Animal Science 434 Reproductive Physiology Endocrinology: Part B.
Animal Science 434
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Transcript of Animal Science 434
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Animal Science 434
Lecture 11: The Luteal Phase of the Estrous and Menstrual Cycle
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Day of the Estrous Cycle
Relative Progesterone Level (Blood)
Lute
olys
is
P4
Production(Diestrus)
CLFormation(Metestrus)
Rel
ativ
e Pr
oges
tero
ne L
evel
s (B
lood
)
Folli
cula
r Pha
se
Luteal Phase
Ovulation Ovulation
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• steroid synthesis– progesterone
• collagenase– theca interna
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• present 1-3 days following ovulation
• blood vessels in follicle wall rupture
• walls collapse
• cells intermix
• old basement membrane becomes connective tissue of CL
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• increases in size– papilla forms
• composed of cells from the granulosa and theca interna
• progesterone production increases
• a small cavity may be present where the folliclular antrum was present
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Luteal Tissue
• Large cells from granulosa
• Small cells from the theca interna
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Mitochondria
SecretoryGranules
- Oxytocin- Relaxin
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Functional Capability of CL• the number of luteal cells
– large cells undergo hypertrophy (3 fold)– small cells undergo hyperplasia (5 fold)
• vascularization of CL– Initiated by angiogenic factors from
follicle– Vascularity effects CL steroid synthesis
and delivery of hormones• Insufficient CL function
– Failure to maintain pregnancy– Important in domestic animals
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Progesterone TargetsAveolar
Development
Blocks EstrusNegative Feedback
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Progesterone Production by Luteal Cells
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Luteolysis
• Uterus• PGF2
• Oxytocin
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Luteolysis in Cows,
Ewes, Sows
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Luteolysis
• Uterus• PGF2
• Oxytocin
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Prostaglandin F2Control of LuteolysisProgesterone fromCL stimulatesproduction of uterine PGF2afterday 15 in cow
Uterine Horn
UterineVein
Prostaglandin synthesisby uterine endometriumis released into the uterine vein.
Oviduct
Ovary
CorpusLuteum
PGF2 is picked up by ovarian artery through counter current exchangeand delivered back to theovary where it causeslysis of the CL
Uterine Artery
Ovarian Pedicle
PGF
PGF into Artery
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Luteolysis in Mares
50% of CL’s maintained
CL regresses on day 17
%50 of CL’s maintained
CL maintained >30 days
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Blood Supply to Uterus and Ovary in the Mare
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PGF Not Effective (Cow, Ewe, Mare)
PGF Not Effective (Sow)
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Luteolysis
• Uterus• PGF2
• Oxytocin
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Relationship of Oxytocin and PGF2
Uterus
Ovary
CL
PGF2
Anterior Pituitary
Posterior Pituitary
Oxytocin
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Luteolysis
• decreased blood flow
• cellular response– apoptosis– progesterone synthesis
• Immune response– Lymphocytes– Macrophages
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ER
IP3
Ca++
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Luteolysis
• decreased blood flow
• cellular response– apoptosis– progesterone synthesis
• Immune response– Lymphocytes– Macrophages
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Menstrual Cycle
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FSHLH
Estradiol
Progesterone
FollicleOvulation
Corpus LuteumCorpus
Albicans
2 4 6 8 10 14 16 18 20 22 24 26 28 212
Anterior Pituitary
Hormones
Ovarian Hormones
Ovary
UterineEndo-
metrium
RecruitmentSelection DominanceRecruitment
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Luteolysis in the Primate• Does not require the uterus• CL lifespan in the human is 12-14 days unless
pregnancy occurs– In the absence of pregnancy, CL self destructs– Possible intra-ovarian oxytocin receptors and PGF2
production• Menstruation
– Drop in P4 and E2
– Endometrial PGF2, vasoconstriction, necrosis– Endometrial inflammation and tissue degeneration