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General embryology

General embryology. Langman’s Medical Embryology, 9th Ed. Jun Zhou ( 周俊） School of Medicine, Zhejiang University. 20121225. Onset of last M.C. 14 days. a science which study the processes and regulations of development of human fetus.(from 1 cell (zygote) to (5-7) x10 12 cells)

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General embryology

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  1. General embryology Langman’s Medical Embryology, 9th Ed Jun Zhou (周俊） School of Medicine, Zhejiang University 20121225

  2. Onset of last M.C. 14 days • a science which study the processes and regulations of development of human fetus.(from 1 cell (zygote) to (5-7) x1012 cells) • In general the length of pregnancy is considered to be 280 days or 40 weeks after the onset of the last menstruation, or more accurately, 266 days or 38 weeks after fertilization. Fertilization 266 days Labor 280 days

  3. Total 38 weeks: • Preembryonic period: before 2 weeks • Embryonic period: 3-8 weeks • Fetal period: after 9 weeks

  4. Preembryonic period: before 2 weeks • Embryonic period: 3-8 weeks • Fetal period: after 9 weeks

  5. Fertilization • Definition: the process by which the male and female gametes(sperm and ovum) unite to give rise to zygote • place: in the ampullary region of the oviduct

  6. conditions: 1)  maturation of oocyte 2)  maturation of spermatozoa

  7. 3)  capacitation and acrosome reactionof spermatozoa: R5 • capacitation factor: secreted by epi. cells of oviduct, capacity • of releasing acrosome enzymes • 4)quality and quantity of spermatozoa: • 2-6 ml, 100,000,000/ml, • <1.5 ml; or <10,000,000; abnormal sperm >30%; or • capacity for mobile< 70% • 5) meeting of sperm and ovum within 24 hrs

  8. Processes of fertilization: • Phase I • penetrate the corona radiata, acrosomal release • Phase II • ZP with receptors – zona pellucida spongy – the release of local enzymes • Phase III • Success formation of zygote

  9. Entry – response • Cortical or zona reactions -Compaction - impermeable to more sperm • Oocyte finishes 2nd meiotic division • Female /Male pronucleus • Metabolic activationof the egg • Results of fertilization • Diploid • Genetic sex • Cleavage

  10. Cleavage • Mitosis and cytoplasmic division • Blastula - blastomeres • Morula • inner cell mass • embryoblast • outer cell rim • trophoblasts • Blastocyst • Blastocoele • The cells of morula secrete fluid • Zona pellucide disappears

  11. Uterus at Time of Implantation • Puberty – menstruation (28 days) • Hormonal regulation • GnRH • FSH • LH • Granulosa/theca cells • Estrogens • Progesterones • The endometrium of the uterus is • in the secretory phase

  12. Implantation • -Passage through the uterine tube • Day 5 –Day 11 Uterus • Orientation of implantation • Location - ant or post, fundus • Trophoblasts overlying the embryoblast pole attach to the endometrium, erosion into deep uterine vessels

  13. Processes • zona pellucide disappear → polar trophoblast touch the endometrium→secrete enzymes →dissolve the endometrium → embedded into endometrium → coagulation plug seal the space

  14. Implantation site • Normal:ant or post wall of the uterus • Abnormal • Tubal • Internal os of the cervix • Ovarian • Abdominal

  15. endometrium →decidua: • -decidua basalis • -decidua capsularis • -decidua parietalis • conditions: • -endometrium is in secretory phase • -morula reach the cavity of uterus on time • -zona pellucide disappears in time

  16. Bilaminar Germ Disc (Second week of development) • Implantation - sinks deeper • The outer cell layer • Trophoblasts • cytotrophoblasts • syncytiotrophoblasts • Inner cell mass (embryoblast) • Fluid collection – amnion • Epiblasts & hypoblasts

  17. Week two – Day 9-12 • Implantation • Covered the endometrium- fibrin plug • Complete – slight bulge • Trophoblasts • Vacuoles within syncytiotrophoblasts- fuse and form lacunar networks • Uteroplacental circ • Extra-Embryonic Mesoderm • btwn troph & cavity • Somatic/splanchnic

  18. Week 2 – Day 13-14 • Trophoblasts • Primary villi • Yolk sac • Primary to seconday • Chorionic plate • Connecting stalk

  19. The Bilaminar Embryo • Disc btwn • Amnion • Yolk sac • Bilaminar disc • Epiblasts • Hypoblasts

  20. End of the Week of Twos • 2 major cell masses • Trophoblasts • Inner cell mass • Trophoblasts • Cytotrophoblasts • Syncytiotrophoblasts • Embryonic Cavities • Amniotic cavity • Yolk sac • Germ Disc • Epiblasts • Hypoblasts

  21. OBJECTIVES • The definition of Embryology • The major phases of fertilization and the site where fertilization typically occurs • Endometrial changes that enable implantation and the hormones that modulate this change • Normal sites of implanation and the most abnormal sites • Morphologic changes in the zygote that occur enroute to the uterus • The development roles of the inner cell mass and the outer cell mass • Bilaminar germ discs

  22. Merry Christmas!

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