Lect 27: female reproductive Flashcards
when is embryo known as fetus
after first two months of intrauterine development
ovaries secrete what two hormones
- estrogen
- progesterone
function of estrogen
- ova maturation and release
- female secondary sexual characteristics
function of progesterone
- prepares uterus for nourishment of developing embryo/fetus
- contributes to breasts ability to produce milk
primordial germ cells undrgo mitosis until
20-24 weeks gestation
oogonia are present from
- 8-9 gestational weeks to 6 months after birth
When do oogonia become primary oocytes
- enter prophase I of meiosis
- development arrested here until just before ovulation
for how long are primary oocytes arrested in prophase I of meiosis? when does meiosis resume
- development arrested here until just before ovulation
- meiosis resumes only in the oocyte released at ovulation
When does mitotic proliferation of oogonium cells occur
prior to birth!
after puberty, how many primary oocytes reach maturity
only one a month
the first meiotic division is completed just prior to ovulation, when is the second meiotic division completed?
after fertilization
the first meiotic division of primary oocyte is completed just prior to ovulation and creates what two things
- first polar body
- secondary oocyte
what happens to secondary oocyte without fertilization
secondary oocyte is discarded in menses without ever completing oogenesis
what happens to secondary oocyte with fertilization
- sperm entry triggers second meiotic division yeilding
- second polar body
- mature haploid ovum which unites with haploid sperm completing fertilization
in conclusion, each primary oocyte yeilds how many ovum
- 1 cytoplasm-rich ovum and 3 cytoplasm-poor polar bodies that disintegrate
The ovarian cycle consists of what two phases? What separates these phases?
- Follicular phase: dominated by maturing follicles
- ovulation: mid-point between phases
- Luteal phase: characterized by corpus luteum
Describe the process of development from a primordial follicle to a preantral follicle
- primordial follicle: a primary oocyte is surrounded by single layer of granulosa cells
- granulosa cells proliferate and form zone pellucida around oocyte
- surrounding ovarian tissue differentiates into thecal cells which converts the primary follicle into a preantral follicle
- **oogenesis stops here and regresses in prepubertal ovary
When does the follicular phase operate
first half of cycle
give a nice summary of follicular phase
- granulosa cells of primary follicles proliferate and secrete zona pellucida
- surrounding ovarian tissue differentiates into theca cells
- granulosa and theca cells secrete estrogen
- oocyte inside follicle enlarges
- follicle ruptures to release oocyte from ovary -> ovulation
What are the follicular cells? function?
- granulosa cells: secrete zona pellucida
- thecal cells -> secrete estrogen (with granulosa cells)
Where is estrogen stored in oocyte during follicular phase
- inside the antrum (fluid filled cavity)
What is the Graafian follicle
the follicle that grows and matures more rapidly during the follicular phase. remaining follicles degenerate
When does the luteal phase occur
last 14 days of ovarian cycle
give a nice summary of luteal phase
- old follicular cells form corpus luteum
- luteal cells enlarge and produce estrogen and progesterone
- if released oocyte is not fertilized and does not implant, corpus luteum degenerates -> corpus albicans
“yellow body” due to storage of cholesterol
corpus luteum
“white body” due to fibrous tissue
corpus albicans
what happens to corpus luteum if fertilization occurs
corpus luteum continues to grow and produce estrogen and progesterone: becomes the corpus luteum of pregnancy
Theca cells contain what enzyme that is responsible for converting cholesterol -> androgens during follicular phase? What stimulation is needed for this to occur?
- cholesterol desmolase
- LH stimulation
what happens to androgens produced by theca cells during the follicular phase
- diffuse to granulosa cells
granulosa cells contain what enzyme that converts androgens to estradiol? Stimulation from what hormone is needed?
- aromatase
- FSH stimulation
When do theca and granulosa cells secrete progesterone
- only after being converted into lutheal cells (during lutheal phase)
estrogen is transported bound to
sex hormone binding globulin (SHBG)
progesterone is transported bound to
corticosteroid binding globulin (CBG)
What increases levels of SHGB? Decreases?
- estrogen and thyroxine increase SHBG
- progesterone and androgens decrease SHBG
Gonadotropin releasing hormones is released in a pulsatile manner. What hormone is stimulated by a low pulse frequency of GnRH? What hormone is stimulated by a high pulse frequency of GnRH?
- low: FSH
- high: LH
function of FSH
- stimulates ovarial follicles and induces Inhibin release from granulosa cells
Inhibin has negative feedback on
FSH release
Prolactin, stress, exercise, endorphins, and chronic illness have what effect on GnRH release
inhibit
estrogen levels are what during ovulation? function
- High
- this high estrogen has a positive feedback
- increase GnRH release from hypothalamus
- increase in GnRH receptors on pituitary gland
- leads to explosive LH surge at midcycle
Which pituitary hormone surges durin ovulation?
- LH -> leads to ovulation
- FSH does not rise as much due to Inhibin
List the effects of the LH surge
- process of meiosis resumes
- antral follicle -> Graafian follicle
- stimulates production of proteolytic enzymes -> digest follicle
- increases prostaglandins
- differentiate follicle cells into corpus luteum
What keeps a second LH surge from occuring during the luteal phase
- luteal cells make progesterone and estrogen
- progesterone has a negative feedback on hypothalamus and pituitary which suppressed the positive feedback of estrogen, suppressing a second LH surge
- low LH -> corpus luteum declines
during follicular phase, a rise in what hormone signals ovarian follicle to secrete more estrogen
FSH
