Reproductive system (basic anatomy and physiology)

Question 1

Where is GnRH released from?

Answer 1

-hypothalamus

Question 2

What does GnRH do?

Answer 2

-stimulates anterior pituitary to release LH and FSH

Question 3

What do FSH and LH do?

Answer 3

-stimulate the development of follicles in the ovaries which in turn then release oestrogen

Question 4

What cells secrete oestrogen?

Answer 4

-the theca granulosa cells around the follicles in ovaries

Question 5

What effect does oestrogen have on the hypothalamus and pituitary gland?

Answer 5

-oestrogen has negative feedback on the hypothalamus and anterior pituitary to suppress release of GnRH, LH and FSH

Question 6

What is oestrogen?

Answer 6

-a steroid sex hormone produced by the ovaries in response to LH and FSH

Question 7

What is the most prevalent and active form of oestrogen?

Answer 7

17-beta oestradiol

Question 8

What does oestrogen act on?

Answer 8

-tissues with oestrogen receptors to promote female secondary characteristics

Question 9

What does oestrogen stimulate?

Answer 9

• breast tissue development
• growth and development of female sex organs (vagina, vulva and uterus) at puberty
• blood vessel development in the uterus
• development of the endometrium

Question 10

What is progesterone?

Answer 10

-a steroid sex hormone produced by the corpus luteum after ovulation

Question 11

Where is progesterone produced during pregnancy?

Answer 11

-mainly by the placenta from 10 weeks gestation onwards

Question 12

What does progesterone act on?

Answer 12

-tissues that have previously been stimulated by oestrogen

Question 13

What does progesterone do?

Answer 13

• thickens and maintains the endometrium
• thickens the cervical mucus
• increases body temp

Question 14

What happens to these sex hormones during puberty?

Answer 14

-they start to increase which leads to development of female secondary sexual characteristics and onset of menstrual cycle

Question 15

What age does puberty usually begin in women?

Answer 15

-8-14 years

Question 16

How long does puberty usually last?

Answer 16

-about 4 years

Question 17

Why might there be delayed puberty in girls with low weight/eating disorders?

Answer 17

• aromatase is an enzyme found in adipose tissue
• it is important in the creation of oestrogen
• low weight means less adipose tissue so less aromatase for oestrogen production

Question 18

Describe the puberty stages in order in women

Answer 18

breast bud development–> pubic hair—> menstrual periods

Question 19

Describe the hormonal changes in puberty

Answer 19

• GH increases intially causing growth spurt
• GnRH is released during sleep at first then throught the day later in puberty
• GnRH stimulates release of FSH and LH whihc then stimulate release of oestrogen and progesterone from ovaries
• FSH levels plateau about a year before menarche while LH levels spike just before menarche

Question 20

What are the 2 phases of the menstrual cycle?

Answer 20

• follicular phase

- luteal phase

Question 21

When does follicular phase start?

Answer 21

-follicular phase is from the start of menstruation to moment of ovulation (first 14 days in 28 day cycle)

Question 22

When does luteal phase start?

Answer 22

-luteal phase is from ovulation to the start of menstruation (last 14 days of cycle)

Question 23

What are oocytes?

Answer 23

in the ovaries a finite number of cells that have potential to develop into eggs

Question 24

What are follicles formed from?

Answer 24

-granulosa cells surrounding oocytes

Question 25

What are the four stages of development that follicles go through in the ovaries?

Answer 25

- primordial follicles - primary follicles - secondary follicles - antral follicles (Graafian)

Question 26

Describe the process of primordial follicles maturing into primary and secondary follicles during follicular phase

Answer 26

- it is always occurring independent of the menstrual cycle - once the follicles reach secondary follicle stage, they develop receptors for FSH - further development for secondary follicles requires stimulation from FSH

Question 27

Describe the effect of FSH on secondary follicles during follicular phase

Answer 27

- at start of menstrual cycle, FSH stimulates development of secondary follicles - they grow and the granulosa cells surrounding them secrete increasing amounts of oestradiol(oestrogen) - oestrogen has negative feedback on FSH and LH and also causes cervical mucus to become more permeable-> allows spem to penetrate the cervix around time of ovulation - one of the follicles will develop further than others to become the dominant follicle

Question 28

Describe the effect of LH on the dominant follicle during follicular phase

Answer 28

-LH spikes just before ovulation causing dominant follicle to release the ovum (unfertilised egg) from the ovary

Question 29

When does ovulation happen?

Answer 29

14 days before end of menstrual cycle, e.g day 14 of 28 day cycle or day 16 of 30 day cycle

Question 30

Describe what happens during the luteal phase after the dominant follicle has release ovum after ovulation

Answer 30

- the follicle that release the ovum collapses and becomes the corpus luteum - the corpus luteum secretes high levels of progesterone which maintains the endometrial lining - progesterone also causes cervical mucus to become thick and no longer penetrable - the corpus luteum also secretes small amounts of oestrogen

Question 31

Describe what happens during the luteal phase when fertilisation occurs

Answer 31

- the syncytiotrophoblast of the embryo secretes hCG - hCG maintains the corpus luteum--> without it, it degenerates - pregnancy tests check for hCG

Question 32

Describe what happens during the luteal phase when no fertilisation occurs

Answer 32

- no fertilisation of ovum --> no production of hCG --> corpus luteum degenerates and stops producing oestrogen and progesterone - this fall in oestrogen and progesterone causes the endometrium to break down and menstruation occurs

Question 33

What additional substance promotes the break down of endometrium during menstruation?

Answer 33

-stromal cells of endometrium release prostaglandins which encourage break down of endometrium and uterus contraction

Question 34

What does menstruation involve?

Answer 34

- it involves the superficial and middle layers of the endometrium seperating from the basal layer - the broken down tissue in the uterus is released via the cervix and vagina resulting in a release of fluid containing blood - this lasts 1-8 days