Puberty Flashcards
Criteria to define puberty in the female
- Age at first estrus (heat)
- Age at first ovulation
- Age at which female can support pregnancy
without deleterious effects
what is the surge center responsible for?
large scale “surge” of GnRH which triggers ovulation
function of preoptic area kisspeptin neurons
- project to proximal GnRH neurons indicating gonadal steroid (and sometimes circadian inputs) to drive the preovulatory surge of LH
function of arcuate kisspeptin neurons
-project to distal GnRH neurons to generate pulsatile (low level) secretion of LH
GnRH secreting neurons mechanism of action
- GnRH neurons release GnRH into the median eminence portal system
- GnRH acts on the anterior pituitary to create gonadotrophin which releases LH and FSH
half life of GnRH
very short, GnRH is rapidly degraded
Hypothalamic Secretion of
GnRH Before puberty
GnRH neurons in the tonic and surge center release LOW amplitude and LOW frequency pulses of GnRH
hypothalamic secretion of GnRH after puberty
- the tonic center secretes consistent levels of GnRH, slightly higher than pre-puberty
- surge center control preovulatory surges of GnRH
FSH is preferentially stimulated at
low GnRH pulse frequencies
LH is preferentially stimulated at
high GnRH pulse frequencies
FSH and LH regulate
aspects of mammalian
sexual maturation and reproductive
function including:
- gametogenesis,
- steroidogenesis (synthesis of estradiol and
progesterone)
- ovulation
FSH and LH at the onset of puberty
slowly rise and begin to oscillate at regular intervals
FSH during fetal life and infancy
peak then fall to low levels during the rest of childhood
At late gestation
- secretion of estradiol dramatically increases
- causes inhibitory action to suppress GnRH release
during postnatal life
- many GnRH pulses
- LH and FSH secretion
prepubertal life
- hypothalamic-pituitary system is highly sensitive to negative feedback inhibition by gonadal steroids
- suppression of GnRH/LH release
Onset of puberty
- reduced sensitivity of the hypothalamic-pituitary system to
negative-feedback inhibition by gonadal steroids - triggers preovulatory GnRH/LH release and onset of puberty
Post-pubertal life:
The levels of steroids required to block gonadotropin release
progressively increase. Thus, the sensitivity of the hypothalamic-pituitary system to
inhibition by sex steroids reaches low level that is characteristic of the adult.
LH Pulse Frequency in Heifers
Before and After Puberty
Substantial time required (~2
months-shaded area) for the
pulse frequency to become
high enough for puberty to
be achieved
factors influencing the onset of puberty
- genetics
- environment
- nutrition
- season
glucose and hypothalamic control of GnRH secretion
moment-to-moment
regulation of GnRH occurs only when significant glucose is available for metabolism
functions of uterus
- Facilitates sperm transport
- Regulates the function of the corpus luteum (luteolysis)
- Nurtures the embryo and initiates its implantation
- Participates in placentation
- Maintains pregnancy
- Supports fetal growth
- Facilitates parturition (labor)
function of cervix
- Barrier between internal and external genitalia
- Facilitates sperm transport
- Sperm reservoir
- Passage for fetal expulsion
- Produces thin and watery mucus
- Forms cervical seal of pregnancy
cow characteristics (ovaries, body of uterus, UTJ, horns, cervix, vagina)
OVARIES= almond shaped, cortex on outside, medulla inside
BODY OF UTERUS= short
UTJ= flexure/kink
UTERINE HORNS= long and coiled
CERVIX= cervical rings
VAGINA= Vaginal fornix
LIGAMENTS
Broad ligament is attached to the illium making the uterine horns look like a ram
Intercornual ligament connects the uterine horns to each other in the center
ewe characteristics (ovaries, UTJ, ligaments)
OVARIES= almond shaped
UTJ= flexure/kink
LIGAMENTS
Broad ligament attached to ilium= rams horn
sow characteristics
OVARIES= berry shaped
BODY OF UTERUS= very short
UTERINE HORNS= long
UTJ= long and finger-like
CERVIX= interdigitating prominences
