General embryology (I) Jun Zhou（周俊） zhjjwm300@zju.edu.cn School of Medicine, Zhejiang University 20170612

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, 2017组织胚胎学

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。

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 受精 分娩 末次月经的第一天 受精龄， 266天 月经龄， 280天

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

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

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

5) meeting of sperm and ovum within 24 hrs 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

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

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

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

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

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

-Passage through the uterine tube 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.

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

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

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

In vitro 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）。

(Second week of development) 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

Week two – Day 9-12 Implantation Trophoblasts Extra-Embryonic Mesoderm 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

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

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

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

THE END!