related to placenta.
2. Explain abnormalities related to length of
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cord.
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? Placenta is a remarkable organ
? Has a relative short life span, it undergoes rapid
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growth ,differentiation and maturation.
? A unique fetal ?maternal communication
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system which creates a hormonal environmentthat helps initially to maintain pregnancy and
eventually initiates the events leading to
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parturition
The human placenta is:
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? Discoid
? Hemochorial
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? DeciduateDevelopment of placenta-
Two sources
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? Fetal ? chorion Frondosum
? Maternal- decidua basalis
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PLACENTA AT TERM:Placenta is a discoid organ
15 ? 20cm in diameter
3cm Thick at center
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Placental membrane
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Total area-4 to 14 sq mSimilar to absorbtive area in adult git
In later part of pregnancy the membrane
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thickness reduces from 0.025mm to0.002mm
Is classified as haemochorial
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PLACENTAL BARRIER
?
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Inspite of close proximity , there is no mixing of the maternaland fetal blood.
?
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They are separated by placental membranes or barrier.
PLACENTAL
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CIRCULATION
UTEROPLACENTAL
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FETOPLACENTALCIRCULATION
CIRCULATION
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UTEROPLACENTAL CIRCULATION? It is concerned with the circulation of maternal
blood through the intervillous space.
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? Divided in 3 parts
1. Arterial circulation
2. Venous drainage
3. Circulation in intervillous space
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? Blood in the intervil ous space is temporarily outside
maternal circulatory system.
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? These vessels discharge into the intervil ous space throughgaps in the cytotrophoblastic shel .
? Blood flowing from spiral arteries is pulsatile and is propel ed
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in jet-like fountains by the maternal blood pressure.
? Welfare of the embryo and fetus chiefly depends on adequate
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bathing of branch vil i with maternal blood.? Reduction in utero-placental circulation result in fetal hypoxia
and IUGR.
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Arterial circulation
? About 120-200 spiral arteries open into
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intervillous space.Spiral artery remodelling
? There is cytotrophoblastic invasion into the spiral
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arteries upto the intradecidual portion within
12weeks of pregnancy.
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? Endothilial and muscoelastic media is destroyedand replaced by fibrinoid material
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? There is secondary invasion of trophoblast between12-16 weeks.
? It extends upto the radial arteries within the
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myometrium.
? SPIRAL ARTERIES are remodled into large bore
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UTEROPLACENTAL ARTERIES.INTERVILLOUS HEMODYNAMICS
Volume of blood in mature placenta
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500mlVolume of blood in intervil ous space
150ml
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Blood flow in intervil ous space
150ml
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Pressure in intervil ous space1) During uterine contraction
30-50mm Hg
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2)During uterine relaxation
10-15mm Hg
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Pressure in supplying uterine artery70-80mm Hg
Pressure in draning uterine vein
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8mm Hg
FETOPLACENTAL CIRCULATION
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? Two umbilical arteries enter the chorionic plate
underneath the amnion, each supplying one half of
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placenta.? The arteries breakup into small branches which
enter the stems of chorionic villi.
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? Each in turn divides the primary, secondary and
tertiary vessels of the corresponding villi.
? This system provides a very large area for
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exchange of metabolic and gaseous products
between maternal and fetal blood streams.
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? Well-oxygenated fetal blood in fetal capillariespasses into thin walled veins.
? This follow chorionic arteries to site of
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attachment of the umbilical cord, where they
converge to form umbilical vein.
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? This large vessel carries oxygen-rich blood tothe fetus.
One (usual) or more smal lobes of placenta, size of
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cotyledon, may be placed at varying distances fromthe placental margin.
In cases of absence of communicating blood
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vessels, it is called placenta spuria.
Incidence: 3%
If the succenturiate lobe is retained, fol owing
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birth of the placenta, it may lead to:
1. Postpartum haemorrhage
2. Subinvolution
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3. Uterine sepsis4. Polyp formation
Whenever the diagnosis of missing lobe is made,
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exploration of the uterus and removal of the lobeunder general anaesthesia is to be done.
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The fetal surface is divided into a central depressed zonesurrounded by a thickened white ring which is usualy
complete.
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Vessels radiate from the cord insertion as far as the
ring and then disappear from view.
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The peripheral zone outside the ring is thickerand the edge is elevated and rounded.
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There is increased chance of:Abortion
Antepartum haemorrhage FGR
baby
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Preterm deliveryRetained placenta or membranes
? Encroachment of some part over the lower segment.
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? Imperfect separation in the third stage.
? Chance of retained placenta is more and manual removal becomes difficult.
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? These abnormalities are serious variations in which trophoblastic tissues invade the
myometrium to varying depths.
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? They are much more likely with placenta previa or with implantation over a prior uterineincision or perforation.
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The condition is usually associated? when the placenta is implanted in lower segment
(Placenta praevia)
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or over the previously injured sites as in caesarean
section
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?dilatation and curettage operation? manual removal
?myomectomy
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The diagnosis is only made
? during attempted manual removal when the plane
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of cleavage between the placenta and uterine wallcannot be made out.
? Ultrasound imaging, colour Doppler and MRI have all
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been valuable in the diagnosis.
? Absence of decidua basalis
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? Absence of Nitabuch's fibrinoid layer
? Varying degree of penetration of the villi into the
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muscle bundle (increta) or upto the? serosal layer(percreta).
? The risk includes hemorrhage, shock,infection and
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rarely inversion of the uterus.
Abnormal length of cord
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Short cordLess than 20cm
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1. Prevent descent of the presenting partspecial y during labour
2. Separation of normal y situated placenta
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3. Favour malpresentation
4. Acute inversion
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5. Fetal growth restriction6. Intrapartum distress
7. Failure of external version
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8. Two fold risk of fetal death
Clinical Significance
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? cord prolapse? cord entanglement round the neck or the body
? True knot
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? False knots
Battledore placenta
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? The cord is attached to the margin of the placenta.
? If associated with low implantation of the placenta,
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there is chance of cord compression in vaginal deliveryleading to fetal anoxia or even death; otherwise, it has
got little clinical significance.
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Velamentous placenta
? The umbilical vessels spread within the membranes at
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a distance from the placental margin, which they reach
surrounded only by a fold of amnion.
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? Although their incidence is approximately 1 percent,velamentous insertion develops in more commonly
with placenta previa and multifetal gestations.
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If the leash of blood vessels happen to traverse through the
membranes overlying the internal os, infront of the presenting
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part,the condition is called vasa praevia.
? In the presence of fetal bleeding, urgent delivery is
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essential either vaginally or by caesarean section.
? The newborn's haemoglobin is estimated and if
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necessary, blood transfusion be carried out.? If the baby is dead, vaginal delivery is awaited.
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KnotsFalse Knots
False knots appear as knobs protruding from the cord
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surface and are focal redundancies of a vessel or Wharton
jelly, with no clinical significance.
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