Lecture 34: Menstrual Cycle and Ovulation (Part 1) Flashcards
Before puberty, at what stage of development are the females’ follicles at?
Arrested in Prophase I
-due to elevated levels of cAMP
A follicle selected for ovulation will arrest at what stage of development?
Metaphase II
- polar body 1 is extruded
- elevated levels of MAPK proteins
When does an follicle finish meiosis completely?
After fertilization
Briefy, what happens during the follicular phase?
Follicles in ovary mature
What surrounds a primordial follicle?
Pre-granulosa cells
What surrounds a primary follicle?
Granulosa cells (cuboidal shape)
- follicle is bigger
- zona pellucida forms
A primary follicle in secretes what type of glycoprotein?
ZP1-4
What surrounds a secondary follicle?
- Several layer of cuboidal granulosa cells
- thecal cells: important role of vascularization
What is the function of the zona pellucida?
- Provide binding sites for sperm
- protecting for oocyte
What receptors are found on granulosa cells?
FSH receptors
What receptors are found on thecal cells?
LH receptors
What marks the beginning of the antral phase?
Appearance of antrum
- portion of an ovarian follicle filled with follicular fluid
- marks change from a primary follicle to a secondary follicle
- oocyte suspended in fluid
What happens during antral phase?
100x increase in granulosa cells
- Mural granulosa: outer wall
- Cumulus cells (corona radiata): maintain gap junctions
During the antral follicular stage, how does the theca interna respond to LH?
Synthesize androgens from cholesterol
- major product is androstenedione
- limited estrogen produced
During the antral follicular stage, how does the granulosa cells respond to FSH?
Convert androgens from theca cells to estrogen
What makes an oocyte competent to finish meiosis I?
-Sufficient amount of cell cycle components (CDK-1 and cyclin B)
What prevents an oocyte to finish meiosis I?
1) Needs LH surge
2) Oocyte has elevated cAMP levels that arrests it in Prophase I
How is the dominant follicle selected?
Largest follicle with most FSH receptors
-known as Graffian follicle
When is the periovulatory phase?
Onset of LH surge to ovulation (32-36 hours)
During the periovulatory phase, what do the theca and mural granulosa cells prepare for?
1) Prepares cells for luteinization
2) Formation of corpus luteum
3) Increased production of progesterone
Briefly, what happens in the luteal phase?
Formation of corpus luteum and ends in either pregnancy or luteolysis
-marked by high levels of progesterone
During the luteal phase, what do the theca cells start making?
1) Inhibition of aromatase expression and estrogen production
2) Low levels of LH promotes progesterone production
What structural changes are seen with an LH surge?
1) Breakdown of follicle wall, tunica albuginea, and surface epithelium
2) Cumulus-oocyte detaches and floats in antrum
3) Basal lamina degraded
4) Oocyte continues into meiosis (arrests in metaphase II)
What is the corpus luteum?
temporary structure in ovaries
- produces progesterone and moderate levels of estradiol and inhibin
- remains of ovarian follicle that released a mature ovum during during ovulation
- often yellow due to carotenoid pigments
