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Reproductive Pathophysiology > Section 3: Equine > Flashcards

Section 3: Equine Flashcards

1
Q

what forms the first seal that protects the female reproductive tract?

A

vulvar seal

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2
Q

what is normal conformation of the vulva and perineum important for?

A

preventing contamination of the anterior genital tract with air and bacteria

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3
Q

where does the clitoris lie?

A

within clitoral fossa at the ventral aspect of the vulvar commissure

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4
Q

what are the three main physical barriers to protect the uterus?

A

vulva
vestibule
cervix

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5
Q

what forms a vestibulovaginal seal?

A

transverse fold and vestibular constrictor muscles

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6
Q

what seal should prevent air and contaminants from entering the vagina even if the vulvar lips are parted?

A

vestibulovaginal seal

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7
Q

is the vagina sterile?

A

no
small numbers of commensal bacteria are found

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8
Q

what type of folds does the mare cervix have?

A

longitudinal mucosal folds

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9
Q

does the mare’s cervix have obstructing fibrous rings like ruminants and pigs?

A

no

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10
Q

how does the mare’s cervix change during the estrous cycle?

A

estrus: soft and easily dilated
diestrus and pregnancy: firm and tightly closed, projecting into cranial vagina

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11
Q

what suspends the uterus within the abdomen?

A

two large broad ligaments

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12
Q

is the endometrium glandular?

A

highly glandular

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13
Q

what type of folds does the endometrium have?

A

prominent longitudinal folds

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14
Q

mare ovaries are _____________ than ovaries of the other farm species

A

larger

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15
Q

how is the mare ovary unique?

A

arrangement of the cortex and medulla are reversed compared to other animals

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16
Q

where does the cortex of the mare ovary reach the surface?

A

ovulation fossa only

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17
Q

does the corpus luteum protrude from the surface of the ovary in a mare?

A

no

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18
Q

the mare’s udder consists of two mammary glands, with ________________ streak canals per teat

A

two, sometimes three

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19
Q

what part of the oviduct attaches to the ovary?

A

infundibulum with fimbriae

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20
Q

when does puberty occur in the filly?

A

12-24 months of age

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21
Q

when do most breeders wait until to breed a filly?

A

3 years or older

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22
Q

what type of breeders are mares?

A

seasonally polyestrus long day breeders

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23
Q

when is the mare’s breeding season centered around?

A

June 21st

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24
Q

what does increased day length in early spring lead to from the hypothalamus?

A

increase in GnRH

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25
Q

how long is the estrous cycle in the mare?

A

around 21 days

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26
Q

what are most of the mare ovaries like in winter?

A

small and firm with not palpable follicles or functional luteal tissue

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27
Q

what percentage of mares do not undergo anestrus and continue to cycle in winter?

A

20-25%

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28
Q

what happens with behavior and ovulation in the fall transition period?

A

behavior and ovulation become more erratic

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29
Q

what does increased GnRH from the hypothalamus lead to in the spring transition?

A

gradual rise in LH but not enough to ovulate
persistent follicles, prolonged estrogen production and irregular/lengthy ovulation periods

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30
Q

how are mares housed to advance their first ovulation to breed them earlier for the racing and performance industries?

A

under 16 hours of light a day
starting December 1st

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31
Q

what do small and infrequent pulses of GnRH lead to in anestrus?

A

baseline LH and baseline high FSH that fluctuates randomly without negative feedback from ovarian inhibin and estrogen

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32
Q

what is the size of the follicle at ovulation and how much does it grow per day?

A

40mm
3mm per day

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33
Q

how long is diestrus usually in the horse estrous cycle?

A

14-15 days

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34
Q

what does the variability of the length of estrus depend on?

A

size of follicles present on mare’s ovaries at the end of diestrus and length of time it takes to grow dominant follicle and grow it

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35
Q

what is the preovulatory luteinizing hormone surge like in the mare?

A

long and drawn out
can last over a week

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36
Q

how rapid is ovulation?

A

complete evacuation of follicular fluid takes 2-7 minutes

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37
Q

when does ovulation occur compared to estrus?

A

within 48 hours of the end of estrus

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38
Q

how often to double ovulations occur?

A

16% of time

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39
Q

what horse breeds are more likely to have double ovulations?

A

thoroughbreds
warmbloods

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40
Q

what does the luteal phase begin with?

A

formation of progesterone-secreting corpus luteum

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41
Q

is estrus behavior indicative of high estrogen levels?

A

no, absence of high progesterone

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42
Q

what can diestrus ovulations lead to?

A

prolonged diestrus if resultant corpus luteum is too immature to respond to endogenous release prostaglandin

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43
Q

what are the physical changes during estrus?

A

mucous membranes of vulva and vagina moist and hyperemic
cervix edematous, relaxed, dilated
uterus flaccid and edematous

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44
Q

what are the physical signs of diestrus?

A

pale, dry vaginal mucous membranes
tightly closed, narrow, tubular cervix
increased tubularity of the uterus

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45
Q

what are the ovaries like in anestrus?

A

small and firm with no palpable follicles or functional luteal tissue

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46
Q

what does testicular size correlate with?

A

quantity of sperm produced

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47
Q

what should the total scrotal width be?

A

at least 8cm

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48
Q

how are the stallion testicles oriented?

A

long axis horizontal
tail of epididymis directed caudally and head directed cranially

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49
Q

why is the head of the epididymis hard to palpate?

A

flattened nature
cremaster muscle lies on top of it

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50
Q

what is the normal time frame for testicular descent into the scrotum?

A

by birth up to 6 months

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51
Q

when does puberty occur for the stallion?

A

12-18 months of age

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52
Q

when does sexual maturation occur for the stallion?

A

6 years of age

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53
Q

does the reproductive activity of the stallion decrease in winter?

A

somewhat, not as great as what happens in mare
reduction in testicular size and daily sperm output

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54
Q

what is the volume of the stallion’s ejaculate?

A

20-150 cc

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55
Q

what is the concentration of the stallion’s ejaculate?

A

50-250 million sperm per ml

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56
Q

what is the percentage of morphologically normal sperm in the average stallion’s ejaculate?

A

50%

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57
Q

where does the stallion ejaculate into?

A

directly into uterus through relaxed cervix

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58
Q

what is ejaculation accompanied by?

A

flagging of tail due to contraction of bulbospongiosus muscle

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59
Q

what is the main drawback to pasture breeding?

A

possibility of injury to mares and stallion

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60
Q

with in-hand breeding, how often are mares bred?

A

once day until they no longer show signs of heat

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61
Q

what are the main disadvantages of in-hand breeding?

A

failure of heat detection
breeding more frequently and earlier in the estrus than the stallion probably would on his own

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62
Q

what are the options of semen for artificial insemination?

A

fresh semen
shipped cooled semen
frozen semen

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63
Q

when using frozen semen, when must insemination be performed?

A

12 hours prior to or within 6 hours after ovulation to maximize pregnancy rates

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64
Q

what is non-return to estrus behavior at 17 to 21 days postovulation strongly suggestive of?

A

pregnancy

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65
Q

when can pregnancy in the mare be palpated?

A

28-30 days postovulation
embryonic vesicle large enough to be palpated per rectum
day 18 increased tone strongly suggestive

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66
Q

when can pregnancy in the mare be diagnosed via ultrasound?

A

day 14: embryonic vesicle
heart beat visible around day 25

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67
Q

how are sperm transported mainly to the oviducts?

A

uterine contractions

68
Q

fertilization must occur no later than ______________ after ovulation to result in a viable embryo

A

12 hours

69
Q

when does the embryo enter the uterus?

A

day 6 post-ovulation

70
Q

what does the embryo secrete once it reaches the compact morula stage?

A

prostaglandin E2

71
Q

what does prostaglandin E2 from the embryo do?

A

relaxes smooth muscle fibers in the wall of the oviduct
allows embryo’s passage into uterus

72
Q

when does the embryo migrate constantly through the entire uterus?

A

until day 15

73
Q

what causes the embryo to be immobilized at day 15?

A

sudden increase in myometrial tone and increased size of embryo

74
Q

what is migration of the embryo throughout the entire uterus necessary for?

A

maternal recognition of pregnancy

75
Q

when is the yolk sac stage?

A

days 11-21

76
Q

when is the allantoic sac stage?

A

days 21-40

77
Q

what does the equid fetus do around day 35 that is unique?

A

form endometrial cups: specialized cells invade deeply into adjacent maternal endometrium
cells proliferate

78
Q

what cells form the endometrial cups?

A

trophoblastic cells from fetus

79
Q

when are the endometrial cups active?

A

form day 35
around day 40 to day 120 of gestation

80
Q

when are the placental attachments complete?

A

day 150

81
Q

is placental transfer of large protein molecules possible in the equid placenta?

A

no

82
Q

what is required to provide adequate nutrient and gas exchange for a single fetus?

A

entire endometrial surface

83
Q

luteal progesterone is necessary to maintain pregnancy until about day ____

A

80

84
Q

when do luteal progesterone levels peak?

A

about day 100

85
Q

what is produced from the fetoplacental unit to maintain pregnancy?

A

5 alpha pregnanes mainly: dihydroprogesterone
not progesterone

86
Q

when does the fetoplacental unit start to produce estrogens?

A

day 50

87
Q

what is the gestation length of mares?

A

about 11 months: 342 days +/- 2 weeks
320-400 days

88
Q

what are estrogens levels during gestation?

A

high in late gestation
begin to fall just before parturition

89
Q

what are some signs of impending parturition?

A

relaxation of pelvic ligaments and tailhead
elongation of vulva
fullness of udder and leaking colostrum

90
Q

how long does the first stage of labor last?

A

1-4 hours

91
Q

what happens in the first stage of labor?

A

cranial portion of fetus rotates into dorsosacral position with head and limbs extended
early uterine contractions
cervical dilation and relaxation

92
Q

how long does the second stage of labor last?

A

20 minutes
10 minutes to an hour

93
Q

what happens in the second stage of labor?

A

active abdominal contractions
caudal portion of fetus now rotates into dorsosacral position
delivery of foal

94
Q

how long does the third stage of labor last?

A

up to 3 hours post foaling

95
Q

if the placenta is not expelled within _____________ it is considered retained and treatment is begun

A

3-6 hours

96
Q

when should the foal stand?

A

within one hour of being born

97
Q

when should the foal nurse?

A

within 2 hours of being born

98
Q

what should the mare uterus be like by day 15 postpartum?

A

no fluid in uterine lumen

99
Q

what is “foal heat”?

A

the first estrus after foaling

100
Q

what caslick index values are associated with a normal anatomic arrangement/better fertility?

A

less than 100
approaching 150 is worse

101
Q

what can incompetence of the vestibulo-vaginal seal/sphincter lead to?

A

pneumovagina
endometritis
reduced fertility

102
Q

what does the cervix do during copulation?

A

lubricates vagina

103
Q

what does the cervix do to prevent infection?

A

flushes out foreign material and bacterial contamination
protective seal during pregnancy and diestrus

104
Q

what is the clitoral fossa important for in the mare?

A

contagious equine metritis testing

105
Q

the mare uterus has prominent ________________ folds

A

endometrial

106
Q

where do the corpora lutea protrude into in the mare?

A

ovarian tissue
not to ovarian surface: cannot palpate per rectum

107
Q

what is the seasonality of mare breeding primarily controlled by?

A

photoperiod

108
Q

when do mares transition?

A

autumn
spring

109
Q

when is a mare in anestrus?

A

winter

110
Q

what hormones control the seasonality of the mare’s estrous cycle?

A

melatonin: pineal gland
decreases GnRH

111
Q

what might mares have during the autumnal transition?

A

reduced fertility
persistent, anovulatory follicles
possibly prolonged periods of estrus

112
Q

when is the mare breeding season?

A

April to Sept-Oct

113
Q

how does length of estrus vary with season?

A

follicular growth faster at peak of breeding season
duration of estrus shorter as season progresses
size of ovulatory follicle tends to be smaller at peak season

114
Q

when does LH peak with mares?

A

1-3 days post ovulation

115
Q

how predictable is ovulation relative to onset of behavioral estrus?

A

not as predictable as other species

116
Q

do mares have a countercurrent exchange mechanism for luteolysis?

A

no

117
Q

can mares ovulate in the face of high progesterone?

A

yes sometimes

118
Q

what are the behavioral signs of diestrus?

A

ears pinned
tail switching
squeal
kick, bite, strike

119
Q

what does the uterus look like during estrus?

A

flaccid, edematous folds
“spoking” pattern on ultrasound

120
Q

what is the erectile tissue enclosed by?

A

tunica albuginea

121
Q

what is the erectile tissue in the equine penis?

A

corpus carvernosum
corpus spongiosum

122
Q

when do stallions have a reduction in testicle size and daily sperm output?

A

late autumn and winter

123
Q

what mounts are used to collect semen?

A

estrus mare
ovariectomized, estrogen treated mare
phantom

124
Q

what is the motility of stallion sperm?

A

60/40%
total/progressive

125
Q

what is the total breeding time of equines?

A

2-5 minutes

126
Q

what are the options for natural breeding?

A

pasture breeding
in-hand breeding

127
Q

how often are mares bred in in-hand breeding?

A

every other day until they go out of heat

128
Q

what is the minimum insemination dose for cooled semen?

A

500 million live, progressively motile sperm

129
Q

what is the insemination window for shipped cooled semen?

A

36-48 hours before to 12 hours after ovulation

130
Q

what is unique to equids with their oviducts and embryos?

A

differential transport of embryo vs oocytes
oocytes stay in oviduct

131
Q

what do the endometrial cups produce?

A

equine chorionic gonadotropin

132
Q

what does equine chorionic gonadotropin do?

A

has luteinizing hormone like activity
causes ovulation and luteinization of follicles: form secondary and accessory corpus lutea

133
Q

what do endometrial cups do?

A

prevent return to estrus even if pregnancy is lost

134
Q

what type of placenta do equids have?

A

diffuse, microcotyledonary, epitheliochorial

135
Q

what is the progesterone source during the second luteal response?

A

endometrial cups’ eCG causes resurgence of primary corpus luteum

136
Q

when is luteal progesterone necessary to maintain pregnancy until?

A

day 80

137
Q

how can milk be used to predict parturition?

A

increase in calcium just prior
drop of pH to <6.4 within 24 hours of parturition

138
Q

when does the first stage of labor end?

A

chorioallantois ruptures, releasing allantoic fluid

139
Q

what is a red bag delivery?

A

premature separation of outer placental membrane from uterine wall may lead to protrusion of the intact fluid-filled chorioallantois through the vulva

140
Q

why is a red bag delivery an emergency?

A

detachment leads to a rapid decrease in oxygen transport to fetus

141
Q

what can failure to treat retained fetal membranes lead to?

A

metritis
endotoxemia
death

142
Q

how long is estrus?

A

6-7 days usually

143
Q

do double ovulations increase the chance of conception?

A

yes

144
Q

where is PGF2alpha released?

A

into systemic circulation

145
Q

what is the uterus like in diestrus?

A

firm tone
uniform echogenicity on ultrasound

146
Q

what do the ovaries look like in estrus?

A

one or more large follicles palpable and visible on ultrasound

147
Q

what do the ovaries look like during diestrus?

A

various sized follicles present
corpus luteum visible with ultrasound

148
Q

what is at the cranial dorsal aspect of each testis in the stallion?

A

spermatic cord

149
Q

what is another name for the glans penis?

A

corpus spongiosum glandis

150
Q

what can the urethral sinus have?

A

“bean”

151
Q

where is sperm storage?

A

tail of the epididymis

152
Q

what accessory sex glands do stallions have?

A

ampullae
seminal vesicles
prostate lobes
bulbourethral glands

153
Q

what is the longevity of fresh stallion semen?

A

48 hours

154
Q

what is the morphology of stallion semen?

A

50% normal

155
Q

how long does intromission and ejaculation take?

A

less than 1 minute

156
Q

what is a downside of repeat breeding?

A

can lead to breeding-induced endometritis

157
Q

where is semen deposited in artificial insemination?

A

body of uterus
tip of uterine horn on the side of ovulation

158
Q

when is the embryo covered by a capsule?

A

until days 21-22

159
Q

when and where does the fetus attach?

A

day 15-16
base of a horn

160
Q

when is the fetus highly mobile?

A

60-120 days

161
Q

what are the progesterone sources throughout pregnancy?

A

1st luteal response: embryo migration prevents demise of corpus luteum
2nd luteal response: endometrial cups’ equine chorionic gonadotropin cause resurgence of primary corpus luteum
3rd luteal response: equine chorionic gonadotropin causes ovulation and luteinization of follicles to form secondary and accessory corpus luteums
fetoplacental unit

162
Q

before what day of gestation is non-viable?

A

day 300

163
Q

between what days of gestation is considered premature?

A

day 300-320

164
Q

at what point of labor is it considered dystocia?

A

beyond one hour
greater than 30 minutes increases risk of injury/death to foal

165
Q

by what day after parturition should the uterus be contracted down to non-pregnant size?

A

day 30

166
Q

when does foal heat usually occur?

A

days 5-12 postpartum

Reproductive Pathophysiology (12 decks)

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