fertilisasi, implantasi and embriogenesis

8/13/2019 Fertilisasi, Implantasi and Embriogenesis

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Fertilisasi, Implantasi dan

Embryogenesis E. Suryadi,

Anatomy, Embryology and Anthropology Department

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IntroductionEmbryology is the study of the development ofEmbryo or a part of Developmental AnatomyDevelopmental anatomy is continuous process

That begins when an ovum is fertilized by asperm until ends at deathA process of change and growth which transformthe zygote as a single cell into a multi cellular,multi tissues, multi organs in adult human body

Development usually divide into prenatal and postnatal

Natal !birth" is a dramatic event duringdevelopment

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OOCYT &

ZYGOTE


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CleavageCleavage

Blastocystwith blastocoele cavity

Morulasolid ball of cells

Early division of zygote into multiple cellswithout increase in size, partitionscontents

Zygote


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UMUR 3 SAMPAI 7 MINGGU


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Term of Prenatal Period

#ygote$ the cell result from fertilization of anovum by a sperm%leavage$ &itotic division of zygote

'ormation of daughter cells !blastomeres" becomesmaller and smaller(lastomere is totipotent cell or multi)potent cell

&orula$ when *+ blastomeres have formed(lastocyst !blastula" ! forming a cavity thisconverts from the morula into a blastocystEmbryo$ developmental stage from thebilaminar embryonic disc form until all ma orstructure are present - nd / th wee0 gestation"

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'etus$1renatal period after the embryonic

period / th" to birth

%oncepts$The product of conception it includes all

structure which develop from zygote to

both embryonic and e2tra embryonictissues

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Stages of development

Early development is blastulation the first wee0" 'ormation of the bilaminar embryo and

implantation the second wee0" 'ormation of the trilaminar embryo and

morphogenetion the third wee0" is calledgastrulation

The embryonic period and organogenetion thefourth to the eight wee0"

The fetal period the ninth wee0 to birth"

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The First Week: Fertilisasi. 1roses fertilisasi dibagi dalam 3 tahap

yaitu$ a" penetrasi spermatozoa 0e dalamoosit,

b" a0tivasi oosit setelah penetrasispermatozoa,

c" fusi dan singami antara pronu0leus antan dan betina.

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FERTILISASI

1enetrasi%onsist of the fusion of sperm and a ovum

This process occur as follows*. The Sperm passes through cumulus oovorus-. The sperm passes through the corona radiata

3. The sperm penetrates the zona pellucida4. The sperm head attaches to the surface of

the ovum

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4. The ovum reacts to sperm contact two waysa. %hanges occur in the zona pelluzida andovum5s cell membrane which preventpolysperm

b. The oocyt continue second meiotic divisionprocess and e2pels the second polar bodyand the female pronucleus formation

4. Sperm loses its tail and its head enlarge to formthe male pronuclei

6. The male and female pronuclei approach eachother in the center of the ovum is called singami

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Result of

Fertilization*. 7estoration of diploid chromosome

number-. Species variation3. Se2 determination

4. 8nitiation of cleavage

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Cleava eAs the zigote passes down the uterinetube undergoes cleavage into a numberof small blastomeres

About three days after fertilization a ballform contain *+ blastomeres called themorula, enters the uterus

(lastomere is totipotent cells

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The fi !"

#ee$


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!lastulaA cavity soon forms in morules, called blastocyst

consisting of an inner cell mass or embryoblast", which

gives rises to the embryoA blastocyst cavity, which become primitiveyol0 sacAn outer layer at cell or trophoblast", which

enclose the inner cell mass and blastocystcavity

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9n fourth and fifth day the zona pellucida

degradations and disappears and on si2thday the blastula adheres to the endometrialepitheliumThe trophoblastic cells invade theepithelium and stromes endometriumThe trophoblast gradually differs into twolayer

*" An inner cytotrophoblast-" An outer syncytrotrophablast

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9n seventh day the embryonicendoderm begins to form on the ventralsurface at the inner cell mass. This isthe first primary germ layerThe blastocyst beginning implanted inthe endometrial living of the uterus

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The second week: implantation and chorionformation

Implantation:

begins at the end at the first wee0 and endsduring the second wee08mplantation process as follow*. #ona pellucida disappears 4)6"

-. (lastocyst attaches to endometrial epithelium+"3. Trophoblast erodes epithelium and endometrial

stroma :"4. Trophoblast will be differed into

cytotrophoblastic and syncytiotrophoblastic 21


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6. ;acunae appear in syncytrotrophoblast / to


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Implantation -Implantation - embedding of blastocystinto uterine lining begins at day :

Blastocyst - with blastocoelecavityTrophoblast - outer layer of cellsInner cell mass - will form embryo

Lacunae and primary villi formedby trophoblastAll of these form placental tissues

Fig 28-3

Trophoblast forms syncytialtrophoblast - erodes into endometriumCellular trophoblast - carries nutrientsto inner cell mass


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Chorion Formation(etween s>uamous epithelium inblastocyst cavity and cytotrophoblast

arise mesenchym cell callede2traembryonic mesoderm8n the e2traembryonic mesoderm form

spaces called e2traembryonic coelom

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This coelom splits the e2tra embryonicmesoderm into two layers

E2traembryonic somatic mesodermE2traembryonic splanchnic mesoderm

The cavity of the chorion sac is formed bythe e2traembryonic coelomThe trophoblast and the e2tra embryonicsomatic mesoderm together form chorione

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Se% '(

)ee$


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&a or changes occur as the bilaminarembryonic disc is converted into a trilaminarembryo composed of three primary germlayer gastrulation"8n the third wee0 usually the first sign that a

woman may be pregnant;aboratory pregnant test depend on the

presence of human chorionic gonadotropin?%@", a hormone produced by trophoblastand e2creted in the mother5s urine

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The third "eek


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Gastrulation arly organogenesis Primitive streak formation Notochord Formation Neural Tube Formation Somite Formation Coelom Formation Blood and Blood Vessel Formation Villi Formation

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gastrulation$The primitive strea0 stria

primitiva" and intraembryonicmesodermThe primitive strea0 appears at about *6days as a midline thic0ening of the

embryonic ectodermAt the primitive strea0 give rise tomesenchymal cells which migratelaterally and cranially between theectoderm and endoderm layers andorganize into the third primary germ layercalled intra embryonic mesoderm

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#otochord Formation9pening develops in the floor at thenotochord canal which soon coalesce,leaving the notochord plate.The notochord plate in folds to form thenotochord

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Somite FormationThe mesoderm on each side at thenotochord thic0ens to form longitudinalbundle colum" of para2ial mesoderm

Division of para2ial mesoderm into pairsat somites begin cranially by the end atthe third wee0

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Coelom FormationThe entry embryonic coelom arises as isolatedspaces in the lateral plate mesoderm andcardiogenic area

The coelomic space subse>uently coalesce toform a single horseshoe)shaped cavity, whicheventually give rise to the body cavities

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oo n oo


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oo n oo%essel

Angiogenesis ! blood vessel formation?aemopoesis ! blood cell formation

*. &esenchymal cells aggregate to formisolated masses and cords 0nown as blood

islands called angioblast-. Spaces appear within these islands3. Angioblast arrange themselves around the

cavity to form the primitive endotheliumformation

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4. 8solated vessels fuse to form networ0s at

endothelial channel6. essels e2tend into ad acent areas by

endothelial budding

+. &esenchymal cells surrounding the primitiveendothelial vessel differentiate into muscularand connective tissue

:. The primitive heart is formed in the cardiogenicarea

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/. 1rimitive plasma and blood cell develop fromthe endothelial cell as the vessels developon the yol0 sac and allantois. 8n embryo firstblood formation occurs in the liver, late in the

spleen, bones marrow and lymph nodes


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%illi Formation

The primary villi form on the outer surface atthe chorionic sac from cytotrophoblast cell

proliferate(y day *6 the primary villi have begun tobranch and develop central cone atmesenchyme$ its are called secondary villi%apillaries develop in the villi transformingthem into tertiary villi

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Intervillous S&ace;acunas enlarge and lying betweentertiery villis, called intervillous spacespatium intervillosum"

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Th F th T S th


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The Four th To SeventhWeeks

The beginning of all ma or e2ternal andinternal structures during this period

This critical period at development, ifteratogen e2posure this period will causema or congenital malformationThe three primary germ layers will bedifferentiated into various tissues and organsThe end at this period the main organsystem have been established

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Foldin At The Em$r 'o

;ongitudinal and transverse folding convertsthe flat trilaminar embryo disc into a %shaped cylindrical embryoThe formation at head, tail and lateral foldsis a continue se>uence of events and resultin a constriction between the embryo andthe yol0 sacThe dorsal part at yol0 sac is incorporatedinto the embryo as the primitive gut

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;iterature &oore B.;.,1ersaud T. .N. The

Developing ?uman edisi 0e):. Saunder.CSA -==3. *+)4-

%arlson (.&.1atten5s 'oundations ofEmbryology edisi 0e)+.&c@raw)?ill.Newor0.*

fertilisasi, implantasi and embriogenesis

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