Reproductive system 4

Question 1

What is Oogenesis

Answer 1

Formation and development of female gamete (oocyte) from oogonia

Question 2

What does Oogenesis require

Answer 2

Mitosis and meiosis

Question 3

When does Oogenesis occur

Answer 3

Lifetime supply produced before birth

Continues between puberty and menopause

Question 4

Where do Oocytes develop

Answer 4

Within ovarian follicles - 1 per follicle

Question 5

How often is each cycle

Answer 5

1 ovulation every 28 days (average)

Question 6

Describe Oogenesis before birth

Answer 6

Oogonium in gonad - 46 (2n)
Pop. of oogonia increase by mitosis (stops before birth)
Differentiate to form primary oocytes - 46 (2n)
Primary oocytes undergo atresia - start meiosis (halts at prophase 1 until puberty)

Question 7

Where are primary oocytes encased

Answer 7

In primordial follicle

Question 8

How many oocytes do females have at puberty

Answer 8

300,000

Question 9

What does GnRH influence

Answer 9

Small number of follicles recruited each ovarian/menstrual cycle

Question 10

How many oocytes will complete development and ovulate

Answer 10

Only one - within dominant follicles

Question 11

What happens when the primary Oocyte completes meiosis 1

Answer 11

Forms a secondary oocyte and 1st polar body - haploid n=23

Question 12

What start meiosis 2

Answer 12

Secondary oocytes - halts at metaphase 2 - suspended until fertilation

Question 13

When does meiosis 2 resume

Answer 13

When the sperm penetrates plasma membrane of the ovum at fertilisation

Question 14

What happens if fertilisation doesn’t occur

Answer 14

Will degenerate - atresia - and never complete meiosis

Question 15

Describe developing follicle

Answer 15

Multi-layered
Granulosa cells
Theca cells

Question 16

What do granulosa cells produce

Answer 16

oestradiol

Question 17

What happens during ovulation

Answer 17

Oocyte and corona radiata released into peritoneal cavity

Question 18

What are the female reproductive hormones

Answer 18

GnRH
FSH
LH
Estradiol 
Inhibin 
Progesterone

Question 19

Where is GnRH released

Answer 19

Hypothalamus

Question 20

Where is FSH and LH produced

Answer 20

Anterior pituitary

Question 21

Where is Estradiol, inhibin and progesterone produced

Answer 21

Ovary
Follicles - Estradiol and inhibin
Corpus luteum - Inhibin and progesterone

Question 22

What does GnRH do

Answer 22

release of FSH and LH

Question 23

What does FSH do

Answer 23

Stimulates growth of ovarian follicles

Question 24

What does LH do

Answer 24

Surge of LH involved in ovulation - formation of corpus luteum

Question 25

What does estradiol do

Answer 25

``` Assists follicle growth Bone and muscle growth Endometrial growth Secondary sex characteristics Feedback to anterior pituitary ```

Question 26

What does inhibin do

Answer 26

Negative feedback of anterior pituitary to suppress FSH

Question 27

What does progesterone do

Answer 27

Negative feeds back to suppress GnRH Endometrial maturation Maintains pregnant state

Question 28

What does the ovarian/menstrual cycle do

Answer 28

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

Question 29

Describe menarche (menstrual period)

Answer 29

Part of puberty - increase in sex steroid production (estrogens)

Question 30

Why does menopause occur

Answer 30

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

Question 31

What are the two phases of the reproductive cycle

Answer 31

Follicular - preovulatory phase: day 1-14 | Luteal - postovulatory: day 15-28

Question 32

Describe the follicular (preovulatory) phase

Answer 32

Increased FSH from AP - stimulates follicular growth - secrete estradiol and inhibin - reduces FSH (negative feedback) - follicles undergo atresia, except dominant follicle - secretes large amounts of estradiol (positive feedback) - surge of LH Follicle ruptures and ovulation occurs - oocyte enters peritoneal space/collected into uterine tube

Question 33

Describe luteal (postovulatory) phase

Answer 33

Ovulation follicle collapses and forms corpus luteum - secretes progesterone, estradiol and inhibin - Decrease FSH and LH - Negative feed back to hypothalamus

Question 34

What happens if fertilisation doesn't in the luteal (postovulatory) phase

Answer 34

If fertilisation and implantation don't occur corpus luteum involutes (luteolysis) Fall in progesterone and estradiol Removes negative feedback on FSH and LH and cycle starts again

Question 35

Describe the menstrual and proliferative phase

Answer 35

Endometrium breaks down and bleeds Estradiol stimulates endometrial growth (days 6-14) Rapid tissue growth - growth of glands and vasculature

Question 36

Describe secretory phase

Answer 36

Days 15-28 After ovulation corpus luteum secretes progesterone Progesterone promotes endometrial maturation - glands become secretory - Spiral arterioles grow and coil

Question 37

Describe secretory phase if fertilisation and implantation doesn't occur

Answer 37

Corpus luteum atrophies Progesterone levels fall Spiral arteries contract Endometrial tissue breaks down and bleeding occurs Shed tissue and blood removed via cervix and vagina