Download GENERAL EMBRYOLOGY

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
Animal
Plant
Human
？
Development of embryology
Aristotle, B.C 384-322
Semen+menstration
Harvey, 1651:
All life from oocyte
Malpighi, 1675:
A micro-chicken in an egg
Leewenhoek, 1677 :
A micro-human in a sperm
Haeckel, 1868
Biogenetic law
Spemann, 1869-1941
Experimental embryology
Wilmut,1997
Dolly
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
Process of fertilization
Sperm bind to sperm receptor ZP-3 induce
Acrosome reaction：release of acrosomal enzyme
Penetration and
release of acrosomal
nucleus acrosome enzyme
Cell
membrane
of ovum
ovum
fertilized ovum
sperm
Zona reaction: Cortical granules→perivitelline space
→degrade ZP-3, alteration of zona pellucida →barrier
for sperm penetration
 The second meiotic division
of the secondary oocyte is
rapidly lifted and the second
polar body is released,
leaving a haploid female
nucleus.
Contac of sperm and ovum
Sperm penetrate into the ovum
Formation of female and male pronucleus
Fusion of pronuclei
Process of fertilization
① Fusion of the
membrane of
sperm and ovum
② The nucleus
of sperm
penetrate into
ovum
③ Formation of
pronuclei
Alteration of ovum
④ Fusion of
pronuclei
24 h
2.Condition of fertilization
① Normal ovum
② Normal sperm
sufficient numbers
③ Certain time
12-24h
④ Free reproductive tract
3.Significance of fertilization
① A new life
② Diploid
inheritance and aberrance
③ 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
①Syncytiotrophoblast：outer layer, fused each other, cell
boundaries disappear
②Cytotrophoblast：inner layer， cell boundaries distinct,
simple cuboidal cells
Movement and implantation of fertilized egg
Implantation at 7th day
Cytotrophoblast
Inner cell mass
Polar trophoblast
Endometrium
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 mass→2 layers of cell in disc
(7th day)
Epiblast: columnar cells adjacent to trophoblast
Hypoblast: cuboidal cells adjacent to blastocoele
Epiblast
Columnar cells
Hypoblast
Cuboidal cells
Bilaminar
germ disc
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
Primary yolk sac
Hypoblast
Epiblast
Amniotic cavity
Syncytiotrophoblast
Bilaminar germ disc
Decidua
Syncytiotrophoblast
Epiblast
Hypoblast
Primary
yolk sac
Cytotrophoblast
Amniotic
cavity
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
Epiblast
Hypoblast
Amniotic
cavity
Primary
yolk sac
Cytotrophoblast
Extraembryonic
mesoderm
Syncytiotrophoblast
Embryo at 13th day
Extraembryonic cavity
Primary yolk sac
Secondary yolk sac
Body stalk
Bilaminar germ disc
Primary stem
villus
Body stalk
Extraembryonic
mesoderm
Visceral layer
Extraembryonic
mesoderm
Parietal layer
Secondary
yolk sac
Extraembryonic
cavity
Formation of trilaminar germ
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
Primitive
streak
Hypoblast
Epiblast
Primitive
streak
Hypoblast
Epiblast
Significance of
primitive streak
Primitive
node
Determine
the
Primitive
pit
direction of the
Primitive
groove
embryo
Primitive
streak
notochord
Formation of endoderm
Epiblast
Primitive
streak
Endoderm
Hypoblast
Formation of mesoderm
Epiblast
Mesoderm
Endoderm
Trilaminar germ disc
Ectoderm
Mesoderm
Endoderm
proliferation
Epiblast
Head
Primitive pit process
Notochordal
tube
Neurenteric
canal
Significance of notochord ?
Notochord
No mesoderm
Buccopharyngeal
membrane
Cloacal
membrane
Differentiation of trilaminar germ and
formation of embryo
Differentiation of trilaminar germ
1.Differentiation of ectoderm
①Neural 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
Neural fold
Neural tube
closed at 22nd day, from 4th somite
Posterior neuropore closed at 27th
Unclosed Anterior neuropore
Unclosed Posterior neuropore
②Neural crest： blastema of PNS
chromaffin cell, parafollicular cell
some of bone, cartilage and
muscle of head
③Superficial ectoderm: after formation of neural tube
epidermis
2.Differentiation of mesoderm
①Paraxial mesoderm：somite
17th day
at 20th day, from the head
Dermotome→ dermis, hypodermis
Myotome → skeletal muscle,
Sclerotome → axial skeleton.
②Intermediate mesoderm：urinary and
reproductive system
③Lateral mesoderm：parietal mesoderm，
viseral mesoderm，
intraembryonic coelomic cavity
Somite
Differentiation of lateral mesoderm
Dermatome
Sclerotome
Parietal mesoderm
Intraembryonic
coelomic cavit
Visceral mesoderm
Differentiation of lateral mesoderm
Intraembryonic coelomic cavity
Extraembryonic coelomic cavity
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)
20-30th day
Disc folds
Column
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
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
Chorinic 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

Stem villus


Free villus
Anchoring villus
Cytotrophoblastic column
Cytotrophoblastic shell
Evolvement of chorion
Chorion laeve：adjacent to decidua capsularis
Chorion frondosum： adjacent to decidua basalis
6th weeks
Chorion laeve
Chorion frondosum
Abnormility of chorion：
Hydatidiform
Picture
•
Chorion carcinoma
Hydatidiform
Hydatidiform
Hydatidiform
Chorion carcinoma
Chorion carcinoma
Chorion carcinoma
2. Yolk sac：5th-6th week, atresia
Abnormality:
① Meckel’s diverticulum
② Umbilical fistula
① Primitive blood cells
② Primordial germ cells
3. Amnion：
amniotic membrane: 0.2-0.5mm
amniotic epithelium + extraembryonic mesoderm
amniotic fluid: 500-1000ml
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 vein
Umbilical artery
Decidua bsalis
Placenta septa
Uterus vein
Spiral artery
2.Placental membrane：
Structure between the blood of mother and fetus
①Syncytiotrophoblast；
②Cytotrophoblast and its basal lamina；
③Connective tissue；
④Endothelium and its basal lamina
protection
Fetal membrane
Syncytiotrophoblast
Cytotrophoblast
Blood of
mother
Nutriment
Metabolic product
胎
儿
血
Basal lamina
Connective tissue
Basal lamina
Endothelium
3.Function：
① Substance exchange
O2, nutriment,
CO2, waste
② Hormone
Human chorionic gonadotropin, HCG;
Human placental lactogen, HPL;
Human placental progesterone, HPP,
Human placental estrogen, HPE
Placenta
Function
① Substance exchange
Capillary of fetus
Blood of mother
Ｏ2
Nutriment
water、salt、others
water、salt、others
ＣＯ2
Metabolic waste
Placenta
Placenta
Function
② Barrier
Capillary of fetus
Blood of mother
s
Most of
microorganism
No way
！
Placenta barrier
Placenta
Function
② Barrier
Capillary of fetus
Blood of mother
Most of drugs
Most of
microorganism
Some of
microorganism
Placenta barrier
Placenta
Function
③ Endocrine
Hormone
HCG
HCS
Function
Corpus luteum
Pregnancy
Mammary
gland
Appearance
Fastigium
3rd week
8th week
2nd month
8th month
HPE
Corpus luteum
4th month
8th month
HPP
Corpus luteum
4th month
8th 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
Blastocyst
2 Amnion
2 Chorion
2 Placenta
Monozygotic twins
separation of blastomere, of ICM,
Blastocyst
2 ICM
2 Amnion
2 Chorion
2 Placenta
2 Amnion
1 Chorion
1 Placenta
of primitive streak
2 primitive streak
1 Amnion
1 Chorion
1 Placenta