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GENERAL EMBRYOLOGY

GENERAL EMBRYOLOGY. 1. Development of embryology 2. Germ cell and fertilization 3. Blastocyst and implantation 4. Formation of the germ layer 5. Differentiation of trilaminar germ and formation of embryo 6. Fetal membrane and placenta 7. Twins and multiple birth.

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GENERAL EMBRYOLOGY

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  1. GENERAL EMBRYOLOGY 1. Development of embryology 2. Germ cell and fertilization 3. Blastocyst and implantation 4. Formation of the germ layer 5. Differentiation of trilaminar germ and formation of embryo 6. Fetal membrane and placenta 7. Twins and multiple birth

  2. Preembryonic period:1st week to end of 2nd week fertilization to formation of bilaminar germ disc Embryonic period: 3rd week to end of 8th week formation of embryo Fetal period: 9th week to birth growth Perinatal stage: 26th week to 4 week after birth

  3. Animal • Plant Human ？

  4. Development of embryology • Aristotle, B.C 384-322 Semen+menstration • Harvey, 1651: All life from oocyte • Malpighi, 1675: A micro-chicken in an egg • Leewenhoek, 1677: A micro-human in a sperm

  5. Haeckel, 1868 • Biogenetic law • Spemann, 1869-1941 • Experimental embryology • Wilmut,1997 • Dolly

  6. Germ cell and fertilization Germ cell spermatozoon and ovum 1.Spermatozoon Capacitation：In female reproductive tract, the sperms were enabled to bind to the zona pellucida receptors. removal of glycoproteins (decapacitation factor) which cover the sperms 2.Ovum secondary oocyte arrested at metaphase in the second meiotic division

  7. Fertilization:The process in which the spermatozoon penetrates into the ovum to formfertilized ovum. In the ampulla of oviduct

  8. Process of fertilization Sperm bind to sperm receptor ZP-3 induce Acrosome reaction：release of acrosomal enzyme Cell membrane of ovum Penetration and release of acrosomal enzyme nucleus acrosome

  9. ovum fertilized ovum sperm

  10. Zona reaction:Cortical granules→perivitelline space →degrade ZP-3, alteration of zona pellucida →barrier for sperm penetration • The second meiotic division of the secondary oocyte is rapidly lifted and the second polar body is released, leaving a haploid female nucleus.

  11. Contac of sperm and ovum

  12. Sperm penetrate into the ovum

  13. Formation of female and male pronucleus

  14. Fusion of pronuclei

  15. Process of fertilization ② The nucleus of sperm penetrate into ovum ③ Formation of pronuclei ④ Fusion of pronuclei ① Fusion of the membrane of sperm and ovum 24 h Alteration of ovum

  16. 2.Condition of fertilization ① Normal ovum ② Normal sperm sufficient numbers ③ Certain time 12-24h ④ Free reproductive tract

  17. 3.Significance of fertilization ① A new life ② Diploid inheritance and aberrance ③ Sex determination

  18. Formation of blastocyst and implantation Cleavage and formation of blastocyst 1.Cleavage： early division of fertilized egg 2.Blastomere：daughter cells from cleavage 3.Morula：12 to 16- cell stage,enclosed in the zona pellucida, like morus 4.Blastocyst：about 100 blastmeres blastocoele、inner cell mass and trophoblast polar trophoblast

  19. 2-cell stage 18~36h Fertilized egg 4-cell stage 36~48h 8-cell stage 48~60h Phase of cleavage

  20. Morula 12 to 16-cell stage The third day

  21. Appearance and inner structure of blastocyst Appearance Inner structure

  22. Movement of fertilized egg in the oviduct

  23. Implantation (imbed) The process by which the blastocyst settles into endometrium. 6th day to 11th day Fundus and body of uterus zona pellucida disappear at the 5th day 1.Trophoblast：proliferate and differentiate into two layers ①Syncytiotrophoblast：outer layer, fused each other, cell boundaries disappear ②Cytotrophoblast：inner layer， cell boundaries distinct, simple cuboidal cells

  24. Movement and implantation of fertilized egg

  25. Implantation at 7th day Cytotrophoblast Inner cell mass Polar trophoblast Endometrium

  26. 2.Decidua： endometrium implantation decidua decidual response Decidua basalis：under the implantation site Decidua capsularis：between the implantation site and the uterine lumen Decidua parietalis：remaining endometrium

  27. Decidua

  28. Formation of germ layer Bilaminar germ disc 1.Bilaminar germ disk： Inner cell mass→2 layers of cell in disc (7th day) Epiblast:columnar cells adjacent to trophoblast Hypoblast:cuboidal cells adjacent to blastocoele

  29. Epiblast Hypoblast Epiblast Columnar cells Bilaminar germ disc Hypoblast Cuboidal cells

  30. 2.Amnion：8th day epiblast → amnioblast → aminiotic membrane → amniotic cavity → amniotic fluid 3.Primary yolk sac： 9th day hypoblast →extraembyronic endoderm →primary yolk sac

  31. Bilaminar germ disc at 9th day Primary yolk sac Hypoblast Epiblast Amniotic cavity Syncytio-trophoblast

  32. Bilaminar germ disc Decidua Syncytiotrophoblast Cytotrophoblast Amniotic cavity Epiblast Hypoblast Primary yolk sac

  33. 4. Extraembryonic mesoderm: 10th-11th day 5. Extraembryonic cavity: 12th-13th day Extraembryonic mesoderm: visceral layer parietal layer 6. Secondary yolk sac: 13th day 7. Body stalk: 14th day

  34. Embryo at 10th day Primary yolk sac Extraembryonic mesoderm Germ disc Amnion

  35. Bilaminar germ disc Decidua Amniotic cavity Epiblast Primary yolk sac Hypoblast Cytotrophoblast Extraembryonic mesoderm Syncytiotrophoblast

  36. Embryo at 13th day Extraembryonic cavity Primary yolk sac Secondary yolk sac Body stalk

  37. Bilaminar germ disc Primary stem villus Body stalk Extraembryonic mesoderm Visceral layer Secondary yolk sac Extraembryonic cavity Extraembryonic mesoderm Parietal layer

  38. Formation of trilaminar germ Trilaminar germ disc primitive streak, primitive groove 3rd week primitive node, primitive pit 3rd week 1. Endoderm: primitive groove →hypoblast → endoderm 2. Mesoderm： primitive groove →between epiblast and hypoblat →mesoderm 3.Ectoderm：epiblast →ectoderm

  39. Primitivestreak Epiblast Hypoblast Epiblast Primitive streak Hypoblast

  40. Determine the direction of the embryo • notochord Significance of primitive streak Primitive node Primitive pit Primitive groove Primitive streak

  41. Formation of endoderm Epiblast Primitive streak Endoderm Hypoblast

  42. Formation of mesoderm Epiblast Mesoderm Endoderm

  43. Trilaminar germ disc Ectoderm Mesoderm Endoderm

  44. proliferation Head process Notochordaltube Neurentericcanal Notochord Epiblast Primitivepit Significance of notochord ?

  45. No mesoderm Buccopharyngealmembrane Cloacal membrane

  46. Differentiation of trilaminar germ and formation of embryo Differentiation of trilaminar germ 1.Differentiation of ectoderm ①Neural tube：blastema of CNS neural plate (18th-19th day) Neuro-epithelium (neural ectoderm): pseudostratified columnar →neural groove , neural fold → neural tube (closed at 22nd day)

  47. Neural groove Paraxial mesoderm Intermediate mesoderm

  48. Neural groove Paraxial mesoderm intermediate mesoderm

  49. Neural groove Neural crest Notocord

  50. 1、Differentiation of ectoderm Anterior neuropore closed at 25th Neural fold Neural tube closed at 22nd day, from 4th somite Posterior neuropore closed at 27th

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