Difference between revisions of "Corpus Luteum Regression - Anatomy & Physiology"

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{{review}}
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<big><center>[[Female Reproductive Tract -The Ovary - Anatomy & Physiology|'''BACK TO THE OVARY''']]</center></big>
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<big><center>[[Female_Reproductive_Tract_-The_Ovary_-_Anatomy_%26_Physiology#Processes_Taking_Place_In_The_Ovary|'''BACK TO PROCESSES TAKING PLACE IN THE OVARY''']]</center></big>
  
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== The Luteolytic Mechanism ==
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* Prostaglandin F2 (PGF2)
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* PGF2 from the uterus is transported to the ipsilateral ovary through a vascular counter-current exchange mechanism.
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* Prostaglandin F2α (PGF2α)
 
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* PGF2α from the uterus is transported to the ipsilateral ovary through a vascular counter-current exchange mechanism.
 
 
* This involves two closely associated blood vessels in which blood from one vessel flows in the opposite direction to that of the adjacent vessel.
 
* This involves two closely associated blood vessels in which blood from one vessel flows in the opposite direction to that of the adjacent vessel.
 
* Low molecular weight substances in high concentrations in one vessel cross over into the adjacent vessel, where they are low in concentration.
 
* Low molecular weight substances in high concentrations in one vessel cross over into the adjacent vessel, where they are low in concentration.
 
* The ovarian artery lies in closs association with the utero-ovarian vein.
 
* The ovarian artery lies in closs association with the utero-ovarian vein.
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* By counter-current exchange, PGF2α is transferred across the wall of the uterine vein into the ovarian artery by passive diffusion.
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* By counter-current exchange, PGF2 is transferred across the wall of the uterine vein into the ovarian artery by passive diffusion.
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* This ensures a high proportion of PGF2α produced by the uterine glands will be transported directly to the ovary and corpus luteum without dilution in the systemic circulation.
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* This ensures a high proportion of PGF2 produced by the uterine glands will be transported directly to the ovary and corpus luteum without dilution in the systemic circulation.
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* This is an important  mechanism, because much PGF2α is denatured during one pass through the circulatory system.  This is about a 90% loss in the ewe and cow.
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* This is an important  mechanism, because much PGF2 is denatured during one pass through the circulatory system.  This is about a 90% loss in the ewe and cow.
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== Luteolysis in Ruminants ==
 
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* The ruminant corpus luteum secretes large amounts of oxytocin as well as progesterone.
 
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* In the late luteal phase, oxytocin receptors develop on the uterine endometrium.
 
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* Binding of oxytocin to the receptors stimulates the pulsatile release of PGF2α.
 
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* PGF2α secretion by the endometrium is almost non-existant during the first half of the luteal phase.
 
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* During the late luteal phase, pulses of PGF2α secretion increase in frequency and amplitude as the end of the luteal phase approaches.
 
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* A critical number of PGF2α pulses are required within a given time span to induce complete luteolysis.
 
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** In the ewe, this is ~5 pulses in 24 hours.
 
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* During the first half of the cycle, progesterone prevents the secretion of PGF2α by blocking the formation of oxytocin receptors on the uterus.
 
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* Oxytocin and PGF2α stimulate each other in a positive feedback manner.
 
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* The greater the number of  endometrial oxytocin receptors, the greater the ability of oxytocin to stimulate PGF2α synthesis.
 
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[[Category:Female Reproduction]]
 
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[[Category:Bullet Points]]
 

Revision as of 21:11, 12 September 2008

BACK TO THE OVARY
BACK TO PROCESSES TAKING PLACE IN THE OVARY
  • Prostaglandin F2 (PGF2)
  • PGF2 from the uterus is transported to the ipsilateral ovary through a vascular counter-current exchange mechanism.
  • This involves two closely associated blood vessels in which blood from one vessel flows in the opposite direction to that of the adjacent vessel.
  • Low molecular weight substances in high concentrations in one vessel cross over into the adjacent vessel, where they are low in concentration.
  • The ovarian artery lies in closs association with the utero-ovarian vein.
  • By counter-current exchange, PGF2 is transferred across the wall of the uterine vein into the ovarian artery by passive diffusion.
  • This ensures a high proportion of PGF2 produced by the uterine glands will be transported directly to the ovary and corpus luteum without dilution in the systemic circulation.
  • This is an important mechanism, because much PGF2 is denatured during one pass through the circulatory system. This is about a 90% loss in the ewe and cow.
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