Lecture 10 - Reproductive endocrinology part II Flashcards
What is fergusons reflex?
The Ferguson reflex (also called the fetal ejection reflex) is the neuroendocrine reflex comprising the self-sustaining cycle of uterine contractions initiated by pressure at the cervix, more precisely, the internal end of cervix, or vaginal walls.
It is an example of positive feedback in biology.
the density of oxytocin receptors in the uterus increase as much as 200-fold etc.
layers of a ovarian follicle wall (3)
internal granulosa cell layer,
a basement membrane
and an external theca cell layer.
How is the oocyte situated in a follicle?
he oocyte is attached to the granulosa cells by the cumulus cells and is surrounded by follicular fluid present in the antrum of the follicle.
Estradiol synthesis in ovarian follicles.
LH binds to thecal cells and stimulates testosterone and other steroidal
androgen production.
FSH binds to the granulosa cells and stimulates the conversion of the androgens, produced in the theca cells, to estradiol.
Which 2 hormones are needed for estradiol synthesis by a follicle?
FSH & LH
How does the LH surge induce ovulation exactly?
The surge of LH increases PGE2 and histamine in the ovaries
These increase ovarian blood flow and cause hyperemia
Then edema
PGF2alfa joins.
These all cause follicular pressure,
the follicular wall weakens
and finally the oocyte is released.
The preovulatory LH surge causes what 6 biochemical events?
histamine up
PGE2 up
PGF2aalfa up
shift from estradiol to P4
Follicular surface epithelium changes
Gap junctions break down between granulosal cells and oocyte
In camelids (camels, alpacas, llamas)
ovulation is induced by
seminal plasma (SP).
Ovulation-inducing factor has been
identified from SP as a neurotrophin,
the β subunit of nerve growth factor (β-NGF).
The luteal phase begins after
ovulation.
The luteal phase is divided into
metestrus and diestrus
Corpus luteum is formed during what phase
during metestrus
called luteinization
highest progesterone levels are during which phase
diestrus
What cell types are found in an ovarian follicle?
theca cells
granulosa cells
technically also the oocyte
Define what a Corpus hemorrhagicum is
During ovulation, many small blood vessels in the ovarian follicle rupture causing local hemorrhage.
This hemorrhage appears as a blood clot on the surface of the ovary that sometimes penetrates into the center of
the follicle after ovulation.
During ovulation the follicle implodes and is “thrown” into folds. The cells of the theca interna and the granulosa begin to mix. The basement membrane forms the connective tissue substructure of the corpus luteum.
What cell types are found in a CL?
The corpus luteum is a mixture of large luteal cells; LLC (formerly granulosa cells) and many small luteal cells: SLC (formerly thecal cells).
CL size and weight is due to
an increase in volume of large luteal cells coupled with increase in the number of small luteal cells.
PHYSIOLOGICAL EFFECTS OF PROGESTERONE (6)
- Reduces basal GnRH amplitude and frequency
- Prevents follicles from reaching preovulatory status by suppressing GnRH and thus FSH
- Prevents behavioral estrus by suppressing the estradiol
- Stops preovulatory LH surge
- Reduces myometrial tone (except in the mare)
Function of a luteal cell.
To produce progesterone!
The hormone to induce production of progesterone by luteal cells?
Luteinizing hormone
Why do PGF2alfa concentrations increase?
Its due to oxytocin receptors density which differs throughout an estrus cycle. When oxytocin is bound, PGF2alfa is released.
Uterine luminal epithelium (LE)
has oxytoxin receptors .
Inhibition of progesterone synthesis
Leydig cells: are the male equivalent
of the female…?
follicular thecal cells
the leydig cells have LH rceptors on them.
Sertoli cells are the male equivalent
of the female…?
follicular Granulosa cells
Sertoli cells have FSH receptors on.
Sertoli cells produce which hormones?
testosterone is converted to both dihydrotestosterone and estradiol by the sertoli cells.
Inhibin produced where in males?
By sertoli cells
Function of inhibin in males.
Produced by sertoli cells and suppresses the release of FSH.
MRP factor in cow and ewe
IFN-tau from the conceptus prevents luteolysis in the cow and ewe.
(Interferon tau)
IFN-tau is secreted by
the trophoblastic cells of the blastocyst (cow and ewe).
MRP factor in the sow
The blastocyst produces estradiol (on day 11/12) which reroutes PGF2a to prevent luteolysis in the sow.
The PGF2α is rerouted into the uterine lumen, where it is destroyed, thus preventing luteolysis.
Production of Equine Chorionic Gonadotropin (eCG) is Closely Related
to what feature of pregnancy?
to the Weight of the Endometrial Cups
Without eCG, P4 would change how?
Without eCG, P4 would continue to decrease (dashed line) and the
pregnancy would terminate.
But upon stimulation by eCG, the primary CL is stimulated and P4 in the maternal
blood again increases.
If eCG were not produced, P4 would continue to decrease (dashed line).
When does the placenta assume the major P4 producing role in mares?
After day 100, the placenta assumes the major P4 producing role.
Placental lactogen is a polypeptide hormone that is also called
somatomammotropin.
Placental lactogens have been found in which species?
in rats, mice, sheep, cows and humans.
Explain how The fetus triggers the onset of parturition. (3)
- space limitations of the uterus
- adrenocorticotropin (ACTH) to be secreted by the fetal pituitary
- secretion of adrenal corticoids from the fetal adrenal cortex
- removal of the myometrial “progesterone block,” enabling myometrial contractions to begin. P4 goes toward estrogen synthesis instead.
- increased reproductive tract secretions, particularly by the cervix.
removal of the myometrial “progesterone block,” means that P4 instead goes…?
toward estrogen synthesis instead.
