following menopause
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What is the hilum of the ovary
This is the location of Leydig-like androgen producing cells and where the blood vessels enter the ovary
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What is often the cause of an ovarian cyst
- This is when the oocyte is not ovulated, and thus stays in the ovary causing the cyst.
- These are also known as follicular cysts
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By puberty how many oocytes remain
400,000
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What series of hormonal changes take place during female puberty
- Pulsatile release of GnRH
- Increase frequency and amplitude of GnRH pulsations
- GnRH levels eventually evoke LH to trigger ovulation
- First menses
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When is the female done making primordial oocytes
Within the first 2 trimesters of development
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When does the oocyte undergo meiosis I
A few hours before ovulation
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What meiosis phase is the oocyte in at ovulation
Metaphase II (secondary oocyte)
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What regulates the FSH levels of the Graafian follicle
The follicles Estrogen production
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What signals inhibit Pituitary release of FSH and LH
- Follistatin
- Inhibin
- Testosterone
- Estrogen
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What signals trigger the Pituitary to release FSH and LH
- Gonadotropin releasing hormone (GnRH)
- Activin
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Inhibin has what effect where
It down regulates the Release of FSH from the pituitary gland and GnRH from the Hypothalamus
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What signals act on the Hypothalamus effecting GnRH release
- Inhibin (-)
- Dopamine (-)
- Endorphins (-)
- Testosterone (-)
- Estrogen (-)
- Norepinephrine (+)
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How does growth hormone effect puberty
It causes an increase in gonadal function causing them to make estrogen and testosterone
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How does IGF-1 effect puberty
- Increases GnRH secretion
- Increases gonadal function making testosterone and estrogen
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How does Dopamine effect Prolactin secretion
It is a Prolactin inhibitor
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Testosterone is converted to 17ß-estradiol via
Aromatase in the granulosa cells
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Theca cells synthesize and secrete
Testosterone
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LH stimulates Desmolase in
Theca cells
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Desmolase is an important reaction in
Conversion of cholesterol to pregnenolone which eventually is converted to progesterone, estrogen, or testosterone
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What stimulates aromatase in granulosa cells
- FSH
- "Esther stops falling, but falling stimulates Esther"
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Progesterone is made by what cells
- Lutein granulosa cells following ovulation stimulated by LH
- "Progressives stop leuters, but Leuters promote progressives"
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Inhibin is made by what cells
Granulosa cells
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Follistatin has what effects
- Inhibition of activin actions
- Stimulates progesterone synthesis
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What signals dominate in early follicles and mature follicles respectively
- Activin in early follicles
- Inhibin and follistatin in mature follicles
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What is the name of the first 12-13 days of the menstrual cycle
Follicular phase (follicular development)
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How do the levels of FSH compare during a monthly menstrual cycle
- From day 1 to around day 5 the levels gradually increase
- After day 5 to around day 10 they gradually decrease at the same rate as the earlier increase
- Just prior to ovulation the levels rise slightly and then dip to the lowest levels and remain there until the beginning of the next cycle
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Through out the menstrual cycle, how do the LH levels change
The levels are consistently low until a few days before ovulation peaking at ovulation, and then returning to the low levels until the next ovulation
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How do estrogen levels compare through out the menstrual cycle
Level increase from the first day of the cycle and peak just before ovulation, following ovulation the levels fall and then have a slow increase followed by a decrease just before the next cycle
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Through out the menstrual cycle how do progesterone levels compare
The levels are low until after ovulation where they rise, and then drop before the beginning if the next cycle
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What happens in days 13-14 of the menstrual cycle
Ovulation
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What is the last phase of the menstrual cycle
Luteal phase (Corpus luteum is secreting large amounts of progesterone)
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What is the feedback mechanism of the follicular phase
Estrogen has a negative feedback on the pituitary preventing the release of FSH and LH until right before ovulation when it stimulates them
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What is the active feedback mechanism of the Ovulatory phase
Estrogen has a positive feedback on the Anterior pituitary promoting the release of FSH and LH
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What is the feedback mechanism in the Luteal phase
Progesterone having a negative feedback on the pituitary when high
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What effects do FSH and LH have during the Follicular stage
They stimulate the synthesis and secretion of estradiol by follicular cells
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How does estradiol effect the Ovulatory phase
- The levels are risen sharply as a result of the follicular phase making estradiol.
- Once a critical point is reached, instead of a negative feedback, it has a positive feedback on the Pituitary releasing LH and FSH triggering ovulation
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What is found in high amounts 2 days before ovulation
6-10 fold increase in LH, this causes the granulosa cells to secrete progesterone
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What do increased levels of progesterone indicate
Ovulation has taken place
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What happens to estrogen levels before ovulation
The levels begin to fall about a day before ovulation
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During the Ovulation cycle, what effect does the rise in LH cause
It induces prostaglandins thromboxanes, and leukotrienes inducing intrafollicular pressure causing the follicle to burst
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During the Ovulation phase what effect does the FSH surge have
Stimulates plasminogen activator which in turn activates plasmin (this enzyme breaks down the follicular wall)
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How long is the Ovum viable after ovulation
Up to 72 hrs
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Corpus hemorrhagicus
The follicle remaining after ovulation containing hemorrhaging thecal vessels
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Corpus Luteum
Structure in the ovary following the corpus hemorrhagicus, it secretes progesterone
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14 days following ovulation, what causes the corpus luteum to continue to release progesterone
hCG release, indicating pregnancy has taken place
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What happens if pregnancy doesn't occur 14 days following ovulation
Endocrine glands will cause luteolysis, regression of the corpus luteum to corpus albicans
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The proliferation phase of the Endometrial cycle is driven by
Estradiol increasing the thickness of the endometrium
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The secretory phase of the Endometrial cycle is driven by what, having what effect
Progesterone, increasing the vascularity of the endometrium, and the Uterine lining becomes filled with glycogen granules and nutrients
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What happens to the endometrial cycle if fertilization fails to take place
- Progesterone secretion is lowered by corpus luteum
- Endothelium sheds
- Uterine contractions shedding endometrium due to the low Progesterone levels
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When is the highest flow of the menstrual cycle
2nd day
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One of the effects of progesterone on the anterior pituitary is
Inhibition of FSH and LH secretion
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What are the three different types of Estrogen
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What are the three phases of the endometrial cycle
- Menstrual
- Proliferative
- Secretory
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What is the precursor to all of the estrogens
Progesterone
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What is the immediate precursor to Estradiol and Estriol
Testosterone
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What are the effects of Estradiol in respect to preparing for pregnancy
- Inhibit growth of cohort follicles
- Evoke LH surge
- Prepare endometrium for secretory phase
- Induce transport of ovum in fallopian tube
- Alter cervical mucous for optimal sperm transport
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Why is the action of Estrogens, Progestins, and Androgens slow
Because their effects are on the transcription of proteins and the proteins have to be made
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What are the hormonal effects of Menopause
Plasma levels of Estrogen and Progesterone decrease causing a decrease in negative feedback on the pituitary. This results in plasma levels of LH and FSH increase due to the absence of negative feedback
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