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Animal Science 434

Animal Science 434. The Follicular Phase of the Estrous Cycle. Tonic and Preovulatory Surge of GnRH. Hypothalamus. Progesterone. (-). Estradiol. GnRH. (-). Anterior Pituitary. Inhibin (-). LH, FSH. Estradiol. LH, FSH. LH. CL. Follicle. Ovary.

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Animal Science 434

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  1. Animal Science 434 The Follicular Phase of the Estrous Cycle

  2. Tonic and Preovulatory Surge of GnRH

  3. Hypothalamus Progesterone (-) Estradiol GnRH (-) Anterior Pituitary Inhibin (-) LH, FSH Estradiol LH, FSH LH CL Follicle Ovary

  4. Tonic and Preovulatory Surge of GnRH

  5. Follicular Phase

  6. Progesterone (-) Estradiol (-) LH CL Hypothalamus GnRH Anterior Pituitary Inhibin (-) LH, FSH Estradiol LH, FSH Follicle Ovary

  7. (+) Estradiol Hypothalamus GnRH Anterior Pituitary Inhibin (-) LH, FSH Estradiol LH, FSH Follicle Ovary

  8. Follicular Phase

  9. Primary Secondary Tertiary Follicular Progression Primordial

  10. Growth and Atresia of Follicles Atresia

  11. Fate of follicles and oocytes Total # of follicles At birth 100,000 12 months 75,000 4-6 years 21,000 Aged cow 2,500 Follicles undergo atresia at all stages of development. Maximum number of oocytes ovulated for a cow 17 cycles/year x 8 year = 136 oocytes ovulated / lifespan

  12. Fate of follicles and oocytes Total # of follicles At birth 100,000 12 months 75,000 4-6 years 21,000 Aged cow 2,500 Follicles undergo atresia at all stages of development. Maximum number of oocytes ovulated for a cow 17 cycles/year x 8 year = 136 oocytes ovulated / lifespan 100 Days of Gestation 2.9 million Superovulation; rescue follicles from undergoing atresia with FSH treatment.

  13. Initial Follicular Growth Small AntralFollicle 50 - 60 days Gonadotropin Independent FSH Recruitment

  14. Recruitment Dominance Selection Follicular Waves in Cattle Atresia Follicular Size Ovulation FSH Sensitive Pool 9 16 21 Ovulation Day After Ovulation

  15. Progesterone Recruitment Dominance Selection Follicular Waves in Cattle Atresia Follicular Size Ovulation FSH Sensitive Pool 9 16 21 Ovulation Day After Ovulation

  16. estradiolinhibin Atresia FSH estradiol (-) inhibin (-) Dominance Selection FSH estradiol (-) inhibin (-) Recruitment FSH estradiol (-) Follicular Waves in Cattle Progesterone FSH Follicular Size 9 16 21 Ovulation Day After Ovulation

  17. Follicular Waves in Cattle Progesterone Follicular Size Atresia Dominance Selection Recruitment 9 16 21 Ovulation Day After Ovulation

  18. Follicular Waves in Cattle Progesterone Follicular Size 9 16 21 Ovulation Day After Ovulation

  19. Follicular Waves in Cattle Progesterone Follicular Size 9 16 21 Ovulation Day After Ovulation

  20. Ovulation Dominance Selection Recruitment Follicular Waves in Cattle Progesterone Follicular Size 9 16 21 Ovulation Day After Ovulation

  21. Two Follicular Waves Progesterone Dominance Follicular Size Atresia Ovulation Selection Recruitment Ovulation 10 21 Day After Ovulation

  22. Follicular Wave Emergence • Recruitment = Emergence • FSH always controls emergence • Increase in FSH precedes emergence

  23. Cl-progesterone Cl-progesterone, inhibin Species Variation in Follicular Waves • Cattle - 2 or 3 / cycle • Sheep - 4 or 5 / cycle • Pigs - 1 / cycle • Horses - 1 / cycle • Human - 1 / cycle

  24. Gonadotropin Action Withinthe Follicle

  25. Antral Follicle Theca Internal Granulosa

  26. Theca Interna LH Receptor cAMP Cholesterol PKA Testosterone FSH Receptor Blood cAMP Testosterone PKA Estradiol Granulosa

  27. Theca Interna Selection LH LH Receptor Receptor Dominant Follicle Express LH Receptor cAMP Cholesterol PKA Testosterone FSH Receptor Blood cAMP cAMP Testosterone PKA Estradiol Granulosa

  28. Ovulation

  29. Germinal Epithelium Tunica Albuginea Theca Externa Theca Interna Basement Membrane Granulosa

  30. Blocking of these events in the follicle prevents ovulation. • protein synthesis • steroid synthesis • prostaglandin synthesis • plasminogen activator synthesis

  31. Cumulus Expansion Oocyte Separates From Follicular Wall Preovulatory LH Surge Ovulation

  32. Cumulus Expansion Hyaluronic Acid and Protein Production Unexpanded Expanded

  33. Cumulus and Oocyte Separation

  34. Cumulus Expansion Protein synthesis changes in and around Follicle Progesterone Plasminogen Activator Prostaglandin Synthesis PGE and PGF Oocyte Separates From Follicular Wall Preovulatory LH Surge Ovulation

  35. Cumulus Expansion Increased Blood Flow to Ovary and Follicle Protein synthesis changes in and around Follicle Vascular Permeability Progesterone Plasminogen Activator Prostaglandin Synthesis PGE and PGF Plasminogen Oocyte Separates From Follicular Wall Histamine PGE2 Preovulatory LH Surge Edema Follicularpressure Ovulation

  36. Cumulus Expansion Increased Blood Flow to Ovary and Follicle Protein synthesis changes in and around Follicle Vascular Permeability Progesterone Plasminogen Activator Prostaglandin Synthesis PGE and PGF Collagenase (inactive) Plasminogen Plasmin Oocyte Separates From Follicular Wall Collagenase (active) Follicular Wall Weakens Histamine PGE2 Preovulatory LH Surge Edema Follicularpressure Ovulation

  37. Cumulus Expansion Increased Blood Flow to Ovary and Follicle Protein synthesis changes in and around Follicle Vascular Permeability Progesterone Plasminogen Activator Prostaglandin Synthesis PGE and PGF Collagenase (inactive) Plasminogen Plasmin Oocyte Separates From Follicular Wall Collagenase (active) Contraction of Smooth Muscle Follicular Wall Weakens Histamine PGE2 Preovulatory LH Surge Edema Follicularpressure Ovulation

  38. Types of Ovulators

  39. Spontaneous Ovulators

  40. Induced Ovulators

  41. Sensory Neurons Penis Induced Ovulators Nerve endings sensing copulation Copulation

  42. Hypothalamus Blood LH Time (hr) GnRH Posterior Pit. Stimulation LH Anterior Pit. Spinal Chord

  43. Sensory Neurons Penis LH Nerve endings sensing copulation Copulation

  44. Cats • Induced Ovulators • Single copulation • Only works 50% of the time • Multiple copulations • Higher LH surge

  45. Spontaneous Ovulators • Retain some neural control of ovulation • heifers can alter the timing of the LH surge by clitoral stimulation • human rape cases result in higher than expected pregnancy rates

  46. Migration to germinal ridge Mitotic divisions Follicle Cells Initiation of Meiosis Interphase DNA synthesis Meiotic prophase begins Prophase of Meiosis leptotene zygotene pachytene diplotene dictyotene Meiotic Arrest zona pellucida formation mRNA production protein synthesis cortical granule formation nuclear maturation cytoplasmic maturation Oogenesis Primordial Germ Cells Oogonia Primary Oocyte Growth Gonadotropin Independent Gonadotropin Dependent

  47. Oogonia in Egg Nest Fetal Pig Ovary

  48. Oogonia and Primary Oocytes

  49. Primary Oocytes in Primordial Follicles

  50. Primary Oocyte in Primary Follicle

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