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VM744: THERIOGENOLOGY > Reproductive Cycles and Ovarian Function > Flashcards

Reproductive Cycles and Ovarian Function Flashcards

1
Q

What are the (5) behavioral phases of the reproductive cycle?

A

Proestrus
Estrus (heat)
Metestrus
Diestrus
Anestrus

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2
Q

What are the (2) physiological phases of the reproductive cycle?

A

Follicular phase
Luteal phase

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3
Q

Graph the behavioral stages of the reproductive cycle

A
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4
Q

Graph the physiological stages of the reproductive cycle

A
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5
Q

What occurs physiologically during the follicular phase?

A

Proestrus + Estrus
LH matures follicle, causes it to ovulate
Estradiol, LH, and FSH rise
Progesterone falls

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6
Q

What occurs physiologically during the luteal phase?

A

Metestrus + Diestrus + Proestrus
CL formation followed by luteolysis
Progesterone rises
Low estradiol, LH, FSH

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7
Q

What are morphological characteristics of primordial follicles?

A

Oocyte
Granulosa cells (flat) - ‘follicular cells’ or ‘follicle cells’
Basement membrane

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8
Q

What type of follicle?

A

Primordial follicle

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9
Q

What are morphological characteristics of primary follicles?

A

Larger oocyte
Zona pellucida formed around oocyte
Cuboidal granulosa cells - single layer

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10
Q

What type of follicle?

A

Primary follicle

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11
Q

What are morphological characteristics of secondary follicles?

A

Multiple layers of cuboidal granulosa cells surrounding oocyte
Theca cells visible outside of basement membrane

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12
Q

What type of follicle?

A

Secondary Follicle
Red Arrow = granulosa cell
White Arrow = theca cells

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13
Q

What are physiological characteristics of tertiary follicles?

A

FSH and LH receptors develop
FSH stimulates initial follicular development
Fluid-filled antrum forms within granulosa cell layer (follicular fluid produced by the granulosa cells)

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14
Q

What type of follicle?

A

Tertiary (‘Graafian’) follicle

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15
Q

What are physiological characteristics of preovulatory follicles?

A

Granulosa cells secrete estrogens
LH receptors form on granulosa cells
LH surge occurs in response to increased estradiol production and increased GnRH pulse frequency

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16
Q

What occurs during ovulation?

A

LH surge stimulates production of relaxin and prostaglandins from granulosa cells
Connective tissue in follicular wall disrupted
Rupture of follicle occurs
Oocyte is released and ‘caught’ by oviduct

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17
Q

What occurs during induced ovulation?

A

Follicular development stimulated by FSH
Estrogen levels increase - stimulates estrus
Coitus induces LH surge and ovulation
Ovulation-inducing factor in semen (nerve growth factor-beta)

18
Q

What species are induced ovulators?

A

Cats, rabbits, ferrets, camelids

19
Q

What occurs in the absence of mating with induced ovulators?

A

Cycle consists of only a follicular phase - no luteal phase
Mating stimulates LH surge and ovulation

20
Q

What structure forms after ovulation?

A

Corpus luteum

21
Q

What is the primary function of the corpus luteum?

A

Secretion of progesterone
Progesterone is required for the maintenance of pregnancy

22
Q

What hormone is required for the maintenance of pregnancy?

A

Progesterone
Secreted by the CL

23
Q

How does the CL form?

A

After ovulation, the lumen of collapsed follicle fills with blood, forming corpus hemorrhagicum
Blood clots, fibrin strands develop within clot
Granulosa and theca cells invade the CH along the fibrin strands
Luteinization of cells occurs

24
Q

When does luteinization begin?

A

With the onset of the LH surge

25
Q

When do progesterone levels begin to increase?

A

Most species: 1 to 2 days after ovulation
Dogs: prior to ovulation

26
Q

What is the most important luteotropic hormone in domestic animals?

A

LH
Prolactin and estrogens are luteotropic in some species

27
Q

What maintains CL function?

A

Pulsatile LH release

28
Q

What is the significance of CL regression?

A

Non-pregnant females must regress their CL in order to initiate another cycle
The duration of luteal function in large animals is 14 to 18 days, depending on the species

29
Q

What causes the CL to regress in large animals?

A

Prostaglandin (produced by the endometrium of the uterus)
Prostaglandin has no role in CL regression in cats, dogs, and primates

30
Q

How is prostaglandin transferred from the uterus to the ovary?

A

Local counter-current system (ruminants)
General systemic circulation (horses and pigs)

31
Q

Explain the counter current prostaglandin transfer in ruminants

A

Prostaglandins diffuse from the utero-ovarian vein (high concentration) to the ovarian artery (low concentration)
Prostaglandins can regress the CL in the ipsilateral ovary only!!

32
Q

Explain the counter current prostaglandin transfer in horses and pigs

A

Prostaglandins secreted into general circulation
Causes destruction of a CL on either ovary

33
Q

What induces prostaglandin release?

A

Estradiol induces formation of oxytocin receptors on endometrial cells
Oxytocin secreted from the CL stimulates uterine prostaglandin release

34
Q

What is the pattern in which prostaglandin is released?

A

Pulsatile

35
Q

What occurs after destruction of the CL?

A

Destruction of CL results in formation of the non-functional corpus albicans
CA does not produce progesterone

36
Q

How long is the luteal phase in non-pregnant dogs and cats? What is occurring physiologically?

A

Dogs = 70d
Cats = 35d
Progesterone production slowly decreases, then stops
Dogs and cats do not utilize progesterone for early regression of the CL following a non-conceptive cycle

37
Q

What occurs in luteolysis in the llama?

A

Prostaglandin release occurs by day 10 to 12 following ovulation - progesterone production ends

38
Q

What can prolong luteal function?

A

Pregnancy
Pregnancy loss after maternal recognition of pregnancy
Chronic uterine infection
Inadequate prostaglandin release

39
Q

What can shorten luteal function?

A

Prostaglandin administration
Endometritis

40
Q

What occurs during follicle selection?

A

Dominant follicle produces estradiol and inhibin (suppressing FSH)
Smaller follicles begin to regress
Dominant follicle continues to develop under influence of LH (leading to maturation and ovulation)

VM744: THERIOGENOLOGY (31 decks)

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