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Menstrual Cycle 2


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Name 3 changes that occur when female child matures to adult
1. development of secondary sex characteristics
2. growth spurt
3. achievement of fertility
what is adrenarche and when does it occur?
regeneration of zona reticularis in adrenal cortex and production of androgens.

between ages of 6 and 8 yrs
what is gonadarche and when does it occur?
pulsatile GnRH secretion from hypothalamus is increased -> pulsatile secretion of LH and FSH from anterior pituitary -> ovary stimulation and estrogen release

around age 8
does gonadarche lead to any phenotypic changes?
not at first. initially, hormonal changes occur during sleep. eventually, LH and FSH pulsatility lasts throughout the day, leading to ovary stimulation and estrogen releases
what is thelarche and when does it happen?
breast development

begins at 10 yrs
what is pubarche and when does it happen?
pubic and axillary hair growth

11.2 yrs
when does peak height velocity or maximal growth occur?
12 yrs
when does menarche occur?
13 yrs
on average how much time elapses from breast bud development to menarche?
2.5 yrs
what are the 3 hormones produced as a result of adrenarche?
1. dehydroepiandrosterone sulfate (DHEAS)
2. dehydroepiandosterone (DHEA)
3. androstenedione
what is the first phenotypic sign of puberty and when does it occur?
breast bud development, or thelarche, at around 10yrs
what causes thelarche?
increased estrogen circulation
usually, what comes first, thelarche or pubarche?
usually thelarche, but the reverse order is a normal variant
what is a likely cause of peak height velocity?
estrogen, leading to increased levels of growth hormone and somatomedin-C
how long after menarche does the menstrual cycle become regular?
about 2 years later
what 4endocrine structures are involved in maintaining the menstrual cycle?
1. hypothalamus
2. pituitary
3. ovaries
4. uterus
what are the 2 phases of the menstrual cycle that describe changes in the ovary?
1. follicular phase
2. luteal phase
what are the 2 phases of the menstrual cycle that describe changes in the endometrium?
1. proliferative phase
2. secretory phase
big picture: what happens during follicular phase?
FSH from pituitary -> development of primary ovarian follicle -> follicle makes estrogen -> estrogen causes uterine lining to proliferate
on day 14, LH spike leads to what?
LH stimulates ovulation, the release of ovum from follicle
when does luteal phase start?
after ovulation
remnants of follicle left behind in ovary is called what? what does it do?
corpus luteum

secretes progesterone to maintain endometrial lining in preparation to receive ovum
what does progesterone do during the menstrual cycle?
Progesterone Prepares
lining to receive ovum
what happens in absence of fertilization?
corpus luteum degenerates and progesterone levels fall
what is menstruation and what triggers it?
endometrial lining is sloughed off in response to low progesterone
FSH release from pituitary signals beginning of menstrual cycle. what causes FSH release?
withdrawal of estrogen and progesterone during luteal phase of prior cycle
what does FSH at beginning of cycle actually do?
stimulates growth of 5-15 primordial follicles, initiating the follicular phase
how is estrogen introduced into the cycle?
one primordial follicle becomes dominant and starts maturing; the developing follicle produces estrogen
what is the role of estrogen in the menstrual cycle?
estrogen enhances follicular maturation and increases production of LH and FSH receptors in an autocrine fashion; LH also rises, stimulating the synthesis of androgens, which are converted back to estrogen
rising estrogen provides negative feedback on FSH production by the pituitary. how is the dominant follicle protected from the FSH drop?
increase number of FSH receptors
what signals the end of the follicular phase and start of luteal phase?
rise in estrogen to critical level -> LH spike from anterior pituitary -> LH spike leads to ovulation
how much time is available for fertilization before ovum degenerates?
fertilization must occur within 24 hrs of ovulation
how long does it take released ovum to pass into fallopian tube and then into uterus?
3 to 4 days
what cells of the follicle become the corpus luteum?
granulosa and theca interna cells
what does the corpus luteum make?
estrogen and lots of progesterone
specifically, how does progesterone affect teh endometrium?
becomes more glandular and secretory to prepare for implantation of fertilized ovum
good way to remember roles of estrogen and progesterone?
Estrogen Enlarges Endometrium
Progesterone Prepares it
if there is fertilization, how is the corpus luteum kept functional?
upon fertilization, developing trophoblast makes human chorionic gonadotropin (HCG), a glycoprotein similar to LH, to maintain the corpus luteum
when does the placenta start making its own estrogen and progesterone to maintain the endometrium?
at 8 to 10 weeks gestation
what hormone negatively feeds back on pituitary FSH production?
how long does it take the corpus luteum to degenerate?
about 14 days
estrogen production by the corpus luteum is a two cell, two step process. explain.
theca interna cells produce androstenedione in response to LH

granulosa cells convert androstenedione to estradiol in response to FSH

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