General Embryology -...

Anhui Medical University


General Embryology

Email:[email protected] of Histology and Embryology

School of Basic Medicine


Xie Fenfen



1. The location of fertilization. The formation time of morula

and blastocyst.

2. The component and formation time of trilaminar germ disc.

3. The main differentiation of trilaminar germ disc.

4. The component and function of fetal membrane.

5. The structure and function of placenta.

6. Blastocyst; Placental barrier.

Key points



General Description

Definition: Embryology is a science involved in researching the process and mechanism of ontogenesis and fetus development.

description embryology chemical embryology comparative embryology experimental embryology molecular embryology



① Preembryonic period

② Embryonic period

③ Fetal period

It takes 38 weeks(266 days) from fertilization to

parturition of a mature fetus.

It can be divided into 3 periods:



1) Preembryonic period:

First 2 weeks, fertilization to formation of the bilaminar germ disc.



2) Embryonic period :

Weeks 3 – 8, primordial of all major organs develop fromthe three germ layers.



3) Fetal period :

Week 9 – birth, Growth of the organ systems.



General Information of Embryology



Cotents

Maturation of germ cells and Fertilization

Cleavage, Blastocystformation and Implantation

The formation of embryonic disc

The differentiation of trilaminar germ disc and

Embryonic folding

Fetal membrane and Placenta



1. germ cell

germ cell / gamete: sperm and ovum

haploid cell

sperm karyotype: 23 , X / 23 , Y

ovum karyotype: 23 , X



Sperm

(1)spermatogenesis: Seminiferous Tubule

(2)functional maturation: Epididymal duct

(3)sperm capacitation: The female reproductive duct



spermatogenesis

Spermatogonium

Primary spermatocyte

Sperm

Spermatid

Secondary spermatocytespermiogenesis

SpermatogoniumSpermatogoniumSpermatogoniumSpermatogoniumSpermatogoniumSpermatogonium



• Head: acrosome and DNAThe acrosome contains enzymes

which are released when sperm

reaches ovum.

• Tail: microfilament for movement Middle section contains mitochondria.

Sperm



Head of sperm wiping off glycoprotein

glycoproteinmembrane

acrosome

As sperm moving in uterus and oviduct, the glycoprotein, which cover the outside head of them to inhibit release of acrosome enzyme, is removed so that sperm gains the capability of fertilization.

Capacitation of Sperm



Ovum

Twice meiosis division of oocyte:

(1) The first meiosis: 36 - 48 hours before ovulation, Ovary

(2) The second meiosis: Fertilization, Oviduct

Corona radiata

Zona pellucida



oogenesis

Primordial follicle

Mature follicle Secondary follicle

Primary follicle



*Definition: The process by which the male and female gametes (sperm and ovum) unite to give rise to a zygote.

*Place: in the ampulla of oviduct

2. Fertilization

.



(1)Penetration of corona radiata

(2)Penetration of zona pellucida

(3)Fusion of the oocyte and sperm cell membranes

Three phases of fertilization

卵母细胞

cumulus cell

polar body

Phase 1

卵母细胞oocyte

Zona pellucida

Corona radiata

Phase 2

Phase 3



Fertilized Egg Formation

1. Sperm-egg fusion 2. Male pronuclear, Female pronuclear

3. Chromosome mixture 4. Fertilized egg formation



The Process of Fertilization



Fusion of the oocyte and sperm



Acrosome Reaction

After sperms bind to zona pellucida, they release of enzymes from acrosome, which is needed for sperm penetration of the zona pellucida.



Zona becomes impenetrable to other sperm (monospermy), through enzyme release from cortical granules of oocyte to change structure and composition of the zona.

Zona Reaction



Fertilization



Scanning Electron Micrograph

Sperm binding to the zona pellucida



Sperm entering the egg



Human Embryo and Sperm



(1)Restoration of the diploid number of chromosomes

(2)Determination of the sex of the new individual

(3)Initiation of cleavage

X+X

Significance of Fertilization

How does the fertilized egg carry out cell division?

Y+X boy

girl



Cotents

Maturation of germ cells and Fertilization

Cleavage, Blastocystformation and Implantation

The formation of embryonic disc

The differentiation of trilaminar germ disc and

Embryonic folding

Fetal membrane and Placenta



Cleavage: Fertilized egg undergoes a series of mitotic divisions.

Blastomere: The cells which become smaller with each

cleavage division.

1. Cleavage and Blastocyst formation

2-cell stageFertilized egg 4-cell stage 8-cell stage



Cleavage



* 3 days after fertilization, cleavage divisions produce a

solid ball of cells called a morula.

morula

Morula

12-16 cells



* 4 days after fertilization, about 100 blastomeres,

intercellular spaces a single cavity,blastocyst forms.

Component: Blastocele

Trophoblast

blastocyst

* Blastocyst

Inner cell mass



Blastocyst formation

morula blastocyst



Embryonic Stem Cell



OvulationFertilizationCleavageBlastocyst formation



Next, where is the blastocyst arrived in the uterine cavity going ？？？

OvulationFertilizationCleavageBlastocyst formation



Definition: The process of the embryo completely embedding

itself within the endometrium.

2. Implantation



zona pellucide disappear → polar trophoblast touch the

endometrium → secrete proteolytase → erode the endometrium → embedded into endometrium →coagulation plug seal the space

Processes of implantation



Cytotrophoblast

Syncytiotrophoblast

Surface epithelium

* Trophoblast become into two layers when blastocyst is embedding into endometrium.

Change of Trophoblast

Uterine gland

Blood vessle

StromaCytotrophoblast

Syncytiotrophoblast



green cells - trophoblast layer of the conceptus

blue cells - epiblast layer of the bilaminar embryo

yellow cells - hypoblast layer of the bilaminar embryo

white cells - uterine endometrium epithelium

red - maternal blood vessel

Implantation

http://php.med.unsw.edu.au/embryology/index.php?title=E�

http://php.med.unsw.edu.au/embryology/index.php?title=H�



Time：the 5th-6th day begin the 11th-12th day complete

*Place：Posterior wall of uterine fundus and Uterine body

Implantation

Ectopic Pregnancy

Placenta Previa



Test-tube Baby

in vitro fertilization ＋ embryo transfer

（体外人工受精）（胚胎移植）



6-day-embryo transfering to uterine cavity



In 1978, the first test-tube baby in the world England

In 1988, the first test-tube baby in China Beijing Medical

University

In 1998, the first test-tube baby in Anhui province Anhui

Medical University

General Embryology -...

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