Animal%20Science%20434

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Animal Science 434

• Lecture 11 The Luteal Phase of the Estrous and
  Menstrual Cycle

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Ovulation
Ovulation
Luteal Phase
CL Formation (Metestrus)
Follicular Phase
P4 Production (Diestrus)
Relative Progesterone Levels (Blood)
Luteolysis
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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
Secretory Granules
- 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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Blocks Estrus Negative Feedback
Progesterone Targets
Aveolar Development
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Progesterone Production by Luteal Cells
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Luteolysis

• Uterus
• PGF2a
• Oxytocin

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Luteolysis in Cows, Ewes, Sows
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Luteolysis

• Uterus
• PGF2a
• Oxytocin

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Prostaglandin F2a Control of Luteolysis
Uterine Horn
Progesterone from CL stimulates production of
uterine PGF2a after day 15 in cow
Corpus Luteum
Oviduct
Ovary
Uterine Vein
Ovarian Pedicle
PGF
PGF2a is picked up by ovarian artery through
counter current exchange and delivered back to
the ovary where it causes lysis of the CL
PGF into Artery
Uterine Artery
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Luteolysis in Mares
CL maintained gt30 days
CL regresses on day 17
50 of CLs maintained
50 of CLs maintained
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Blood Supply to Uterus and Ovary in the Mare
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PGF Not Effective (Sow)
PGF Not Effective (Cow, Ewe, Mare)
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Luteolysis

• Uterus
• PGF2a
• Oxytocin

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Relationship of Oxytocin and PGF2a
Posterior Pituitary
Anterior Pituitary
CL
Ovary
Uterus
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Luteolysis

• decreased blood flow
• cellular response
• apoptosis
• progesterone synthesis
• Immune response
• Lymphocytes
• Macrophages

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IP3
Ca
ER
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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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Anterior Pituitary Hormones
LH
FSH
Progesterone
Ovarian Hormones
Estradiol
Ovulation
Corpus Albicans
Follicle
Corpus Luteum
Ovary
Dominance
Selection
Uterine Endo- metrium
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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
  PGF2a production
• Menstruation
• Drop in P4 and E2
• Endometrial PGF2a, vasoconstriction, necrosis
• Endometrial inflammation and tissue degeneration