Class 6: Female Reproduction

Question 1

Oocyte, egg

Answer 1

female sex cell, oocyte is the egg cell after two meiotic divisions

Question 2

Follicle

Answer 2

compartments in the ovaries where oocytes develop, where FSH gets its name! Develops through folliculogenesis from preantral (gonadotropin independent) to antral stage (gonadotropin-dependent.) Analogous to the seminiferous tubules in men.

Question 3

Antrum

Answer 3

fluid filled cavity in the follicle

Question 4

Oogenesis

Answer 4

process by which oocytes are created in female animals.

Question 5

Prophase I arrest

Answer 5

ggs are arrested in Prophase I during fetal period (ie before fetus is even born). Oocytes exit this arrest with ovulation progress through Meiosis I and go halfway into Meiosis II (to metaphase.)

Question 6

Metaphase II arrest

Answer 6

Eggs will only exit from Metaphase II arrest and complete meiosis if fertilized

Question 7

Theca cell

Answer 7

it outside the follicular compartment (they are analogous to leydig cells in males which sit outside the seminiferous tubule)
-LH acts on the Theca cells. Theca cell produces androgen (androstenedione – a weaker androgen, precursor to T). Androgen moves into the granulosa cell.

Question 8

Granulosa cell

Answer 8

Sit within the follicle and surround the oocyte. FSH acts on the granulosa cell. Signal transduction results in production of aromatase. Aromatase converts androgen to estrogen (estradiol)

Question 9

Two-cell, two gonadotropin mechanism

Answer 9

Estrogen conversion process which involves LH and FSH acting on theca and granulosa cells. LH acts on Theca cells, producing testosterone. T acts on granulosa cells creating estrogen (with the help of aromatase created by the action of FSH on the granulosa cells!)

Question 10

Aromatase

Answer 10

Signal transduction from FSH on the granulosa cell results in aromatase enzyme which converts androgens to estrogen in granulosa.

Question 11

Menstrual cycle

Answer 11

characterized by three primary stages: follicular phase, ovulation and luteal phase.

Question 12

Positive feedback

Answer 12

when estrogen is at a high enough concentration it overrides negative feedback and creates a positive feedback cycle where accumulation of product means you create more of that product. More granulosa cells means more estrogen which in turn means more granulosa cells

Question 13

Ovulation

Answer 13

ollicular rupture facilitated by enzyme activity weakening the follicle wall combined with increased fluid in the antrum. Complex of oocyte moves into the oviduct.

Question 14

Corpus luteum

Answer 14

develops from the ovarian follicle from a collection of granulosa cells during the luteal phase of the menstrual cycle. The corpus luteum secretes progesterone to develop and maintain the endometrium. If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approx 14 days).

Question 15

Follicular phase

Answer 15

first half of menstrual cycle where the actions in the follicle are the driving force of hormone actions. Estrogen increase leads to LH surge and increase in FSH.

Question 16

Luteal phase

Answer 16

second half of menstrual cycle where the actions in the corpus luteum are the driving force of hormone actions. LH and FSH decrease, progesterone production high, estrogen also high. Cervix is firm and mucus is dry and viscous.

Question 17

Proliferative phase

Answer 17

thickening of the endometrial lining driven by estrogen (during follicular phase)

Question 18

Secretory phase

Answer 18

some further proliferation of the endometrial lining driven by progesterone, leading to a focus on maintenance.

Question 19

Menses

Answer 19

in the absence of progesterone, the uterine (endometrial) lining is sloughed. (menses).

Question 20

Cervix; Phases of the cervix : Cervix

Answer 20

opening to the uterus from the vagina. Preovulatory phase: mucus gradually increasing elasticity, ovulation: cervical muscles are relaxed, mucus has a higher water content, more stretchy. Luteal (progestational) phase - cervix is firm, mucus dry and viscous.

Question 21

Chorionic gonadotropin (hCG)

Answer 21

early during the implantation of the embryo in the endometrium, the early embryo begins producing chorionic gonadotropin (hCG). hCG “rescues” the corpus luteum, allowing the CL to continue to produce progesterone. In the presence of progesterone, the uterine (endometrial) lining is maintained.

Question 22

Endometrium

Answer 22

the innermost glandular layer functioning as a lining for the uterus. Implantation occurs in the endometrium.

Question 23

Implantation

Answer 23

while traveling through the oviduct to the uterus (~5-6 days) implantation can occur in the endometrium. Embryo adheres to the walls of the uterus. At this stage the embryo is a blastocyst.

Question 24

Hormones by days of the menstrual cycle

Answer 24

Day 2-8: GnRH–> FSH/LH–>Ovary (increase Estrogen)
FSH: Facilitates Aromatase production in Granulosa Cells, Increases LH-R in GC
LH: Facilitates Androgen production in Thecal Cells
Estrogen Production: In Granulosa cells via Androgen conversion utilizing Aromatase. Estrogen induces Granulosa cell proliferation.

Day 8-12:
Negative feedback from Estrogen resulting in small decrease FSH.
BUT due to GC proliferation Estrogen increases beyond a threshold resulting in Positive Feedback.
Day 12-14:
Positive Feedback from Estrogen results in LH Surge, some increase in FSH.
LH attaches to LH-R on Granulosa Cells inhibiting androgen-estrogen conversion. This results in formation of Corpus Luteum formation.
LH binding also result in GC production of COX-2 → prostoglandins (“pain”)–>proteases (protein eater)–> breaks through follicle membrane–>follicle rupture–>OVULATION.
Day 15+:
Corpus luteum produces Progesterone which inhibits FSH & estrogen binding. Overall decrease in estrogen.
If No fertilization:
Corpus luteum degenerates, Progesterone gradually declines, endometrial lining sloughed (menses)
If Egg Fertilized:
Embryo produces hCG which binds LH receptors of Corpus Luteum.
Corpus Luteum continues Progesterone production & endometrial lining stays in tact.
Fertilized egg travels oviduct (5-6 days): zygote (one cell)–>2-cell–>Morula–>Blastocyte
Implantation occurs