The placenta and its abnormalities

bio

1. DR. R.E. MBU 2006DR. R.E. MBU 2006 11
THE PLACENTA AND ITS THE PLACENTA AND ITS
ABNORMALITIESABNORMALITIES
Dr. Robinson E. MbuDr. Robinson E. Mbu
Senior LecturerSenior Lecturer

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PLANPLAN
IntroductionIntroduction
ObjectivesObjectives
StructureStructure
Foetal circulationFoetal circulation
Maternal circulationMaternal circulation
FunctionsFunctions
The placental unitThe placental unit
Placental abnormalitiesPlacental abnormalities
The umbilical cordThe umbilical cord

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INTRODUCTIONINTRODUCTION
The concept of placenta was first introduced The concept of placenta was first introduced
by by REALDUS COLUMBUSREALDUS COLUMBUS in 1559 in 1559
MOSSMANMOSSMAN defined the placenta in 1937defined the placenta in 1937
As that part of the foetal membranes fused As that part of the foetal membranes fused
to the uterine mucosato the uterine mucosa
EmbryologicallyEmbryologically
Throphoblasts are formed Throphoblasts are formed
By the blastocystBy the blastocyst
As early as 72hrs. after fertilizationAs early as 72hrs. after fertilization

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INTRODUCTION cont’dINTRODUCTION cont’d
The throphoblasts proliferate rapidlyThe throphoblasts proliferate rapidly
And invade the surrounding deciduaAnd invade the surrounding decidua
Soon after implantationSoon after implantation
As invasion of the endometrium As invasion of the endometrium
proceedsproceeds
Maternal blood vessels are invadedMaternal blood vessels are invaded
Forming intervillous spacesForming intervillous spaces

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OBJECTIVESOBJECTIVES
Holistic understanding of the placentaHolistic understanding of the placenta
–StructureStructure
–FunctionFunction
–Abnormal forms Abnormal forms
–Etc.Etc.

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STRUCTURESTRUCTURE
Measures Measures 15-20cm15-20cm in diameter in diameter
2-3cm2-3cm thick thick
Weighs 1/6Weighs 1/6
thth
of the foetus ( ~ 500gms) of the foetus ( ~ 500gms)
Has two surfaces :Has two surfaces :
–Foetal surface which contains :Foetal surface which contains :
The shinning amnionThe shinning amnion
Under which are vessels plastered by the Under which are vessels plastered by the
chorionchorion
Both arteries and veinsBoth arteries and veins
Insertion of the umbilical cordInsertion of the umbilical cord

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STRUCTURE cont’dSTRUCTURE cont’d
Maternal surface:Maternal surface:
–Contains irregular lobes Contains irregular lobes
–Divided by septaDivided by septa
–Made up of connective tissueMade up of connective tissue
–There are usually 16-18 of these irregular lobesThere are usually 16-18 of these irregular lobes
–Called Called COTYLEDONSCOTYLEDONS
–Formed during placentogenesisFormed during placentogenesis
–They only become larger as pregnancy They only become larger as pregnancy
advancesadvances

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STRUCTURE cont’dSTRUCTURE cont’d
No new cotyledons are formed after No new cotyledons are formed after
this periodthis period
The placenta is located usuallyThe placenta is located usually
Anteriorly or posteriorlyAnteriorly or posteriorly
Near the fundusNear the fundus

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FOETAL CIRCULATIONFOETAL CIRCULATION
Foetal blood flows from the placentaFoetal blood flows from the placenta
Through two unbilical arteriesThrough two unbilical arteries
In which deoxygenated or venous In which deoxygenated or venous
blood is transportedblood is transported
The vessels branch repeatedly and The vessels branch repeatedly and
form capillary networksform capillary networks
In the terminalsIn the terminals
Oxygenated blood returns to the Oxygenated blood returns to the
foetus foetus

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FOETAL CIRCULATION cont’dFOETAL CIRCULATION cont’d
From the placentaFrom the placenta
Through the single umbilical veinThrough the single umbilical vein

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MATERNAL CIRCULATIONMATERNAL CIRCULATION
Maternal blood reaches the placentaMaternal blood reaches the placenta
Propelled by maternal arterial Propelled by maternal arterial
pressurepressure
There is no admixture of maternal and There is no admixture of maternal and
foetal bloodfoetal blood
Venous exits are scattered at randomVenous exits are scattered at random
Over the entire base of the placentaOver the entire base of the placenta

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FUNCTIONS OF THE FUNCTIONS OF THE
PLACENTAPLACENTA
Exchange functions:Exchange functions:
–Waste products from the placentaWaste products from the placenta
–Cross the placental membraneCross the placental membrane
–To the maternal bloodTo the maternal blood
–Oxygen, nutrients and protective Oxygen, nutrients and protective
antibodiesantibodies
–Leave from the mother across the Leave from the mother across the
placental membraneplacental membrane
–To the foetusTo the foetus

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PLACENTAL FUNCTIONS cont’dPLACENTAL FUNCTIONS cont’d
Endocrine functions:Endocrine functions:
–Chorionic gonadotropinChorionic gonadotropin
–HPLHPL
–Chorionic thyrotropinChorionic thyrotropin
–Chorionic adrenocorticotropinChorionic adrenocorticotropin
–Hypothalamic-like releasing hormones of Hypothalamic-like releasing hormones of
the placentathe placenta
–Pregnancy specific proteinPregnancy specific protein

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ENDOCRINE FUNCTIONS cont’dENDOCRINE FUNCTIONS cont’d
EstrogensEstrogens
ProgesteroneProgesterone
ProlactineProlactine

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PROTECTIVE FUNCTIONPROTECTIVE FUNCTION
Destroys the following :Destroys the following :
–BacteriaBacteria
–VirusesViruses
–PlasmodiumPlasmodium
–FungiFungi
–ETC.ETC.

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THE PLACENTAL UNITTHE PLACENTAL UNIT
VF=Foetal vessels, TC=Connective tissue VF=Foetal vessels, TC=Connective tissue
VM=Maternal vesselsVM=Maternal vessels

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PLACENTAL AGINGPLACENTAL AGING
Decrease in thickness of syncytiumDecrease in thickness of syncytium
Partial disappearance of cytotrophoblasts Partial disappearance of cytotrophoblasts
((LANGHANS CELLSLANGHANS CELLS))
Decrease in stromaDecrease in stroma
Thickening of basement of the endothelium Thickening of basement of the endothelium
and trophoblastsand trophoblasts
Obliteration of certain vesselsObliteration of certain vessels
Deposition of fibrin Deposition of fibrin
On the surface of the villi/intervillous spaceOn the surface of the villi/intervillous space
Decrease in efficiency of placental Decrease in efficiency of placental
exchangeexchange

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PACENTA ABNORMALITIESPACENTA ABNORMALITIES
Placenta Bipartita , TripartitaPlacenta Bipartita , Tripartita
Circumvallate or Circummarginate placentaCircumvallate or Circummarginate placenta
Succenturiate placentaSuccenturiate placenta
Battledore placentaBattledore placenta
Placenta acretaPlacenta acreta
Placenta incretaPlacenta increta
Placenta percretaPlacenta percreta
Placenta praevia Placenta praevia

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PLACENTA BIPARTITA , PLACENTA BIPARTITA ,
TRIPARTITATRIPARTITA
Two or three placentasTwo or three placentas
With equal dimensionsWith equal dimensions
Attached to one umbilical cordAttached to one umbilical cord
Clinical importance is that Clinical importance is that
One of them may left in-uteroOne of them may left in-utero
After a normal deliveryAfter a normal delivery

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BIPARTITE AND TRIPARTITE BIPARTITE AND TRIPARTITE
PLACENTASPLACENTAS
AnnotatedAnnotated

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CIRCUMVALLATE OR CIRCUMVALLATE OR
CIRCUMMARGINATE PLACENTACIRCUMMARGINATE PLACENTA
1% of placentas1% of placentas
Small central chorionic plate ( small Small central chorionic plate ( small
placenta)placenta)
Surrounded by a thick whitish ringSurrounded by a thick whitish ring
Composed of a double foldComposed of a double fold
Of amnion and chorionOf amnion and chorion
Predisposes to premature marginal Predisposes to premature marginal
separationseparation
APH, premature delivery, premature death.APH, premature delivery, premature death.

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CIRCUMVALLATE PLACENTACIRCUMVALLATE PLACENTA
AnnotatedAnnotated

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SUCCENTURIATE PLACENTASUCCENTURIATE PLACENTA
Inappropriately divided placentaInappropriately divided placenta
One large placentaOne large placenta
And a small ( succenturiate) lobeAnd a small ( succenturiate) lobe
Clinical significance is that the small Clinical significance is that the small
lobelobe
Could be forgotten in-uteroCould be forgotten in-utero
Following a normal delivery Following a normal delivery

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SUCCENTURIATE PLACENTASUCCENTURIATE PLACENTA
AnnotatedAnnotated

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BATTLEDORE PLACENTABATTLEDORE PLACENTA
Placenta Placenta
Where the cordWhere the cord
Is inserted marginallyIs inserted marginally
Clinical significance is that umbilical vesselsClinical significance is that umbilical vessels
Could run through membranesCould run through membranes
And may ruptureAnd may rupture
Causing foetal bleeding ( Causing foetal bleeding ( VASSA VASSA
PRAEVIAPRAEVIA ) )

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BATTLEDORE PLACENTABATTLEDORE PLACENTA
AnnotatedAnnotated

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THE CRETASTHE CRETAS
Placenta AcretaPlacenta Acreta
–Throphoblastic invasion of the Throphoblastic invasion of the
endometrial basement membrane endometrial basement membrane
Placenta IncretaPlacenta Increta
–Invasion of the myometriumInvasion of the myometrium
Placenta PercretaPlacenta Percreta
–Perforation of the uterusPerforation of the uterus
These are all histological diagnosesThese are all histological diagnoses

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PLACENTA PRAEVIAPLACENTA PRAEVIA
Presence of the placentaPresence of the placenta
In the lower uterine segment ( LUS)In the lower uterine segment ( LUS)
Formed from 28 weeks of gestationFormed from 28 weeks of gestation
Revisit Revisit PLACENTA PRAEVIAPLACENTA PRAEVIA

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THE UMBILICAL CORDTHE UMBILICAL CORD
30-100 cm long ( ~ 55 cm)30-100 cm long ( ~ 55 cm)
1-2.5 cm thick1-2.5 cm thick
Has two arteries and one veinHas two arteries and one vein
The vessels are embedded in a whitish The vessels are embedded in a whitish
substancesubstance
Called WHARTON JELLYCalled WHARTON JELLY
Inserted centrally , laterally or marginallyInserted centrally , laterally or marginally
There is also velamentous insertionThere is also velamentous insertion
This is a rare insertion This is a rare insertion

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THE UMBILICAL CORD THE UMBILICAL CORD
cont’dcont’d
In velamentous insertion:In velamentous insertion:
–The cord stops at some distance The cord stops at some distance
–Before sending down vesselsBefore sending down vessels
–Like the maize stemLike the maize stem
–These vessels could be found in the These vessels could be found in the
lower uterine segmentlower uterine segment
–And may bleed during contractions And may bleed during contractions
–Or vaginal examinationOr vaginal examination

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UMBILICAL CORD INSERTIONSUMBILICAL CORD INSERTIONS
AnnotatedAnnotated