Lecture 37

Question 1

What are the stem cells that produce oocytes?

Answer 1

oogonia

Question 2

Is an oogonia cell haploid or diploid?

Answer 2

Diploid (2n = 46)

Question 3

What does oogenesis require?

Answer 3

mitosis and meiosis

Question 4

When is oogenesis initiated?

Answer 4

Before birth

Question 5

What does oogenesis supply?

Answer 5

A life time supply of gametes produced before birth

Question 6

Where do the oocytes develop?

Answer 6

Within ovarian follicles

Question 7

How does the population of oogonia cells increase?

Answer 7

Via mitosis which stops before birth

Question 8

What do oogonia differentiate into?

Answer 8

Primary oocytes

Question 9

Are primary oocytes haploid or diploid?

Answer 9

Diploid (2n = 46)

Question 10

What is the primary oocyte encased by?

Answer 10

The primary follicle

Question 11

What happens to many of the primary oocytes?

Answer 11

They undergo atresia, a form of apoptosis

Question 12

What do primary oocytes initiate?

Answer 12

Meiosis

Question 13

Where does meiosis halt?

Answer 13

Prophase 1

Question 14

When does meiosis procede?

Answer 14

At the beginning of puberty

Question 15

What is menarche?

Answer 15

The first menstrual cycle

Question 16

When puberty is reached, how many oocytes do females have?

Answer 16

~300,000

Question 17

What happens in meiosis 1 after puberty has begun?

Answer 17

The primary oocyte will divide into a secondary oocyte and the first polar body

Question 18

Is the secondary oocyte haploid or diploid?

Answer 18

Haploid (n)

Question 19

What is a polar body?

Answer 19

A small haploid cell that cannot be fertilised and dies

Question 20

What starts meiosis 2?

Answer 20

The secondary oocyte

Question 21

Where does meiosis 2 halt?

Answer 21

At metaphase 2

Question 22

When does meiosis 2 procede?

Answer 22

When fertilised - when the sperm penetrates the plasma membrane of the ovum

Question 23

What happens to the secondary oocyte if fertilisation does not occur?

Answer 23

It will degenerate and undergo atresia, not completing meiosis

Question 24

What does one primary oocyte ultimately form?

Answer 24

One ova and three polar bodies

Question 25

Where does oogenesis occur?

Answer 25

Within the developing follicle

Question 26

What are follicles?

Answer 26

Multilayered cell systems containing oocyte

Question 27

What are the two types of cells within the follicle?

Answer 27

Granulosa and theca cells

Question 28

What do granulosa cells produce?

Answer 28

Estradiol which surrounds oocyte

Question 29

What is ovulaition?

Answer 29

When the oocyte and corona radiata are released into the peritoneal cavity

Question 30

What is the female reproductive hormone released from the hypothalamus?

Answer 30

Gonadotropin-releasing hormone (GnRH)

Question 31

What does GnRH do?

Answer 31

Stimulates release of follicle simulating (FSH) and luteinising hormone (LH)

Question 32

Where is FSH and LH released from?

Answer 32

The anterior pituitary gland

Question 33

What does FSH do?

Answer 33

Stimulates the growth of ovarian follicles

Question 34

What does LH do?

Answer 34

Is involved in ovulation; the formation of the corpus luteum

Question 35

What hormones do the ovary follicles secrete?

Answer 35

Estradiol (an estrogen) and inhibin

Question 36

What hormones do the ovary corpus luteum secrete?

Answer 36

Inhibin and progesterone

Question 37

What does estradiol do?

Answer 37

Assists follicle growth, bone and muscle growth, endometrial growth and secondary sex characteristics Feeds back to anterior pituitary

Question 38

What does inhibin do?

Answer 38

Negative feedback to anterior pituitary to suppress FSH

Question 39

What does progesterone do?

Answer 39

Negatively feeds back to hypothalamus to suppress GnRH (therefore LH and FSH too). Also involved in endometrial maturation and maintains the pregnant state

Question 40

What is the purpose of the ovarian cycle?

Answer 40

To prepare an oocyte for fertilisation and the endometrium for embryo implantation

Question 41

When does menarche occur?

Answer 41

Around 12-13 years old

Question 42

What is one part of puberty orchestrated by?

Answer 42

The increase in sex steroid production (estrogens) by the gonads

Question 43

What happens in menopause?

Answer 43

The reduction of estradiol and progesterone due to the absence of or lack of response by follicles. The anterior pituitary feedback is no longer active and therefore FSH and LH are high

Question 44

What is the follicular phase?

Answer 44

The preovulatory phase; day 1 - 14

Question 45

What is the luteal phase?

Answer 45

The postovulatory phase; day 15 - 28

Question 46

What happens during the follicular phase?

Answer 46

Increase FSH stimulates follicular growth, which secretes estradiol and inhibin in turn reducing FSH from negative feedback. Growing follicles undergo atresia, except dominant. High estradiol stimulates a surge of LH from positive feedback, the follicle ruptures and ovulation occurs - oocyte enters the peritoneal space

Question 47

What happens during the luteal phase?

Answer 47

Ovulated follicle collapses and forms corpus luteum which secretes progesterone, estradiol and inhibin. These all negatively feedback to the hypothalamus, decreasing FSH and LH secretion.

Question 48

What happens in the luteal phase if fertilisation and implantation do not occur?

Answer 48

The corpus luteum involutes (luteolysis), there is a fall in progesterone and estradiol and the negative feedback on the hypothalamus is removed. FSH and LH increase again for the cycle to begin again.

Question 49

What is the menstrual and proliferative phase?

Answer 49

Day 1-14 for the endometrium

Question 50

What is the secretory / premenstrual phase?

Answer 50

Day 15 - 28 for the endometrium

Question 51

What happens in the menstrual and proliferative phase?

Answer 51

Endometrium breaks down and bleeds during menstruation. Estradiol stimulates endometrial growth from days 6-14and rapid tissue growth occurs including the growth of glands and vasculature

Question 52

What happens in the secretory phase?

Answer 52

After ovulation (day 14) corpus luteum secreted progesterone which promotes endometrial maturation. Glands become secretory and spiral arterioles grow and coil

Question 53

What happens at the end of the secretory phase if fertilisation does not occur?

Answer 53

Corpus luteum atrophies, progesterone levels fall and spiral arteries contract. Endometrial tissue breaks down and bleeding occurs. Shed tissue and blood removed via cervix and vagina