06 - Female Reproduction

Question 1

(Introduction)

If we accept the argument that the biological imperative of any individual is propagation of the species, and more specifically their own genes within that species, then if a sexually mature female doesn’t become pregnant at one mating (or period of matings), she (biologically) wants to give herself another opportunity. To this end, in most species, she will have repeated fertile intervals until pregnancy occurs. These repeated episodes are termed cycles.

Question 2

(Estrous Cycles)

1. The first division of female cycles is their classification as estrous or menstraul. This is based on the most visible/readibly detectable event that occurs
2. How many animals menstruate?

in species that don’t the most obvious manifestaion of ovarian cycllicity is what?

3. What is the estrous cycle?

Answer 2

2. the vast majority don’t

estrus (aka heat) - the time when she will accept mating

3. time between 2 episodes of estrus, or 2 heat periods

(strictly speaking, estrus is a behavioral phenomenon (albeit in response to physiological - endocrinologic - cues)

Question 3

(Menstrual Cycles)

1. These are restricted to what?

Answer 3

1. humans and old-world (Asian and African) primates

(However only women do not also have an estrus (behavioral) cycle as well. The other primates can be classified as having both estrus and menstraul cycles, depending on how you want to observe them)

Question 4

(Stages of the estrous cycle)

(note: not all species will experience all of these phases)

(NAME THAT STAGE!)

1. stage of follicular growth prior to estrus
2. time when female will accept mating by male
3. immediately following ovulation. the stage of the developing corpus luteum, preparing for pregnancy
4. the stage of corpus luteum (CL) dominance of the cycle. Uterus prepared for and receptive to pregnancy. window of opportunity for embryo to establish itself
5. Time of reproductive quiescence. Not pregnant, no follicles, no CL

also give 7 types

Answer 4

1. proestrus
2. estrus
3. metestrus
4. diestrus
5. anestrus

juvenile, seasonal, behavioral, lactational, senile, pathological, nutritional

Question 5

(Interestrus)

1. term sometimes used for what?
2. if they go from proestrus into esturs and then aren’t mated they do what?

Answer 5

1. induced ovulators
2. go out of heat for a hilw until the next wave of follicles grow back and put them in estrus

(instead of using anesturs for this period,,, interestrus is used)

Question 6

(Follicuar and Luteal Phases)

1. usually used in reference to the human menstraul cycle, but also occasionally used for estrous
2. The follicular phase is the time when what happens?
3. The luteal phase is the time when there is what?

Answer 6

2. when follicles are growing and there is no CL present on the ovaries (in most estrous cycles this would include proestrous and estrous)
3. there is an active (progesterone secreting) CL present on one of the ovaries

Question 7

(Continuous vs. Seasonal Breeders)

1. In the absence of pregnancy, some species will go through repeated extrous cycles thorughout the yeat
2. examples are what?
3. Other species cycle at particular times of the year, usually designed so that birth occurs in the spring. Because of this, the time of year they breed will depend on what?
4. Animals with very short pregnancies, of weeks to a couple of months, tend to breed when?

some examples?

aka?

5. Animals with gestation periods of 5-6 months tend to breed when?

examples?

aka?

6. Those with very long gestations of around a year, breed when?

examples?

aka?

Answer 7

2. cow, sow, humans (these are continuous or non-seasonal breeders)
3. the gestastion lengh
4. late winter/spring

mink, cats

long day breeder

5. fall

sheep and goats

short-day breeder

6. spring (so they can give birth at the same time next year

horse (11 months)

long-day breeder

Question 8

(Monoestrous vs. Polyestrous Species)

Different species will also vary the number of sequential cycles they have if they don’t get pregnant

1. Which have just 1 cycle after which they become anestrus?

examples?

2. Which, in the absence of pregnancy, will have repeated, sequential, cycles (most of the species we deal with are this)?

Which may do this continuously throughout the year?

which may eventually be interrupted by a seasonal anestrus in seasonally breeding animals?

Answer 8

1. monoestrous

domestic dog (non-seasonally monoestrous); wolf and roe deer (seasonal monoestrous)

2. polyestrous

cow, sow, human

sheep, horse

Question 9

(Spontaneous vs. Induced Ovulators)

Many of the species we deal with are spontaneous ovulators.

1. When a large, mature follicle is present at the right time of the cycle (estrus - low progesterone) it will trigger what that causes what?

examples?

2. These species will go though which cycle irrespective of mating or the presence of a male?

Answer 9

1. a hormonal cascade that causes its own ovulation

sheep, pigs, cows, dogs, horses, and humans

2. (proestrus)-estrus-(metestrus)-diestrus

Question 10

(Spontaneous vs. Induced Ovulators: cont)

1. Other species, like the house cat and most mustelids, will come into proestrus and estrus… but if they are not mated what happens?
2. They just do what?
3. They will continue this cycle until what happens?

what also does this but is non-seasonal?

Answer 10

1. they don’t ovulate
2. Go out of estrus (innterestrus) until a new wave of follicle development brings them back to proestrus
3. until mated or they become seasonally anesturs

llamas

Question 11

(Ultra-Short, Short and Long Cycles)

Lifespan of the corpus luteum determines cycle length

1. eutherian mammals can be categorized based on how long the corpus luteum functions for in what?
2. The shortest wave would be what?

Answer 11

1. the non-fertile estrous cycle
2. the induced ovulators where no ovulation occurs in the absence of mating and there is no luteal phase at all

(if we leave these out the the rest (spontaneous ovulators) have been categorized as having either ultra short, short, or long cycles

Question 12

(Ultra Short Cycles (non-functional corpoa lutea))

1. These occur in what?
2. In the absence of mating they ovulate but what doesn’t form?
3. length of the estrous cycle?
4. In this case the CL doesn’t fully differentiate and only minimal progesterone is secreted
5. If a sterile mating (ie vasectominzed male) occurs then what happens?
6. This CL lasts how long; with support from what?

Answer 12

1. the mouse and rat
2. a fully functional CL
3. 4-5 days
4. a functional CL does form in response to the luteotropic action of an initial mating-induced prolactin secretion
5. 12-14 days under continued support from diurnal prolaction secretion from the pituitary

Question 13

(Short Cycles (short-lived corpora lutea))

1. In primates and most polyestrous (because they continually cycle in the absence of pregnancy) farm animals th eCL of a normal cycle functions fro how long?
2. Is there a functional pregnancy in the uterus? What happens to the CL

what happens to the “natural lifespan” of the corpus luteum?

Answer 13

1. 2 and 2.5 weeks (cycle length is from about 2.5-4 weeks)
2. no; it is actively destoryed to permit another opportunity for estrous and mating

is shortened

Question 14

(Long cycles)

This pattern is seen in some monoestrous species

1. In this case a fully functional CL forms after ovulatino irrespective of mating and its lifespan is fairly independent of what?
2. This is the pattern in dogs where in both pregnancy and non-pregnancy the CL lasts for around how many days?

Answer 14

1. whether pregnancy is established or not
2. 60 (often it actually lasts a bit longer in non-pregnancy thatn pregnancy)