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Animal Science 434

Animal Science 434. Lecture 12: Spermatogenesis. Production of Fertile Sperm. hormonal regulation of the testis mitotic division of spermatogonia meiotic divisions of spermatocytes morphologic transformation of spermatids into spermatozoa. Hormonal Regulation of the Testis. LH. LH. LH.

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Animal Science 434

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  1. Animal Science 434 Lecture 12: Spermatogenesis

  2. Production of Fertile Sperm • hormonal regulation of the testis • mitotic division of spermatogonia • meiotic divisions of spermatocytes • morphologic transformation of spermatids into spermatozoa

  3. Hormonal Regulation of the Testis

  4. LH LH LH LH GnRH GnRH GnRH GnRH FSH FSH FSH FSH

  5. Time of Day (24 hr) Pulses are important !

  6. FSH on Sertoli Cells • estradiol • inhibin • ABP • tight junctions Negative Feedback of Estradiol and Inhibin To Epid. Negative Feedback of Androgens FSH LH ABP + T E2 Inhibin T ABP Hypothalamus GnRH Ant. Pituitary Leydig Cells Sertoli Cells TJ Germ Cells Seminiferous Tubule

  7. Spermatogenesis

  8. Spermatogenesis Every 13.5 Days sperm are released from this point Spermatozoa Round Spermatid Secondary Spermatocyte Sertoli Cells Primary Spermatocyte Spermatogonia Every 13.5 Days a new group of cells initiate the cycle Myoid Cells

  9. Sertoli Cell

  10. Typical Sequence of Spermatogenesis A Spermatogonia (A, intermediate, B) A A Spermato-cytogenesis I I B B Primary Spermatocyte Mitosis P P Meiosis S S SecondarySpermatocyte RS RS Round Spermatid Spermio-genesis Spermatozoa SP SP Spermiation Rete Testis

  11. Many Sperm are Produced Potential Sperm Produced 1 A 2 A A 4 I I 8 B B 16 P P 32 S S 64 RS RS SP SP

  12. Mitotic Divisions • species dependent • between 2 and 6 divisions (4 to 64 potential daughter cells produced) • classifications vary among species and investigators • A1, A2, A3, A4, B 1, B2, P • Ad, Ap, B, P • As, A0, A1,A2, I, B, P • cytoplasmic bridges form between daughter cells

  13. Degenerating Spermatogonia (Apoptosis, as high as 75%) Cytoplasmic Bridges Present Among Daughter Cells All develop surrounded by 1 Sertoli cell !

  14. Germ Cells / Sertoli Cell Species Primary Round Max. Potential Spermatocytes Spermatids Spermatids Equine 3.0 ± 0.2 10.9 ± 0.9 64 Bovine 1.2 ± 0.1 5.2 ± 0.6 64 Human 1.3 ± 0.1 4.2 ± 0.2 16

  15. Apoptosis of Germ Cells • Season • Disease • Trauma or heat • Hormone levels • Normal part of spermatogenesis

  16. Stem Cell Renewal • To keep spermatogenesis going indefinitely • Replenish testis incase of injury, trauma, or high heat

  17. FSH Periodic Entry of Cells into Mitosis A2 Spermatogonial Renewal in the Rat and Bull A1 Stem Cell Pool A3 A4 In B P

  18. FSH Ap Spermatogonial Renewal in the Primate Ad Stem Cell Pool B P

  19. Stem Cell

  20. Spermiogenesis

  21. Golgi Phase Development of Acrosome Migration of Centrioles

  22. Cap Phase Acrosome Development Continues Flagellum Elongates

  23. Acrosomal Phase Acrosome Manchette Elongation

  24. Maturation Phase Manchette disapears Mitochondria migrate Dense fibers form

  25. Spermiation

  26. Spermiation

  27. Bull Spermatogenesis

  28. Stallion Spermatogenesis

  29. Bull Spermatogenesis

  30. Stages • Specific cellular associations within a small segment of a seminiferous tubule • stages are not the same length in time

  31. Stages

  32. Stages

  33. Stages

  34. Stages

  35. Stages • Specific cellular associations within a small segment of a seminiferous tubule • stages are not the same length in time

  36. Cycles and Stages 57 days Stallion

  37. Cycles and Stages

  38. Cycles and Stages

  39. Cycles and Stages

  40. Cycles and Stages

  41. Cycle • progression through sequence of all stages

  42. Cycles and Stages 57 days (12.2 days/cycle) * (4.7 cycles) = 57 days

  43. Bull Ram Boar Stallion Man cycle (days) 13.5 10.4 8.3 12.2 16 Spermatogenesis61 47 39 57 75 Duration of Spermatogenesis

  44. Coordination of Stages Form Waves • some portion of seminiferous tubule is always releasing sperm

  45. Compartmentalization of Spermatogenesisand theBlood Testis Barrier

  46. Seminiferous Tubule andInterstitial Tissue

  47. Blood Vessel Interstitial Tissue • Vascular System Provides • Nutrients • Oxygen • Growth Factors • Hormones

  48. Blood Vessel

  49. Compartments Myoid Cells Tight Junctions Luminal Adluminal Basal

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