Animal Science 434

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Animal Science 434

• Lecture 11 The Luteal Phase of the Estrous 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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Bovine Luteal Anatomy
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Bovine Luteal Anatomy
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Ovine Luteal Anatomy
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Ovine Luteal Anatomy
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Swine Luteal Anatomy
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Equine Luteal Anatomy
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Equine Luteal Anatomy
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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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Progesterone Targets
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Action of Progesterone

• reduces GnRH pulse amplitude and frequency
• prevents behavioral Estrus
• stops the preovulatory LH surge
• reduces mymetrial tone
• stimulates endometrial gland development and
  secretion
• stimulates aveolar development in mammary gland

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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)
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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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4
6
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10
14
16
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26
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2
12
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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

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Anterior Pituitary Hormones
LH
FSH
Progesterone
Ovarian Hormones
Estradiol
Ovulation
Follicle
Corpus Luteum
Ovary
Uterine Endo- metrium
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4
6
8
10
14
16
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20
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24
26
28
2
12
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Variation in Menstrual Cycle Length
14 days
5 days
6 days
14 days
5 days
9 days
35-day cycle
5 days
16 days
14 days
Ovulation
Breast Tenderness
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Menstural Cycle Length

• AGE
• Length
• 15 - 19 year olds 35 days
• 30 year olds 30 days
• 35 year olds 28 days
• Variation
• More in teenagers
• Less in women in peak reproductive years

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Hypothalamus
GnRH
Anterior Pituitary
LH, FSH
LH, FSH
LH
CL
Follicle
Ovary
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Hypothalamus
()
Estradiol
GnRH
Anterior Pituitary
LH, FSH
LH, FSH
Follicle
Ovary
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LH mIU/ml
FSH mIU/ml
Estradiol pg/ml
Prog. ng/ml