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Fertilization

Fertilization

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Fertilization

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  1. Fertilization • Fertilization – fusion of egg and sperm into a single diploid cell, the zygote. • External • Internal

  2. External Fertilization • Sperm spread over egg cells • Requires water • Most aquatic animals • Examples: most fish, corals, starfish • Inefficient • Spermatophore – sperm packaged into capsule • Some terrestrial animals • Examples: salamanders, scorpions, octopus

  3. Internal Fertilization • Requires copulation • Most common method for terrestrial animals • Less sperm and eggs needed

  4. PHASES OF FERTLIZATION • Passage of sperm through the corona radiata of the oocytes by the use of hyaluronidase which is released by the acrosome of the sperm and movement of the tail • Penetration of Zona Pellucida- helped by the enzymes esterase, acrosin, and neuraminidase Once penetration occurs there is a biochemical zona reaction that causes the egg to become impermeable to other sperm.

  5. PHASES OF FERTLIZATION 3. Fusion of the plasma membranes of the oocyte and sperm 4. Completion of second meiotic division of the oocyte and formation of the female pronucleus 5. Formation of the male pronucleus

  6. PHASES OF FERTLIZATION 6. Breakdown of pronuclear membranes, condensation of chromosomes, and arrangement of chromosomes for mitotic cell division

  7. Fertilization • Acrosome discharges enzymes to digest zona pellucida • Once single sperm enters egg • Egg releases enzymes that harden zona pellucida preventing other sperm from entering • Sperm nucleus enters egg and fuses with egg nucleus

  8. Figure 7.8(1) Events Leading to the Fusion of Egg and Sperm Plasma Membranes Recognition of egg and sperm; 1. Chemoattraction of the sperm to the egg by soluble molecules 2. The exocytosis of the acrosomal vesicle to release its enzyme 3. The binding of the sperm to the extracellular envelop of the egg 4. The passage of the sperm through this envelop 5. Fusion of egg and sperm cell membrane

  9. The Entry of Sperm into Sea Urchin Eggs Entry of Sperm into Golden Hamster Egg

  10. Entry of Sperm into Golden Hamster Egg

  11. Formation of the Fertilization Envelope and Removal of Excess Sperm The slow block to polyspermy; Cortical granule fuse with egg cell memb; -release contents; -protease; clips off the binding receptor and sperm attached -mucosaccharides; osmotic gradient that cause water to rush into the space btwn mem and vitelline envelp– envelop expanding and becomes the fertilization envelop. -peroxidase; hardens the fertilization envelop by crosslinking Tyr rsidues am adjacent proteins -hyalin; forms a coating around the egg; ; hylain layer In mammals; the cortical granule reaction— Enzymes; modify the ZP sperm receptor; no longer binding

  12. Cortical Granule Exocytosis

  13. Wave of Calcium Release across Sea Urchin Eggs During Fertilization The calcium as the initiator of the cortical reaction Intracellular free Ca increase-the cortical granule memb fusion-release contents ( Ca from intracelluar (ER); wave of Ca)

  14. The activation of egg metabolism to the sperm Postulated Pathway of Egg Activation in the Sea Urchin

  15. The Roles of Inositol Phosphates in Releasing Calcium from theER and the Initiation of Development

  16. Possible Mechanisms of Egg Activation

  17. Possible Mechanisms of Egg Activation

  18. Possible Mechanisms of Egg Activation

  19. Nuclear Events in the Fertilization of the Sea Urchin Fusion of the genetic material The sperm nucleus, centriole Mito and flagellar disintegrate inside egg; Mitochondrial DNA from egg , not from sperm Sperm nucleus undergo dramatic changes; --nulcear lamin breakage--pronucleus --cAMP-dependent protein kinase phosphorylate the sperm specific Histone --decondensation- sperm specific Histone are replaced by histone from egg --

  20. Reorganization of Cytoplasm in the Newly Fertilized Frog Egg

  21. PROSES FERTILISASI TERDIRI DARI 2 ASPEK: • EMBRIOLOGIS • PENGAKTIFAN SEL TELUR • GENETIS • PENURUNAN UNSUR KEBAKAAN (DNA) DARI PEJANTAN UNSUR-UNSUR YANG BERPERAN: • SEL TELUR YANG MATANG • SPERMA DEWASA

  22. TEMPAT : KAUDA AMPULA (1/3 TF) • WAKTU : TERGANTUNG SPESIES SEL TELUR TERDIRI DARI: • INTI. • SITOPLASMA (PROTEIN, BUTIR-BUTIR LEMAK, ENZIM). • MEMBRAN PLASMA (MENGATUR ALIRAN ION-ION, TERUTAMA WAKTU FERTILISASI).

  23. SPERMATOZOA : • KEPALA  INTI, AKROSOM • LEHER  CENTRIOLE • EKOR KAPASITASI : SERANGKAIAN PERUBAHAN YANG TERJADI GUNA MEMPERSIAPKAN SPERMA UNTUK BERTEMU DAN BERINTERAKSI DENGAN OVUM PADA SAAT FERTILISASI. • TEMPAT : DI BAGIAN BAWAH ISMUS

  24. KAPASITASI PENTING, KARENA : • MENGEMBANGKAN MOTILITAS YG HIPERAKTIF • MENGANTARKAN PENETRASI SPERMA KE CUMULUS OOPHORUS • MEMPERSIAPKAN SPERMA MENJALANI REAKSI AKROSOME REAKSI AKROSOME : • TERJADI PERUBAHAN MEMBRAN KEPALA SPERMA  STRUKTUR LIPID • ALBUMIN  COATING FACTOR

  25. ASPEK-ASPEK DALAM PROSES KAPASITASI : • MORFOLOGIS • FISIOLOGIS • BIOKIMIA • PERUBAHAN LIPID • PERUBAHAN PROTEIN • REGULASI ION-ION  Ca2+ >>

  26. JALUR JELAJAH SPERMATOZOA DALAM SALURAN KELAMIN JANTAN : TUB. SEM (SPERMA INMOTIL)  RETE TESTIS DUKT. EFEREN EPIDIDIMIS (KAPUT, KORPUS, KAUDA (PENDEWASAAN) : - [ ] - MENGKERUT DUKT. DEF - AKROSOM < - MOTIL URETRA EJAKULASI  SEMEN (SPERMA + PLASMA SEMEN)

  27. DALAM SALURAN KELAMIN BETINA VAGINA : MAMALIA SERVIK : BABI UTERUS : KUDA TRANSPOR : 1. AKTIF  GERAKAN SPERMA 2. PASIF  KONTRAKSI OTOT UTERUS UTJ BARRIER  MENGHALANGI PERJALANAN SPERMA KE TEMPAT FERTILISASI

  28. LAPISAN SEL TELUR YANG HARUS DILEWATI SPERMA : 1. SEL-SEL KUMULUS  EZM. HYALORONIDASE 2. ZONA PELUSIDA  ZONA LIZIN 3. SELAPUT VITELIN

  29. AKTIVITAS UTAMA YANG TERJADI PADA PROSES FERTILISASI : 1. PENGENALAN SPERMA DAN SEL TELUR • TERJADI PERLEKATAN KEPALA SPERMA DAN SEL TELUR  RESEPTOR Z. P. • MENCEGAH PERLEKATAN  ANTIBODI ANTI ZONA / TRYPSIN • SPERMA : ANTIBODI ANTI SPERMA 2. PENETRASI SPERMA KE DALAM SEL TELUR - KAPASITASI  REAKSI AKROSOME : -ZONALYSIN / AKROSIN -MOTILITAS SPERMA

  30. 3. FUSI GAMET SPERMA  MENEMBUS Z. P. KEPALA KONTAK M. VITELIN ROTASI FUSI MEMBRAN M. PLASMA SPERMA LEPAS INTI : DEKONDENSASI  PRONUKLEUS JANTAN

  31. SPERMA M. VITELIN REDUKSI II  PB II 1. POLY SPERMA BLOCK : • PERUBAHAN RESEPTOR ZONA PELUSIDA SPERMA MENEMBUS Z. P.  RESEPTOR MODIFIKASI  Z. P. BERUBAH TIDAK DIKENALI SPERMA LAIN 2. SLOW BLOCK POLYSPERMA/REAKSI KORTEKS M. VITELIN  BUTIR KORTEK  LEPAS  RONGGA PERIVITELIN