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Embryology

Embryology. 1. Embryology (the term, varieties) 2. Periods of ontogenesis 3. Germ cells 4. Stages and processes of embryogenesis 5. Extraembryonic organs (fetal membranes…) 6. Types of embryo nutrition 7. Critical (crucial) periods 8. Extracorporal fertilization.

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Embryology

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  1. Embryology 1. Embryology (the term, varieties) 2. Periods of ontogenesis 3. Germ cells 4. Stages and processes of embryogenesis 5. Extraembryonic organs (fetal membranes…) 6. Types of embryo nutrition 7. Critical (crucial) periods 8. Extracorporal fertilization

  2. General embryologySpecial embryology Periods of the human life: 1. Progenesis 2. Prenatal (conceptus, embryo, fetus) 3. Postnatal Differences between germ and somatic cells • Chromosomal set • May fuse • Dye without fusion

  3. Yolk inclusions Alecytal Olygolecytal Polilecytal Nucleus location Primary Secondary Types of oocytesHuman oocyte – oligolecytal II isolecytal

  4. Spermatozoa A lot of … Constantly Motile Types Androspermium 22+y Gynecospermium22+x

  5. Biologic significance of oocyte in fertilization 1.Gives half of a necessary amount of chromosomes2. Supplies the nutrition of embryo3. Protection of embryo at the early stages of development Biologic significance of spermatozoon in the fertilization 1. Active passage forward to the ovum 2. Gives 23 “father’s” chromosomes 3. Sex of embryo depends on spermatozoon type 4. Gives the centriole 5. Mitochondrial DNA 6. Introduces special cleavage signal protein 7. Stimulies oocyte meiosis

  6. Stages and processes ofembryogenesis

  7. Fertilization The biological significances of fertilization: 1. The restoration of karyotype. 2. Determination of the embryo sex. 3. Initiation of a cleavage. Distant stage Contact stage

  8. Distant stage 1. Capacitation– special activation of spermatozoa . 2. Taxis–active movement of spermatozoa. A. Chemotaxis (chemo tropism). B. Rheotaxis. C. Stigmotaxis.

  9. Contact stage 1. Acrosomal reaction – exfusion of acrosomal enzymes. 2. Denudation – dispersion of the corona radiate. 3. Penetrationof zona pellucida. 4. Cortical reaction – passage of the oocyte cortical granules content outside. Tunica of fertilization + perivitelin space

  10. Corona radiata cells Stage 1 Stage 2 Polar body division Penetration Acrosome Meiotic division of secondary oocyte Nucleus Cell membrane Fusion of oocyte and spermatozoon membranes Stage 3

  11. Zygote formation Zona pellucida Corona radiata Penetration Male pronucleus Female pronucleus Centrosome Metaphase plate Meiotic division

  12. Synkarion, two blastomeres

  13. Cleavage(full subequal asynchronic )

  14. Morula

  15. Blastocyst Embryoblast Blastocyst cavity Trophoblast

  16. Implantation 1. Blastocyst inculcation into the endometrium. 2. Phases of implantation: adhesion and invasion. 3. Duration - 40 hours. 4. Normal site – in the uterine body. Abnormal implantation sites (ectopic pregnancy)

  17. Implantation adhesion Endometrial epithelium Endometrial stroma Trophoblast Trophoblast cells Blastocyst cavity Embryoblast

  18. Gastrulation appearance and development of germ layers Peculiarities of the human embryo gastrulation 1. Full subequal asynchronic cleavage – blastocyst 2. Forestall development of extraembryonic organs3. Embryo implantation into endometrium and placenta formation4. All (three) germ layers are forming from primary ectoderm

  19. Implantation invasion

  20. Early gastrulation7th -14th days 1. Embryoblast delaminates into epiblast and hypoblast 2. Amnion originate from epiblast (primary ectoderm) 3. Yolk sac – from hypoblast (primary endoderm) 4. Trophoblast differentiates into cytotrophoblast and syncytiotrophoblast 5. Embryonic disc – the attachment of amniotic vesicle bottom and the roof of yolk sac 6. Embryo’s body has one layer – the amniotic vesicle bottom/ Late gastrulation14th 17th days 1. Migration with primitive streak formation 2. Extraembryonic mesoderm migrate from embryonic disc 3. Three layers of embryo body are formed at the same time from embryonic ectoderm

  21. EXTRAEMBRYONIC ORGANS 1. Amnion 2. Yolk sac 3. Umbilical cord 4. Allantois 5. Chorion 6. Placenta

  22. Vitelotrophic – 30 hours, by yolk inclusionsHistiotrophic – 2nd day –3rd month, by tissuesHematotrophic– 3rd month …

  23. Human placenta II discoidal hemochorial • Umbilical cord • Fetal placenta • Maternal plac. • Cotyledon • Amnion • Vessels

  24. CRITICAL (crucial) PERIODS1944 Norman Gregg (austral) 1960 P Svetlow (rus) 1. Progenesis or gametogenesis 2. Fertilization 3. Implantation 4. Placentation 5. Growth of the brain 6. Organo- and systemogenesis 7. The birth 8. Neonatal period and first year of life 9. Pubertation 10. Menopause

  25. EXTRACORPORAL FERTILIZATION 1976 Luisa Brown (GB) Edvards and Stantow 1. Special surgical manipulation 2. Fertilization “in vitro” 3. Incubation for 3-4 days (cleavage) 4. Blastocyst (18-32 blastomeres) – “free blastocyst” in uterus 5. Implantation begins (15 % successful)

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