1 / 53

Animal Science 434

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

dtaveras
Download Presentation

Animal Science 434

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

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

  3. Tonic and Preovulatory Surge of GnRH

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

  5. Steps Leading to the Preovulatory LH Surge P4 from Cl GnRH FSH and LH  FSH Inhibin Proestrual Follicular Development Preovulatory LH surge  Estradiol to threshold

  6. Relationship of Hypothalamus, Anterior Pituitary and Ovary In the Absence of Progesterone

  7. Tonic and Preovulatory Surge of GnRH

  8. Hormone Changes During the Folliclular Phase Progesterone LH FSH Estradiol

  9. Follicle Progression

  10. Growth and Atresia of Follicles

  11. Follicular Growth Gonadotropin Independent Small Antral Follicle Recruitment Initiated by FSH

  12. Progesterone FSH FSH FSH E2 Inhibin Inhibin LH LH Deviation!!!

  13. Folliclular Waves in Cattle

  14. Follicular Waves

  15. Follicular Waves

  16. Growing Phase • Initial growth (recruitment) is under influence of FSH • Inhibin secreted to decrease FSH and development of subordinate follicles (estrogen also; selection) • Dominant follicle becomes less dependent on FSH for growth • FSH induces LH receptors in granulosa • Dominant follicle produces estradiol and androgens in response to LH and FSH • Androgens, lack of FSH may cause subordinate follicles to become atretic (dominance)

  17. Static Phase • Inhibin production stops • FSH increase stimulates follicular wave • Estradiol from dominant follicle decreases and androgens increase, this may initiate atresia of dominant follicle

  18. Regressing Phase • Dominant follicle becomes atretic and looses steroidogenic capability

  19. Follicular Waves

  20. Growing Phase • Initial growth (recruitment) is under influence of FSH • Inhibin secreted to decrease FSH and development of subordinate follicles (estrogen also; selection) • Dominant follicle becomes less dependent on FSH for growth • FSH induces LH receptors in granulosa • Dominant follicle produces estradiol and androgens in response to LH and FSH • Androgens, lack of FSH may cause subordinate follicles to become atretic (dominance)

  21. Growing Phase • LH continues to increase in response to estradiol positive feedback in the absence of progesterone • Dominant follicle increases in size and estrogen production • LH surge occurs to trigger ovulation of the dominant follicle

  22. Hormone Changes During the Folliclular Phase Ovulation Follicular Phase Progesterone LH FSH Estradiol

  23. Two Follicular Waves Dominance Follicular Size Atresia Ovulation Selection (Deviation) Recruitment Ovulation 10 21 Day After Ovulation

  24. Ovulation Three Follicular Waves Follicular Size 9 16 21 Ovulation Day After Ovulation

  25. Follicular Waves

  26. 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 grow to tertiary characteristic and degenerate. 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 Can increase with superovulation with FSH to stimulate the rescue of follicles which would have undergone atresia

  27. Gonadotropin Action Withinthe Follicle

  28. Theca Interna Granulosa

  29. 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

  30. Ovulation

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

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

  33. Pathways of Ovulation increased cyclic AMP Increased blood flow to follicle LH Mature follicle Protein synthesis Cumulus cell production of hyaluronic acid and proteins Increased vascular permeability of follicle (cellular differentiation) Steroid biosynthesis Prostaglandin biosynthesis (PGE and PGF ) Cumulus expansion Progesterone 2 2 Plasminogen activator (granulosa) Separation of cumulus and oocyte from granulosa cells Increased plasminogen in tissue and follicular fluid Plasmin (protease) Inactive Collagenase (theca) Active Collagenase Breakdown of theca and tunica albuginea collagen and tensile strength of follicle wall Follicle ruptures with only a slight increase in follicular pressure PGF stimulates smooth muscle contractions around follicle Expulsion of follicular contents

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

  35. Cumulus Expansion Hyaluronic Acid and Protein Production Unexpanded Expanded

  36. Cumulus and Oocyte Separation

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

  38. Types of Ovulators

  39. Spontaneous Ovulators

  40. Induced Ovulators

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

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

  43. LH Sensory Neurons Penis 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. Manipulating Ovulation • will cover latter in class

  47. 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

  48. Fetal Oocyte Development Mitosis Meiosis Fertilization Birth Cow 280 d Sow 114 d Mouse 19 d

  49. Corona Radiata Oocyte Cortical Granules Zona Pellucida Gap Junctions Cortical Granules

More Related