Lecture 37: FEMALE REPRODUCTIVE SYSTEM 2

Question 1

What is oogenesis?

Answer 1

Formation and development of the oocyte from oogonia

Question 2

What does oogenesis require?

Answer 2

Mitosis and meiosis

Question 3

What is produced before birth?

Answer 3

A lifetime supply of gametes

Question 4

When does oogenesis occur?

Answer 4

It is initiated before birth and continues between puberty and menopause

Question 5

How is oogenesis described?

Answer 5

Cyclic (1 ovulation every 28 days on average)

Question 6

Where do oocytes develop?

Answer 6

Within an ovarian follicle (stationary) - 1 oocyte per follicle

Question 7

What is in the gonad before birth?

Answer 7

oogonium (diploid, 2n=46)

Question 8

What happens to the population of oogonia?

Answer 8

They increase by mitosis (stops before birth)

Question 9

What do oogonia do?

Answer 9

Differentiate to form primary oocytes (diploid, 2n=46)

Question 10

What are primary oocytes encased in?

Answer 10

Primordial follicle

Question 11

What happens with many primary oocytes?

Answer 11

They undergo atresia

Question 12

What do primary oocytes start?

Answer 12

Meiosis

Question 13

When does meiosis halt?

Answer 13

At prophase 1 until puberty begins

Question 14

How many oocytes do females have at puberty?

Answer 14

Approximately 300,000

Question 15

What happens under GnRH influence?

Answer 15

A small number of follicles recruited each ovarian/menstrual cycle

Question 16

What does only one oocyte do?

Answer 16

Complete development and ovulate (within the dominant follicle)

Question 17

What does the primary oocyte complete?

Answer 17

Meiosis 1 to form a secondary oocyte and first polar body (both haploid, n=23)

Question 18

What does the secondary oocyte start?

Answer 18

Meiosis 2

Question 19

When does meiosis 2 halt?

Answer 19

At metaphase 2 which is suspended until fertilisation

Question 20

When does meiosis 2 resume?

Answer 20

When the sperm penetrates the plasma membrane of the ovum at fertilisation

Question 21

What happens if the secondary oocyte is not fertilised?

Answer 21

It will degenerate by atresia and therefore never complete meiosis

Question 22

What does one primary oocyte form?

Answer 22

1 ova and 3 polar bodies will also form which under go atresia

Question 23

What are the layers of the follicles?

Answer 23

Granulosa cells inside and theca cells outside

Question 24

What do granules cells produce?

Answer 24

Inhibin

Question 25

What happens in ovulation?

Answer 25

Oocyte and corona radiata released into peritoneal cavity

Question 26

What are the female reproductive hormones?

Answer 26

GnRH, FSH, LH, estradiol, inhibit and progesterone

Question 27

Where is GnRH released from?

Answer 27

The hypothalamus

Question 28

What does GnRH do?

Answer 28

Stimulate the release of FSH and LH

Question 29

Where is FSH released from?

Answer 29

The anterior pituitary

Question 30

What does FSH do?

Answer 30

Stimulate growth of ovarian follicles

Question 31

Where is LH released from?

Answer 31

Anterior pituitary

Question 32

What does LH do?

Answer 32

Surge of LH is involved in ovulation, formation of corpus luteum

Question 33

Where is estradiol released from?

Answer 33

Developing follices

Question 34

What does estradiol do?

Answer 34

Assists follicle growth (with FSH), bone and muscle growth, endometrial growth, secondary sex characteristics, feedback to anterior pituitary

Question 35

Where is inhibin released from?

Answer 35

Granulosa cells

Question 36

What does inhibit do?

Answer 36

Negative feedback to anterior pituitary to suppress FSH

Question 37

Where is progesterone released from?

Answer 37

The corpus luteum

Question 38

What does progesterone do?

Answer 38

Negatively feeds back to suppress GnRH (therefore LH and FSH), endometrial maturation, maintains pregnant state

Question 39

What are the ovarian/menstrual cycles?

Answer 39

The regular cyclic changes in the ovary and uterus that prepare an oocyte/ova for fertilisation and the endometrium for embryo implantation

Question 40

When does the menstrual cycle occur?

Answer 40

On approximately monthly basis (average 28 days) between menarche and menopause

Question 41

What is menarche?

Answer 41

First menstrual period

Question 42

When does menarche occur?

Answer 42

At age 12-13 on average

Question 43

What is menarche part of?

Answer 43

Puberty - orchestrated by increase in sex steroid production (oestrogen's) by the gonads

Question 44

What is menopause?

Answer 44

Cessation of menstruation

Question 45

When does menopause occur?

Answer 45

Typically in early 50's

Question 46

What is menopause caused by?

Answer 46

Reduction of estradiol and progesterone due to absence of or lack of response by follicles. Anterior pituitary negative feedback no longer active therefore FSH/LH high

Question 47

What are the phases of the ovarian cycle?

Answer 47

follicular (preovulatory) phase and luteal (postovulatory) phase

Question 48

When does the follicular phase occur?

Answer 48

Days 1-14

Question 49

When does the luteal phase occur?

Answer 49

Days 15-28

Question 50

What happens in the follicular phase?

Answer 50

Increased FSH from the anterior pituitary stimulates follicular growth

Question 51

What do growing follicles secrete?

Answer 51

Estradiol and inhibin

Question 52

What does growing follicles secreting estradiol and inhibin cause?

Answer 52

reduced FSH from anterior pituitary (negative feedback) and growing follicles undergo atresia (except the dominant follicle)

Question 53

What does the dominant follicle secrete?

Answer 53

Large amounts of estradiol

Question 54

What does high estradiol stimulate?

Answer 54

Surge of LH (positive feedback)

Question 55

what happens because of the surge of LH?

Answer 55

The follicle ruptures and ovulation occurs

Question 56

What happens in ovulation?

Answer 56

Oocyte enters peritoneal space/collected into uterine tube

Question 57

What happens in the luteal phase?

Answer 57

Ovulated follicle collapses and forms corpus luteum

Question 58

What does the corpus luteum secrete?

Answer 58

Progesterone, estradiol and inhibin

Question 59

What do progesterone, estradiol and inhibin do?

Answer 59

Decrease FSH and LH secretion - negative feedback on hypothalamus

Question 60

What happens if fertilisation and implantation don't occur?

Answer 60

The corpus luteum involutes (luteolysis) and eventually forms the corpus albicans

Question 61

What happens to hormones if fertilisation doesn't occur?

Answer 61

A fall in progesterone and estradiol which removes negative feedback on FSH and LH so the cycle starts again

Question 62

What are the phases of the menstrual cycle?

Answer 62

Menstrual and proliferative, then secretory

Question 63

When do the menstrual and proliferative phases occur?

Answer 63

day 1-14

Question 64

When does the secretory phase occur?

Answer 64

Day 15-28

Question 65

What happens in the menstrual phase?

Answer 65

Endometrium breaks down and bleeds (from spiral arterioles)

Question 66

What happens from approximately days 6-14 of the menstrual and proliferative phase?

Answer 66

Estradiol stimulates endometrial growth. Rapid tissue growth, including growth of glands and vasculature

Question 67

What happens after ovulation (day 14)?

Answer 67

Corpus luteum secretes progesterone

Question 68

What does progesterone promote?

Answer 68

Endometrial maturation

Question 69

What happens in endometrial maturation?

Answer 69

Glands become secretory and spiral arterioles grow and coil

Question 70

What happens if fertilisation and implantation do not occur?

Answer 70

Corpus luteum atrophies (breaks down), progesterone levels fall, spiral arteries contract, endometrial tissue breaks down and bleeding occurs, shed tissue and blood removed via cervix and vagina (menstruation/menses)