Transcript Animal Science 434

Animal Science 434
Lecture 11: The Luteal Phase of the
Estrous and Menstrual
Cycle
Ovulation
12
10
CL
Formation
(Metestrus)
8
P4
Production
(Diestrus)
6
4
2
Follicular Phase
Luteal Phase
14
Luteolysis
Relative Progesterone Level (Blood)
Relative Progesterone Levels (Blood)
Ovulation
0
0
2
4
6
8
10
12
14
16
Day of the Estr ous Cycle
18
20
22
• steroid synthesis
– progesterone
• collagenase
– theca interna
• present 1-3 days
following ovulation
•
blood vessels in
follicle wall rupture
• walls collapse
• cells intermix
• old basement
membrane becomes
connective tissue of
CL
• 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
Luteal Tissue
• Large cells from granulosa
• Small cells from the theca interna
Mitochondria
Secretory
Granules
- Oxytocin
- Relaxin
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
Blocks Estrus
Negative Feedback
Progesterone Targets
Aveolar
Development
Progesterone
Production by
Luteal Cells
Luteolysis
• Uterus
• PGF2a
• Oxytocin
Luteolysis
in Cows,
Ewes,
Sows
Luteolysis
• Uterus
• PGF2a
• Oxytocin
Prostaglandin F2a Control of Luteolysis
Uterine Horn
Prostaglandin synthesis
by uterine endometrium
is released into the
uterine vein.
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
Luteolysis
in Mares
CL regresses on day 17
%50 of CL’s maintained
CL maintained >30 days
50% of CL’s maintained
Blood Supply to Uterus and Ovary in the Mare
PGF Not Effective (Sow)
PGF Not Effective (Cow, Ewe, Mare)
Luteolysis
• Uterus
• PGF2a
• Oxytocin
Relationship of Oxytocin and PGF2a
Posterior
Pituitary
Anterior
Pituitary
CL
Oxytocin
PGF2a
Ovary
Uterus
Luteolysis
• decreased blood flow
• cellular response
– apoptosis
– progesterone synthesis
• Immune response
– Lymphocytes
– Macrophages
IP3
Ca++
ER
Luteolysis
• decreased blood flow
• cellular response
– apoptosis
– progesterone synthesis
• Immune response
– Lymphocytes
– Macrophages
Menstrual Cycle
Anterior
Pituitary
Hormones
LH
FSH
Progesterone
Ovarian
Hormones
Estradiol
Follicle
Ovulation
Corpus Luteum
Corpus
Albicans
Ovary
Recruitment
Dominance
Selection
Recruitment
Uterine
Endometrium
2
4
6
8
10 12 14 16 18 20 22 24 26 28
2
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