Exam 1: Canine Physiology (AI experiment) Flashcards
What is puberty in female dogs defined as?
The first observed heat
Puberty occurs between 6 to 24 months of age, with an average onset of 10 to 12 months.
At what age do small breeds typically reach puberty compared to large breeds?
Small breeds come into heat earlier than large breeds
This varies based on the size of the breed.
What is a characteristic of pubertal estrus in female dogs?
It may be a split or false heat
Early pubertal estrus can be induced by housing with cycling females.
How often do bitches cycle on average?
Every 7 months
Some breeds cycle more frequently, such as German Shepherds and Rottweilers, which may cycle every 4.5 to 5 months.
Which breeds are known to cycle less frequently?
Basenjis, dingos, and wolf-crosses
These breeds typically cycle yearly.
What is the average length of proestrus in female dogs?
9 days
The range can be from 0 to 17 days.
What physical changes occur during proestrus?
The vulva is enlarged and firm
Vulvar discharge may range from serous to serosanguinous.
How do female dogs behave during proestrus when male dogs are present?
They do not stand for breeding and often tuck their tail under tightly
Other behaviors may include sitting down or turning on the male dog.
What is the follicular stage of the cycle in endocrinology?
This is the stage where estrogen concentrations rise during proestrus and peak at the end of this stage
Serum progesterone and luteinizing hormone (LH) concentrations are low during this stage.
What happens to RBCs during the follicular stage?
RBCs may be present throughout the stage
Their presence does not indicate a specific phase but is noted throughout the follicular stage.
What is the presence of PMNs in vaginal cytology during the follicular stage?
PMNs are present early in this stage but disappear as estrus nears
This correlates with changes in the vaginal epithelium.
How does the vaginal epithelial cell population change during the follicular stage?
It gradually changes from completely non-cornified to completely cornified
Cornification will be complete about 2 days before estrogen peaks.
When does cornification of the vaginal epithelium complete?
About 2 days before estrogen peaks, about 4 days before standing heat begins
This timing is critical for understanding reproductive cycles.
Fill in the blank: During the follicular stage, serum progesterone and _______ concentrations are low.
luteinizing hormone (LH)
This is significant in differentiating between stages of the reproductive cycle.
What is the average length of estrus in bitches?
9 days average, range 3 to 21 days
Estrus is the period in which female dogs are receptive to mating.
What physical changes occur in the vulva as a bitch enters standing heat?
The vulva may become less turgid and the vulvar discharge may become straw-colored
Discharge can range from serous to serosanguinous in a normal bitch.
Define estrus in terms of behavior.
Standing = remaining motionless as the male investigates her hindquarters
Flagging = deflection of the tail laterally and muscular elevation of the vulva.
What happens to estrogen concentrations at the beginning of estrus?
Estrogen concentrations fall
This decrease is necessary for the appearance of breeding behaviors.
What hormonal change occurs at the onset of estrus?
A preovulatory rise in progesterone occurs
This rise presumably elicits the LH surge.
What is released from the pituitary on or about the first day of estrus?
A surge of LH
This surge causes ovulation of a primary oocyte 2 days later.
What forms after ovulation in the bitch?
CLs (corpus lutea) form and progesterone production begins
Is measurement of serum LH routinely performed?
No, it is not routinely performed
However, measurement of serum progesterone concentrations is easily performed.
What does vaginal cytology show during estrus?
The vaginal epithelial cell population is completely cornified, with greater than 50% anuclear squames
No PMNs or debris are present.
Can vaginal cytology predict ovulation time prospectively?
No, it cannot predict ovulation time prospectively
However, changes in vaginal cytology occur 6 days after ovulation.
What types of bacteria are commonly present in vaginal cytology during estrus?
Intra- and extracellular bacteria are commonly present
RBCs may or may not be present.
What is the average length of diestrus in days?
60 days average, range 50 to 80 days
What are the characteristic physical changes or behaviors in diestrus?
There are no characteristic physical changes or behaviors
Some bitches may still stand to be bred early in this stage.
What may be present during diestrus in terms of vulvar discharge?
Small amounts of mucoid vulvar discharge may be present
How long does the corpus luteum (CL) maintain in bitches during diestrus?
About 60 days whether they were bred or not
What are the progesterone concentrations like throughout diestrus?
Progesterone concentrations are high throughout
What signifies the end of diestrus?
A decline in serum progesterone to less than 2 ng/ml
This decline can be associated with whelping or false pregnancy.
What is the sole source of progesterone during pregnancy in the bitch?
The corpus luteum (CL)
What happens to the vaginal epithelial cell population on the first day of diestrus?
The population abruptly shifts to complete non-cornification
This shift is a key indicator in vaginal cytology.
What types of cells may be present in vaginal cytology during diestrus?
PMNs, metestrum cells, and/or foam cells
PMNs are polymorphonuclear leukocytes, and metestrum cells contain leukocytes.
Diestrus may end with whelping if the bitch is _______.
pregnant
