Reproductive Physiology Flashcards
gonad
generic term refering to the reproductive organs of both genders
germ cells
cells that produce gametes
what type of regulation cycle is used by most primates
menstrual cycles
estrous cycles
variable reproductive cycles such as going into heat or a rut
menstrual cycle
the periodic release of an egg from the ovary to a prepared uterus, and the shedding of the uterine lining if the egg is not fertilized
what are the two key componenets of a menstrual cycle
- release of generally one egg
- growth and maturation of the uterine lining
define menarche
what is the average age?
the range?
the onset of menstration
12.8
9-15.5
what is the length and standard deviation of a normal menstrual period?
28 +/- 3 days
what is the mean for the onset of menopause? the range
51
35-65
four functions of the hypothalamus
- temperature control
- hunger
- thirst
- pituitary stimulation
what happens if the anterior pituitary is stimulated by the hypothalamus?
what happens if there is no communication between the hypothalamus and anterior pituitary
the anterior pituitary will secrete the appropriate hormones for its stimulation
prolactin will be produced because there will be no inhibiting factors from the hypothalamus
what stops the anterior pituitary from secreting large amounts of prolactin
inhibition from dopamine produced in the hypothalamus
arcuate nucleus
a collection of neurons that produce GnRH in the hypothalamus
what was Knobils experiment
he removed the arctuate nucleus from monkeys and gave them endogenous GnRH to see how the they would respond to differently levels
what were two important early discoveries from Knobils experiment
- when the arctuate nucleus was removed prolactin stayed high
- increasly high doses of GnRH only increased LH levels to a certain amount before they dropped off
why did the monkeys in Knobils experiment stop producing LH despite increasing levels of GnRH
the target cells downregulated their receptor production because there was too much GnRH
what were three final conclusions from Knobils experiments
- the ovary and production of steroids are most important to menstruation
- GnRH is secreted in pulses
- constant GnRH will cause down regulation of receptors
knowing the effect of GnRH what are twoclinical applications
- GnRH infusing pumps to stimulate the ovaries
- Downregulation of GnRH receptors
what effect can clinical down regulation of GnRH receptors have
reversible menopause or andropause
Lupron
a GnRH agonist that will bind to receptors and stop the release of sex hormones
what drives the rhythm of the menstrual cycle
maturation of the follicle and oocyte
how does the hypothalamus regulate ovarian function (2examples)
provides fine tuning in response to environment by increasing or decreasing amplitude and frequency of GnRH pulses (sick or starving)
when do women make primary oocytes and primordial follicles?
prior to birth
what happens when a woman has no more eggs
menopause
what are the three steps in the life cycle of a follicle
- resting phase
- active phase
- ovulation or death
what determines the activation of a follicle
it is a spontaneous daily event that happens with no known contributatory factors
what four actions signal follicle activation
- flattened granulosa cells becoming cuboidal
- proliferation of granulosa
- formation of the zona pelucida
- growth of the oocyte
what are the three phases of the ovarian cycle
- follicular
- ovulation
- luteal
what three events happen in the follicular phase
- menses
- follicle recruitment
- selection of the dominant follicle
when is FSH the highest during the follicular phase? when does it decrease?
FSH is the highest during menses, decreasing during follicle recruiment
what happens hormonally during ovulation
there is a surge in LH
what three events happen during the luteal phase
- progesterone production
- corpus luteum apoptosis
- Luteal rescue by HCG
what are the general time periods for the follicular phase, ovulation, and the luteal phase of the menstrual cycle
- follicular phase: day 1-14
- ovulation: day 14
- luteal phase: day 14-28
if follicles are activated every day, what happens to the activated follicles?
they die unless in the follicular phase (FSH is present)
what hormone allows for follicular growth
FSH
Follicle cohort
all of the recently activated follicules stimulated by FSH
T/F the size of the follicular cohort varies with age
true
what two hormones are secreted by growing follicles?
what is their effect on menstruation
estradiol and inhibin B
decrease production of FSH by through negative feedback at the hypothalamus and anterior pituitary
what stops more follicles from growing during the follicular phase
estradiol and inhibin B decease the amount of FSH, which slows follicular growth
what are the four states of a follicle
- primordial
- preantral
- antral
- preovulatory
FSH is needed to progess between what two follicular states?
preantral and antral
T/F preovulatory follicles can be seen under a microscope
true
how is the “leading follicle” chosen from the follicle cohort?
how does the criteria change as the mother ages
the follicle that tolerates the decline in FSH is considered the leading follicle
younger mothers select the fittest follicle, older mothers select the first follicle that is activated
describe the hormonal process during menstruation (6)
- FSH stimulates the production of follicles
- follicles produce estrodiol and inhibit to decrease FSH
- high estradiol produces an LH surge which triggers ovulation within 38 hours
- follicle remains form the corpus luteum which produces progesterone
- fertilized egg produces HCG which saves the corpus luteum
- without fertilization estrogen and progesterone decrease and lead to menstruation
what hormones are produced by theca cells in response to LH?
what how are these hormones altered by granulosa cells stimulated by FSH
androsteinedione and testosterone
aromatized into esterone and estradiol
can estrogen be converted back into testosterone
no, they are converted by one way enzymes
what two factors allow a follicle to become the “dominant follicle”
- increased number of FSH receptors
- increased vascularity
what happens when extrogenous FSH is given during selection of the dominant follicle?
when might this be useful
more follicles survive the selection phase to ovulate
IVF to harvest more eggs
how much estradiol needs to be present for ovulation to occur
200 picograms/mL for 24 hrs
how long does the LH surge during ovulation lasat
48-50 hours
what are three specific responses to the LH surge during ovulation
- resumption of meosis with the expulsion of the 1st polar body
- release of collagenase and prostaglandins to weaken follicle wall
- follicular rupture
what will a mature oocyte look like on microscopy
a single large cell surrounded by cumulus cells
what is a denuded oocyte? how can one be made?
a oocyte with all the cumulus cells stripped away by pipetting or enzymes, leaving only the zona pellucida
ovum pickup
the process by which a ovulated mature oocyte is released by the ovaries and picked up by the fallopian tubes
where does ovum pick up occur
in the “pouch” formed by the peritoneum between the bladder and the anterior wall of the uterus
what are the three major events of the luteal phase
- progesterone production
- corpus luteum death without a fertilized egg
- CL saved by HCG produced by a fertilized egg
why is 28 days a normal cycle?
because it takes 14 days for a oocyte to mature, and 14 more days before the corpus luteum dies so the cycle can restart
what type of tissue makes up most of the uterus
smooth muscle
what hormone causes proliferation of the endometrium
estradiol
what is the effect of progesterone on prolferative endometrium
switches cells from hypertrophy to secretion to stop growth and supply nutrients for a fertilized egg
what is HCG?
what produces it?
human chorionic gonadotropin
a fertilized embyro implanted into the uterus
how is it possible that a sperm can enter the fallopian tubes within one hour of sexual intercourse
there are cillia that beat and help it move
what are three descriptors of normal cervical mucosa
- scant
- thick
- cloudy
what is cervical mucosa like around ovulation
copius, clear, and supportive
what causes the change in cervical mucosa throughout the menstrual cycle
estradiol
what are three functions of the fallopian mucosa
- produce suppportive secretions for the egg and sperm
- help the egg and sperm move
what happpens one a sperm penetrates an egg?
why is this relevant
cortical granules inside the egg release their contents to harden the egg
it is unlikely that one sperm would fertilize one ovum, so it prevents polyspermia
syngamy
the fusion of two cells, in our case to produce a zygote
how long after syngamy will the first mitotic division take place
24 hours
under microscopy a zygote appears to have three protonuclei
what does that mean
polyspermia
what is totipotency?
why is a relevant?
the ability for any cell from a blastocyst to produce a fetus
blastomeres can be removed for genetic testing
at what point does an embryo lose totipotency
when it enters the uterus 5 days after ovulation
what happens 6 days after ovulation
“hatching” when the blastocyst breaks out of the zona pellucida
what is the state of the embryo 7 days after fertilization
it should be implanted on the uterus
what is the hormonal cause of spotting during early pregnancy
as the corpus luteum dies the placent takes over producing progestrone, and sometimes there is too much of a decrease
statistically speaking older mothers are less likely to carry to term and more likely to produce a fetus with birth defects
why?
because older eggs are less capable
what happens to an older mother who is fertilized with older eggs
she has a success rate higher than she would using her own eggs
how does male endocrine control differ from female
FSH acts on the testes to stimulate sperm production
LH stimulates secretion of androgens
what are the negative feedback mechanisms that control male endocrine function
inhibin from sertoli cells reduces FSH
increased circulating testosterone decreases LH
estrogen aromatized from testosterone deceases FSH
what cells in the testes secrete testosterone
leydig cells
list the androgens from least to most potent
dihydroepiandrosterone, androstenedione, testosterone
what is testosterone converted into
dihydrotestosterone
what is the enzyme that converts testosterone into DHT
5 alpha reductase
what is the key andogren for skin and prostate
DHT
what are 3 specific effects of androgens
- hair thickening and darkening on the face, pubic, and axilla
- muscle growth and maintenance
- vocal cord changes
what is the function of the sertoli cells
secrete androgen binding protein to keep levels of testosterone between the cells high where it can act on developing spermatocytes
what two hormones are secreted by sertoli cells
- androgen binding hormone
- mullerian inhibiting hormone
how do sperm cells develop as they move toward the lumen of seminiferrous tubules
spermatogonium –> primary spermatocyte –> secondary spermatocyte –> spermatids –> spermatozoa
what three things are needed for sperm production (what do they do)
- FSH (sertoli cell function)
- LH (stimulates leydig cells to make androgens)
- high levels of intratesticular testosterone
what would happen if a 30 yr old person were given high doses of testosterone
estrogen would increase through aromatase
increased estrogen and testosterone would decrease FSH and LH
decreased FSH and LH would lead to a lower sperm count
semen
the 1.5-5mL of fluid emitted at ejaculation
what percent of the total sperm content semen are motile and morphologically normal
about 1/2
T/F sperm counts have increasesed 1-2% a year since 1985
3 possible causes
false
- increased scrotal temperature
- environmental estrogens
- high stress
hormonally what happens during menopause
the ovaries no longer secrete estrogen so the hypothalamus and anterior pituitary produce FSH and LH to try and increase estrogen
if a male were to present with extremely high levels of FSH and LH what would you expect
primary testicular failure caused by infection or pituitary tumor
is andropause natural
yes and no, there will be a decrease in testosterone and sperm production around 50 but men will continue tot produce until death
amenorrhea
absence of menstration
primary amenorrhea
never had a period before
secondary ammenorrhea
the absence of a period for three months in a women who prevously had them
primary ovarian failure
dysfunction of the ovaries that doesnt allow for menstruation
secondary ovarian failure
pituitary gland malfunction leading to decreased LH and FSH
tertiary ovarian failure
hypothalamic failure to produce GnRH
what are three possible causes of primary ovarian failure
- turners syndrome
- gonadal dysgenesis
- premature menopause
gonadal dysgenesis
failure of the germ cells to migrate to the gonads during development
at what age would menopuase be considered premature
younger than 35
what lab values would you expect in primary ovarian failure
increased LH and FSH as the pituitary tries to stimulate estrogen production
what lab values would you expect in secondary ovarian failure
defininatly decreased FSH and LH
possibly increased prolactin or decreased TSH leading to hypothyroid
what would you expect to see in tertiary ammenorrhea
low BMI, high stress level, or delayed puberty
what hormonal activity signals the start of puberty
nocturnal secretion of GnRH
what will stimulate the onset of puberty
increased body size, specifically body fat, that stimulates leptin production
leptin
a peptide secreted by adipocytes that regulates eating behavior, energy, and reproduction
what is the sequence of female pubertal development
- breasts
- pubic hair
- growth
- menarche
if estradiol levels are found to be normal in an amenorrheic patient what can we conclude
that her ovaries, pituitary, and hypothalamus are all working properly
how can a chromosomal XY fetus end up without male genitalia
if the androgen receptors in development are not sensitive the testes will not descend and male genitalia will not form
what are the four determinants of gender
- genetic
- gonadal
- ductal
- genital
what determines if somone is genetically male of female
a male will have a Y chromosome with a functional SRY gene
SRY
sex determining region of the Y chromosome which determines if ovaries or testes will form
what is the ductal determinant between males and females
females will have muellarian ducts, men will have vestigial muellarian ducts and prominent wolffian ducts
what is the gentital determinant of gender
whether there are ovaries or testes indicated by high levels of androgens
how can a genetically male person produce enough estrogen to have normal female sex characteristics
aromatase produced in adipose tissue will convert testosterone into estradiol
what will a fetal ovary produce that will determine gender
estradiol and oocytes
what will fetal testes produce that determine gender
testosterone to maintain the wolffian ducts and anti-muellarian hormone to regress the muellarian ducts
what do the wollfian ducts and mullerian ducts determine
internal genital development
what will the wolffian ducts form into
vas deferens, seminal vesicles, prostate
what will the mullerian ducts form into
fallopian tubes, uterus, upper vagina
what is the default phenotype of the external genitalia
female
what hormonal process must happen to masculinize the the external genitalia
testosterone must be converted into DHT with 5 alpha reductase
what happens to the wolffian and mullerian ducts if there is no SRY gene present
the wolffian ducts will regress, the mullerian ducts will develop, the external genitalia will be female
androgen insensitvity syndrome
non functional androgen receptors that lead to formation of the wolffian ducts but no DHT to masculinize the external genitalia
what are three indicators of androgen sensitivity syndrome
- 46 XY genome
- absent uterus and upper vagina
- no androgen receptors mean no pubic or axillary hair
two ways to produce a functiona vagina
progressive vaginal dilation or surgery
what might be suspected besides menstration when a pediatric patient presents with vagina bleeding
- foreign body
- sexual abuse
- trauma
what hormone would be absent with a lack of pubic hair
androgens
what hormone is elevated in a pediatric patient with an enlarged uterus and early onset period
estradiol
explain how high TSH can cause early onset period
TSH in high doses can cross react with GnRH receptors in the ovary and produce estradiol
what four hormones are capable of cross reacting with other receptors at high doses
- FSH
- LH
- HCG
- TSH
how can low thyroid cause an increase in estradiol
low T3/4 will not give negative feedback to the hypothalamus/pituitary to inhibit TRH and TSH
TSH can cross reaction with FSH and LH receptors to stimulate the production of estradiol
a patient presents with early onset menses, elevated TSH, and an enlarged uterus
what would be the prescribed treatment
Thyroxine (T4) that will provide negative feed back to inhibit TSH production and stop FSH and LH cross-reactivity
what are three causes of precocious puberty
- central lesion in the CNS
- peripheral increase in estrogen
- obesity
why would obesity cause precocious puberty
adipose tissue contains aromatase which will convert androgens into estrogens and stimulate menses and breast development
a patient with precocious puberty needs treatment, what are two options and why would they be effective
1) estrogens, because it will suppress GnRH production but won’t decrease estrogen
2) GnRH antagonists to down regulate GnRH receptors in the pituitary, deceasing FSH and LH production
leuprolide
GnRH antagonist used to decrease estrogen or androgen production by downregulating GnRH receptors
what is the most common cause of secondary ammenorrhea
pregnancyq
why would low BMI cause hypothalamic amenorrhea
the hypothalamus would react to low body fat by inhibiting production of GnRH
what are two causes of hypothalamic amennorhea
low bf
stress
what is one long term side effects of hypothalamic amenorrhea
- osteoporosis caused by low estrogen
three treatments of hypothalamuc amenorrhea
- estrogen replacement
- GnRH to stimulate FSH and LH production
- direct FSH and LH
what causes menopause
primary ovarian failure
why would high BMI delay menopause
because aromtase conversion of androgens to estrogens will continue to stimulate the uterus
four symptoms of menopause
- amenorrhea
- vasomotor flushes
- decreased vaginal lubrication
- accelerated calcium loss
when do menopausal women have the highest instances of hot flashes
the first 3 year post menopause
why does menopause cause hot flashes
no estrogen production stimulates increased GnRH production
increased hypothalamic activity causes the hypothalamus to assume core temp is too high
why does the menopause cause peripheral dilation, perspiration, compensatory tachycardia
hypothalamic disregulation causes the hypothalamus to think body temp is too high and tries to cool down
what are the benefits of estrogen replacement therapy
- reduce intensity and frequency of hot flashes
- prevent osteoporosis
- maintain bladder and uterus function
- reduce the risk of colon cancer
potential risks of estrogen supplementation
- increase risk of MI
- increased risk of breast cancer
- increase risk of DVT
