Exam 2 - Canine Estrus Cycle Flashcards
What is puberty?
The ability of the hypothalamic neurons to produce sufficient GnRH
What does the Proestrus stage of the canine cycle entail?
initiation of overt activity
What does the Estrus stage of the canine cycle entail?
time for breeding (acceptance of the male)
What is the Diestrus stage of the canine cycle? (AKA what?)
AKA - Luteal phase
This is the stage in which either prenancy or pseudopregnancy occurs
What is the Anestrus stage of the canine cycle
period of quiescence & repair
What are the average lengths of the proestrus & estrus stages
Average duration is 7-9 d (total 14-18d)
actual range can be 2-21d
Each bitch is unique, needs individual breeding plan
How long is Anestrus in the canine
anestrus is usually 90 - 150+ d
how long is Diestrus in the canine cycle?
Fixed at 60 days whether pregnant or not!
what is the interestrus period?
the time from beginning of one estrus to the beginning of the next estrus
what is the minimum cycle length?
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!
what is the max cycle length?
normal = 12 mos
breed predispositions: Basenji, sight hounds
if >12 m then investiation indicated for cause (e.g. hyperprolactemia)
what is the vaginal cytology pattern during cycle?
normal thin: 2-4 cell layers in anestrus
under influence of estrogens = 20-40 cells thick by end of proestrus
What purpose does the thickening of the vaginal epithelium serve?
protect vagina against trauma
prevent bacterial entry
what can’t cytology of the cornification of vaginal epithelial cells tell us?
doesn’t accurately predict time of receptivity, LH surge or ovulation
what can cytology of the cornification of vaginal epithelial cells help with?
predict if the bitch is progressing & still in her fertile period
What is the best way to use cytology of vaginal epithelial cells when examining the bitch?
coordinate cytology with hormone concentrations & speculum examination!
What are the physical changes seen in proestrus?
what causes the physical changes?
turgid swelling of vulva
hemorrhagic vulvar discharge
Diapedesis of RBC’s through uterine vessels - varies in individuals
What would the vaginal cytology look like in proestrus?
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
during proestrus stage what changes can be seen by vaginal speculum?
early = vaginal mucosa edematous
late = starts shrinking, less edema
what is a bitches behavior like during proestrus?
attracts males, but non receptive!
which hormone dominates the proestrus stage?
Estrogen dominates!
Gonadotropins LH & FSH are low
Progesterone low (< 1 ng/mL)
what are the physical changes in estrus stage?
softening of vulvar swelling
scant blood discharge
what will vaginal cytology during estrus show?
cornification continues
looking through vaginal speculum during estrus what is seen?
early = more shrinking of mucosa
late = max shrinkage called crenulation. angled mucosa
what is a bitches behavior like during estrus stage?
stands to be mounted & bred
What hormones are doing what during estrus stage?
progesterone rising
estrogen falling
LH & FSH peaks
describe hormone activity (profile) during estrus
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
The bitch isn’t pregnant yet! What is the rise in progesterone due to during estrus?
Preovulatory rise is due to follicular estrual luteinization
When estrus ends, P4 is already greatly elevated over baseline
What is diestrus all about?
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
how does diestrus cease?
We don’t know!
No known luteolytc PGF2a from uterus in non pregnant bitch
And back to anestrus goes the bitch! How might that look?
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)
