Exam 2 Flashcards
Sry
activates cells within the gonads to produce testes determining factor
What develops first female or male tract
male tract
Anti-Mullerian Duct Hormone
regresses the female tract
What allows the wolfian duct in females to regress
absence of testorone
Male external genetalia growth
urethral groove grows and becomes the body of the penis, scrotal swelling and the phallus grows
Female external genetalia growth
the phallus shrinks and there is labial swelling
What causes homosexual behavior in cattle
high estrogen
Why don’t males need a surge center
once at a certain age they are constantly producing sperm cells as opposed to females who have a limited number of oocytes and need the surge to ovulate.
How does the surge center regress in males
It starts as indifferent
Then the testorone circulates and due to it being a small steroid it passes through the blood brain barrier
Then in the brain aromatase converts the testorone to estrogen
The high concentration of estrogen in the brain does not allow for growth of the surge center
Why doesn’t estrogen knock out the surge center in females
The females have alphafetal protein which binds to the estrogen in the body and because of the large protein size it can not go through the blood brain barrier
Sexual Dimorphism in the brain
The pre optic area is bigger in males than females as it helps them find mates
True hermaphrodites
both male and female internal and external genetalia
EX: some fish release both ova and sperm released from separate orifices and the fertilization is external
XY Genetic Pseudo-Hermaphrodite
Mixed internal tract, external female, the cells are not responsive testerone
XX Genetic Pseudo-Hermaphrodite
Ovary,, Mixed tract, external male, adrenal produces excess androgen
Freemartinism
both male and female tracts are present. Most commonly occurs in cattle
When does freemartinism most often occur
It occurs when cow has twins and one is a heifer calf and one is a bull calf. The bull calf develops normally and the female is the free Martin
How/Why does freemartinism occur in cattle
-The bull calf becomes a bull first, and the cows share placental blood until day 84. The reduced concentrations of AMH and androgens in the heifer calf from the blood of the bull calf causes the change in developing tract and start of sexual differentiation
Female sexual development in hyenas
-have an enlarged clitoris that resembles a penis
-nonfunctional vagina
-does not have an obvious phenotypic sex
How do female hyenas mate and give birth if they have a nonfunctional vagina
-mating occurs through the clitoris
-painful due to the small size that the fetus has to pass through
Why do female hyenas have these charecteristics
A lot of androgen production by the dam when pregnant and because of that there is natural virilization of the females in utero and changes how external genetalia forms
Puberty Definition
the time at which an animal becomes functionally capable of reproducing
Why can’t the age when behavioral traits are expressed not be an indicator of puberty in males
-can be influenced by other factors and can happen at a very young age
Why can’t the age at 1st ejaculation be an indicator of puberty in males
The first ejaculations often are
-not fertile
-only seminal plasma
-can not cause pregnancy
Why can’t when spermatozoa 1st appear in ejacualte not be an indicator of puberty in males
usually does not reach the critical threshold that would deem them functionally capable of producing
Why can’t when spermatozoa first appear in the urine be an indicator of puberty in males
it varies to much and leaking can occur at other times
What is defined as the indicator of puberty in males
age when ejaculate contains a threshold number of sperm (varies by species)
Why can’t the age of first estrus be an indicator of puberty in females
-usually no ovualtion occurs
-can happen as early as 2 months
-can simply be induced with estrogen
Why can’t the age of first ovulation be an indicator of puberty in females
-not fertile
-not easily detectable
-an developed hypothalamus, pituitary axis is needed to mature the ovary
What is defined as the indicator of puberty in females
age of reproductive competence
-time when production can be carried to term
-often defined by hormone levels
(progesterone)
HHLHHL
Why is it important to know the age of puberty in livestock
the early onset of puberty, the earlier get can become production ready.
Prepuberty in females
-Infrequent GnRH pulses
-Little follicle growth
-low estradiol
Hypothalamic control in female puberty
hypothalamus stimulate pituitary gland which then releases growth hormone which then causes the ovaries and testes to respond and produce sex hormones
Puberty in the female
-negative and positive feedback to estradiol is established
-follicular growth
-LH surge mechanism in place
What triggers puberty in females
estrogen coming from the ovaries, jump starts the surge to start puberty
Factors that influence puberty
-genetics (breed difference)
-Body weight (% body fat)
-Environment (seasons)
-Social Factors (male effect)
-Stress
Frisch Theory
A critical body fat and body weight are required for the onset of puberty
What did an experiment show with an increased plane of nutriton
It displayed an additional estrus prior to breeding
Spring Born Ewe Lambs
-reach puberty at 7 months
-less synchronously
-long day length programs the hypothalamus pituitary axis
Fall born ewe lambs
-puberty 12 months
-more synchronous
need to experience long day length to program the hypothalamus pituitary axis
Vandenburgh Effect
-male present=earlier onset of puberty
-females only=later onset of puberty
might be a way of regulating population density
Puberty in Humans
-growth spurt begins
(girls start earlier and are typically taller between ages 11-13)
-Full adult height
-reached about 3 years earlier in girls
Menarche
-first menstrual cycle
-typically occurs by age 12-13
-initally may involve anovulatory, irregular cycles
Spermarche
first ejaculation
-typically occurs by age 15
initial period of sterility
what hormone to follicles produce
estrogen
what hormone do corpus leuteum produce
progesteronw
Sign of standing heat in cows
cow that is standing to be mounted by another cow
Sign of standing heat in sheep
ewe turning head to tell the ram to come hither
Sign of standing heat in mares
display excessive uriniation and winking of the vagine
sign of standing heat in sows
Lordosis
applying pressure to the back causes them to stand
Hormone levels during estrus
estrogen is high and progesterone is low
Polyestrus
display estrus through the year
-cows,pigs,cats,mice and rats
Seasonally Polyestrus
display more than one estrous cycle during a specific time of year
Short day breeders
deer and sheep
-typically breed in the fall most come into estrus between September 1st and December 31st
Long day breeders
hamsters and horses
Melatonin and Breeding in short day breeders
-light goes down which stimulates the pineal gland which then releases melatonin
-the melatonin then raises GnRH and FSH and Lh
Monoestrus
displays estrus once a year
Why are rabbits an execption the rule
always half large amounts of follicles and do not have an estrus cycle
Spontaneous Ovulator
ovulates with a regular frequency and do not require copulation
Reflex (induced) Ovualtor
Ovulation induced only after stimulation of the vagina and/or cervix
-need a stimulus to ovulate
ex: rabbits, cats, ferrets, camels, llamas and alpacas
Follicular Phase
-Growth of Follicles
-dominant structure-preovulatory follicle
-dominant hormone is estradiol
starts with the regression of corpora lute and ends with ovulation
relatively short
Luteal Phase(description)
Growth of corpus lute (corpora lute)
-dominat structure-corpus luteum
-dominant hormone-progesterone
-starts with ovulation
-ends with luteal regression
Stages of the estrous cycle in the follicular phase
proestrus and estrus
Luteal Phase
metaestrus and diestrus
Proestrus
-increased estrogen secretion
-follicle growing
-progesterone decreasing
-due to cl regression
Estrus
-Sexual receptivity
-peak estrogen production
-LH and FSH surges
-Ovulation in mares and sows (since their estrus is fairly long)
Metaestrus
-increasing progesterone production
-formation of the CL following ovulation
-Ovulation in cows and ewes
-LH and estradiol is low
Diestrus
-Sustained progesterone production
-cl domination structure
-follicles continue to grow in waves
-shift in LH and FSH
-longest period of cycle
Cattle cycle length and duration of estrus
Estrus: 8-16H
Cycle length: 21 days