placenta and fetal membranes 2010 1

8/10/2019 Placenta and Fetal Membranes 2010 1

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PLACENTA AND THEFETAL MEMBRANES

(chorion,amnion, yolk sac, allantois)


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First !!k o" #!$!lo%m!nt

Oocyte(fertilization)zygote4-cell stage (2 days)morula(ball)blastocysteinner cell mass (embryo)

outer cell mass(trophoblast)

(extraembronic membranes)

From

oocyte to

blastocyst


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#&O30 "##$

#piblast and hypoblast

mnion and yol5 sac

!rophoblast%

yncytiotrophoblast% 6acunae appear in thesyncytiotrophoblast maternal blood flo1s into the

lacunae77uteroplacental circulation+2 day77ad8acent lacunae ad8acent lacunae ha'e fused to

form lacunar net1or5s gi'ing a sponge li5e appearance to the

!rophoblast

#ndometrium%aternal endometrial capillaries ha'e dilatedand become congested to form sinusoids

9rimary chorionic 'illi% cellular extensions of the cytotrophoblas in tothe syncytiotrophoblast


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!/IR0 "##$

!RI6I3R :#R 0I&

9RII!I;# !R#$* 3O!O&/OR0 30 3#


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Plac!nta

fetomaternal organ for nutrient and gas

exchange

Fetal portion% de'elops from the chorionic sacaternal portion% de'elops from the

endometrium7decidua


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F&NCT'NS

9rotection

3utrition

Respiration#xcretion

/ormone production


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DEC'D&A

!hree regions 0ecidua basalis% deep to conceptus 0ecidua capsularis% o'erlying the conceptus

0ecidua parietalis% the remainings the coneeptus enlarges the dicidua capsularis

bulges ingt he uteine ca'ity and e'entually contactsthe decidua paritalis* obliterating the uterine ca'ityand by 22-24 1ee5s it degenerates due to reduced

blood supply !he smooth chorion fuses 1ith the decidua

capsularis


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mooth chorion> in the eighth 1ee5 the 'illi in

the decidua capsularis become compressed

reducing blood supply to them producing a

relati'ely a 'ascular area the smooth chorion

or chorion la'ae

,ushy chorion%!he 'essels associated 1ith

the basalis branch profusely and enlargeforming bushy chorion or chorion frondosum


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9lacenta de'elops from the decidua basalis and the chorionfrondusom

It is usually discoid in shape

s the chorion in'ades the decidua se'eral 1edge shaped areasare formed in the decidua the placental septa theat pro8ectto1ard the chorionic plate !hese septa di'ide the fetal part ofthe placenta into irregular con'ex area called cotyledons

!he iner'illous space is di'ided by the into compartments by theplacental septa aternal blood enters the spaces through spiral

arteries and is drained into endometrial 'eins !he placental membrane% until 2? 1ee5s it consists of

syncytiotrophoblast* cytotrophoblast* connecti'e tissue of 'illi*endothelium of fetal capillaries

fter 2?th1ee5 cytotrophablast o'e rthe branch 'illi is attenuatedlea'ing patches of syncytiotrophoblast 3o1 th placental

membrane consists of three layers In some areas the placentalmembrane becomes extremely thin* at hese sites thesyncytiotrophoblast comes in direct contact 1ith the fetalcapillary endothelium


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@Implantation 1ith inner cell mass to1ards uterine 1all@!rophoblast

@&ytotrophoblast777cells around the inner cell mass@yncytiotrophoblast7syncytium of cells that becomes placenta


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Plac!nta "ormation

6acunae form 1ithin synctiotrophoblast--maternal blood fillsthese spaces

;ili form 1ith embryonic capillaries do1n middle


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Plac!nta "ormation

;illi bathed in maternal blood in lacunae--exchange of nutrients* O2*&O2

fter + 1ee5s* full placenta--panca5e-shaped organ


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th!r !tra!m*ryonic tiss+!s &ellular trophoblast forms

amnion* yol5 sac Fetal cells shed into amniotic

ca'ity 1hich fills 1ith fluidfrom fetal 5idneys extretedthrough ureter* bladder*urethra

mniocentesis--sample ofamniotic fluid ta5en 1ithhypodermic needle

9art of yol5 sac Asuc5edB intoembryo to form endermicbladder


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Em*ryo %ro%!r

I& forms hypoblast (yello1--becomes endoderm) and epitblast(blue--becomes ectoderm)

ee handout for all adultderi'ati'es of embryonic tissues--/O" FR "#C;# &O#DD

Animated movie of fetal deveopment

http://www.cvillepregnancy.org/fetal.html
http://www.cvillepregnancy.org/fetal.htmlhttp://www.cvillepregnancy.org/fetal.htmlhttp://www.cvillepregnancy.org/fetal.htmlhttp://www.cvillepregnancy.org/fetal.html


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Fig. 24.27


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placenta and fetal membranes 2010 1

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