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Complex Approach To Organ Systems > Reproduction > Flashcards

Reproduction Flashcards

1
Q

What is the highest regulation centre of reproductive processes?

A

Hypothalamus

Reproductive and non-reproductive peripheral; signals are integrated in hypothalamic GnRH cells (main integrator and effective of the regulation of reproduction)

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2
Q

Gonadotropin- releasing hormone (GnRH) is produced by ___?

A
  • produced in hypothalamus by parvocellular group
  • axonial transport -> portal circulation -> FSH and LH producing cells
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3
Q

GnRH frequency is influenced by ___?
(3 parameters)

A
  • oestrus phase (hormones)
  • season (melatonin)
  • energy balance
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4
Q

The quick GnRH increase is followed by an ___ peak and results in ___

A

LH, ovulation

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5
Q

Kisspeptin — ?

A

Kisspeptin is a neuropeptide with a critical role in the function of the hypothalamic–pituitary–gonadal (HPG) axis.

Kisspeptin is produced by two major populations of neurons located in the hypothalamus, the rostral periventricular region of the third ventricle (RP3V) and arcuate nucleus (ARC).

These neurons project to and activate gonadotrophin-releasing hormone (GnRH) neurons (acting via the kisspeptin receptor, Kiss1r) in the hypothalamus and stimulate the secretion of GnRH. Gonadal sex steroids stimulate kisspeptin neurons in the RP3V, but inhibit kisspeptin neurons in the ARC, which is the underlying mechanism for positive- and negative feedback respectively, and it is now commonly accepted that the ARC kisspeptin neurons act as the GnRH pulse generator.

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6
Q

Follicle stimulating hormone (FSH). Role

A
  • stimulates the growth and recruitment of immature ovarian follicles; survival factor that rescues the small follicles from apoptosis
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7
Q

FSH during luteal phase

A

In the luteal-follicle phase transition period (metestrus) the serum levels of progesterone and estrogen (primarily estradiol) decrease and no longer suppress the release of FSH (and GnRH).

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8
Q

FSH. Where is produced?

A

Hypophysis

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9
Q

Secretion of FSH is regulated by ___ ?

A
  • GnRH
  • sexual steroids (estrogen, progesterone)
  • inhibin
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10
Q

Inhibin is secreted by ___ ?

A

By dominant follicle.

Inhibin blocks the FSH secretion. (Dominant follicle has more FSH receptors so even the blood FSH level decreases it has a high concentration of the hormone)

Later, the GnRH surge is a stronger signal therefore the FSH concentration increases again together with the LH —> ovulation —> GnRH (and FSH) decreases

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11
Q

Luteinising hormone (LH). Role

A
  • ovulation, luteinization
  • supports theca cells in the ovaries that provide androgens and hormonal precursors for estradiol production
  • LH surge triggers ovulation not pnly releasing the egg from follicle but also initiating the conversion of the residual follicle into a corpus luteum that produces progesterone to prepare the endometrium for a possible implantation
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12
Q

LH secretion is regulated by ___ ?

A
  • GnRH
  • sexual steroid (E2 +; P4 - )
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13
Q

Prolactin (PRL). Role

A
  • blocks the progesterone-androstenedione conversion in matured follicle => increase of progesterone
  • in the end of pregnancy PRL increases -> lactation
  • acyclia in lactating mothers
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14
Q

Human chorionic gonadotropin (hCG)

A
  • produced in the human placenta
  • recognition of pregnancy in human
  • corpus luteum stimulation (-> P4 production increases)
  • in animals: LH-like effect
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15
Q

Equine chorionic gonadotropin (eCG)

A
  • produced by the chorion of pregnant mares
  • in mare: production of accessory CL during pregnancy (extra P4 production)
  • other animals: FSH-like effects
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16
Q

Estrogens

A

Mostly estradiol (E2)
- produces by the follicle
- FSH stimulates the production
- plays important role in female sexual cycle (secondary sexual characteristics, ovulation, endometrial, cervical and vaginal mucosa changes; sexual behaviour etc)

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17
Q

Progesterone (P4) produced by, stimulated by — ?)

A
  • produced by corpus luteum
  • LH stimulates the production
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18
Q

Role of progesterone in female sexual cycle?

A
  • implantation and pregnancy
  • increases the endometrium’s blood supply
  • makes vaginal epithelium and cervical mucus thick and impenetrable to sperm
  • inhibits lactation during pregnancy
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19
Q

Prostaglandin F2 alpha (PGF2alpha)
Site of production and role

A

Produced by uterus.
Main role is luteolysis (after the refractory period of the corpus luteum)

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20
Q

Follicular maturation

A
21
Q

Primordial follicle

A
  • develops in ovaries before birth
  • only one layer of flat granulosa cells around the oocyte
  • 0,003 - 0,005 mm
22
Q

Primary follicle

A
  • develops in ovaries after birth
  • oocyte in diplotene meiotic phase
  • one layer of cuboidal granulosa cells around the oocyte
  • 0,1 mm
23
Q

Secondary follicle

A
  • develops in puberty and every cycle
  • presence of theca cells, multiple layers of granulosa cells
  • oocyte in diplotene meiotic phase (same as in primary)
  • 0,2 mm
24
Q

Territory follicle (Graaf/antral follicle)

A
  • fully formed antrum, no further cytodifferentiation, no novel progress
  • 4-6 cm in mare, 2-3 cm in cow
25
Q

What is oestrous cycle?

A

Period between 2 consecutive ovulations

26
Q

What are stages of oestrus cycle?

A
  1. Proestrus
  2. Estrus
  3. Metestrus
  4. Diestrus

Lack of oestrus cycle is called anestrus

27
Q

Hormonal profile during ovulation

A
  • high level of estradiol
  • GnRH then LH peak
28
Q

What induces the ovulation?

A

LH peak (200x times higher concentration than baseline LH secretion) induces the ovulation and luteinisation process

29
Q

LH peak in different animals

A
  • in rabbit and cow: short (6-8 hours)
  • in pig: 12-18 hours
  • in horse: 3-5 DAYS

That’s why to induce ovulation in mares repeated injections are needed or implants

30
Q

Hormonal profile after ovulation

A
  • E2 decreases
  • FSH decreases (negative effect of progesterone on the hypothalamus -> decrease of GnRH ?? )
  • luteinisation in progress
  • PRL increases
  • progesterone starts increasing
  • follicular development and stimulation is stopped
31
Q

Hormonal profile of early phase of CL

A
  • slow increase of P4 levels
  • PRL increases
  • in domestic animals in this stage new generation of follicular cohort start developing but increasing P4 stops the process (little elevations in E2 and FSH concentrations)
32
Q

Hormonal profile in flourishing corpus luteum stage

A
  • high level of P4
  • E2 is very low
  • other hormones are on baseline concentration
33
Q

What is special in dogs and their hormones in ovulation?

A

In dogs P4 levels start elevating BEFORE the ovulation (~24h)

34
Q

Hormonal profile in luteolysis (early follicular development)

A
  • if the animal is not pregnant, PGF2-alpha is produced by the uterus causing the lysis of the CL (=> sharp drop in P4)
  • oxytocin increases PGF2-alpha production
  • due to decreasing P4 levels, FSH starts increasing
35
Q

Hormonal profile in follicular development and selection

A
  • increasing FSH
  • inhibin increases (in some spectra’s will cause sharp drop in plasma FSH levels)
  • due to constantly high level of E2 and FSH, GnRH peak -> LH peak -> next ovulation
36
Q

2 aspects (centres) of GnRH secretion

A
  1. Tonic releasing centre - basic plasma levels for normal gonadal function
  2. Pulsation releasing (surge) centre:
    - produces a peak every cycle
    - stimulates by the high level of E2
    - p4 in high concentrations inhibits the centre
37
Q

Tonic centre of GnRH release

A

Tonic centre is located in ventromedial hypothalamic nuclei
- ensures base level of GnRH secretion necessary for functioning
- E2 and P4 - negative feedback loop

38
Q

Cycle or surge centre of GnRH release

A
  • located in preoptic area
  • stimulated by E2 and inhibited by P4
  • rise of pre-ovulatory E2 directly prepares the GnRH and LH peaks and therefore the ovulation
39
Q

What happens to corpus luteum in case of fertilisation

A

It transforms into corpus luteum graviditatis

40
Q

Effect of the LH on the follicle

A
  • relaxin and prostaglandins are going to be released in the tertiary follicle
  • follicular wall gets thinner and inner pressure increases
  • rupture of the tertiary follicle -> ovulation
  • The primary oocyte is under the influence of “oocyte inhibiting factors” OIF (dormant oocyte in the first, diplotenic phase) that will be blocked by LH (termination of meiosis).
  • Granulosa cells are under the influence of “luteinization-inhibiting factors”, LIF, it will also be blocked, and luteinization begins
41
Q

Luteolysis (in cow)

A
  1. High P4 stimulates Oxytoc-R expression on endometrium
    2.Oxytocin produced by OVARY stimulates PGF2-alpha synthesis in endometrium
  2. PGF is released into the uterine vein
  3. PGF is picked up by the ovarian artery and delivered back to the ovary where it causes lysis of the corpus luteum

In the cow the special proximate locations of arteria ovarica and vena uterine ensures the transportation of PGF2-alpha to the corpus luteum

42
Q

Length of the oestrus cycle in different species

A
  • Sheep: 17 days
  • Cat: 10-22 days
  • Dog: ~2 months
  • Human: 28 days
43
Q

General overview of 4 stages of oestrus cycle

A
  1. Proestrus:
    End of the follicular maturation, fast growth of the dominant follicle. E2 level increasing but female is not ready yet for computation
  2. Estrus:
    Sexual receptivity with all the necessary morphological and behavioural changes
  3. Metestrus: after the oestrus, rising P4 concentration (CL)
  4. Diestrus: the longest part of the oestrus cycle, high P4 level
44
Q

Types of estruses

A
  1. Based on the seasonality:
    - continuous: cow, sow - no anoestrus (only during lactation)
    - periodical: dogs, cats, horses, goats, sheep
  2. Based on the type of ovulation:
    - reflex ovuation (cat, rabbit) - ovulation is induced by coitus
    - spontaneous ovulation
45
Q

Oestrus of the cattle

A
  1. Proestrus: 3-4 days
  2. Estrus: 4-18 hours
  3. Metestrus: 2 days
  4. Diestrus: 15 days
    repeat

Ovulation after estrus! (30h after the beginning of estrus)
Pregnancy: 279 days

46
Q

Oestrus cycle in swine

A
  1. Proestrus: 2 says
  2. Estrus: 2-3 days
  3. Metestrus: 2 days
  4. Diestrus: 14 days
    repeat

Ovulation of in the last third of estrus
Pregnancy: 114 days

47
Q

How long is the pregnancy in the dog? How long is the cycle?

A

Pregnancy: 58-68 days
Length of cycle: 80 days
Ovulation on the 11th day after beginning of proestrus, i.e. on the second day after beginning of estrus

48
Q

How long is the pregnancy in the sheep? How long is the cycle?

A

Pregnancy: 144 days
Cycle: 17 days
Ovulation is in the last third of estrus

Estrus cycle starts in autumn, fertilisation in autumn or winter, 5 months of pregnancy, lambs are born in good weather and access to fresh grass

49
Q

How long is the pregnancy in the horse? How long is the cycle?

A

Pregnancy: 336 days (~11 months)
Cycle: 21 days
Ovulation: 1-2 days before the end of estrus

Complex Approach To Organ Systems (1 decks)

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