Flashcards in 4 - Repro - Gamete development 2 Deck (38)
What causes oocytes to arrest in the Diplotene stage of prophase I?
Oocyte Maturation Inhibitor (OMI)
- from follicular cells
Which cells secrete Oocyte Maturation Inhibitor (OMI), and which stage of meiosis does this arrest oocytes in?
Diplotene stage of prophase I
Why is there an increased risk of imperfect oocytes as a woman ages?
More time an oocyte is arrested in development
= increased risk of mutations
Approx how many oocytes are present when a woman reaches puberty?
How many oocytes start to mature each month after a woman reaches puberty?
only one fully matures each month
What are the 3 stages of oocyte maturation?
What occurs in the pre-antral stage of oocyte maturation?
- Follicular cells change from simple squamous to stratified cuboidal granulosa cells
- Stromal cells form the theca folliculi (theca interna and theca externa)
Which cells form a fibrous capsule around the developing oocyte?
Which cells secrete the zona pellucida?
How are the granulosa cells and thecal cells arranged around the developing oocyte?
- Granulosa cells surround oocyte
- Thecal cells surround granulosa cells
What occurs in the antral stage of oocyte development?
- Granulosa cells proliferate and secrete fluid, forming the antrum
- Theca interna cells bind LH = stimulates androgen production
- Granulosa cells bind FSH = stimulates conversion of androgens to oestrogens
Which cells surrounding the oocyte bind LH?
Theca interna cells
Which cells surrounding the oocyte bind FSH?
Which cells surrounding the oocyte secrete androgens?
Theca interna cells
Which cells surrounding the oocyte convert androgens to oestrogens?
Name the 3 types of oestrogen in the female body:
Name the type of follicle produced in the antral stage of development:
What is the precursor of the androgens and oestrogens produced in the ovary?
When does a secondary/Graafian follicle enter the pre-ovulatory stage of development?
~ 37 hrs before ovulation
What occurs in the pre-ovulatory stage of oocyte maturation?
- LH receptors appear on granulosa cells, and are stimulated by the LH surge
- LH surge restarts meiosis I
- Oocyte arrests in Metaphase II ~ 3hrs before ovulation
In what stage of meiosis is an oocyte arrested in, in the pre-ovulatory stage of develoment?
When is meiosis II of an oocyte completed?
Completed if the oocyte is fertilised
At ovulation, what is the size of the follicle?
~ 25 mm
What causes the follicle to rupture at ovulation?
= increases collagenase activity
If an oocyte is fertilised at the ampula, how many days does it take for it to reach the uterine lumen?
~ 3-4 days
Which cells secrete progesterone?
Granulosa lutein cell (of the corpus luteum)
Name the 2 types of cells in the corpus luteum:
1) Granulosa lutein cells
2) Theca lutein cells
How long does the corpus luteum survive if the oocyte is not fertilised?
~ 14 days
Becomes corpus albicans (fibrotic scar tissue)
The change in which hormone precipitates menstrual bleeding?
Decrease in progesterone
- due to death of corpus luteum
What prevents the degradation of the corpus luteum if the oocyte is fertilised?
Developing embryo secrete hCG, which maintains the corpus luteum
If fertilisation occurs, for how long does the corpus luteum secrete progesterone?
until the 4th month of development, as placenta can then take over
Decribe the release of GnRH from the hypothalamus:
Pulsatile release ~ 1-3 hrs
Which G- protein does LH and FSH stimulate in the gonads? Therefore which enzyme is the effector?
Which male hormone has a circadian rhythm?
Which cell secretes Androgen-binding globulin (ABG), to keep testosterone in the testes?
Which cells secrete inhibin?
Females = granulosa cells
Males = sertoli cells
Which hormone prevents oestrogen causing +ve feedback to the hypothalamus and anterior pituitary?