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General embryology (I)

Explore the processes and structures of human embryonic development from fertilization to implantation, including key concepts and stages. Learn through detailed explanations, illustrations, and clinical relevance.

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General embryology (I)

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  1. General embryology (I) Jun Zhou（周俊） zhjjwm300@zju.edu.cn School of Medicine, Zhejiang University 20180612

  2. Histology & Embryology: • Final score: • Attendence (Lab , Lecture): 10% • Quiz: 15% • Lab test: 25% • Final written exam.: 50% • Final written exam: • Histology: 70-80%, • Embryology: 20-30% • Item type： • Single choice: 50, 1 point/per (50%) • Filling the blank: 50, 0.5 point/per (25%) • Brief question: 5, 5 points/per (25%)

  3. 1. Langman’s Medical Embryology，13 th Edition 2.高英茂主编，《组织胚胎学》，全国八年制教材，人民卫生出版社，2010 3.课程网站：m-learning.zju.edu.cn, 2018组织胚胎学

  4. OBJECTIVES • 1.说明受精的过程和意义。 • 2.试述胚胎植入的定义、过程、部位以及植入后的子宫蜕膜分部。 • 3.试述两胚层胚盘的形成过程和组成。 • 4.三胚层胚盘的形成和初步分化。 • 5.胎膜、蜕膜及胎盘的结构与功能。 • 6.先天性畸形。

  5. 末次月经的第一天 受精 受精龄， 266天 分娩 月经龄， 280天 • a science which study the processes and regulations of development of human fetus.(from 1 cell (zygote合子) to (5-7) x1012 cells) • total 38 weeks: 280 /266 days

  6. preembryonic period（胚前期）: before 2 weeks • embryonic period（胚期）: 3-8 weeks • fetal period（胎儿期）: after 9 weeks

  7. Fertilization（受精） • Definition: the process by which the male and female gametes(sperm and ovum) unite to give rise to zygote • site: in the ampullary region（壶腹部）of the oviduct

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

  9. 3)  capacitation（获能）and acrosome reaction（顶体反应）of spermatozoa • 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

  10. Processes of fertilization: • Phase I • Penetration of the corona radiata（放射冠）, acrosomal release • Phase II • Penetration of the zona pellucide（透明带） • ZP with receptors – zona pellucida spongy – the release of local enzymes • Phase III • Entrance, formation of zygote

  11. 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

  12. Cleavage （卵裂） • Mitosis • Two cell stage (30h) • Morula（桑椹胚） (72h) • inner cell mass • embryoblast • outer cell rim • trophoblasts • Blastocyst （胚泡）(5d) • Blastocoele • The cells of morula secrete fluid • Zona pellucide disappears

  13. Blastocyst （胚泡） trophoblasts （滋养层） • blastocoele （胚泡腔） inner cell mass （内细胞群）

  14. 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

  15. Implantation（植入） • -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 and begin to invade.

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

  17. Implantation site • Normal:ant or post wall of the uterus, fundus • Abnormal: • Internal os of the cervix (placenta previa) • Ovarian • Abdominal • Tubal(most common) Ectopic pregnancy （宫外孕）

  18. endometrium →decidua: • -decidua basalis （底蜕膜） • -decidua capsularis（包蜕膜） • -decidua parietalis（壁蜕膜） • conditions: • -endometrium is in secretory phase • -morula reach the cavity of uterus on time • -zona pellucide disappears in time

  19. Invitro fertilisation • 体外受精联合胚胎移植技术（IVF）：又称试管婴儿，是指分别将卵子与精子取出后，置于试管内使其受精，再将胚胎前体---受精卵移植回母体子宫内发育成胎儿的过程。 Preimplantation Genetic Diagnosis • 植入前遗传学诊断(PGD) • 从发育到4-8细胞的胚胎中，取出一个细胞进行细胞遗传学或分子遗传学检查，再将检查结果正常的胚胎放入子宫内,以达到优生优育目的。 • 目前主要用于已知患有遗传性疾患夫妇或高风 险遗传疾患携带者（如高龄妇女）。

  20. Bilaminar Germ Disc （二胚层胚盘） (Second week of development) • Implantation - sinks deeper • The outer cell layer • Trophoblasts • Cytotrophoblasts • 细胞滋养层 • Syncytiotrophoblasts • 合体滋养层 • Inner cell mass (embryoblast) • Fluid collection – amnion • Epiblasts & hypoblasts

  21. 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

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

  23. The Bilaminar Embryo • Disc btwn • Amnion（羊膜腔） • Yolk sac（卵黄囊） • Bilaminar disc • Epiblasts（上胚层） • Hypoblasts（下胚层）

  24. 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

  25. THE END!

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