Presented by: Ahmad mukhtar Consultant and Lecturer of Obstetrics and Gynecology, Faculty of MEDICINE, Zagazig University.

1. ‫ةةةةةة‬:
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2. Presented by
Ahmed MukhtarAhmed Mukhtar
MD.,M.B.B.Ch., M.Sc Obstetrics and GynecologyMD.,M.B.B.Ch., M.Sc Obstetrics and Gynecology
Consultant and Lecturer of Obstetrics and Gynecology, Faculty ofConsultant and Lecturer of Obstetrics and Gynecology, Faculty of
MEDICINE, Zagazig UniversityMEDICINE, Zagazig University..
Implantation,conception,Implantation,conception,
development of placenta anddevelopment of placenta and
establishment ofestablishment of
fetomaternal circulationfetomaternal circulation

3. GametogenesisGametogenesis
Maturation of two highly specialized cellsMaturation of two highly specialized cells
spermetozoon in males and ovum inspermetozoon in males and ovum in
femalesfemales

4. Oogenesis- Development of matureOogenesis- Development of mature
ovumovum
In female gonad , the germ cells undergo rapid mitotic division andIn female gonad , the germ cells undergo rapid mitotic division and
differentiate into oogoniadifferentiate into oogonia
↓↓
Oogonia enter into prophase of first meiotic division - Primary oocytesOogonia enter into prophase of first meiotic division - Primary oocytes
↓↓
Primary oocytes do not finish the first meiotic division until puberty isPrimary oocytes do not finish the first meiotic division until puberty is
reachedreached
↓↓
Primary oocyte undergoes first meiotic division – secondary oocyte andPrimary oocyte undergoes first meiotic division – secondary oocyte and
first polar bodyfirst polar body
↓↓
Ovulation occurs soon after the formation of the secondary oocyteOvulation occurs soon after the formation of the secondary oocyte
↓↓
Secondary oocyte completes the second meoitic division after fertilizationSecondary oocyte completes the second meoitic division after fertilization
by the sperm in falliopian tube- ovum and second polar body. In theby the sperm in falliopian tube- ovum and second polar body. In the
absence of fertilization the secondary oocyte does not complete theabsence of fertilization the secondary oocyte does not complete the
second meiotic divison and degeneratesecond meiotic divison and degenerate

5. OvulationOvulation
•Is the process whereby secondary oocyte isIs the process whereby secondary oocyte is
released from the ovary following rupture ofreleased from the ovary following rupture of
mature graaafian follicle and become availablemature graaafian follicle and become available
for conceptionfor conception
•Only one secondary oocyte is likely to rupture inOnly one secondary oocyte is likely to rupture in
each ovarian cycle which starts at puberty andeach ovarian cycle which starts at puberty and
ends in menopauseends in menopause
•In relation to the menstrual period event occursIn relation to the menstrual period event occurs
about 14 days prior to the expected periodabout 14 days prior to the expected period

6. Changes in the follicle beforeChanges in the follicle before
ovulationovulation
• -Graafian follicle becomes enlarged ( 20mm )-Graafian follicle becomes enlarged ( 20mm )
• Follicular wall near the ovarian surface becomesFollicular wall near the ovarian surface becomes
thinner.thinner.
• -Stigma develops as conical projection which-Stigma develops as conical projection which
penetrates the outer surface of the ovary andpenetrates the outer surface of the ovary and
persist as thin layerpersist as thin layer
• -Cumulus escapes out of the follicle as a slow-Cumulus escapes out of the follicle as a slow
oozing, process taking about 1-2 minoozing, process taking about 1-2 min
• -Stigma is closed by a plug of plasma-Stigma is closed by a plug of plasma

7. Changes in oocyte before ovulationChanges in oocyte before ovulation
• Increase in cytoplasmic volumeIncrease in cytoplasmic volume
• Changes in the number and distribution ofChanges in the number and distribution of
mitochondria and in the Golgi apparatusmitochondria and in the Golgi apparatus
• Completion of arrested first meiotic divisionCompletion of arrested first meiotic division
occurs with formation of secondary oocyte andoccurs with formation of secondary oocyte and
first polar body each containing haploid numberfirst polar body each containing haploid number
of chromosomes(23X )of chromosomes(23X )

8. Cause of ovulationCause of ovulation
Combined FSH/LH midcycle surge is responsible for the final stage ofCombined FSH/LH midcycle surge is responsible for the final stage of
maturation, rupture of the follicle and expulsion of the oocytematuration, rupture of the follicle and expulsion of the oocyte
LH surge-LH surge-
• Sustained peak levels of oestrogen for 24-36 hours in the lateSustained peak levels of oestrogen for 24-36 hours in the late
follicular phase cause LH surge from anterior pitutary.follicular phase cause LH surge from anterior pitutary.
• Ovulation occurs apprx 16-24 hours after LHsurgeOvulation occurs apprx 16-24 hours after LHsurge
• LH stimulates completion of reduction division of the oocyte,initiatesLH stimulates completion of reduction division of the oocyte,initiates
leutinisation of the granulosa cells, synthesis of progestrone andleutinisation of the granulosa cells, synthesis of progestrone and
prostaglandinsprostaglandins

9. FSH riseFSH rise
• Preovulatory rise of progestrone facilitates thePreovulatory rise of progestrone facilitates the
positive feed back action of estrogen to inducepositive feed back action of estrogen to induce
FSH surgeFSH surge
• FSH surge causes increase in plasminogenFSH surge causes increase in plasminogen
activator which converts plasminogen intoactivator which converts plasminogen into
plasmin , which in turn causes lysis of the wall ofplasmin , which in turn causes lysis of the wall of
the folliclethe follicle

10. Structure of a mature ovumStructure of a mature ovum
• Largest cell in the bodyLargest cell in the body
• Consists of cytoplasm and a nucleus with its nucleolus in eccentricConsists of cytoplasm and a nucleus with its nucleolus in eccentric
positionposition
• Contains 23 chromosomes (23 X )Contains 23 chromosomes (23 X )
• Sorrounded by a cell membrane called a vitelline membraneSorrounded by a cell membrane called a vitelline membrane
• Outer transparent mucoprotein envelope is called zona pellucidaOuter transparent mucoprotein envelope is called zona pellucida
• Tiny channels in zona pellucida are for the transport of the materialsTiny channels in zona pellucida are for the transport of the materials
from the granulosa cells to the oocytefrom the granulosa cells to the oocyte
• Space between the vitelline membrane and zona pellucida is calledSpace between the vitelline membrane and zona pellucida is called
perivitelline space which accomodates the polar bodiesperivitelline space which accomodates the polar bodies

11. SpermatogenesisSpermatogenesis
• Spermatogenesis-Development of spermatidsSpermatogenesis-Development of spermatids
from the primodial male germ cells and theirfrom the primodial male germ cells and their
differenciation into spermatozoadifferenciation into spermatozoa
• In man time required for a spermatogonium toIn man time required for a spermatogonium to
develop into a mature spermatozoon is aboutdevelop into a mature spermatozoon is about

12. SpermatogenesisSpermatogenesis
• Primodial germ cells undergo mitosis in seminiferous tubules toPrimodial germ cells undergo mitosis in seminiferous tubules to
develop into spermatogoniadevelop into spermatogonia
• ↓↓
• Spermatogonia differenciates into primary spermatocytes (46 XY)Spermatogonia differenciates into primary spermatocytes (46 XY)
which remain in the stage of prophase of the first meiotic divisionwhich remain in the stage of prophase of the first meiotic division
• ↓↓
• With completion of first meiotic division – two secondaryWith completion of first meiotic division – two secondary
spermatocytes are formed( 23 X or 23 Y )spermatocytes are formed( 23 X or 23 Y )
• ↓↓
• Immediately follows the second meiotic division- 4 spermatids areImmediately follows the second meiotic division- 4 spermatids are
formed, containing haploid number of chromosomesformed, containing haploid number of chromosomes
• ↓↓
• Spermatids undergo extensive morphological changes to convertSpermatids undergo extensive morphological changes to convert
them into spermatozoathem into spermatozoa

13. Structure of a matureStructure of a mature
spermatozoonspermatozoon
• It has head and a tailIt has head and a tail
• Head consist of nucleus and a acrosomalHead consist of nucleus and a acrosomal
cap,rich in enzymescap,rich in enzymes
• The tail is divided into four zones-The tail is divided into four zones-
neck,middle piece,the principal piece andneck,middle piece,the principal piece and
the end piece.the end piece.

14. Sperm capacitation and acrosomeSperm capacitation and acrosome
reactionreaction
• Capacitation is the physiochemical change inCapacitation is the physiochemical change in
the sperm by which sperm become hypermotilethe sperm by which sperm become hypermotile
and is able to bind and fertilize a secondaryand is able to bind and fertilize a secondary
oocyteoocyte
• Activation of acrosomal enzyme causes releaseActivation of acrosomal enzyme causes release
of hyaluronidase, hydrolytic enzymes,of hyaluronidase, hydrolytic enzymes,
proacrosin,acrosin that help the sperm to digestproacrosin,acrosin that help the sperm to digest
the zona pellucida and to enter the oocytethe zona pellucida and to enter the oocyte

15. FertilizationFertilization
• Is the process of fusion of spermatzoon with the matureIs the process of fusion of spermatzoon with the mature
ovumovum
• Fertilization occurs in the ampullary part of the uterineFertilization occurs in the ampullary part of the uterine
tubetube
• Ovum , following ovulation is picked by tubal fimbriaeOvum , following ovulation is picked by tubal fimbriae
and is transported to the ampullary partand is transported to the ampullary part
• Out of the hundreds of millions sperm deposited in theOut of the hundreds of millions sperm deposited in the
vagina at single ejaculation only thousand capacitatedvagina at single ejaculation only thousand capacitated
spermatozoa enter the tube while only 300-500 reachspermatozoa enter the tube while only 300-500 reach
the ovumthe ovum

16. • Fertilisable life span of oocyte ranges from 12-24 hoursFertilisable life span of oocyte ranges from 12-24 hours
where as that of sperm is 48-72 hourswhere as that of sperm is 48-72 hours
• Complete disolution of the cells of the corona radiataComplete disolution of the cells of the corona radiata
occurs by the chemical action of the hyaluronidaseoccurs by the chemical action of the hyaluronidase
liberated from the acrosomal cap of the spermsliberated from the acrosomal cap of the sperms
• Penetration of the zona pellucida is facilitated by thePenetration of the zona pellucida is facilitated by the
release of hyaluronidase from the acrosomal caprelease of hyaluronidase from the acrosomal cap
• After the one spermatozoon has entered the ovum ,After the one spermatozoon has entered the ovum ,
others are prevented from entering by zona reactionothers are prevented from entering by zona reaction

17. • Completion of the second meiotic division of theCompletion of the second meiotic division of the
oocyte immediately follows resulting in theoocyte immediately follows resulting in the
female pronucleus (23 X) and 2female pronucleus (23 X) and 2ndnd
polar bodypolar body
• At the same time the head of the spermetazoaAt the same time the head of the spermetazoa
separates from middle piece and tail andseparates from middle piece and tail and
transforms into male pronucleus (23Xor 23Y)transforms into male pronucleus (23Xor 23Y)

18. • Male and female pronucleus unite at theMale and female pronucleus unite at the
center resulting in formation of zygote (46center resulting in formation of zygote (46
XX or 46XY)XX or 46XY)
• Sex of the child will depend on the patternSex of the child will depend on the pattern
of sex chromosome supplied by the spermof sex chromosome supplied by the sperm

19. CleavageCleavage
• RepeatedRepeated mitoticmitotic division ofdivision of
zygotezygote
• Begins aboutBegins about 30 hours30 hours afterafter
fertilizationfertilization
• There is rapid increase inThere is rapid increase in
number of cells. The cells,number of cells. The cells,
blastomeresblastomeres, become smaller, become smaller
with each divisionwith each division
• Normally occurs as the zygoteNormally occurs as the zygote
passes along the uterine tubepasses along the uterine tube
to the uterusto the uterus
• During cleavage, zygote liesDuring cleavage, zygote lies
within thewithin the zona pellucidazona pellucida

20. Cleavage cont’dCleavage cont’d
• 16 cell stage is called morula.16 cell stage is called morula.
It is formed about 3 days afterIt is formed about 3 days after
fertilization and enters thefertilization and enters the
uterusuterus
• Internal cells of the morula,Internal cells of the morula,
inner cell mass, areinner cell mass, are
surrounded by a layer of cellssurrounded by a layer of cells
that form the outer cell massthat form the outer cell mass
• Outer cell layer later give riseOuter cell layer later give rise
to trophoblast and inner cellto trophoblast and inner cell
mass give rise to embryomass give rise to embryo
properproper

21. Cleavage cont’dCleavage cont’d
• Fluid filled space called theFluid filled space called the
blastocyst cavity (blastocele)blastocyst cavity (blastocele)
appears inside morulaappears inside morula
• Blastomeres are separated into:Blastomeres are separated into:
 Outer cell layer, theOuter cell layer, the
trophoblasttrophoblast, which gives rise, which gives rise
to embryonic part of placentato embryonic part of placenta
 Centrally located,Centrally located, inner cellinner cell
mass (embryoblasts)mass (embryoblasts) whichwhich
gives rise to embryogives rise to embryo

22. Cleavage cont’dCleavage cont’d
• At this stage, theAt this stage, the
conceptus is calledconceptus is called
BlastocystBlastocyst. It has two. It has two
poles:poles: embryonicembryonic &&
abembryonicabembryonic
• Zona pellucidaZona pellucida graduallygradually
degenerates anddegenerates and
disappears soon after thedisappears soon after the
morula reaches the uterinemorula reaches the uterine
lumenlumen
• Blastocyst takes itsBlastocyst takes its
nourishment fromnourishment from uterineuterine
secretionssecretions and enlarges inand enlarges in
size. It is ready to getsize. It is ready to get
attached and implanted toattached and implanted to
the uterine wallthe uterine wall
Abembryonic pole
Embryonic pole

23. Formation of germ layers , chorionFormation of germ layers , chorion
and amnionand amnion
• Some cells of the inner cell mass become flattened andSome cells of the inner cell mass become flattened and
come to lie on its free surface and constitute thecome to lie on its free surface and constitute the
endodermendoderm
• Remaining cells of inner cell mass become columnarRemaining cells of inner cell mass become columnar
and constitute the ectodermand constitute the ectoderm
• A space appears between the ectoderm and theA space appears between the ectoderm and the
trophoblast . This is the amniotic cavity filled by amniotictrophoblast . This is the amniotic cavity filled by amniotic
fluidfluid
• The roof of the cavity is formed by amniogenic cellsThe roof of the cavity is formed by amniogenic cells
derived from the trophoblast, while its floor is formed byderived from the trophoblast, while its floor is formed by
the ectodermthe ectoderm

24. • Flattened cells arising from the endodermFlattened cells arising from the endoderm
spread and line the inside of the blastocysticspread and line the inside of the blastocystic
cavitycavity
• In this way , a cavity lined on all sides by cells ofIn this way , a cavity lined on all sides by cells of
endodermal origin is formed. This cavity is calledendodermal origin is formed. This cavity is called
primary yolk sacprimary yolk sac
• Cells of the trophoblast give origin to a mass ofCells of the trophoblast give origin to a mass of
cells called extra-embryonic mesoderm orcells called extra-embryonic mesoderm or
primary mesodermprimary mesoderm
• These cells come to lie between the trophoblastThese cells come to lie between the trophoblast
and the flattened endodermal cells lining the yolkand the flattened endodermal cells lining the yolk
sacsac

25. The process by which theThe process by which the
developing mass getsdeveloping mass gets
embedded within the uterineembedded within the uterine
wallwall

26. ImplantationImplantation
• BeginsBegins 6 days6 days afterafter
fertilization:fertilization:
 The blastocyst attaches toThe blastocyst attaches to
the endometrial epithelium,the endometrial epithelium,
usually adjacent to theusually adjacent to the
embryonic poleembryonic pole
 The blastocyst goes deeperThe blastocyst goes deeper
and deeper into the uterineand deeper into the uterine
mucosa till whole of it comesmucosa till whole of it comes
to lie with in the thickness ofto lie with in the thickness of
the endometrium. This isthe endometrium. This is
called interstitial implantationcalled interstitial implantation

27. Implantation cont’dImplantation cont’d
• By the end ofBy the end of 77thth
dayday, the, the
blastocyst getsblastocyst gets
implanted in theimplanted in the
superficial compactsuperficial compact
layer of endometriumlayer of endometrium
and derives itsand derives its
nourishment from thenourishment from the
eroded endometriumeroded endometrium

28. Implantation cont’dImplantation cont’d
• The blastocyst graduallyThe blastocyst gradually
embeds deeper in theembeds deeper in the
endometriumendometrium
• ByBy 1010thth
dayday it is completelyit is completely
buried within theburied within the
‘Functional layer’ (stratum‘Functional layer’ (stratum
compactum + stratumcompactum + stratum
spongiosum) of thespongiosum) of the
endometriumendometrium

29. Normal Implantation SitesNormal Implantation Sites
The implantation siteThe implantation site
determines the site ofdetermines the site of
formation of theformation of the
placentaplacenta
Normally it occurs inNormally it occurs in
thethe upper part of theupper part of the
body of uterusbody of uterus, more, more
often on theoften on the posteriorposterior
wallwall

30. • After the implantation of the embryo, the uterineAfter the implantation of the embryo, the uterine
endometrium is called the deciduaendometrium is called the decidua
• When the morula reaches the endometrium , it isWhen the morula reaches the endometrium , it is
in the secretory phasein the secretory phase
• After implantation , features of the endometriumAfter implantation , features of the endometrium
in secretory phase are intensified- stromal cellsin secretory phase are intensified- stromal cells
enlarged , become vacuolated and storeenlarged , become vacuolated and store
glycogen and lipids. This change in stromal cellsglycogen and lipids. This change in stromal cells
is called decidual reactionis called decidual reaction

31. • The portion of the decidua where the placenta isThe portion of the decidua where the placenta is
to be formed ( deep to the developingto be formed ( deep to the developing
blastocyst ) is called decidua basalisblastocyst ) is called decidua basalis
• Part of the decidua that separates the embryoPart of the decidua that separates the embryo
from the uterine lumen is called deciduafrom the uterine lumen is called decidua
capsulariscapsularis
• Part of the decidua lining the rest of the uterinePart of the decidua lining the rest of the uterine
cavity is called decidua parietaliscavity is called decidua parietalis

32. Formation of the chorionic villiFormation of the chorionic villi
• The essential functional elements of the placenta areThe essential functional elements of the placenta are
very small finger like processes or villivery small finger like processes or villi
• These villi are surrounded by maternal bloodThese villi are surrounded by maternal blood
• In the subustance of the villi, there are capillariesIn the subustance of the villi, there are capillaries
through which fetal blood circulatesthrough which fetal blood circulates
• Exchanges between maternal and fetal circulations takeExchanges between maternal and fetal circulations take
place through the tissues forming the walls of the villiplace through the tissues forming the walls of the villi

33. • The villi are formed as offshoots from the surface of theThe villi are formed as offshoots from the surface of the
trophoblasttrophoblast
• As the trophoblast along with the underlying extra-As the trophoblast along with the underlying extra-
embryonic mesoderm constitutes chorion, the villi areembryonic mesoderm constitutes chorion, the villi are
known as chorionic villiknown as chorionic villi
• Chorionic villi are first formed all over the trophoblast andChorionic villi are first formed all over the trophoblast and
grow into the surrounding deciduagrow into the surrounding decidua
• Those related to decidua capsularis are transitory andThose related to decidua capsularis are transitory and
degenrate and this part of the chorion becomes smoothdegenrate and this part of the chorion becomes smooth
and is called chorion laevaeand is called chorion laevae

34. • The villi that grow into the decidua basalisThe villi that grow into the decidua basalis
undergo considerable developmentundergo considerable development
• Along with the tissues of the decidua basalisAlong with the tissues of the decidua basalis
these villi form a disc shaped mass which isthese villi form a disc shaped mass which is
called the placentacalled the placenta
• The part of the chorion that helps to form theThe part of the chorion that helps to form the
placenta is called the chorion frondosumplacenta is called the chorion frondosum

35. Formation of the chorionic villiFormation of the chorionic villi
 Trophoblast proliferates rapidlyTrophoblast proliferates rapidly
and differentiates into two layers:and differentiates into two layers:
 inner cellularinner cellular cytotrophoblastcytotrophoblast
or Langhan’s layeror Langhan’s layer
 outer mass ofouter mass of
syncytiotrophoblastsyncytiotrophoblast
(multinucleated protoplasm(multinucleated protoplasm
with no cell boundaries)with no cell boundaries)
 Finger like processes ofFinger like processes of
syncytiotrophoblastsyncytiotrophoblast extendextend
through the endometrium andthrough the endometrium and
invade the endometrialinvade the endometrial
connective tissueconnective tissue

36. Implantation cont’dImplantation cont’d
•Small cavities, theSmall cavities, the
lacunaelacunae appear inappear in
syncytiotrophoblast,syncytiotrophoblast,
and get filled withand get filled with
maternal blood,maternal blood,
establishingestablishing primitiveprimitive
uteroplacentaluteroplacental
circulationcirculation

37. • The syncitotrophoblast grows into the endometriumThe syncitotrophoblast grows into the endometrium
• As the endometrium is eroded , some of its bloodAs the endometrium is eroded , some of its blood
vessels are opened up and blood from them fills thevessels are opened up and blood from them fills the
lacunar spacelacunar space
• Each trabeculus is , initially, made up entirely ofEach trabeculus is , initially, made up entirely of
sycytiotrophoblastsycytiotrophoblast
• Later on, cells of cytotrophoblast grow into theLater on, cells of cytotrophoblast grow into the
trabeculus , followed by extra embryonic mesoderm andtrabeculus , followed by extra embryonic mesoderm and
blood vessels giving rise to primary villus, secondaryblood vessels giving rise to primary villus, secondary
villus and tertiary villus respectivelyvillus and tertiary villus respectively

38. • Blood vessels of the villus establish connectionsBlood vessels of the villus establish connections
with the circulatory system of the embryowith the circulatory system of the embryo
• Fetal blood now circulates through the villi, whileFetal blood now circulates through the villi, while
the maternal blood circulates through thethe maternal blood circulates through the
intervillous spaceintervillous space
• Intially cytotrophoblast that that grows into theIntially cytotrophoblast that that grows into the
trabeculus does not penetrate the entiretrabeculus does not penetrate the entire
thickness of syncytiumthickness of syncytium

39. • At a later stage ,cells of the cytotrophoblast emergeAt a later stage ,cells of the cytotrophoblast emerge
through the syncytium and spread out to form a layerthrough the syncytium and spread out to form a layer
that completely cuts off the syncytium from the deciduathat completely cuts off the syncytium from the decidua
and is called cytotrophoblastic cellsand is called cytotrophoblastic cells
• The villi that are first formed are attached on the fetalThe villi that are first formed are attached on the fetal
side to the embryonic mesoderm and on the maternalside to the embryonic mesoderm and on the maternal
side to the cytotrophoblastic shell and are calledside to the cytotrophoblastic shell and are called

40. • Each anchoring villus consists of a stem (truncusEach anchoring villus consists of a stem (truncus
chorii); this divides into a number of brancheschorii); this divides into a number of branches
( rami chorii ) which in turn divide into finer( rami chorii ) which in turn divide into finer
branches (ramuli chorii )branches (ramuli chorii )
• Anchoring villi give off numerous branches whichAnchoring villi give off numerous branches which
grow into the intervillous space as free villigrow into the intervillous space as free villi
• As a result , the surface area available forAs a result , the surface area available for
exchanges between maternal and fetalexchanges between maternal and fetal
circulation becomes enormouscirculation becomes enormous

41. Circulation of blood throughCirculation of blood through
placentaplacenta
• Maternal blood in the intervillous space isMaternal blood in the intervillous space is
constantly in circulationconstantly in circulation
• Both arteries and the vein open into theBoth arteries and the vein open into the
roof of the cotyledon and that the pressureroof of the cotyledon and that the pressure
of the blood in the artery is sufficient toof the blood in the artery is sufficient to
drive blood to the fetal end of thedrive blood to the fetal end of the
intervillious spaceintervillious space