Part 1: Folliculogenesis Flashcards
The three parts of a 28-day menstrual cycle:
- follicular/proliferative phase (day 1-14).
- ovulation (day 14).
- luteal/secretory phase (day 15-28).
When do menses occur during a 28-day menstrual cycle?
- at the end of one cycle and the first few days of the next cycle.
In addition to one oocyte, each preovulatory follicle contains two cell populations:
theca cells and granulosa cells.
Follicular fluid location and contents:
- Location: antrum of preovulatory follicles.
- Contents: hormones and growth factors.
Steroids produced by Granulosa cells (3):
- estrone
- estradiol
- progesterone
Steroids produced by Theca cells (3):
- progesterone
- androstenedione
- testosterone
Hormone released with:
(1) slow GnRH pulse frequency:
(2) rapid GnRH pulse frequency:
- Slow: FSH secretion.
- Rapid: LH secretion.
The hypothalamic-pituitary-ovarian axis:
- GnRH released in pulses from hypothalamus.
- LH and FSH released in pulses from anterior pituitary.
- FSH stimulates granulosa cells and granulosa-lutein cells.
- LH stimulates theca cells and granulosa-lutein cells.
- Negative and positive feedback on GnRH by follicular steroids.
The ovaries produce what steroids via Theca and granulosa cells?
- androstenedione and testosterone.
- estrone and estradiol-17-beta.
- pregnenolone and progesterone.
Steroid sulfatase function:
- removes sulfate group of DHEAS.
- “S” of DHEA is a sulfate group that acts as a binding protein to DHEA and prolongs DHEA’s half-life.
- removing sulfate group from DHEAS makes DHEA available for ovarian use.
The three cytochrome p450s required for ovarian steroid synthesis:
- CYP11A (20,22-desmolase).
- CYP17 (cholesterol to pregnenolone).
- CYP19 (aromatase).
Function of CYP11A and ovarian cells located in:
- Converts cholesterol into pregnenolone.
- Theca cells and granulosa cells.
Function of CYP17 and ovarian cells located in:
- Produces androgens.
- Converts progesterone into androstenedione.
- Converts pregnenolone into DHEA.
- Theca cells only.
Function of CYP19 (aromatase) and ovarian cells located in:
- Produces estrogens.
- Converts androstenedione into estrone.
- Converts testosterone into E2.
- Granulosa cells only.
The anatomical sequence of follicular growth is (6):
- primordial.
- primary.
- secondary (preantral).
- tertiary (antral).
- preovulatory (dominant or Graafian).
- corpus luteum.
At what state in follicular growth do theca cells and granulosa cells begin to secrete steroids?
secondary (preantral)
Theca cell and granulosa cell secretions during the secondary (preantral) stage of follicular growth:
- Theca: Andro > T > P4 (low levels).
- Granulosa: E2 > P4 (low levels).
Theca-lutein cell and granulosa-lutein cell secretions during the corpus luteum stage of follicular growth:
- Theca: P4 only (high levels).
- Granulosa: E2 = P4 (high levels).
Draw the general pattern of Theca cell and granulosa cell secretions during the stages of follicular growth:
What serves as the precursors to estrogens produced by the Granulosa cells / Granulosa-lutein cells?
- Theca cell produced androstenedione and testosterone.
What signal transduction cascade is activated upon gonadotropin binding to receptors on theca cells or granulosa cells?
cAMP/PKA
Receptors expressed by both preovulatory theca cells and theca-lutein cells:
LH only.
Receptors expressed by both preovulatory granulosa cells and granulosa-lutein cells:
- Preovulatory: FSH only.
- Granulosa-lutein: LH and FSH.
What occurs when LH binds to preovulatory Theca cells?
- androgens produced and secreted.
- androstenedione >> testosterone.
