04-07 Basics Review

Question 1

OBJECTIVE: Contrast oogenesis and spermatogenesis throughout the life cycle.

Answer 1

Max endownment of oocytes is in utero and declines from there while spermatogenesis begins at puberty and continues throughout the lifetime.

Question 2

OBJECTIVE: Contrast estrogen production in the ovaries with androgen production in the testes.

Answer 2

OVARIES: estrogen production is tied to ovulation, is cyclican. It requires two cells: androstenedione is produced in thecal cells and then diffuses and is aromatized in granulosa cells
TESTES: testosterone production is separate from spermatogenesis; LH stimulates Leydig cells separate from FSH’s stimulation of spermatogenesis in the Sertoli cells

Question 3

OBJECTIVE: Describe the phases of the menstrual cycle.

Answer 3

—follicular (proliferative) phase is the first phase; it is on average 14 days long but is variable
—luteal (secretory) phase is the second phase; it is INvariant (i.e. always 14 days)

Question 4

OBJECTIVE: Teach the hormonal changes of the ovulatory menstrual cycle.

Answer 4

Ok here we go:

1. the menstrual cycle begins on the first day of flow; at this point FSH begins to stimulate new follicles to grow.
2. after a few days the level of FSH drops and (usually) only one follicle is able to mature.
3. that follicle makes more estrogen triggering positive feedback of GnRH to LH.
4. the follicle ruptures = ovulation
5. the follicular remnants are now referred to as the corpus luteum which secretes progesterone which helps to maintain the hypertrophied endometrial lining
6. if fertilization occurs, hCG from the placenta will help to maintain the endometrium, otherwise the period is lo que pasa

Question 5

OBJECTIVE: Explain positive and negative feedback.

Answer 5

If you don’t know this by now…it’s just…yeah…

Question 6

Clicker Q: When will a female achieve her maximum number of oocytes?

Answer 6

in utero

Question 7

Clicker Q: When will a male achieve his maximum number of spermatocytes?

Answer 7

later in life (depends how you count this; max all at once is like in 30s-40s, max lifetime total is cumulative with age)

Question 8

In what phase are oocytes arrested?

Answer 8

Prophase of Meiosis I

Question 9

Clicker Q: Effect of constant infusion of GnRH on FSH levels?

Answer 9

decreases FSH; recall that GnRH must be released in pulsatile fashion for normal repro fxn. When GnRH is administered in a constant fashion, the GnRH receptors on the pituitary get down-regulated.

Question 10

GnRH is produced in what region of the hypothalamus?

Answer 10

the arcuate nucleus

Question 11

GnRH stimulates:

a) equal amount of LH and FSH
b) LH > FSH
c) FSH > LH

Answer 11

b) LH > FSH; remember that it used to be called LHRH!

—When GnRH is suppressed the pituitary will release small amount of FSH but no LH

Question 12

FSH stimulates which cells in females? In males?

Answer 12

FSH stimulates germ cell production
—females - granulosa cells
—males - seminiferous tubules

Question 13

LH stimulates which cells in females? In males?

Answer 13

LH stimulates sex steroid production
—females - theca cells -> androstenedione —aromatase in granulosa cells—> estradiol
—males - Leydig cells -> testosterone

Question 14

Negative feedback of estrogen and testosterone occurs at the level of the ________.

Answer 14

hypothalamus

Question 15

When does positive feedback occur in the menstrual cycle?

Answer 15

when rising estrogen levels from the one dominant follicle (of the cohort stimuated by FSH) triggers the LH surge: +++Estrogen -> +++GnRH -> +++LH -> ovulation

Question 16

Describe the two cell theory of estrogen production.

Answer 16

The current model is the two-cell model which says that theca cells stimulated by LH secrete androstenedione which diffuses into the granulosa cell. When the granulosa cell has been activated by FSH its aromatase