Puberty

Question 1

Criteria to define puberty in the female

Answer 1

• Age at first estrus (heat)
• Age at first ovulation
• Age at which female can support pregnancy
  without deleterious effects

Question 2

what is the surge center responsible for?

Answer 2

large scale “surge” of GnRH which triggers ovulation

Question 3

function of preoptic area kisspeptin neurons

Answer 3

• project to proximal GnRH neurons indicating gonadal steroid (and sometimes circadian inputs) to drive the preovulatory surge of LH

Question 4

function of arcuate kisspeptin neurons

Answer 4

-project to distal GnRH neurons to generate pulsatile (low level) secretion of LH

Question 5

GnRH secreting neurons mechanism of action

Answer 5

• GnRH neurons release GnRH into the median eminence portal system
• GnRH acts on the anterior pituitary to create gonadotrophin which releases LH and FSH

Question 6

half life of GnRH

Answer 6

very short, GnRH is rapidly degraded

Question 7

Hypothalamic Secretion of
GnRH Before puberty

Answer 7

GnRH neurons in the tonic and surge center release LOW amplitude and LOW frequency pulses of GnRH

Question 8

hypothalamic secretion of GnRH after puberty

Answer 8

• the tonic center secretes consistent levels of GnRH, slightly higher than pre-puberty
• surge center control preovulatory surges of GnRH

Question 9

FSH is preferentially stimulated at

Answer 9

low GnRH pulse frequencies

Question 10

LH is preferentially stimulated at

Answer 10

high GnRH pulse frequencies

Question 11

FSH and LH regulate

Answer 11

aspects of mammalian
sexual maturation and reproductive
function including:
- gametogenesis,
- steroidogenesis (synthesis of estradiol and
progesterone)
- ovulation

Question 12

FSH and LH at the onset of puberty

Answer 12

slowly rise and begin to oscillate at regular intervals

Question 13

FSH during fetal life and infancy

Answer 13

peak then fall to low levels during the rest of childhood

Question 14

At late gestation

Answer 14

• secretion of estradiol dramatically increases
• causes inhibitory action to suppress GnRH release

Question 15

during postnatal life

Answer 15

• many GnRH pulses
• LH and FSH secretion

Question 16

prepubertal life

Answer 16

• hypothalamic-pituitary system is highly sensitive to negative feedback inhibition by gonadal steroids
• suppression of GnRH/LH release

Question 17

Onset of puberty

Answer 17

• reduced sensitivity of the hypothalamic-pituitary system to
  negative-feedback inhibition by gonadal steroids
• triggers preovulatory GnRH/LH release and onset of puberty

Question 18

Post-pubertal life:

Answer 18

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.

Question 19

LH Pulse Frequency in Heifers
Before and After Puberty

Answer 19

Substantial time required (~2
months-shaded area) for the
pulse frequency to become
high enough for puberty to
be achieved

Question 20

factors influencing the onset of puberty

Answer 20

• genetics
• environment
• nutrition
• season

Question 21

glucose and hypothalamic control of GnRH secretion

Answer 21

moment-to-moment
regulation of GnRH occurs only when significant glucose is available for metabolism

Question 22

functions of uterus

Answer 22

• 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)

Question 23

function of cervix

Answer 23

• 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

Question 24

cow characteristics (ovaries, body of uterus, UTJ, horns, cervix, vagina)

Answer 24

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

Question 25

ewe characteristics (ovaries, UTJ, ligaments)

Answer 25

OVARIES= almond shaped

UTJ= flexure/kink

LIGAMENTS
Broad ligament attached to ilium= rams horn

Question 26

sow characteristics

Answer 26

OVARIES= berry shaped
BODY OF UTERUS= very short
UTERINE HORNS= long
UTJ= long and finger-like
CERVIX= interdigitating prominences