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
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
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
Fertilization: The process in which the spermatozoon penetrates into the ovum to form fertilized ovum. In the ampulla of oviduct
nucleusacrosome Penetration and release of acrosomal enzyme Cell membrane of ovum Process of fertilization Sperm bind to sperm receptor ZP-3 induce Acrosome reaction release of acrosomal enzyme
ovum fertilized ovum sperm
The second meiotic division of the secondary oocyte is rapidly lifted and the second polar body is released, leaving a haploid female nucleus. Zona reaction: Cortical granulesperivitelline space degrade ZP-3, alteration of zona pellucida barrier for sperm penetration
Contac of sperm and ovum
Sperm penetrate into the ovum
Formation of female and male pronucleus
Fusion of pronuclei
Fusion of the membrane of sperm and ovum The nucleus of sperm penetrate into ovum Formation of pronuclei Fusion of pronuclei Process of fertilization Alteration of ovum 24 h
2.Condition of fertilization Normal ovum Normal sperm sufficient numbers Certain time 12-24h Free reproductive tract
3.Significance of fertilization A new life Diploid inheritance and aberrance Sex determination
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
Phase of cleavage Fertilized egg 2-cell stage 18~36h 4-cell stage 36~48h 8-cell stage 48~60h
Morula 12 to 16-cell stage The third day
Appearance and inner structure of blastocyst Appearance Inner structure
Movement of fertilized egg in the oviduct
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 Syncytiotrophoblast outer layer, fused each other, cell boundaries disappear Cytotrophoblast inner layer cell boundaries distinct, simple cuboidal cells
Movement and implantation of fertilized egg
Implantation at 7th day Endometrium Polar trophoblast Inner cell mass Cytotrophoblast
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
Decidua
Formation of germ layer Bilaminar germ disc 1.Bilaminar germ disk Inner cell mass2 layers of cell in disc (7th day) Epiblast: columnar cells adjacent to trophoblast Hypoblast: cuboidal cells adjacent to blastocoele
Bilaminar germ disc Epiblast Hypoblast Columnar cells Cuboidal cells Epiblast Hypoblast
2. Amnion 8th day epiblast amnioblast aminiotic membrane amniotic cavity amniotic fluid 3.Primary yolk sac 9th day hypoblast extraembyronic endoderm primary yolk sac
Bilaminar germ disc at 9th day Hypoblast Epiblast Amniotic cavity Syncytio- trophoblast Primary yolk sac
Bilaminar germ disc Decidua Syncytiotrophoblast Epiblast Hypoblast Primary yolk sac Amniotic cavity Cytotrophoblast
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
Embryo at 10th day Primary yolk sac Extraembryonic mesoderm Germ disc Amnion
Bilaminar germ disc Decidua Amniotic cavity Epiblast Hypoblast Extraembryonic mesoderm Primary yolk sac Cytotrophoblast Syncytiotrophoblast
Embryo at 13th day Extraembryonic cavity Primary yolk sac Secondary yolk sac Body stalk
Bilaminar germ disc Body stalk Secondary yolk sac Extraembryonic cavity Primary stem villus Extraembryonic mesoderm Visceral layer Extraembryonic mesoderm Parietal layer
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 Formation of trilaminar germ
Primitive streak Epiblast Hypoblast Epiblast Hypoblast Primitive streak
Determine the direction of the embryo notochord Primitive node Primitive pit Primitive groove Primitive streak Significance of primitive streak
Hypoblast Epiblast Primitive streak Endoderm Formation of endoderm
Epiblast Endoderm Formation of mesoderm Mesoderm
Ectoderm Endoderm Mesoderm Trilaminar germ disc
Epiblast proliferation Primitive pit Head process Notochordal tube Neurenteric canal Notochord Significance of notochord ?
No mesoderm Buccopharyngeal membrane Cloacal membrane
Differentiation of trilaminar germ and formation of embryo Differentiation of trilaminar germ 1.Differentiation of ectoderm Neural 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)
Neural groove Paraxial mesoderm Intermediate mesoderm
Neural groove Paraxial mesoderm intermediate mesoderm
Neural groove Neural crest Notocord
1 Differentiation of ectoderm Anterior neuropore closed at 25th Posterior neuropore closed at 27th Neural tube Neural fold closed at 22nd day, from 4th somite
U nclosed Anterior neuropore Unclosed Posterior neuropore
Neural crest blastema of PNS chromaffin cell, parafollicular cell some of bone, cartilage and muscle of head Superficial ectoderm: after formation of neural tube epidermis
2.Differentiation of mesoderm 17th day Paraxial mesoderm somite at 20th day, from the head Dermotome dermis, hypodermis Myotome skeletal muscle, Sclerotome axial skeleton. Intermediate mesoderm urinary and reproductive system Lateral mesoderm parietal mesoderm viseral mesoderm intraembryonic coelomic cavity
Somite
Parietal mesoderm Intraembryonic coelomic cavit Visceral mesoderm Differentiation of lateral mesoderm Dermatome Sclerotome
Extraembryonic coelomic cavity Intraembryonic coelomic cavity Differentiation of lateral mesoderm
3. Differentiation of endoderm Epithelium of primitive gut epithelium of digestive tract, digestive gland, respiratory tract and lung Primitive pharynx 5 pairs of pharyngeal pouch
Formation of primitive gut A B
Parietal mesoderm Intraembryonic coelomic cavity Visceral mesoderm
Formation of embryonic body (4-8th week) DiscColumn folds the number of somite increase face development, formation of branchial pouch breach of buccopharyngeal membrane 5th week: upper and lower limb buds 6th week: hand and foot plates 7th week: formation of face, disappear of somite 8th week: breach of cloacal membrane 20-30th day
At the end of 8th week a small human
Fetal membrane and placenta Fetal membrane Chorion Amnion Yolk sac Allantois Umbilical cord
Amnion Yolk sac Umbilical cord Placenta
1.Chorion Secondary stem villus +chorinic plate Primary stem villus 2nd week Outer syncytiotrophoblast+ Inner cytotrophoblast C horinic plate : extraembryonic mesoderm + trophoblast
Secondary stem villus 3rd week Outer syncytiotrophoblast+ Intermedial extraembryonic mesoderm+ Inner cytotrophoblast Tertiary stem villus end of 3rd week, Blood vessels Anchoring villus, Free villus cytotrophoblastic cell column cytotrophoblastic shell
Primary stem villus at 2nd week cytotrophoblast Secondary stem villus at 3rd week extraembryonic mesoderm Tertiary stem villus at the end of 3rd week blood vessels
Anchoring villus Free villus Cytotrophoblastic shell Cytotrophoblastic column Stem villus
Evolvement of chorion Chorion laeveChorion frondosum 6th weeks Chorion laeve adjacent to decidua capsularis Chorion frondosum adjacent to decidua basalis
Abnormility of chorion Hydatidiform Hydatidiform Chorion carcinoma Chorion carcinoma Picture
Hydatidiform
Chorion carcinoma
2. Yolk sac 5th-6th week, atresia Abnormality: Meckels diverticulum Umbilical fistula Primitive blood cells Primordial germ cells
3. Amnion amniotic membrane: mm amniotic epithelium + extraembryonic mesoderm amniotic fluid: ml abnormality: 500 ml, oligohydramnios 2000 ml, polyhydramnios protection
4. Allantois degeneration Abnormality: Urachal fistula 2 pairs of blood vessel 1 umbilical vein 1 pair of umbilical artery
5. Umbilical cord 50 cm (CT, umbilical vein umbilical artery, degenerated yolk sac and allantois) covered with amniotic membrane Abnormality: 80 cm, 35 cm connect fetus with placenta
Fetal membrane
Placenta 1.Placenta: Chorion frondosum + Decidua basalis disk: 15-20cm Sandwich: chorinic plate (fetus) villi basal plate (mother) basal plate: decidua + cytotrophoblastic shell placental septa cotyledon (incomplete)
Umbilical artery Umbilical vein Spiral artery Uterus vein Decidua bsalis Placenta septa
2.Placental membrane Structure between the blood of mother and fetus Syncytiotrophoblast Cytotrophoblast and its basal lamina Connective tissue Endothelium and its basal lamina protection
Syncytiotrophoblast Cytotrophoblast Basal lamina Connective tissue Basal lamina Endothelium NutrimentMetabolic product Fetal membrane Blood of mother
3.Function Substance exchange O 2, nutriment, CO 2, waste Hormone Human chorionic gonadotropin, HCG; Human placental lactogen, HPL; Human placental progesterone, HPP, Human placental estrogen, HPE
Function Substance exchange Substance exchange Placenta Capillary of fetusBlood of mother 2 Nutriment water salt others 2 Metabolic waste Placenta membrane
Function Barrier Barrier Placenta Capillary of fetusBlood of mother s Placenta barrier No way Most of microorganism
Function Barrier Barrier Placenta Capillary of fetusBlood of mother Most of drugs Placenta barrier Most of microorganism Some of microorganism
Function Endocrine Placenta Hormone Function AppearanceFastigium HCG Corpus luteum Pregnancy 3rd week8th week HCS Mammary gland 2nd month8th month HPE Corpus luteum4th month8th month HPP Corpus luteum 4th month8th month
Twins and multiple birth 1.Twins monozygotic twins dizygotic twins
2. Multiple birth monozygotic multiple birth polyzygotic multiple birth mixed multiple birth
Dizygotic twins Blastocyst 2 Amnion 2 Chorion 2 Placenta
Monozygotic twins separation of blastomere, of ICM, of primitive streak Blastocyst 2 ICM 2 primitive streak 2 Amnion 2 Amnion 1 Amnion 2 Chorion 1 Chorion 1 Chorion 2 Placenta 1 Placenta 1 Placenta