Reprductive system

Question 1

Hypothalamic-Pituitary-Gonadal Axis pathway 7 steps

Answer 1

. hypothalamus releases GnRH

2. GnRH stim ANT pit
3. Ant pit makes LH and FSH
4. LH and FSH stimulate development of follicles in ovaries
5. Theca granulose cells around the follicles secrete oestrogen
6. Oestrogen has NEG FB effect on hypothalamus + ant pit
7. GnRH so LH and FSH release suppressed

Question 2

What is the most prevalent and active version of oestrogen?

Answer 2

17-beta oestradiol

Question 3

What does oestrogen stimulate?

Answer 3

secondary female characteristics...
Breast tissue development
Growth and development of the female sex organs (vulva, vagina and uterus) at puberty
Blood vessel development in the uterus
Development of the endometrium

Question 4

what produces progesterone in pregnancy and when?

Answer 4

produced by the corpus luteum after ovulation.

When pregnancy occurs, progesterone is produced mainly by the placenta from 10 weeks gestation onwards.

Question 5

where can progesterone act and what is its function x3

Answer 5

Progesterone acts on tissues that have previously been stimulated by oestrogen.
Progesterone acts to:
-Thicken and maintain the endometrium
-Thicken the cervical mucus
-Increase the body temperature

Question 6

What age does puberty start?

Answer 6

girls 8-14
boys 9-15

takes 4 years from start to finish

Question 7

why do fat kids enter puberty earlier?

Answer 7

Aromatase is an enzyme found in adipose (fat) tissue, that is important in the creation of oestrogen.
More aromatase if fat

Question 8

what are the 3 stages of puberty in girls

Answer 8

1. . breast buds
2. pubic hair
3. menstrual periods (2 years from start)

Question 9

What is Tanner staging used for?

Answer 9

The stage of pubertal development can be determined using the Tanner scale, based on examination findings of secondary sexual characteristics.

Question 10

what are the hormonal changes during puberty?

Answer 10

1. GH inc 1st –> growth spurt
2. hypo secretes GnRH –> FSH and LH –> oes and prog
3. FSH levels plateau 1 year pre menarche
4. LH levels continue to rise and spike just before they induce menarche

Question 11

what hormone induces menarche?

Answer 11

LH spike

Question 12

Dates of 2 phases of menstrual cycle

Answer 12

follicular phase = start of menstruation to ovulation (day 1-14)

luteal phase = ovulation to start of menstruation (final 14 days)
fixed 14 days

Question 13

4 stages of follicles

Answer 13

Primordial follicles
Primary follicles
Secondary follicles
Antral follicles (also known as Graafian follicles)

primordial –> 1y and 2y 24/7
2y –> develop R for FSH

Question 14

what hormone stimulates 2y follicles to develop into Graafian (Antral) follicles

Answer 14

FSH

• -> grow by granulose cells surround follicle –> secrete +++ estradiol
• -> NEG FB at ant pit so dec LH and FSH

Question 15

How does oestrogen affect cervical mucus at time of ovulation

Answer 15

++ oestrogen from granulosa cells of follicle –> mucus becomes more permeable so sperm can penetrate the cervix

Question 16

what hormone causes ovulation

Answer 16

1 dominant follicle
LH spike just before ovulation –> follicle releases ovum

LH causes smooth muscle of the theca externa to squeeze, and the follicle to burst
–> released into peritoneal cavity, then swept up by fimbriae of Fallopian tubes

Question 17

what happens when fertilisation occurs?

Answer 17

the syncytiotrophoblast of the embryo secretes human chorionic gonadotrophin (HCG).
HCG maintains the corpus luteum –> secretes +++progesterone and ++oestrogen

Without hCG, the corpus luteum degenerates

Question 18

what causes menstruation?

Answer 18

no HCG from embryo to maintain corpus luteum

• -> no long secretes +++progesterone and oestrogen
• -> endometrium breaks down

Question 19

what do stromal cells of endometrium release in menstruation?

Answer 19

prostaglandins –> encourage the endometrium to break down and the uterus to contract.

Question 20

When does the 1st and 2nd polar body develop?

Answer 20

just before ovulation, primary oocyte –> meiosis
diploid cell –> 2x haploid cells
1x 23 chr float away = polar body
…then 2y oocyte

sperm try to penetrate corona radiata and zone pellucida
23 chr of egg x2
–> 23 W chr combine with 23 M chr
–> other 23 chr float away = 2nd polar body

Question 21

how long does it take for blastocyst to enter uterus?

Answer 21

8-10 days after ovulation

Question 22

how can baby get oxygen from placenta

Answer 22

fetal hb has higher affinity for o2 than adult hb

–> fetal hb more attractive to o2 mols so shifts

Question 23

what happens to hCG levels in pregnancy and why?

Answer 23

The syncytiotrophoblast produces hCG (outermost layer of blastocyst)
hCG levels increase in early pregnancy, plateau at around ten weeks gestation, then start to fall.
HCG helps to maintain the corpus luteum until the placenta can take over the production of oestrogen and progesterone.
HCG can cause symptoms of nausea and vomiting in early pregnancy.

Question 24

why does placenta produce oestrogen?

Answer 24

so softens tissues –> flexible
muscles and ligaments of the uterus and pelvis can expand, and the cervix to become soft and ready for birth.
enlarges and prepares the breasts and nipples for breastfeeding.

Question 25

why does placenta produce progesterone?

Answer 25

to maintain pregnancy
It causes relaxation of the uterine muscles (preventing contraction and labour) and maintains the endometrium. It causes side effects by relaxing other muscles, such as the lower oesophageal sphincter (causing heartburn), the bowel (causing constipation) and the blood vessels (causing hypotension, headaches and skin flushing). It also raises the body temperature between 0.5 and 1 degree Celsius.