All eutherian mammals possess placenta. Human placenta is discoid, chorio-deciduate organ. Maternal and fetal tissue come in direct contact without rejection. It presents foetal and maternal surfaces and peripheral margins.

1. Dr. Padamjeet

2. placenta
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3. placenta
• All eutherian mammals possess placenta.
• Human placenta is discoid, chorio-deciduate organ.
• Maternal and fetal tissue come in direct contact without
rejection.
• It presents foetal and maternal surfaces and peripheral
margins.
• Measurements
– Diameter 15-20cm
– Thickness 3cm (at center)
– Weight 500gms.
– Proprotional wt between placenta and foetus.
• 1st month 6:1
• 4th month 1:1
• At birth 1:7
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4. placenta
• The placenta is the primary site of nutrient
and gas exchange between the mother and
fetus.
• The placenta is a fetomaternal organ that has
two components:
– A fetal part that develops from the chorionic sac
– A maternal part that is derived from the
endometrium
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5. placenta
• It has two parts:
– The fetal part of the placenta is formed by the
villous chorion. The chorionic villi that arise from it
project into the intervillous space containing
maternal blood.
– The maternal part of the placenta is formed by
the decidua basalis, the part of the decidua
related to the fetal component of the placenta.
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6. The Decidua
• Decidua refers to the gravid endometrium, the
functional layer of the endometrium in a pregnant
woman that separates from the remainder of the
uterus after parturition (childbirth).
• The three regions of the decidua are named according
to their relation to the implantation site
– The decidua basalis is the part of the decidua deep to the
conceptus that forms the maternal part of the placenta.
– The decidua capsularis is the superficial part of the
decidua overlying the conceptus.
– The decidua parietalis is all the remaining parts of the
decidua.
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7. Parts of Decidua
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8. Chorionic villi
• It cover the entire chorionic sac until the
beginning of the eighth week.
• As this sac grows, the villi associated with the
decidua capsularis are compressed, reducing the
blood supply to them. These villi soon degenerate
producing a relatively avascular bare area, the
smooth chorion.
• As these villi disappear, those associated with the
decidua basalis rapidly increase in number,
branch profusely, and enlarge. This bushy area of
the chorionic sac is the villous chorion
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9. Maternal surface
15- 30
Polygonal area
Peripheral
margin
Continuous
With fetal
membranes
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10. Foetal surface
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11. Structure of placenta
• Chorionic plate (foetal side)
• Basal plate(maternal side)
• Stem villi extending between the plates
• Intervilli spaces between the stem villi
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13. Chorionic plate
• Composed of following structure from within
outward( foetal to mother)
– Primary mesoderm containing branches of
umbilical vessels(foetal)
– Cytotrophoblast
– syncytiotrophoblast
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14. Basal plate
• Consist of from outside inwards(mother to
foetus)
– Stratum spongiosum of decidua basalis
– Outer layer of syncytiotrophoblast which undergoes
fibrinoid degeneration (Nitabuch’s layer).
– Outer shell of cytotrophoblast
– Inner layer of syncytiotrophoblast; it also undergoes
fibrinoid degeneration (Rohr’s stria).
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15. Placental barrier
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16. Constituents of Placental Membrane
The placental membrane is made up of five layers.
From the maternal side to fetal side these are:
• Syncytiotrophoblast
• Cytotrophoblast (up to 20 weeks)
• Basement membrane of cytotrophoblast
• Mesoderm in the core of villus
• Endothelium and basement membrane of fetal
capillaries.
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17. Placental circulation
• The branch chorionic villi provide a large
surface area for exchange across the very thin
placental membrane ("barrier") interposed
between the fetal and maternal circulations,
consisting of extrafetal tissues.
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18. Fetal Placental Circulation
• Poorly oxygenated blood leaves the fetus and passes
through the umbilical arteries to the placenta. At the site of
attachment of the umbilical cord to the placenta, these
arteries divide into several radially disposed chorionic
arteries that branch freely in the chorionic plate before
entering the chorionic villi. The blood vessels form an
extensive arteriocapillary-venous system within the
chorionic villi.
• There is normally no intermingling of fetal and maternal
blood. The well-oxygenated fetal blood in the fetal
capillaries passes into thin-walled veins that follow the
chorionic arteries to the site of attachment of the umbilical
cord. They converge here to form the umbilical vein. This
large vessel carries oxygen-rich blood to the fetus.
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19. Maternal Placental Circulation
• The blood flow from the spiral arteries is pulsatile and is
propelled in the intervillous space and spurts toward the
chorionic plate forming the "roof" of the intervillous space.
• As the pressure dissipates, the blood flows slowly over the branch
villi, allowing an exchange of metabolites and gases.
• The blood eventually returns through the endometrial veins to
the maternal circulation.
• Reductions of uteroplacental circulation result in fetal hypoxia
and intrauterine growth restriction (IUGR).
• The intervillous space contains approximately 150 mL of blood
that is replenished 3 to4 times per minute.
• The intermittent contractions of the uterus during pregnancy
decrease uteroplacental blood flow.
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22. According to the tissues forming the placental barrier,
placenta may be classified phylogenetically as
follows:
(1) Epithelio-chorial (e. g. Pig) -
Here endometrial epithelium
remains intact, and the foetal
and maternal tissues come in
direct contact only. No part of
the decidua is shed at full
term. Hence, this type of
placenta is called non-
deciduate
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23. (2) Syndesmo-chorial (e. g:
Bovine) Endometrial
epithelium disappears, and
the chorion is separated
from the maternal blood by
endometrial stroma and
endothelium of maternal
capillaries.
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24. (3) Endothelio-chorial (e.
g. Dog) - Foetal chorion
erodes the endometrial
stroma upto the
endothelium of the
maternal vessels.
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25. • (4) Haemo-chorial (e.
g. Man) - Here the
endothelium of the
maternal vessels
disappears by the
corrosive action of
the chorion. Maternal
blood directly comes
in contact with the
chorion and its villi
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26. (5) Haemo-endothelial (e.g.
Rabbit) - this is one step
more advanced in
development than human
placenta. The trophoblastic
cells of the chorion
degenerate to such an extent
that only endotheliun of the
foetal vessels intervenes
between maternal and foetal
blood.
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27. • Endothelial-
endothelial
Maternal
vessels
Foetal
vessels
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28. Placental macrophages (Hofbauer cells)
are located close to trophoblast cells and
fetal capillaries, which makes them ideal
candidates for involvement in regulatory
processes within the villous core. They
have a role in production of various
cytokines and prostaglandin (PG)
synthesizing enzymes.
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29. Functions of the Placenta
• The placenta has three main functions:
– Metabolism (e.g., synthesis of glycogen)
– Transport of gases and nutrients
– Endocrine secretion (e.g., human chorionic
gonadotropin hCG)
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30. Umbilical cord
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33. Classification of Placenta :
According to the attachment of the umbilical cord -
(1) Battle-dore placenta, when the umbilical cord is attached close to
the margin of placenta
(2) Velamentous placenta, when the cord fails to reach the placenta
and is attached to the
foetal membrane close to the periphery of the organ.
Battle-dore placenta Velamentous placenta
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34. According to the site of
implantation:
Placenta praevia - This
condition takes place when
the blastocyst is implanted
in the lower part of the
uterine cavity overlapping
the internal os of the
cervix. This produces
serious haemorrhage
before parturition. The
placenta praevia may be
central or marginal
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35. • Accessory placenta -. Sometimes an
accessory lobe of placenta (Placenta
succenturiata) is connected to the
main mass by foetal membrane.
• According to the degree of adhesion
or penetration -
(1) Placenta accreta, when it is adhered
pathologically to the decidua basalis.
(2) Placenta incerta, when it penetrates
into the myometrium.
(3) Placenta perceta, when it penetrates
the entire uterine wall.
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36. • According to the shape-
(1) Lobed placenta - It may
exhibit two or more
lobes.
(2) Placenta membranacea
- It is diffuse and thin,
and the chorionic villi
project from the entire
blastocyst cavity.
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(3) Circumvallate - The peripheral margin of
the placenta is surrounded by a sulcus and
is overlapped by a circular fold of decidua.
(4) fenestrated-

37. According to the distribution of the umbilical
arteries -
(1) Disperse type - The umbilical arteries divide
in dichotomous manner and undergo
successive reduction in calibre.
(2) Magistral type- The arteries maintain almost
a uniform calibre upto the periphery of the
placenta and give off a number of smaller side
branches.
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