Flashcards in Lecture 10: Pregnancy recognition (Pozor) Deck (22):
mechanisms necessary to establish pregnancy (7)
1. successful fertilization
2. cleavage - forming an embryo
3. "descent" of an embryo to the uterus
4. maternal recognition of pregnancy
6. organogenesis and growth
what is a single-celled embryo called?
what is the conceptus called during early embryonic stage?
what is the conceptus called during the pre-implantation stage?
embryo proper and extraembryonic membranes
what is the conceptus called during the post-implantation phase
fetus and placenta
definition of embryo
it has not acquired an anatomical form which is readily recognizable in appearance as a member of the specific species
definition of a fetus
a potential offspring that is still within the uterus, but is generally recognizable as a member of a given species
when does maternal recognition of pregnancy typically occur?
10 - 16 days post ovulation
what is the vital part of maternal recognition of pregnancy
the conceptus must provide a timely biochemical signal or a pregnancy will terminate
effect of prostaglandin (PGF2-alpha) duringluetolysis in the ruminant
- its responsible for luteolysis
- and supplied by endometrium
- necessary factors: oxytocin receptors on endometrial cells, synthesis and release of luteal oxytocin from the ovary
where oxytocin binding receptors located in the ruminant?
in the uterus
what is the effect of estrogen during luteolysis in the ruminant?
estrogen upregulates oxytocin receptor synthesis
what is the effect of progesterone in early diestrous on oxytocin receptors in the ruminant?
it prevents oxytocin receptor synthesis
what is the effect of progesterone in LATE diestrus on oxytocin receptor synthesis in the ruminant?
progesterone loses the ability to block oxytocin receptor synthesis in late diestrus
what is the effect of oxytocin binding to its receptor during late diestrus in the ruminant
it stimulates prostaglandin release which ultimately causes the CL to lyse
what secretes prostaglandin?
how does prostaglandin reach the ovary to lyse the CL?
- delivered to the ovary via the ovarian artery
countercurrent exchange mechanism: cow, ewe, sow
systemic circulation: mare
Interferon properties (4)
effect of INF-tau in the ruminant
decreases estrogen receptors - suppression of estrogen driven up-regulation of oxytocin receptors
how is luteolysis blocked in swine?
1. blastocyst - produces estradiol
2. estradiol causes rerouting of PGF2alpha
3. PGF2alpha is secreted into the uterine lumen and is destroyed
4. luteolysis does not occur
sufficient number of conceptuses (2 per horn) are necessary to block luteolysis!!
how is luteolysis blocked in the mare?
embryonic mobility is necessary (up to 14 days after ovulation)
- no interferon-like factors involved
- equine embryo synthesizes and releases various facotrs
- oxytocin receptors greatly suppressed - similar as in ruminants