Female Phys [this yrs] Flashcards
How many chromosomes does a 1’ oocyte have?
How many chromatids per chromosome?
At what stage in meiosis are 1’ oocytes arrested & what triggers meiosis progression from this point?
1’ Oocyte
- 46 chromosomes; 2 chromatids/chromosome
- present at birth and are arrested in Prophase I of meiosis until puberty
- division/progression to a 2’ oocyte begins in utero and is completed prior to ovulation [thus is LH surge dependent]
How many chromosomes do 2’ oocytes have?
How many chromatids per chromosome?
When are 2’ oocytes formed and what stage of meiosis are they in?
What triggers the progression of oogenesis?
2’ Oocyte
- 23 chromosomes; 2 chromatids/chromo
- 2’ oocytes are formed/present at puberty
- arrested in metaphase II
- Upon fertilization they progress to an Ovum
What happens after a sperm enters a 2’ Oocyte?
Sperm enters a 2’ oocyte…
DNA does NOT combine yet
- 2’ Oocyte undergoes Meiosis II
- produces an **ovum **& a polar body
- DNA of sperm & ovum *combine *now
What is the point of oogenesis?
mitosis: make large # of 1’ oocytes
Meisosis: make cohorts of 1’ oocytes that only 1 haploid 2’ oocyte can be ovulated each month
Which stages of foliculogenesis are hormone independent?
the pre-antral phase
- primordial follicle
- 1’ follicle
- 2’ follicle
[tertiary follicle/antral phase are hormone dependent (LH)]
how many antral stage follicles are present in each follicular wave [mentrual cycle]?\
What happens to these?
MANY!!
- less than or equal to 7 Primary follicles are recruited
- but only 1 [usually] will become ovulatory= Mater or Graafian follicle
- other 6 follicles undergo atresia unless rescued by FSH for another “recruitment”
When does menopause occur?
When primordial/primary follicles are exhausted
What is responsible for basal levels of FSH & LH?
hourly GnRH pulses
What triggers the release of FSH & LH?
What does FSH do?
What does LH do?
Gonadotropin releasing hormone [GnRH] triggers release of FSH & LH
FSH: acts on granulosa cells-->stimulates follicle development & LHR synthesis
- also can trigger inhibin secretion
LH: acts on theca cells–>makes androgens
- critical for indxn of ovulation [required for CL to form]
*****both: ** promote estrogen synthesis!!!
how does estrogen affect LH/FSH secretion?
BOTH (-) & (+) feedback
- when antral follicles are large: estrogen increases–> rapid GnRH pulses–> LH surge–> ovulation [positive feedback]
(inhibin levels also increase–>inhibits FSH secretion–>blocks other follicles develop)
-
when not close to ovulation: estrogen inhibits GnRH release–> decreases LH/FSH
- negative feedback
what does inhibin do?
inhibin inhibits FSH secretion
DOES NOT affect LH
Where is GnRh secreted from?
How?
What does it act on?
- Produced in Arcuate nucleus of Hypothalamus
- Pulsatile secretion [triggers release of FSH/LH]
•Membrane protein receptor
- G-Protein coupled, Gq
- Gq Activates phospholipase C, DAG IP3
where is human chorionic gonadotropin [hCG] secreted from?
What is its role?
Where does it bind?
PLACENTA pulsatilely secretes hCG!!!
- 1st trimester: hCG maintains CL–> which keeps progesterone [& estrogen] levels high–> maintains pregnancy
- 2nd Trimester & on: placenta takes over the role of steroidgenesis & maintains pregnancy
binds to LHR in theca cells!
What happens to LH, FS, & hCG levels if ovarian fxn ceases or ovaries are removed?
serum [] increases
How do theca and granulosa cells work together for steroidgenesis?
ovary requires both LH and FSH for steroidogenesis
- LH stimulates the thecal cells surrounding the follicle to produce progesterone and androgens
- androgens diffuse across the basement membrane to the granulosa cell layer, where, under the action of FSH, they are aromatized to estrogens, mainly estradiol 17b.
What are the 1’ steroids produced by the ovary?
progesterone & estradiol 17B
What are the 2 estrogen R’s and their roles?
ERa: mediates HPO axis response to estrogen
ERBeta: ???
What is happening during the follicular phase of the menstrual/ovarian cycle?
**think big picture
small ^^ in FSH/LH secretion–> foliicular growth–> ^^synth & secretion of ovarian steroid hormones
What happens to cause ovulation?
increase in follicle size–>^^secretion estrogen [FOLLICULAR PHASE]
- ^^estrogen–> surge in LH [inhibin decreases FSH] –> restarts meiosis I of dominant follicle & OVULATION
What happens in the lutenizing phase of menstrual cycle?
**big picture
ovulation induces lutenization
- follicle that ruptured becomes CL
- theca & granulosa cells enlarge
- ^^progesterone & estrogen secretion
- IF no fertilization occurs–> spontaneous luteolysis of CL occurs
- causes P & E levels to drop –> induces menses
Tell me what hormone levels are like in the follicular phase, ovulation & luteal phase of menstrual cycle?
- Progesterone levels are greater during the luteal phase compared to the follicular phase.
- Estrogen levels are high in late follicular phase and in the luteal phase.
- Progesterone falls at the end of the luteal phase
- Spontaneous regression of the corpus luteum ensues
how do most hormonal contraceptives work?
big picture
suppress the LH surge [= no ovulation]
What controls the uterine cycle?
what are the effects of E & P in the uterine cycle?
The ovarian/menstrual cycle!!!
-
Estrogen causes thickening & proliferation of the endometrium
- Endometrial glands develop from cuboidal epithelium to pseudostratified glands
- Stromal and vessel growth occurs
- Uterine lining increases tenfold, to 5 mm thick
-
Progesterone halts further growth of endometrium
- Causes secretion from glands, rather than proliferation of glands
- Changes of progesterone are distinct!!!
What happens to an ovum once released from a follicle?
