Menstrual Cycle and Ovulation (Creamer)

Question 1

What are the two organs primarily involved in the menstrual cycle

Answer 1

Ovaries & Uterus

Question 2

What are the stages of development of the ovarian follicle

Answer 2

1. Follicular phase
2. Ovulatory phase
3. Luteal phase

Question 3

What state is the gamete in as a primordial follicle

Answer 3

Primary oocyte arrested in Prohase I

Question 4

What surrounds a primordial follicle

Answer 4

Single layer of preganulosa cells

Question 5

What does a primary follicle consist of

Answer 5

Growing primary oocyte surrounded by a single layer of cuboidal shaped granulosa cells & early zona pellucida (ZP1-ZP4)

Question 6

What makes up a secondary follicle

Answer 6

Growing primary oocyte surrounded by zona pellucida, 3-6 layers of cuboidal granulosa cells & thecal cells

Question 7

What is the function of the zona pellucida

Answer 7

Provides a binding site for sperm durng fertilization

Question 8

What receptors do granulosa and thecal cells express on their surface?

How do they grow before they start producing ovarian hormones?

Answer 8

Granulosa - FSH receptors

Thecal - LH receptors

They depend on paracrine factors from the oocyte and surrounding cells for growth

Question 9

What is the dense mass of granulosa cells that surrounds the oocyte after the formation of the antrum

Answer 9

Cumulus oophorus/corona radiata

Question 10

During antral development what are the two populations of granulosa cells that are formed

Answer 10

1. Mural/stratum granulosa (outer wall of follicle that become highly steroidogenic)
2. Corona radiata/cumulus oophorus (released during ovulation with oocyte)

Question 11

At what stage does the follicle become responsive to gonadotropins

Answer 11

Devlopment of the antrum

Question 12

What hormone do thecal cells respond to & what is the response

Answer 12

LH

Androgen synthesis from acetate and cholesterol (primarily androstenedione)

Question 13

What hormone do granulosa cells respond to & what is the response

Answer 13

FSH

Converts androgens (androstenedione) from thecal cells to estrogen

Question 14

Why do granulosa cells upregulate LH receptors before ovulation

Answer 14

LH triggers granulosa cells to secrete more inhibin which inhibits FSH secretion. Decreased FSH allows for the establishment of the dominant follicle.

Question 15

What makes an oocyte competent to finish meiosis I at ovulation?

Answer 15

During the antral phase, the follicles become large which allows the oocyte to synthesize sufficient amounts of cell cycle components (CDK-1 and cyclin B) but they stay arrested until the large LH surge

Question 16

How is meiotic arrest achieved even though the large antral follciles gain meiotic competence

Answer 16

Maintenance of elevated cAMP levels keeps the follicle arrested in Prophase I

Question 17

How is the dominant follicle selected?

Answer 17

Mural granulosa cells produce low levels of estrogen and inhibin which will decrease FSH levels. Largest follicle with the most FSH receptors becomes the dominant follicle.

The dominant follicle becomes a large preovulatory follicle known as Graffian follicle

Question 18

What is the periovulatory period

Answer 18

Time between LH surge and ovulation ~32-36 hours

Question 19

What are the effects of luteinization on theca and granulosa cells

Answer 19

• During the LH surge both thecal and granulosa cells have LH receptors.
• Inhibition of aromatase expression and estrogen production
• Low levels of LH promotes progesterone production

Question 20

What structural changes are seen with an LH surge?

Answer 20

OVULATION

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)

Question 21

What is the corpus luteum?

Answer 21

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

Question 22

What is corpus albicans?

Answer 22

Regressed form of the corpus luteum.

• No fertilization occurs: corpus luteum is broken down by macrophages
• Fibroblasts lay down type collagen
• Remains may persist as a scar on the surface of the ovary

Question 23

How does the corpus luteum stay viable?

Answer 23

If fertilization occurs, hCG rescues corpus luteum and will be viable for duration of pregnancy

Question 24

What is the function of the corpus luteum in pregnancy?

Answer 24

Produces increasing amount of progesterone

• Transforms uterine lining into supportive structure important for implantation
• Low levels of LH
• Secrete inhibin A to suppress FSH

Question 25

What is follicular atresia?

Answer 25

• Demise of ovarian follicle (predominant process in the ovary)
• Granulosa cells & oocytes undergoes apoptosis at any time during development
• Thecal cells persist and retain LH receptors & the ability to produce androgens

Question 26

What repopulates cellular stroma of ovaries?

Answer 26

Thecal cells

Question 27

At what point in the menstrual cycle is the basal body temperature lower

Answer 27

Higher levels of estrogen present during the pre-ovulatory (follicular) phase of the menstrual cycle

Question 28

At what point in the menstrual cycle is the basal body temperature high

Answer 28

Higher levels of progesterone released by the corpus luteum after ovulation

Think about how the body misbehaves when you’re ovulating