Exam 2 - Canine Estrus Cycle

Question 1

What is puberty?

Answer 1

The ability of the hypothalamic neurons to produce sufficient GnRH

Question 2

What does the Proestrus stage of the canine cycle entail?

Answer 2

initiation of overt activity

Question 3

What does the Estrus stage of the canine cycle entail?

Answer 3

time for breeding (acceptance of the male)

Question 4

What is the Diestrus stage of the canine cycle? (AKA what?)

Answer 4

AKA - Luteal phase

This is the stage in which either prenancy or pseudopregnancy occurs

Question 5

What is the Anestrus stage of the canine cycle

Answer 5

period of quiescence & repair

Question 6

What are the average lengths of the proestrus & estrus stages

Answer 6

Average duration is 7-9 d (total 14-18d)

actual range can be 2-21d

Each bitch is unique, needs individual breeding plan

Question 7

How long is Anestrus in the canine

Answer 7

anestrus is usually 90 - 150+ d

Question 8

how long is Diestrus in the canine cycle?

Answer 8

Fixed at 60 days whether pregnant or not!

Question 9

what is the interestrus period?

Answer 9

the time from beginning of one estrus to the beginning of the next estrus

Question 10

what is the minimum cycle length?

Answer 10

absolute requirement of 4 m

• fertility is low if < 90d anestrus is not achived*
• Diestrus is the canine luteal phase/progesterone phase -*

pregnancy or pseudopregnancy occurs in this phase!

Question 11

what is the max cycle length?

Answer 11

normal = 12 mos

breed predispositions: Basenji, sight hounds

if >12 m then investiation indicated for cause (e.g. hyperprolactemia)

Question 12

what is the vaginal cytology pattern during cycle?

Answer 12

normal thin: 2-4 cell layers in anestrus

under influence of estrogens = 20-40 cells thick by end of proestrus

Question 13

What purpose does the thickening of the vaginal epithelium serve?

Answer 13

protect vagina against trauma

prevent bacterial entry

Question 14

what can’t cytology of the cornification of vaginal epithelial cells tell us?

Answer 14

doesn’t accurately predict time of receptivity, LH surge or ovulation

Question 15

what can cytology of the cornification of vaginal epithelial cells help with?

Answer 15

predict if the bitch is progressing & still in her fertile period

Question 16

What is the best way to use cytology of vaginal epithelial cells when examining the bitch?

Answer 16

coordinate cytology with hormone concentrations & speculum examination!

Question 17

What are the physical changes seen in proestrus?

what causes the physical changes?

Answer 17

turgid swelling of vulva

hemorrhagic vulvar discharge

Diapedesis of RBC’s through uterine vessels - varies in individuals

Question 18

What would the vaginal cytology look like in proestrus?

Answer 18

Cornification of squamous epithelial lining of vagina,

by mid to late proestrus parabasal & small intermediate cells decrease, superficial & large intermdiate cells increase,

erythrocytes, neutrophils present

Question 19

during proestrus stage what changes can be seen by vaginal speculum?

Answer 19

early = vaginal mucosa edematous

late = starts shrinking, less edema

Question 20

what is a bitches behavior like during proestrus?

Answer 20

attracts males, but non receptive!

Question 21

which hormone dominates the proestrus stage?

Answer 21

Estrogen dominates!

Gonadotropins LH & FSH are low

Progesterone low (< 1 ng/mL)

Question 22

what are the physical changes in estrus stage?

Answer 22

softening of vulvar swelling

scant blood discharge

Question 23

what will vaginal cytology during estrus show?

Answer 23

cornification continues

Question 24

looking through vaginal speculum during estrus what is seen?

Answer 24

early = more shrinking of mucosa

late = max shrinkage called crenulation. angled mucosa

Question 25

what is a bitches behavior like during estrus stage?

Answer 25

stands to be mounted & bred

Question 26

What hormones are doing what during estrus stage?

Answer 26

progesterone rising

estrogen falling

LH & FSH peaks

Question 27

describe hormone activity (profile) during estrus

Answer 27

estrogen begins to fall

progesterone starts to rise - first sharp rise of P4 is correlated with LH peak!

Both estrogen & progesterone necessary for standing behavior

LH & FSH both peak at onset of estrus - may need both for ovulation

Question 28

The bitch isn’t pregnant yet! What is the rise in progesterone due to during estrus?

Answer 28

Preovulatory rise is due to follicular estrual luteinization

When estrus ends, P4 is already greatly elevated over baseline

Question 29

What is diestrus all about?

Answer 29

non acceptance of mating, but may still be attractive

progesterone dominated - luteal phase

vaginal cytology = superficial cells decrease, parabasal/small intermediate cells increase

rounding/smoothing mucosa seen on vaginal speculum, may see variegated red/white areas

pregnancy (pseuopregnancy) normal in bitch

uterine tone develops

60 d duration (45-90 d range)

mammary development in non preg. bitch subtle but reflects Prolactin levels

Question 30

how does diestrus cease?

Answer 30

We don’t know!

No known luteolytc PGF2a from uterus in non pregnant bitch

Question 31

And back to anestrus goes the bitch! How might that look?

Answer 31

Male shows no sexual interest in the female

Female shows no sexual interest in male

Vulva appears not swollen

Vaginal cytology few cells and non-cornified

• Superficial cells absent
• ± Neutrophils & bacteria (low numbers)

Vaginal wall is very thin and appears pale on vaginal speculum

Progesterone is baseline (<1ng/mL)