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Reproductive Anatomy > Control of Reproduction in the Female > Flashcards

Control of Reproduction in the Female Flashcards

1
Q

What are the different definitions of puberty?

A
  • age at first heat
  • age at first ovulation
  • age at which pregnancy is supported without negatively impacting the dam
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2
Q

Define age at first heat as a definition for puberty

A
  • oestrus behaviour
  • silent ovulation in cows and ewes not able to get pregnant
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3
Q

Define age at first ovulation as a definition for puberty

A
  • although able to ovulate doesn’t mean she can carry a pregnancy to full term without detriment
  • unwise to breed here as young mothers tend to have smaller offspring with parturition issues and impared foetal development
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4
Q

In which month does puberty start in each species?

A
  • mare 14-18
  • cow 10-12
  • ewe/sow 6-7
  • bitch 4-9
  • queen 5-9
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5
Q

What can impact age of puberty?

A
  • size of breed
  • environment: season, pasture quality/availability, ruminants, seasonal breeders
  • management: nutrition quality and availability, presence of opposite sex (cattle, pigs)
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6
Q

What are the different types of cyclicity?

A
  • polyoestrus - regular cycles throughout the year
  • seasonally polyoestrus - regular cycles in certain seasons
  • monoestrus - one cycle in certain seasons of the year
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7
Q

How can different cyclicities be visualised?

A

looking at key hormones in cycle on a graph
- Y axis is oestrodiol concentrations
- peaks close to each ovulation

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8
Q

Which type of cyclicity is in each species?

A
  • bitch - monoestrus
  • queen - seasonal polyoestrus (Feb-Oct)
  • sow, cow - polyoestrus
  • ewe - seasonal polyoestrus (Sept-Jan)
  • mare - seasonal polyoestrus (April-Oct)
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9
Q

What type of ovulator is each species?

A
  • bitch, sow, cow, ewe, mare - spontaneous
  • queen - induced
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10
Q

What is different about domestic bitch cycles?

A

can demonstrate 2-4 cycles per year

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11
Q

Describe anoestrus

A
  • periods without cyclicity: seasonal, gestation, lactation
  • most of the year in monoestrus
  • doesn’t occur in mare
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12
Q

Why is lactation problematic in sows?

A
  • polyoestrus to ensure multiple births per year
  • tend to wean piglets too early
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13
Q

When does anoestrus occur in the mare?

A
  • short anoestrus in 4-14days of lactation
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14
Q

What are the 2 main stages of the oestrus cycle?

A
  • oestrus
  • dioestrus
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15
Q

Describe oestrus

A
  • sexually receptive
  • oestradiol in high conc. from follicular growth
  • peak oestradiol during ovulation then drops
  • occurs prior to ovulation then drops in progesterone
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16
Q

Describe dioestrus

A
  • not sexually receptive
  • corpus luteum producing progesterone
  • progesterone dominant hormone
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17
Q

Describe metoestrus and proestrus and when they occur

A
  • occur in dioestrus
  • metoestrus: oestrodiol decreases, progesteron increases
  • proestrus: oestrodiol increases, progesterone decrease, formation of ovarian follicles
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18
Q

How does oestrus and the follicular phase link back to folliculogenesis?

A
  • prior to ovulation
  • drop in progesterone following luteolysis of CL
  • increase in oestrodiol from developing follicle
  • LH (theca interna): selection and development of follicles
  • FSH + LH conversion of cholesterol to oestrodiol
  • follicle development: FSH + LH -> increased oestrodiol
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19
Q

How does the CL link to dioestus and anoestrus?

A
  • after ovulation
  • progesterone increased
  • dampening effect on system
  • oestrodiol produced at basal levels
20
Q

How long is oestrus in each species (days)?

A
  • cow, ewe, sow - 2
  • mare - 5
  • bitch - 9
  • queen - 10
21
Q

How long is dioestrus in each species (days)?

A
  • cow - 19
  • sow - 20
  • ewe - 15
  • mare - 16
  • bitch 60-90
  • queen 14-21
22
Q

how long is the entire oestrus cycle in each species (days)?

A
  • cow, sow, mare - 21
  • ewe - 17
  • bitch ~6months
  • queen - 20-40
23
Q

Describe the endocrine changes in the oestrus cycle

A

HPA axis:
- hypothalamus produces GnRH
- pituitary produces FSH&LH
- ovary produces oestrogens and progesterone from CL formation
- uterus produces prostaglandin F2alpha and E2

24
Q

Describe the role of the hypothalamus in oestrus

A
  • acts on anterior pituitary
  • region of brain controlling thist, hunger and temp
  • connected via neurons and capillary network called hypothalamohypophysial portal system
25
Q

Describe the role of the pituitary gland in oestrus

A
  • master gland
  • anterior pituitary secretes FSH to granulosa and LH to theca interna
  • FSH converts cholesterol to androstenedione for follicle recruitment
  • LH converts androstenedione to oestrodiol for selection and dominance
26
Q

Describe the positive and negative feedback in oestrus

A
  • progesterone has a negative feedback effect on the whole system
  • PGF2alpha - negative on CL - luteolysis
  • overall the system is positive feedback
27
Q

Describe oestrus in seasonal polyoestrus breeders

A
  • controlled by pineal gland
  • light detected by photoreceptors on retina - neural connection to hypothalamus which sends signal to pineal
  • in periods of darkness: pineal produces melatonin from pinealocytes
  • excites HPG axis in short day breeders, increasing GnRH
  • opposite in long day breeders
28
Q

Describe the first ovulation after anoestrus in seasonal breeders such as sheep

A
  • not uncommon for it to be silent
  • follicle developes and ovulates but no secondary oocyte
  • often no oestrus behaviour
29
Q

Describe the role of GnRH

A
  • peptide hormone
  • 80% goes to anterior pituitary, physiological effect
  • 20% to CNS, behavioural effect
  • secreted by hypothalamus, travels by hypothalamohypophyseal portal system to anterior pituitary
30
Q

Why are GnRH levels difficult to quantify?

A

travels via neuronal network

31
Q

Describe the episodic release of GnRH and reproductive hormones

A
  • basal secretion on pituitary gland in small pulses
  • low oestrodiol - negative feedback
  • high progesterone
  • preovulatory surge of GnRH - increases in follicular phase
  • leads to low progesterone and high oestradiol
  • oestradiol positive feedback on hypothalamus to increase GnRH
32
Q

Describe the role of FSH in the cycle

A
  • GnRH increase leads to increased FSH
  • increased progesterone leads to decreased FSH
  • as ovulation approaches, increased GnRH and FSH
  • follicle size increases accompanied by LH - decreased oestradiol
33
Q

Describe FSH in monophasic animals

A
  • FSH increase starts on D13 (ewe) or D14/15 (cow, sow)
  • 1 main peak just prior to ovulation
  • short pre-ovulatory follicle development cycle
34
Q

Describe FSH in the mare

A
  • prolonged peak
  • long follicle development cycle - main increase from D14/15
35
Q

Describe LH in the cycle

A
  • negative feedback on FSH
  • secreted by anterior pituitary on theca cells on follicle in ovary via circulation, triggered by GnRH
  • drives follicle development/recruitment and oestrodiol secretion from theca cells
  • causes ovulation and CL formation
  • removes miotic inhibitors from primary oocyte allowing meiosis I to complete
  • controls GnRH increase - increases LH
  • controls E increase - increases LH
  • controls progesterone increase - decreases LH
36
Q

Describe LH prior to ovulation

A
  • GnRH, progesterone, oestrodiol increase
  • 1 large pre-ovulatory peak: D16 (ewe), D18 (mare), D20 (cow, sow)
  • most mammals - short peak
  • mares: prolonged peak day after ovulation
37
Q

Describe the role of oestradiol

A
  • drives oestrus
  • increases FSH and LH: positive feedback on LH, negative for FSH
  • acts on CNS
  • secreted by large follicles
38
Q

When does progesterone plateu?

A
  • luteal phase
  • mare, cow, sow: D6-15
  • ewe, queen: D6-13
  • bitch: D10 onwards
39
Q

What is the role of progesterone?

A
  • prepare for pregnancy: inhibits HPG axis, reduces LH and FHS
  • if pregnant: CL and progesterone remains
40
Q

Describe what happens to progesterone if not pregnant?

A
  • reduction in progesterone resulting in
  • FSH increase - follicle development
  • oestrodiol increase - start next oestrus
  • LH increase - induce ovulation
  • PGF2a knocks out CL
41
Q

Describe PGF2a

A
  • prostaglandin F2 alpha
  • ends luteul phase - reduces progesterone and ends inhibition of HPG axis
  • allows ovulation and oestrus to occur
  • 21D cycle: D14/15
  • 17D cycle: D13
42
Q

Describe the genital tract changes in dioestrus

A
  • progesterone influence to prepare for implantation/pregnancy
  • cervix tight, white, dry, reduced secretion
  • uterus: wall thickens, epithelium proliferates (cuboidal), increased endometrial gland activity, increased tone
43
Q

Describe the genital tract changes in oestrus

A
  • oestrogen influence
  • aim to allow passage of penis, encourage movement of sperm to ovulated ova
  • vulva swells, reddening (not all species)
  • cervix loose, red/pink and secretions
  • uterus: wall thinner, reduced gland activity, flaccid, myometrial contractions
44
Q

What are the behavioural changes in dioestrus?

A

hostility to male

45
Q

What are the general behavioural differences in oestrus?

A
  • increased locomotion
  • docility
  • acceptance of male
  • urination stance, raised tail
  • mounting activity - not true sign but indicative
46
Q

What are the species differences for behavioural changes in oestrus?

A
  • mare: lengthening and eversion of vulva/clitoris
  • sow - lordosis
  • queen - lordosis and vocalisation

Reproductive Anatomy (10 decks)

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