LEC 29: Oogenesis, Control of Menstrual Cycle

Question 1

Primordial germ cells (PGCs)

Answer 1

Precursor cells to gametes. Migrate from their own origin in the hindgut of the embryo to the gonads. Multiply during migration and become spermatogonia or oogonia.

Question 2

Spermatogonia

Answer 2

Continuous sperm production.

Question 3

Oogonia

Answer 3

Produces a fixed, limited pool of oocytes. Primordial germ cells (oogonia) -> Mitosis stop in fetal life -> all enter meiosis but become arrested in 1st meiotic division

Question 4

Primary oocyte

Answer 4

Complete meiosis I at ovulation

Question 5

Secondary oocyte

Answer 5

Completes meiosis II at fertilization

Question 6

Menstural cycle

Answer 6

Follicular phase, ovulation, then luteal phase (secretory). First part is dominated by estrogen, second part by both estrogen and progesterone

Question 7

Follicule

Answer 7

Shell that holds the egg. Use the size to determine egg maturity (esp in IVF). Becomes corpus luteum.

Question 8

Estrogen

Answer 8

Produced by the follucular growth and it tells your pituitary to make more LH (surge)

Question 9

Progesterone

Answer 9

Made by the corpus leuteum after ovulation

Question 10

Beta ACG

Answer 10

Happens during fertilization to keep the corpus leutem going

Question 11

Control of the Menstrual Cycle

Answer 11

Menstruation is an external indicator of ovarian events controlled by the hypothalamic-pituitary axis

Question 12

Control of Follicular Growth

Answer 12

Hypothalamus makes GnRH -> Pituitary that makes LH and FHS -> Ovaries which makes Estradiol (E2) and Inhibin

Question 13

What does the Hypothalamus make?

Answer 13

GnRH that goes tot he pituitary

Question 14

What does the Pituitary make?

Answer 14

LH and FHS that goes to the ovaries

Question 15

What does the Ovaries make?

Answer 15

Estradiol (E2) and Inhibin (Progesterone)

Question 16

Estrogen and Progesterone Feedback

Answer 16

have a negative feedback on the pituitary and hypothalamus which decreases GnRH and LH and FSH production

Question 17

Antrum

Answer 17

Follicular fluid

Question 18

Zona pellucida

Answer 18

surrounds the egg. barrier

Question 19

Granulosa

Answer 19

FSH receptors which come from the pituitary and then tells the egg to make estrogen

Question 20

Theca cells

Answer 20

LH receptors and make androgens that are converted by the granulosa cells to make estrodiol

Question 21

Two cell - two stage hypothesis

Answer 21

Need both theca cells and granulosa to make estrodiol. without theca cels, granulosa won’t work

Question 22

Inhibin

Answer 22

decreases FSH. Made by granulosa cells

Question 23

Follicular growth

Answer 23

From primordial to graafian stage (dominant follicle)

Question 24

What causes Ovulation?

Answer 24

Caused by the LH surge

Question 25

Positive feedback

Answer 25

High levels of estradiol (E2) maintained for long enough becomes positive feedback, pituitary becomes more sensitive to GnRH and causes a LH surge!

Question 26

Impact of the LH surge on the egg

Answer 26

Tells the egg to complete the first mitotic division and the extrusion of the 1st polar body. Also causes a loosing of the cumulus cells

Question 27

M2, mature egg

Answer 27

Already released the polar body

Question 28

Transformation of ruptured follicle into corpus luteum

Answer 28

Thecal cells and blood vessels invade. Granulosa cells hypertrophy and terminally differentiate (luteinization)

Question 29

Progesterone rise during ovulation

Answer 29

enhances proteolytic enzymes. Digest and rupture the follicular wall. Causes terminal differentiation of stromal cells (decidualization)

Question 30

Uterine changes in the menstrual cycle

Answer 30

Estradoil causes an increase in thickness (proliferative phase). More secretion from the glands -> secretory phase

Question 31

Increase in body temperature

Answer 31

Caused by progesterone that effects the hypothalamic thermoregulatory center. Already ovulated

Question 32

No fertilization

Answer 32

Corpus luteum regresses, abrupt drop in progresterone and estrogen

Question 33

Simplest way to test ovulation

Answer 33

Progesterone test

Question 34

FSH

Answer 34

Primary hormone that stimulates follicle development. Induces aromatase activity in GC to produce estrogens from androgens. Induce the formation of LH receptors. Selection of preovulatory follicle

Question 35

LH

Answer 35

Produce androgens in TC. Stimulate last stages of follicle development. Induce ovulation and final follicle maturation. Stimulate formation of corpus luteum

Question 36

Implantation

Answer 36

Happens around day 6. Blastocyst hatches from zona pellucida. Invasion of trophoblast. Corpus luteum maintained by hCG production from syncytium.

Question 37

Trophoblast cells

Answer 37

Will become the placenta and make all the hormones such as hCG