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ASC 410 > The Estrous Cycle > Flashcards

The Estrous Cycle Flashcards

1
Q

When does estrous cycle in non-pregnant mares begin?

A

when the spring transition ends

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2
Q

What is the first post-partum estrus called?

A

foal heat

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3
Q

When does foal heat begin?

A

7-11 days post partum

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4
Q

Can you breed on foal heat?

A

yes, but not suggested because fertility is often low

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5
Q

When does the 2nd post-partum estrus begin?

A

about 18-21 days after the beginning of foal heat

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6
Q

The vulva, vagina, and cervix are known as:

A

the gateways to the uterus

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7
Q

What is the ideal conformation of the vulva?

A

the lips should form a tight seal and be vertical

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8
Q

What may change the conformation of the vulva?

A

the mares age and number of pregnancies she’s had

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9
Q

Tipped vulva

A

when the vulva starts to tip to one side (become less vertical)
-will occur with more pregnancies
-happens as the back sags down and pulls the vulva

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10
Q

The vulva is the _____ gateway to the reproductive tract

A

the 1st gateway

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11
Q

Caslick’s procedure

A

the upper part of the vulva is staples closed either during pregnancy or before breeding
-keeps the vulva clean
-removed before foaling

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12
Q

Ideal conformation of the cervix

A

must be intact and able to prevent contaminants entering uterus during pregnancy

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13
Q

During estrus, the cervix is:

A

relaxed and open

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14
Q

During pregnancy/diestrus, the cervix is:

A

tight and closed

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15
Q

What is the function of the uterus?

A

-supports the embryo (glands in the uterus produce “uterine milk”)
-supports the fetus through interaction with the placenta (which attaches to the uterus)

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16
Q

What can be done to determine uterine health?

A

-ultrasounds - to identify abnormalities
-endometrial cultures - to identify microbial status (while the mare is in estrus) and determine need for treatment/what treatment
-cytology

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17
Q

Abnormalities of the uterus increase with…

A

age and number of pregnancies

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18
Q

Oviduct function

A

site of fetilization

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19
Q

The oviduct must be open to allow for:

A

-passage of sperm for fertilization of oocyte
-passage of oocyte and then embryo into unterus

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20
Q

If a mare appears to have a normal reproductive tract but is cycling and failing to conceive what might be the issue?

A

blocked oviducts

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21
Q

Ovary function

A

production of oocytes
-two ovaries, but only one is enough
-regulate hormones

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22
Q

Effect of age on ovaries

A

-all oocytes are present in ovaries at birth
-oocytes are recruited from the ovary with each ovulation
-oocyte quality declines with age in mares

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23
Q

The hypothalamus produces:

A

GnRH

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24
Q

The anterior pituitary produces:

A

LH and FSH

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25
Q

The ovary produces:

A

estrogen and progesterone
-follicles produce estradiol and inhibin
-corpus luteum (CL) produces progesterone

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26
Q

The uterus produces:

A

PGF2alpha

27
Q

Follicle stimulating hormone (FSH)

A

stimulates follicle growth and development

28
Q

Estradiol

A

responsible for behavioral and physiological estrus (relaxing of the cervix, increased mucus production, edema in uterus, etc.)

29
Q

Inhibin

A

inhibits FSH

30
Q

Luteinizing hormone (LH)

A

stimulates ovulation and the formation of the CL

31
Q

Progesterone

A

maintains/ prepares uterus for pregnancy, suppresses estrus behavior

32
Q

Prostaglandin 2 alpha (PGF2alpha)

A

lyses the corpus luteum (CL)

33
Q

Ovarian activity during the estrous cycle:

A

-follicular wave begins
-follicular deviation
-preovulatory follicle
-ovulation

34
Q

When does the follicular wave begin

A

day 8-12 post ovulation

35
Q

When does follicular deviation occur

A

day 14-16
-dominance phase, largest follicle 20-25 mm
-growth of other follicles should stop (often doesn’t though)

36
Q

When does the preovulatory phase occur

A

day 17-18
-largest follicle (preovulatory follicle) is about 30 mm; capable of responding to ovulatory stimuli

37
Q

When does ovulation occur?

A

day 19-21 (actual day of ovulation is day 0 of the next cycle)

38
Q

What is the typical size of the follicle at ovulation?

A

35 mm but could be up to 45-55 mm (in larger mares)

39
Q

Day 0 =

A

ovulation

40
Q

Day 2-6 =

A

small follicles

41
Q

Day 8-12 =

A

follicular growth

42
Q

Day 16-19 =

A

one follicle predominates and in 3-5 days ovulation occurs

43
Q

The dominant follicle produces:

A

-inhibin (which suppresses FSH - the development of the other follicles)
-estradiol 17-B (responsible for behavioral estrus which allows for receptivity to stallion; responsible for physiological estrus, relaxation of cervix and edema in uterus)

44
Q

How long is the oocyte fertile for after ovulation?

A

about 18 hours
-might be shorter in older mares

45
Q

If conception occurs, how long is the embryo in the oviduct?

A

about 6 days

46
Q

After fertilization what decreases?

A

estradiol and inhibin

47
Q

When will the mare go out of behavioral estrus?

A

24-48 hours after ovulation

48
Q

After ovulation the follicle becomes the:

A

corpus hemorrhagicum

49
Q

The corpus hemorrhagicum becomes the:

A

corpus luteum

50
Q

The corpus luteum (CL) produces:

A

progesterone

51
Q

Progesterone function:

A

-suppresses behavioral estrus
-tightens the cervix
-increases uterine tone and uterine secretions

52
Q

The embryo is mobile in the uterus until when?

A

about day 14 post-ovulation/fertilization
-believed to be a signal for maternal recognition of pregnancy

53
Q

When fertilization occurs, the corpus luteum is _____

A

retained, progesterone secretions continues

54
Q

When fertilization does not occur what does the uterus release?

A

PGF2alpha about 14 days post ovulation

55
Q

If fertilization does not occur what happens to the CL?

A

it is lysed

56
Q

If fertilization does not occur what happens to progesterone?

A

it decreases

57
Q

In diestrus, what hormones are increased?

A

progesterone and FSH

58
Q

In diestrus what hormones are decreased?

A

estradiol and LH

59
Q

In estrus what hormones are increased?

A

Estradiol, LH, and FSH towards the end

60
Q

In estrus what hormones are decreased?

A

progesterone

61
Q

Hormone regulation:

A

-FSH stimulates the follicular wave
-Estradiol is produced by the follicle and stimulates an increase in LH = mare enters estrus and inhibin produced by the follicle suppresses FSH
-LH stimulates ovulation and formation of CL
-CL produces progesterone = prepares uterus for pregnancy, if no pregnancy the uterus releases PGF2alpha that lyses CL
-Decreased progesterone allows increasing concentrations of estradiol to result in next behavioral and physiological estrus and allows increase in LH

62
Q

Through day 100-120 of pregnancy what occurs with progesterone?

A

additional follicles form secondary CL which is signaled by the chorionic gonadotropin released by the endometrium

63
Q

Beginning at day 40 of pregnancy what happens with progesterone production?

A

uteroplacental tissue begins to produce progestins

64
Q

By day 120 of pregnancy what is the primary producer of progestins that maintain pregnancy?

A

the uteroplacental tissue

ASC 410 (22 decks)

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