2.7 The Oestrus Cycle Pt. 2

Question 1

The time​ it takes for the follicle to become​ ovulated is

Answer 1

6 months

Question 2

time​ it takes for follicles to become pre-ovulatory?

Answer 2

4 months

Question 3

Little artresia happens between ___ and ___

Answer 3

Primordial and small antral

Question 4

50-80 atresia​ happens between ___ and ____

Answer 4

little antral and large antral
- majority die

Question 5

Antrum forms: Gonadotrophin-responsiveness

Answer 5

development continues without FSH, some atresia

Question 6

antrum forms: Gonadotrophin-dependent:

Answer 6

become atretic if FSH falls; high atresia

Question 7

What type of receptors do ovulatory follicles have?

Answer 7

Have LH receptors on granulosa cells and can survive without FSH

Question 8

Ovulation happens in the presence of ?

Answer 8

an LH surge or artesia afterabout 72hrs

Question 9

polyestrous​:

Answer 9

have regular estrus unless it’s interupted by pregnancy​

Question 10

Polyestrus species:

Answer 10

cow, queen, pig, rodent

Question 11

seasonal polyestrus:​

Answer 11

within breeding cycles they have multiple number of cycles

*If they don’t become pregnant after 1st ovulation, they have 2nd, and a 3rd, and so on until they become pregnant, or if they don’t​ become pregnant​ than the season is finished

Question 12

seasonal Polyestrus species: long-day​ breeder

Answer 12

mare
- long day because​ they breed in spring and summer

Question 13

seasonal polyestrous​: short-day breeder species

Answer 13

ewe, doe, elk, nanny
- short day because they breed in autumn

Question 14

Moniestrus:

Answer 14

only have one cycle
- cycle is a bit longer
- if they miss a ​chance have to wait 6-7 months to have another cycle

Question 15

monoestrus species:

Answer 15

dog, wolf, fox, bear

Question 16

Which follicles can produce estradiol?

Answer 16

• secondary/preantral follicles
• antral follicles
• preovulatory follicles

because they have both thecal cells and granulosa cells

Question 17

What do the preovulatory cells respond to?

Answer 17

LH - allowing them to produce progesterone and cause ovulation

Question 18

Key for folliculogenesis and ovaries function?

Answer 18

FSH and LH

Question 19

KEY rules of receptors on follicular cells: Thecal cells ALWAYS

Answer 19

have LH receptors, never FSH

Question 20

KEY rules of receptors on follicular cells: Granulosa ALWAYS

Answer 20

have FSH receptors, LH receptors are acquired from mid-follicular phase onwards

Question 21

KEY rules of receptors on follicular cells: The dominant​ follicle

Answer 21

survives a fall in the levels of FSH by being able to respond to LH

Question 22

2 cell 2 gonadotropin theory:

Answer 22

• LH binds to receptor on the ​Thecal cell and produces androgenm
• Androgen then goes to the Granulosa cell and is converted to estradiol under the influence of FSH

Question 23

What is the substrate for prod​uction of steroid hormones?

Answer 23

cholesterol

Question 24

What makes a follicul become a dominant follicle​?

Answer 24

Like the lottery
- Right place
- Right Stage
- Receive right signal

Question 25

Under the influence of estradiol, granulosa cells which were previously unresponsive to LH acquire

Answer 25

LH receptors and become LH-responsive

Question 26

If there is a high level of estradiol that happens in the pre-ovulatory stage then

Answer 26

then the negative feedback becomes positive

Question 27

Early-mid follicular phase plasma estradiol (E2) exerts

Answer 27

- exerts ​negative feedback on GnRH secretion - It acts mainly at the hypothalmus - Therefore FSH levels start to fall - The inhibitory effects of E2 occur only while the plasma E2 concentration is BELOW a certain threshold value

Question 28

Plasma concentrations rise ABOVE the threshold value:

Answer 28

cause E2 peak in the late follicular phase, it acts on the pituitary to STIMULATE gonadotrophin secretion *This high level of estradiol ultimately gives rise to the surge in LH causeing the negative feedback to become positive feedback

Question 29

key event that induces follicular​ rupture?

Answer 29

surge in LH

Question 30

Ovulutaion occurs when the thin walls of the follicle___

Answer 30

rupture, the secondary oocyte surrounded by the zona pellucida are released​ into the oviduct

Question 31

LH surge consequence:

Answer 31

estradiol production then falls and progesterone starts to increase

Question 32

Luteal cells:

Answer 32

follicle cells that remain within the ovary are transformed through a process called luteinisation

Question 33

What happens before ovulation?

Answer 33

- surge / Peak of LH is happening - LH causes the follicle to rupture and release the egg

Question 34

Once egg is released what has to happen in order for the egg to be fertilized.​

Answer 34

It has to be in the right stage: - meiosis and develop to metaphase II This is called oocyte maturation which initiates after LH surge

Question 35

If a follicle is ruptured what forms in place of it?

Answer 35

corpus luteum

Question 36

Answer 36

Question 37

large luteal cells are thought to arise from?

Answer 37

granulosa cells

Question 38

small luteal cells are thought to arise from

Answer 38

theca cells

Question 39

small luteal cells and large luteal cells ca produce?

Answer 39

progesterone

Question 40

Hormone that cause corpus litheum lysis?

Answer 40

PGF2 alpha cause CL to go down

Question 41

How is the CL causing its own death?

Answer 41

- normally produces progesterone towards the end of the cycle when there is no pregnacy - Then produces oxytocin and binds to receptor in the uterine endometrium - this stimulates the production of PGF2 alpha - PGF2 alpha goes to CL and causes regression

Question 42

Which species have an estrus cycle of 21 days?

Answer 42

horse, cow, pig,

Question 43

Which species have an estrus cycle of 17 days

Answer 43

sheep

Question 44

Which species have an estrus cycle of 93 days

Answer 44

dog

Question 45

cow estrus stage:

Answer 45

12-36 hrs

Question 46

dog estrus stage:

Answer 46

7-13 d

Question 47

cow vs dog estrus stage:

Answer 47

cow = quite short dog = monoesters have lengthy estrus cycle to allow more opportunity to become pregnant​