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Animal Science 434

Animal Science 434. Lecture 11: The Luteal Phase of the Estrous and Menstrual Cycle. Ovulation. Ovulation. Luteal Phase. CL Formation (Metestrus). Follicular Phase. P 4 Production (Diestrus). Relative Progesterone Levels (Blood). Luteolysis. steroid synthesis progesterone

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Animal Science 434

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  1. Animal Science 434 Lecture 11: The Luteal Phase of the Estrous and Menstrual Cycle

  2. Ovulation Ovulation Luteal Phase CL Formation (Metestrus) Follicular Phase P4 Production (Diestrus) Relative Progesterone Levels (Blood) Luteolysis

  3. steroid synthesis • progesterone • collagenase • theca interna

  4. present 1-3 days following ovulation • blood vessels in follicle wall rupture • walls collapse • cells intermix • old basement membrane becomes connective tissue of CL

  5. 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

  6. Luteal Tissue • Large cells from granulosa • Small cells from the theca interna

  7. Mitochondria Secretory Granules - Oxytocin - Relaxin

  8. 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

  9. Blocks Estrus Negative Feedback Progesterone Targets Aveolar Development

  10. Progesterone Production by Luteal Cells

  11. Luteolysis • Uterus • PGF2a • Oxytocin

  12. Luteolysis in Cows, Ewes, Sows

  13. Luteolysis • Uterus • PGF2a • Oxytocin

  14. Prostaglandin synthesis by uterine endometrium is released into the uterine vein. 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

  15. Luteolysis in Mares CL maintained >30 days CL regresses on day 17 %50 of CL’s maintained 50% of CL’s maintained

  16. Blood Supply to Uterus and Ovary in the Mare

  17. PGF Not Effective (Sow) PGF Not Effective (Cow, Ewe, Mare)

  18. Luteolysis • Uterus • PGF2a • Oxytocin

  19. Oxytocin PGF2a Relationship of Oxytocin and PGF2a Posterior Pituitary Anterior Pituitary CL Ovary Uterus

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

  21. IP3 Ca++ ER

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

  23. Menstrual Cycle

  24. Recruitment Recruitment Anterior Pituitary Hormones LH FSH Progesterone Ovarian Hormones Estradiol Ovulation Corpus Albicans Follicle Corpus Luteum Ovary Dominance Selection Uterine Endo- metrium 2 4 6 8 10 12 14 16 18 20 22 24 26 28 2

  25. 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

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