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ASC261 > Female endocrinology 2 > Flashcards

Female endocrinology 2 Flashcards

1
Q

What occurs in the luteal phase…? How can these events be categorised?

A

Follicular cells -> luteal cells
Dev. of CL & prod. of P4 (lutenisation)
Destruction of CL & resumption of follicular phase (luteolysis)
Categorised as events following ovulation

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2
Q

First part of the luteal phase? (Directly after ovulation)

A

metestrus

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3
Q

What occurs during metestrus…?

A

formation of CL (gradual increase in P4)

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4
Q

What phase follows metestrus?

A

diestrus

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5
Q

What occurs during diestrus…?

A

P4 dominating hormone produced by functioning CL

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6
Q

Thecal cells have receptors for… and produce…?

A

LH and produce testosterone

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7
Q

Granulosa cells have receptors for… and produce…?

A

FSH and produce oestrogen

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8
Q

In the pre-ovulatory follicle (oestrus), what happens to the basement membrane?

A

Starts to deteriorate allowing granulosa & thecal cells to contact each other (because of increased pressure build up within follicle - antrum)

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9
Q

What happens to corpus haemorrhagicum (CH) during ovulation…?

A

Follicular walls collapse due to deteriorated basement membrane
Local haemorrhage
Ruptured blood vessels
Gland is formed consisting of thecal & Granulosa cells & connective tissue -> (CL)

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10
Q

What does the corpus luteum (CL) consist of…?

A

Mix of large luteal cells (LLC - granulosa cells) & small luteal cells (SLC - thecal cells)

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11
Q

When does the CL begin to increase in size?

A

Day 3-5

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12
Q

What determines the amount of progesterone produced by the CL?

A

The maximum size of the CL

ie. the bigger the CL, the more P4 produced by it.

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13
Q

Luteal formation in the cow…? What happens to CL, LLCs, SLC…?

A

CL begins to increase in size until halfway thru Luteal phase
Hypertrophy of LLCs, Hyperplasia of SLCs, peak P4 production (diestrus), orange CL colour reflects high beta carotene

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14
Q

Functional capability of CL & progesterone production depends on…?

A

Number of functioning luteal cells

Degree of vascularisation within CL (hormone delivery)

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15
Q

Insufficient luteal function results in…?

A

Reduced ability of uterus to support pregnancy

Reproductive failure

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16
Q

How would you treat insufficient luteal function results in…?

A

Supplement with progesterone

17
Q

Describe progesterone synthesis…?

A
  1. LDL-CHOL bind to membrane receptors -> 2. LH binds to LH receptor on membrane -> 3. activates protein kinase -> 4. CHOL moves into mitochondria -> 5. CHOL -> pregnenolone -> into cytoplasm -> preg -> progesterone -> out of cell to target tissue
18
Q

Physiological effects of progesterone…?

A

Hypothalamus
- -ve feedback on GnRH
- supression of LH & FSH & oestrogen -> behaviour
Uterus
- glandular edometrium -> maximal secretion (in preparation for embryo…fetus…birth)
- Muscular myometrium (muscle layer within uterus) -> inhibition of motility (stop uterine contractions/still/calm)
Mammary gland
- alveolar development (ready for milk production at end of gestation)

19
Q

Describe the events in luteolysis…

A
  • disintegration of CL
  • occurs near end of luteal phase (1-3 days)
  • significant reduction of P4 production
  • regulated by oxytocin, prog. & prostaglandin (PGF2alpha)
20
Q

In sheep studies, what occurred to CL lifespan when uterus was 1. left intact, 2. underwent uterectomy, 3. partial uterectomy contralateral to CL, 4. partial uterectomy ipsilateral to CL?

A
  1. 15 - 17 d
  2. 148 d
  3. 15 - 17 d
  4. 35 d
21
Q

THMessage from sheep uterectomy studies…?

A

Local circulation of PGE 2alpha important for proper CL destruction, if no PGE 2alpha released from uterus -> CL was NOT destructed

22
Q

How does PGE 2alpha get to the ovary?

A

via a vascular counter current exchange system

PGF 2a produced by uterine endometrium -> uterine vein & lymph -> ovarian artery via passive diffusion -> ovary

23
Q

What happens to PGF 2a in normal circulation?

A

denatured thru pulmonary system

24
Q

Why is counter current mechanism important in the cow & sow?

A

As it allows adequate levels of PGF 2a to exert lytic effects directly on functional CL

25
Q

When is PGF 2a effective on the CL in the cow & sow?

A

cow (5-6 days after ovulation)

sow (12-14 days after ovulation)

26
Q

Why would exogenous PG be administered?

A

To artificially lyse CL to syncronise oestrus & induce parturition (eg. sheep to give birth to lamb)

27
Q

What is oxytocin’s role in luteolysis…? Where is it produced & stored? How & when is it released?

A

Produced by luteal cells, stored in secretory granules until threshold is reached.
Released in pulsatile manner towards end of luteal phase -> causes release of PGF 2a from endometrial cells

28
Q

Where & when do oxytocin receptors form?

A

Endometrial cells, 10-12 days after ovulation

29
Q

What blocks formation of oxytocin receptors?

A

progesterone (P4)

30
Q

Requirements for luteolysis in the cow…?

A
  • presence of oxytocin receptors in endometrium
  • presence of critical secretion of oxytocin via LLCs
  • PGF synthesised by endometrium, released in pulsatile secretion & critical number of pulses required for luteolysis
  • presence of PGF 2a receptors on CL
31
Q

Events that occur after luteolysis…?

A
  • Reduction of P4
  • CL forms Corpus Albicans
  • Macrophages & lymphocytes phagocytise damaged luteal cells
  • New follicular dev. & recruitment of antral follicles
32
Q

Main difference between luteolysis in humans/primates compared to other domestic breeds…?

A
  • controlled by hypothalamus & ovary NOT uterus (not required)
  • PGF 2a produced by ovary in response to oxytocin release from posterior pituitary
  • reduction in P4 -> PGF 2a synthesis from endometrium of ovary -> endometrial vasoconstriction, necrosis & sloughing -> MENSES (discharge of blood & cellular debris)
33
Q

What effects does exogenous progesterone have…?

A
  • mimics the luteal phase (lengthen or reduce)
  • provides -ve feedback on hypothalamus -> supress GnRH release
  • suppress oestrus behaviour (horses)
  • allows synchronisation of individuals -> in AI or ET programs
  • contraceptive in humans -> block ovulation & minimise pregnancy
34
Q

What is CIDR?

A

controlled internal drug release

35
Q

How does synchronisation in cows work?

A 
via CIDR (P4 as drug) inserted into vagina & releases P4 diffuses across vaginal mucosa -> blood stream -> suppresses GnRH, follicular dev. & ovulation
eg. administer CIDR for 7 days to all cows then remove => all cows synchronised so that when [P4 plasma] levels fall -> PGF 2a can be injected -> luteolysis in all cows -> proestrus phase -> oestrus phase
36
Q

How can synchronisation be achieved without CIDR?

A

By single injections with PGF2a between day 7 & 18 -> luteolysis -> oestrus 2-3 days later
(Days 1-7 the CL is refractory to PGF2a & will NOT respond)

37
Q

When would a double injection (PGF2a) protocol be used?

A

When a small % of cows aren’t responsive to a single PGF2a dose (14 days apart) -> all cows should cycle together

38
Q

What mechanism does PGF2a use to reach ovary in domestic spp.?

A

utero-ovarian vascular countercurrent diffusion system

39
Q

Which hormone can be used to cause letenisation?

A

LH or hCG (has LH-like activity)

ASC261 (17 decks)

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