Reproductive system

Question 1

What hormones control production of follicle by ovary?

Answer 1

FSH and LH

Question 2

What steroids are produced by the ovary?

Answer 2

oestradiol and progesterone

Question 3

When does ovulation occur?

Answer 3

Day 14

Question 4

What steroids are released during the proliferative phase?

Answer 4

oestrogen

also released during the follicular phase

Question 5

Which hormone does the corpus luteum release?

Answer 5

It makes progesterone

Question 6

How does the combined oral contraceptive pill work?

Answer 6

• combination of oestrogen and progesterone
• Negative feedback, inhibits FSH and LH release
• This prevents follicular development, egg maturation, ovulation, egg transport in fallopian tube
• This causes unreceptive endometrium, cervical mucus is hostile to sperm

Question 7

What happens during ovulation?

Answer 7

Egg comes down tube with scilia, turns into corpus lutem goes into uterus and implants

Question 8

What is the role of trophoblasts?

Answer 8

• They form first around early blastocysts
• Trophoblasts form the placenta and form interface between mother and baby

Question 9

What does hCG do?

Answer 9

• hCG produces fast quantities bc this is the maternal recognition signal that stops egg from being rejected and early miscarriage
• hormone secreted during pregnancy by the trophoblasts which stimulates continued production of progesterone by the ovaries

Question 10

What is placenta previa caused by?

Answer 10

When the placenta is over the cervix, and during pregnancy it ruptures causing massive bleeding and death

Question 11

Which hormone stimulates uterine contractions?

Answer 11

Oxytocin induces uterine contractions in two ways. Oxytocin stimulates the release of PGE2 and prostaglandin F2α in fetal membranes by activation of phospholipase C.

Question 12

What does corticotrophin releasing hormone do and where is it released?

Answer 12

• regulates cortisol in adrenal gland of fetus
• released by the placenta as an indication of maturity

Late CRH release= late pregnancy
Early CRH release= early birth

Question 13

Where is estrogen synthesised and what triggers it?

Answer 13

Adrenal gland synthesises estrogen from progesterone
Stimulated by adrenocorticotrophin (ACTH) released by pituitary

Question 14

What role does estrogen play in labor?

Answer 14

1. stimulates prostaglandin E2 (for cervix dilation)
2. PGF2a secretion (stimulates uterine contractions)

Question 15

Describe the sequence of events for labor initation (how CRH leads to prostoglandin production)

Answer 15

1. Placental CRH matures the fetal HPA axis
2. The now mature fetal adrenal gland makes 17α-hydroxylase enzyme (which kicks off estrogen synthesis)
3. Placental trophoblasts make aromatase (which synthesises estrogen) so they secrete estrogen
4. Estrogen makes myometrium sensitive (stimulates expression of prostaglandin E and F receptors)
5. Estrogen stimulates prostaglandin E2 and PGF2α secretion

Question 16

How do testes produce sperm?

Answer 16

• SSCs and sertoli cells support meoisis of spermatocytes
• Produced/Released from semineferous tubules
• Sperm production is limited by number of sertoli cells and how active SSCs are

Sperm will continue to be produced until sertoli cells or spermatogonial cells are removed

Question 17

What are sertoli cells?

Answer 17

Referred to as nurse cells bc every germ cell are completely dependent on contact to sertoli cells for survival

Somatic cells

Question 18

What are leydig cells?

Answer 18

Surround spermatocytes and make androgens in MALES

somatic cells

Question 19

What are peritubular myoid cells?

aka PTM cells

Answer 19

• They comprise the basemement membrane of se
• They push the sperm through the lumen out to be released

Question 20

How many spermatids are made from one spermatocyte after meiosis?

Answer 20

Four round spermatids are made after two meiotic divisions

Question 21

Do spermatagonial stem cells (SSC) undergo mitosis or meiosis?

Answer 21

Mitosis

Question 22

What are thecal cells?

Answer 22

Make up basal membrane of ovarian follicle
Release androgens (female equivalent of Leydig cells)

Question 23

What are granulosa cells?

Answer 23

Support/nurse single oocyte
Produce estrogen converted from androgens
Female equiv of sertoli cells

Question 24

What are primordial follicles?

Answer 24

Formed when oocytes stop undergoing mitosis and enter meoisis (occurs mid pregnancy)

There fore once primordial follicles formation has stopped the females total possible germ cell number is FIXED. From them on it will only decline, as follicles are lost
Flattened granulosa cells surround primordial follicles

Question 25

How many germ cells are produced after oocyte undergoes meiosis?

Answer 25

After one meiotic division; one germ cell and one polar body After two meiotic divisions; one germ cell and two polar bodies

Question 26

What things occur during estrous cycles that lets males know females are ovulating?

Answer 26

- Pheremonal cues - Flehmen response: male response to female □ male sniffing pheromones to know female in oestrous □ Lions currl upper lip back to sniff odours (pheromones) - Lordosis: female response to males (Female mice arch their backs) - Will allow mounting often adopting different posture in presence of males

Question 27

How does the HPA axis control ovulation?

Answer 27

GnRH stimulates pituitary-> pituitary secretes FSH and LH-> stimulates ovary to grow follicles (dominant follicles selected to grow) -> Mature follicle goes onto ovulate

Question 28

How are follicles 'selected' to mature?

Answer 28

The ones that secrete the most estrogen are the ones that become dominant ## Footnote Estrogen has negative feedback effect on FSH, so when a follicle becomes big enough to secrete enough estrogen that it reduces FSH secretion, this would have a negative impact on the rest of the smaller follicles inhibiting their growth

Question 29

When the mature follicle(s) are approaching pre-ovulatory stage, what happens to estrogen, FSH, and LH levels?

Answer 29

Estrogen levels are VERY high, which induce a release of GnRH which induces a surge of LH and a small surge in FSH

Question 30

What are the different phases of oestrus?

Answer 30

**Proestrus** (follicular phase): follicles grow, are selected, estrogen rises **Oestrus**: mating behavior to signal ovulation, dominant follicles ovulate **Metoestrus**: early luteal, CL forms **Dioestrus**: mid-late luteal, CL at max size, if NO PREGNANCY CL regresses, progesterone output maximal **Anestrus**: cycling stops due to change in day length (only in seasonal breeders) | CL=corpus luteum ## Footnote Luteal phase: process of somatic cells from a follicle developing into a cell within a corpus luteum after ovulation

Question 31

What is the difference between spontaneous and induced ovulators?

Answer 31

Spontaneous: Ovulate each oestrus cycle no matter what happens, ovulation set in motion by HPA (Eg sheep) Induced: Follicles growing to full size but wont ovulate unless female mates at that time (eg cats or ferrets or rabbits)

Question 32

What are some differences between menstrual and oestrus cycle?

Answer 32

Menstrual cycle has... - No oestrus behavioor - No pheremones - No outward event revealing cyclicity - Sexual receptivity throughout | Humans have menstrual cycle

Question 33

What are the differences in sexual dimorphism in animals with oestrus vs menstrual cycles?

Answer 33

- Oestrus: competition for ovulating females is intense (eg male gorillas much bigger than females bc of this) - Menstrual: more monogamous pairing= less competition= less sexual dimorphism

Question 34

Seasonal breeding ensures that...

Answer 34

Babies are born during seasons with prime environmental conditioons (spring/summer)

Question 35

How does the HPG axis and pineal gland regulate ovulation/pregnancy?

Answer 35

- HPG axis detects changes in melatonin secretion from pineal gland - In seasonal breeders, this causes GnRH decrease, which decreases FSH and LH, which shuts down gonad (ovary or testes) - Short day breeders: change from short day-> long day triggers HPG - Long day: change from long day-> short day triggers HPG ## Footnote Pineal gland gets input from the eyes, so during winter; more dark= more melatonin secretion short day breeders only breed during winter (aka short days) Long day breeders only breed during summer (aka long days)

Question 36

Why do some species exhibit embryonic diapause?

Answer 36

Obligate diapause: - Eg polar bears: mate in spring but embryos stay in diapause until autumn then born in the following spring - Eg roe deer: mating around july/aug, but birth around May Facultative diapause: - Eg rodents: (regulated by lactation) Implantation of embryo is delayed to ensure that lactation of current offspring is done by the time that the next offspring is born ## Footnote Embryonic diapause: Embryos develop to the point at which they are ready to implant but then enter a suspended state, delaying implantation, and hence delaying the timing of the birth

Question 37

How does the HPA axis control puberty?

Answer 37

GnRH is released by the hypothalamus GnRH stimulates anterior pituitary to secrete LH and FSH LH and FSH acts on gonads which secrete hormones that have negative feedback on hypothalamus - LH tells leydig to secrete tesosterone, inhibin B, & estrogen - LH/FSH tells ovary to secrete estrogen, inhibin, progesterone

Question 38

What does Anti-Mullerian hormone do? What cells is it secreted by

Answer 38

- If men don’t express this hormone they are born with a uterus, high AMH in men leads to wolffan duct development instead of mullerian - If women express this hormone they are born without fallopian tubes, uterus, or cervix - Secreted by sertoli cells and granulosa cells - High AMH in women is directly correlated to high antral follicle count

Question 39

What is Kallmanns syndrome?

Answer 39

- Lack of GnRH so puberty never happens - Need exogenous GnRH to drive puberty

Question 40

What time of day is LH secreted during puberty?

Answer 40

During the night ## Footnote night pulses turn on gonadal hormone production