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Disturbances in Reproduction > Equine - Anatomy and Reproductive Physiology > Flashcards

Equine - Anatomy and Reproductive Physiology Flashcards

1
Q

What type of uterus does the horse have?

A

bicornuate or Y-shaped

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2
Q

What is the role of the broad liagament in the horse?

A

It suspends structures within the abdominal cavity

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3
Q

What is contained within the broad ligament?

A

arteries, veins, nerves, and lymphatics

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4
Q

What does the mesovarium support?

A

the ovaries

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5
Q

What does the mesosalpinx support?

A

the oviducts

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6
Q

What does the mesometrium support?

A

the uterus/cervix

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7
Q

How many folds are within the cervix?

A

5-10 longitudinal folds

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8
Q

What is the cervix made up of?

A

muscle

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9
Q

How large is the cervix?

A

6-7cm in length

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10
Q

The cervix cannot and should not every be ________.

A

retracted

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11
Q

What separates the vagina and the vestibulum?

A

transverse folds

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12
Q

Where should 2/3 of the vulva be located?

A

below the pelvic brim

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13
Q

What direction is the vulva oriented in?

A

vertical or near vertical orientation

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14
Q

What is the clitoris made up of?

A

a fossa and 3 sinuses (medial and lateral)

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15
Q

What are the three barriers to the internal reproductive tract?

A

vulva, intact vestibulovaginal sphincter, and cervix

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16
Q

What do the three barriers of the internal reproductive tract protect it from?

A

fecal contamination, windsucking, and bacterial ascension of the cranial repro tract

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17
Q

What is the shape of the equine ovary?

A

it is kidney bean shaped

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18
Q

Where does ovulation occur?

A

at the ventral ovulation fossa

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19
Q

Where is the medulla located in the equine ovary? The cortex?

A

the medulla is on the outside, the cortex is on the inside

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20
Q

When does puberty occur in a mare?

A

12-24 months - average is 15 months

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21
Q

When does a mare reach maturity?

A

by 3 years of age

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22
Q

How would you classify a non-pregnant mare’s estrous cycle?

A

long day, seasonally poly estrus

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23
Q

What are the phases of seasonality in the mare?

A

vernal transition (spring), breeding season, autumn transition, and winter anestrus

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24
Q

Winter anestrus is due to ____ days.

A

short

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25
Q

What are the reproductive hormones like during winter anestrus?

A

low levels of LH, estrogen, and progesterone

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26
Q

If there are follicles, what size are they during winter anestrus?

A

less than 5-10 mm in diameter

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27
Q

What type of firmness is the reproductive tract during winter anestrus?

A

flaccidity

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28
Q

How long is vernal transition?

A

1-2 months - average 55-60 days

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29
Q

What estrus behavior occurs during vernal transition?

A

erratic estrus behavior

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30
Q

When does vernal transition naturally occur in the Northern Hemisphere?

A

from february to april

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31
Q

a.

A

increased daylight

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32
Q

b.

A

recognized by retinal photoreceptors

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33
Q

c.

A

pineal gland

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34
Q

d.

A

decreased melatonin secretion

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35
Q

e.

A

hypothalamus

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36
Q

f.

A

increased GnRH secretion

37
Q

g.

A

hypophyseal-portal circulatory system

38
Q

h.

A

anterior pituitary

39
Q

i.

A

increased LH and FSH secretion

40
Q

What occurs during early vernal transition?

A

minor and major anovulatory waves - increased FSH and LH

41
Q

What size are the follicles in early vernal transition?

A

less than or equal to 30 mm

42
Q

What occurs during mid to late vernal transition?

A

There are major ovulatory waves (increased LH and decreased FSH), selection of the dominant follicle, ovulation, and commencement of normal cyclicity

43
Q

When does average ovulation occur for a mare not under a lighting program?

A

April 15th

44
Q

What are some additional findings associated with vernal transition?

A

varying degrees of uterine edema, +/- intrauterine fluid, erratic and prolonged estrus behavior

45
Q

How long is autumnal transition?

A

1-2 month duration - decreasing day length

46
Q

When does autumnal transition occur?

A

it is highly variable - it occurs somewhere between september and December

47
Q

What is autumnal transition the result of?

A

opposite neuronal and hormonal events

48
Q

What are autumnal follicles?

A

hemorrhagic and fibrin filled anovulatory follicules due to failure of ovulation

49
Q

How long is the estrous cycle of the mare?

A

18-24 days - average is 21 days

50
Q

How long is diestrus (luteal phase)?

A

14-17 days

51
Q

How long is estrus (follicular phase)?

A

4 -7 days

52
Q

Typically, how many follicular waves are there in a mare?

A

two

53
Q

True or false: Follicles are only present during estrus.

A

false - they are present during both estrus and diestrus

54
Q

When does diestrus occur?

A

after ovulation

55
Q

What structure is formed during diestrus?

A

the corpus hemorrhagicum

56
Q

When does the corpus hemorrhagicum mature and what does it become?

A

5 days after formation; it becomes the corpus luteum

57
Q

What form may the corpus hemorrhagicum be?

A

it may be solid or cystic - both are normal

58
Q

What hormone influences diestrus?

A

progesterone (P4)

59
Q

What hormone influences the end of diestrus?

A

Prostaglandin

60
Q

What behavioral signs does a mare exhibit under the influence of progesterone?

A

tail clamping/swishing, kicking, striking, or biting, and squealing

61
Q

What physical infleunce does progesterone have on the reproductive tract?

A

There is no uterine edema. Tight, narrow, pale, and dry cervix up off the vaginal floor (high, dry, and tight)

62
Q

What influence does progesterone have on the reproductive hormones?

A

it inhibits anterior pituitary LH release and hypothalamic GnRH production - i.e it inhibits secondary ovulations (usually) and postpones follicular maturation and growth

63
Q

True or False: Progesterone causes immune suppression to the reproductive tract.

A

true

64
Q

What influence does progesterone have on the glands?

A

glandular development and secretion

65
Q

How many waves of follicular activity occur during diestrus?

A

1-2 waves - FSH activity

66
Q

What occurs during diestrus?

A

recruitment and initial follicular growth

67
Q

When does luteolysis typically occur?

A

around day 14 of diestrus

68
Q

What occurs during rapid luteolysis?

A

There is a decline in P4 that is first detectable 4 hours after release. There is a significant decrease in P4 within 40 hours. The lutel structure regresses.

69
Q

a.

A

induction of endometrial E2 receptors

70
Q

b.

A

follicular E2 binding induces endometrial OT receptors

71
Q

c.

A

OT binding induces endometrial prostaglandin production

72
Q

d.

A

travels through the systemic circulation to CL

73
Q

e.

A

vasoconstriction of utero-ovarian vessels

74
Q

f.

A

luteal ischemia

75
Q

What is estrus?

A

the period of continued follicular growth, dominant follicle selection, and further growth and maturation of the dominant follicle(s)

76
Q

What is follicular growth under the influence of?

A

rising LH and FSH

77
Q

What hormone can follicular thecal and granulosa cells produce and how does that hormone affect LH secretion?

A

estrogen which provides positive feedback on LH secretion

78
Q

What size is a dominant follicle in a mare?

A

25 mm

79
Q

What hormone does a dominant follicle produce and how does it affect FSH levels?

A

inhibin tells AP to stop releasing/producing FSH and therefore decreases FSH levels

80
Q

Follicles secrete estrogen. How does that influence FSH and LH levels?

A

estrogen decreases FSH and increases LH

81
Q

What happens to the non dominant follicles during estrus?

A

they go through atresia

82
Q

What behavioral signs does a mare exhibit under the influence of estrogen?

A

Stallion receptivity, raising tail, winking, passive urination, and squatting

83
Q

What reproductive changes does a mare undergo under the influence of estrogen?

A

uterine edema and cervical relaxation

84
Q

What receptors do dominant follicles have and how many mm do they grow a day?

A

They express granulosa LH receptors and grow 3-5 mm/day

85
Q

What is the preovulatory size of follicles in light breeds?

A

30-45mm

86
Q

What is the preovulatory size of follicles in Drafts and Friesians?

A

greater than 40-50mm

87
Q

What is the preovulatory size of follicles in Ponies/Minis?

A

less than 30mm

88
Q

Pending ovulation, what occurs to the follicle, granulosa cell layer, and uterus?

A

The follicle begins to point and lose shape becoming irregular and then softens. The granulosa cell layer thickens. Uterine edema often decreases

89
Q

In relation to estrus, when does ovulation typically occur?

A

routinely 24-48 hours prior to the end of estrus

Disturbances in Reproduction (49 decks)

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