CH 7 Reproductive Cyclicity Flashcards
What happens to female (in general) at puberty?
Female enters state of reproductive cyclicity
What does the estrous cycle do?
Provides female with repeated opportunities to become pregnant
If conception occurs, then female enters period of anestrus during pregnancy which ends after parturition, uterine involution and lactation
What is estrus?
“standing heat” –> period of sexual receptivity
What is the estrous cycle?
Period from 1st estrus to the next
Polyestrus
uniform distribution of estrous cycles throughout the entire year
Seasonally polyestrous
“clusters” of estrous that occur during certain seasons
What animal is a short-day breeder?
sheep
What animal is a long day breeder?
horses
Monoestrus
Only one estrous cycle per year
Periods of estrus last for several days
What are the 2 phases of the estrous cycle?
- Follicular phase
- Luteal phase
What is the follicular phase (including structure and hormone)?
Period of regression of CL to ovulation
Generally short, <20% of cycle
Structure: follicle
Hormone: estradiol
What is the luteal phase (including structure and hormone)?
Period from ovulation to CL regression
Very long, ~80% of cycle
Structure: CL
Hormone: progesterone
However, follicles do continue to grow during this phase
What are the 4 divisions of the estrous cycle?
- proestrus
- estrus
- metestrus
- diestrus
Proestrus
formation of ovulatory follicles + E2 secretion
Estrus
sexual receptivity + peak E2 secretion
Metestrus
Sexual receptivity +CL formation + beginning of P4 secretion + peak E2 secretion + ovulation follicular phase
Diestrus
Sustained luteal secretion of P4
When does proestrus begin and end?
period immediately before estrus
begins immediately when progesterone declines as a result of CL lysis and ends at the onset of estrus
How long is proestrus?
2-5 days in length
What hormones does proestrus switch from and to?
Switch from progesterone dominance to estradiol dominance
What is homrone transition during proestrus due to?
The transition is due to FSH and LH
What is estrus characterized by?
Visible behavioral symptoms such as sexual receptivity and mating
What hormone is dominant during estrus?
Estradiol is dominant and at peak levels
What is lorodosis?
Mating posture
What happens during estrus?
Ovulation - for all species but cow which occurs during metestrus
When does metestrus occur?
Period between ovulation and formation of functional CL
What are hormone profiles during metestrus?
At start, E2 and P4 are relatively low. P4 levels increase over this period.
When does diestrus occurs?
Period from formation of fully-functional CL (high P4) to lysis of the CL
Longest stage of the estrous cycle
What happens during diestrus?
Uterus prepares a suitable development and eventual attachment of the embryo to uterine endometrium
How long does diestrus last?
usually 10-14 days in length
Dog estrous cycle phases
Phases: proestrus, estrus, diestrus, and anestrus
How many estrous cycles do wild canids go through?
1 estrous cycle/ year - usually seasonal
How many estrous cycles do domestic dogs go through and when do they occur?
2 estrous cycles/year
February - May
What type of estrous cycles do cats have?
Polyestrous cycles - uniform distribution of estrous cycles that occur throughout the entire year
What type of ovulators are felids?
Induced ovulators - copulation indices LH surge
What is postestrus in cats?
Inerestrus period following estrus in queen that has not been induced to ovulate by copulation
What happens if there is no copulation in cats?
No ovulation of CL formation. Thus, no metestrus or diestrus
What is anestrus?
“without cyclicity” - ovaries remain inactive
What can anestrus be caused by?
- pregnancy
- lactation
- the presence of offspring
- season
- stress
- pathology
What is the average menstrual cycle in women?
28 days
What is menses?
sloughing of the endometrium to the exterior
What is another name for anestrus in women?
amernorrhea
What animals are polyestrus?
cow, queen, pig, rodents
What animal(s) are long day seasonal polyestrus
horses
What animals are short day seasonal polyestrus?
Ewe, doe, elk, nanny
What animals are monoestrous?
dog, wolf, fox, bear
What does the suckling stimulus do?
Blocks release of GnRH which then reduces LH to stimulate ovary follicular development
What is the ram effect?
placement of male with females will decrease time to estrus. Especially important in ewe
