Female Reproductive Physiology Flashcards
What are the ovaries? what is their function?
primary female reproductive organs that produce ova and secrete female sex hormones
what two major hormones do the ovaries secrete?
estrogen
progesterone
what is the function of estrogen?
1) essential for ova maturation
2) establishment of female secondary sexual characteristics
what are the oogonia?
undifferentiated primordial germ cells in fetal ovaries
What is the order of the different cells in oogenesis?
oogonia
primary oocyte
first polar body (degrades) + secondary oocyte
Secondary polar body (degrades) + mature ovum
what is a primary follicle?
oocyte + granulosa cells
what is a primary follicle? what is it’s two possible fates?
oocyte + granulosa cells
1) reach maturity and ovulate
2) degenerate to form scar tissue (atresia)
what is the function of progesterone?
1) important in preparing suitable environment for nourishing a developing embryo/fetus
2) contributes to breast’s ability to produce milk
what occurs in regards to the follicular cells between puberty and menopause?
follicles develop into secondary follicles on cyclic basis
do oogonia go through meiotic division or mitotic? approx. how many oogonia are produced by 5mo. gestation?
mitotically
6-7 million
what happens during the last part of fetal life in regards to oogenesis?
the early steps of the first meiotic division of primary oocytes begin but does not complete it
remains in meiotic arrest for years until they are ready for ovulation
is the primary oocyte haploid or diploid? how many chromosomes do they have?
haploid # of 46 replicated chromosomes
what occurs just before ovulation?
primary oocyte completes its first meiotic division yielding a first polar body that will degenerate and a secondary oocyte
what happens if the secondary oocyte comes in contact with sperm?
sperm entry triggers second meiotic division which produces a secondary haploid polar body (degenerated) and a mature haploid ovum which unites with haploid sperm during fertilization
how many chromosomes should be in the secondary oocyte before fertilization?
23 chromosomes
how long is the typical ovarian cycle?
28 days
what are the 2 phases of the ovarian cycle?
Follicular phase
luteal phase
what are the 2 things that will disrupt the ovarian cycle?
pregnancy and menopause
what differentiates the follicular phase from the luteal phase?
foll - dominated by presence of maturing follicles
lut - characterized by presence of corpus luteum
when does the follicular phase occur in the ovarian cycle?
first half (first 14 days)
what 4 things occur during the follicular phase?
1) granulosa cells of some primary follicles proliferate
2) oocyte inside each follicle increases
3) theca cells in follicle secrete increasing amounts of estrogen
4) rapid follicular growth continues during follicular phase
approx how long does it take for a follicle to mature?
14 days
what is ovulation?
mature follicle ruptures to release oocyte from the ovary and enters to oviduct where it may or may not be fertilized
when does the luteal phase occur in the ovarian cycle?
last 14 days
what occurs during the luteal phase?
old follicular cells undergo structural transformation to form corpus luteum and becomes highly vascularized
when does the corpus luteum become fully functional?
within 4 days after ovulation (~day 18 or less)
what occurs for the next 4-5 days after corpus luteum becomes functional?
continues to increase in size
what happens to the corpus luteum if the ovum is not fertilized?
degenerates within ~14days after its formation
what hormones increase during follicular phase? why?
FSH - to signal ovarian follicle to secrete more estrogen
LH - to trigger ovulation at peak in mid-cycle
what does increase estrogen do to FSH?
feeds back to inhibit FSH secretion which decreases as follicular phase proceeds
what is the function of the corpus luteum in terms of hormones?
secrete estrogen and progesterone during luteal phase
what does progesterone do when secreted by corpus luteum?
Inhibits release of FSH and LH leading to declined pro levels
what is the first step in hormonal effects by LH and FSH?
stimulates the thecal cells in ovarian follicle
what is the second step in hormonal effects by LH and FSH?
on stimulation, the thecal cells convert cholesterol to androgen
what is the third step in hormonal effects by LH and FSH?
androgen diffuses from the thecal cells into the adjacent granulosa cells
what is the forth step in hormonal effects by LH and FSH?
FSH stimulates granulosa cells in ovarian cycle
what is the fifth step in hormonal effects by LH and FSH?
on stimulation the granulosa cells convert androgen to estrogen
what are the two possible steps (step 6) in hormonal effects by LH and FSH?
6a) part of the estrogen is secreted into the blood, where it exerts systemic effects
6b) part of the estrogen remains within the follicle and contributes to antral formation
what is the last (7th) step in hormonal effects by LH and FSH?
local estrogen along with FSH stimulate proliferation of the granulosa cells
when are FSH and LH levels the highest during the ovarian cycle?
day 14 (ovulation) also start to increase at end of cycle (~day26)
when are estrogen levels highest and progesterone levels highest?
est - day 12
pro -day 21 (est levels also increase here but not as high as day 14)
How does LH control ovulation?
massive LH surge triggers ovulation and subsequent luteinization of the ruptured follicle
what 4 major changes in the follicle? are brought about by the LH surge?
1) halts estrogen synthesis
2) reinitiate meiosis in the oocyte of the developing follicle
3) triggers production of locally acting prostaglandins
4) differentiation of follicular cells into luteal cells
how does LH control the corpus luteum?
LH maintains the corpus luteum; ie: after triggering corpus luteum development, it stimulates ongoing steroid hormone secretion by the ovarian structure
tells corpus luteum to secrete estrogen and progesterone (more)
what is the cyclic uterine changes?
ie menstrual cycle about 28 days long
outward manifestation of cyclic changes in uterus is menstrual bleeding once during each cycle
what are the 3 phases for the menstrual cycle?
a) menstrual phase
b) proliferative phase
c) secretory or progestational phase
what is characteristic of the menstrual phase?
discharge of blood and endometrial debris from vagina
first day of menstruation = start of new cycle
what does the menstrual phase coincide with?
end of ovarian luteal phase and onset of follicular phase
what is released during the menstrual phase?
uterine prostaglandins
what are 2 functions of uterine prostaglandins?
1) causes vasoconstriction of endometrial vessels to disrupt the blood supply and cause death of endometrium
2) stimulate mild rhythmic contractions of uterine myometrium to help expel blood and endometrial debris from uterine cavity out through vagina
what is the proliferative phase?
begins concurrent with last portion of ovarian follicular phase where endometrium starts to repair itself and proliferate under influence of estrogen from newly growing follicles
when does proliferative phase occur?
from end of menstruation to ovulation
how are the estrogen levels in proliferative phase significant?
they peak and trigger LH surge responsible for ovulation
what is the secretory or progestational phase?
occurs after ovulation when new corpus luteum is formed and secretes large amount of progesterone and estrogen
what does the progesterone do in the secretory/progestational phase?
converts endometrium to highly vascularized, glycogen-filled tissue (glycogen secreted by endometrial glands)
what happens in the secretory/progestational phase if no fertilization or implantation occurs?
corpus luteum degenerates and new follicular phase and menstrual phase begin once again
what is menopause? what is the age range for when it occurs?
cessation of a woman’s menstrual cycle
45-55yrs
what may trigger menopause?
midlife hypothalamic change
what occurs before menopause?
period of progressive ovarian failure
increase in irregular bleeding
dwindling estrogen levels
what is climacteric?
period of transition between normal menstruation and menopause
where does fertilization occur?
oviduct (upper third ie: ampulla)
when is fertilization most likely to occur?
within 24 hrs after ovulation
how long can sperm survive in female reproductive tract?
~48 hrs, but can last up to 5 days
how does the female reproductive tract aid in sperm migration?
1) contractions of myometrium
2) upward contractions of oviduct smooth muscle
3) allurin released by mature eggs
what happens when the first sperm reaches the egg?
1) fuses with plasma membrane of ovum
2) triggers chemical change in ovum’s surrounding membrane that makes outer layer impermeable to entry of more sperm
3) head of fused sperm gradually pulled into ovum’s cytoplasm
4) ~1hr later, the sperm and egg nuclei fuse making a zygote
what happens after the zygote is formed?
divides mitotically and grows/differentiates into blastocyst capable of implantation
what happens after blastocyst formation?
blastocyst implants in endometrial lining by means of enzymes released by trophoblasts
what are trophoblasts?
travel into endometrium/decidua and eventually get buried under endometrium
how do the enzymes aid in implantation?
1) carve hole in endometrial for implantation of blastocyst
2) releases nutrients from endometrial cells for use by developing embryo
what is the placenta?
organ of exchange between maternal and fetal blood that acts as a transient, complex endocrine organ that secretes essential pregnancy hormones
what hormones does the placenta secrete? what are their functions?
human chorionic gonadotropin (HCG) - maintains corpus luteum until placenta takes over function in last two trimesters
estrogen - maintain normal pregnancy
progesterone - maintain normal pregnancy
What is an important step in the placenta/amniotic sac formation?
finger-like projections of chorionic tissue extend into the pools of maternal blood
what occurs after the chorionic tissue extends into the pools of maternal blood?
developing embryo sends out capillaries into these chorionic projections to form placental villi
inner cell mass forms a fluid filled amniotic cavity: amniotic sac with amniotic fluid
what is the function of the placenta?
function as digestive system, respiratory system, and kidneys for fetus.
how does the fetus receive oxygen and nutrients and get rid of wastes?
they diffuse from the maternal blood across the thin placental barrier into the fetal blood
wastes simultaneously diffuse into maternal blood
what is the function of the human chorionic somatomammotropin (HCS)?
helps prepare mammary glands for lactation and decreases maternal use of Glc/promotes breakdown of stored fat to make more sugar and FAs available for fetus
when does gestation occur?
~38 weeks from conception
what physical changes does the mother undergo to meet demands for pregnancy? (8pts)
1) uterine enlargement
2) breasts enlarge and develop ability to produce milk
3) volume of blood increases 30%
4) weight gain
5) respiratory activity increses ~20%
6) urinary output increases
7) kidneys excrete additional wastes from fetus
8) nutritional requirements increase
what is partuition?
labour, delivery, birth
what are 2 requirements for partuition?
1) dilation of cervical canal to accommodate passage of fetus from uterus through vagina and to the outside
2) contraction of uterine myometrium that are sufficiently strong to expel fetus
what does the pressure against cervix do in terms of hormones?
causes release of oxytocin secretion
what are 2 functions of oxytocin in partuition?
1) causes stronger contractions
2) Positive feedback cycle progressively increases until cervical dilation and delivery are complete
what are the 3 stages of labour? which stage is the longest?
1) cervical dilation - longest (several hrs - 24hrs)
2) delivery of baby
3) delivery of placenta
when does delivery of baby begin? how long does it typically last?
when cervical dilation is complete
30-90min
how long does delivery of placenta usually take?
15-30min
what hormonal process occurs to allow lactation?
sustained by suckling:
triggers release of oxytocin and prolactin
oxytocin causes milk ejection by stimulating cells surrounding alveoli to squeeze secreted milk out through ducts
prolactin stimulates secretion of more milk to replace ejected milk as baby nurses
how does prolactin influence lactation specifically?
stimulates synthesis of enzymes essential for milk production by alveolar epithelial cells
withdrawal of placental steroids at partuition initiation lactation
what other 2 hormones influence lactation and in what way?
est and pro - promote development of ducts and alveoli in mammary glands
