Equine - Anatomy and Reproductive Physiology

Question 1

What type of uterus does the horse have?

Answer 1

bicornuate or Y-shaped

Question 2

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

Answer 2

It suspends structures within the abdominal cavity

Question 3

What is contained within the broad ligament?

Answer 3

arteries, veins, nerves, and lymphatics

Question 4

What does the mesovarium support?

Answer 4

the ovaries

Question 5

What does the mesosalpinx support?

Answer 5

the oviducts

Question 6

What does the mesometrium support?

Answer 6

the uterus/cervix

Question 7

How many folds are within the cervix?

Answer 7

5-10 longitudinal folds

Question 8

What is the cervix made up of?

Answer 8

muscle

Question 9

How large is the cervix?

Answer 9

6-7cm in length

Question 10

The cervix cannot and should not every be ________.

Answer 10

retracted

Question 11

What separates the vagina and the vestibulum?

Answer 11

transverse folds

Question 12

Where should 2/3 of the vulva be located?

Answer 12

below the pelvic brim

Question 13

What direction is the vulva oriented in?

Answer 13

vertical or near vertical orientation

Question 14

What is the clitoris made up of?

Answer 14

a fossa and 3 sinuses (medial and lateral)

Question 15

What are the three barriers to the internal reproductive tract?

Answer 15

vulva, intact vestibulovaginal sphincter, and cervix

Question 16

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

Answer 16

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

Question 17

What is the shape of the equine ovary?

Answer 17

it is kidney bean shaped

Question 18

Where does ovulation occur?

Answer 18

at the ventral ovulation fossa

Question 19

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

Answer 19

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

Question 20

When does puberty occur in a mare?

Answer 20

12-24 months - average is 15 months

Question 21

When does a mare reach maturity?

Answer 21

by 3 years of age

Question 22

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

Answer 22

long day, seasonally poly estrus

Question 23

What are the phases of seasonality in the mare?

Answer 23

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

Question 24

Winter anestrus is due to ____ days.

Answer 24

short

Question 25

What are the reproductive hormones like during winter anestrus?

Answer 25

low levels of LH, estrogen, and progesterone

Question 26

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

Answer 26

less than 5-10 mm in diameter

Question 27

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

Answer 27

flaccidity

Question 28

How long is vernal transition?

Answer 28

1-2 months - average 55-60 days

Question 29

What estrus behavior occurs during vernal transition?

Answer 29

erratic estrus behavior

Question 30

When does vernal transition naturally occur in the Northern Hemisphere?

Answer 30

from february to april

Question 31

a.

Answer 31

increased daylight

Question 32

b.

Answer 32

recognized by retinal photoreceptors

Question 33

c.

Answer 33

pineal gland

Question 34

d.

Answer 34

decreased melatonin secretion

Question 35

e.

Answer 35

hypothalamus

Question 36

f.

Answer 36

increased GnRH secretion

Question 37

g.

Answer 37

hypophyseal-portal circulatory system

Question 38

h.

Answer 38

anterior pituitary

Question 39

i.

Answer 39

increased LH and FSH secretion

Question 40

What occurs during early vernal transition?

Answer 40

minor and major anovulatory waves - increased FSH and LH

Question 41

What size are the follicles in early vernal transition?

Answer 41

less than or equal to 30 mm

Question 42

What occurs during mid to late vernal transition?

Answer 42

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

Question 43

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

Answer 43

April 15th

Question 44

What are some additional findings associated with vernal transition?

Answer 44

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

Question 45

How long is autumnal transition?

Answer 45

1-2 month duration - decreasing day length

Question 46

When does autumnal transition occur?

Answer 46

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

Question 47

What is autumnal transition the result of?

Answer 47

opposite neuronal and hormonal events

Question 48

What are autumnal follicles?

Answer 48

hemorrhagic and fibrin filled anovulatory follicules due to failure of ovulation

Question 49

How long is the estrous cycle of the mare?

Answer 49

18-24 days - average is 21 days

Question 50

How long is diestrus (luteal phase)?

Answer 50

14-17 days

Question 51

How long is estrus (follicular phase)?

Answer 51

4 -7 days

Question 52

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

Answer 52

two

Question 53

True or false: Follicles are only present during estrus.

Answer 53

false - they are present during both estrus and diestrus

Question 54

When does diestrus occur?

Answer 54

after ovulation

Question 55

What structure is formed during diestrus?

Answer 55

the corpus hemorrhagicum

Question 56

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

Answer 56

5 days after formation; it becomes the corpus luteum

Question 57

What form may the corpus hemorrhagicum be?

Answer 57

it may be solid or cystic - both are normal

Question 58

What hormone influences diestrus?

Answer 58

progesterone (P4)

Question 59

What hormone influences the end of diestrus?

Answer 59

Prostaglandin

Question 60

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

Answer 60

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

Question 61

What physical infleunce does progesterone have on the reproductive tract?

Answer 61

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

Question 62

What influence does progesterone have on the reproductive hormones?

Answer 62

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

Question 63

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

Answer 63

true

Question 64

What influence does progesterone have on the glands?

Answer 64

glandular development and secretion

Question 65

How many waves of follicular activity occur during diestrus?

Answer 65

1-2 waves - FSH activity

Question 66

What occurs during diestrus?

Answer 66

recruitment and initial follicular growth

Question 67

When does luteolysis typically occur?

Answer 67

around day 14 of diestrus

Question 68

What occurs during rapid luteolysis?

Answer 68

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.

Question 69

a.

Answer 69

induction of endometrial E2 receptors

Question 70

b.

Answer 70

follicular E2 binding induces endometrial OT receptors

Question 71

c.

Answer 71

OT binding induces endometrial prostaglandin production

Question 72

d.

Answer 72

travels through the systemic circulation to CL

Question 73

e.

Answer 73

vasoconstriction of utero-ovarian vessels

Question 74

f.

Answer 74

luteal ischemia

Question 75

What is estrus?

Answer 75

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

Question 76

What is follicular growth under the influence of?

Answer 76

rising LH and FSH

Question 77

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

Answer 77

estrogen which provides positive feedback on LH secretion

Question 78

What size is a dominant follicle in a mare?

Answer 78

25 mm

Question 79

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

Answer 79

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

Question 80

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

Answer 80

estrogen decreases FSH and increases LH

Question 81

What happens to the non dominant follicles during estrus?

Answer 81

they go through atresia

Question 82

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

Answer 82

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

Question 83

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

Answer 83

uterine edema and cervical relaxation

Question 84

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

Answer 84

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

Question 85

What is the preovulatory size of follicles in light breeds?

Answer 85

30-45mm

Question 86

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

Answer 86

greater than 40-50mm

Question 87

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

Answer 87

less than 30mm

Question 88

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

Answer 88

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

Question 89

In relation to estrus, when does ovulation typically occur?

Answer 89

routinely 24-48 hours prior to the end of estrus