placenta at term in obs for nursing students

2.  The human placenta is discoid,
haemochorial and deciduate
 The placenta is attached to the uterine
wall and establishes connection between
the mother and fetus through the
umbilical cord

3. Gross Anatomy: The placenta at term is:
a circular disc with diameter of 15-20cm
thickness : 2.5cm
Thin off towards the edge
Feels spongy
weighs: 500gm

4. Choronic plate
Decidua basalis
Intervillious space
Amniotic Membrane
Tertiary stem villi
Syncytiotrophoblast
Cyt otrophoblast
Chorion
laeve
Decidua parietalis
& capsularis
fused

5. It presents two surface
fetal & maternal peripheral margin
surface surface

6.  Fetal surface:
 Covered by smooth and glistening amnion with
the umbilical cord attached at or near its
centre
 At term about four fifth of the placenta is of
fetal origin

7.  Maternal surface :
 Rough and spongy
 Maternal blood gives it a dull red color
 Thin greyish layer: remnant of decidua basalis
 Is mapped out into 15-20 lobes or cotyledons

8.  Numerous small greyish spots are visible: due
deposition of calcium in the degenerated areas
 Only decidua basalis and the blood in the
intervillious space are of maternal origin

9.  PERIPHERAL MARGIN
It is limited by the fused basal and chorionic plates
and is continuous with the chorion laeve and
amnion. Essentially, the chorion and the placenta
are one structure but the placenta is specialised
part of the chorion

10.  Attachment:
 Attached to the upper part of
body of the uterus
encroaching to the fundus
adjacent to the anterior or
posterior wall
 The attachment to the
uterine wall is effective due
to the anchoring villi

11.  Separation
 Placenta separates
after the birth of the
baby and the line of
separation is through
the decidua
spongiosum

12. Amnion :
 It consists of single layer of cubical epithelium
loosely attached to the adjacent chorionic plate.
 It takes no part in formation of the placenta

13.  Helps in formation of amniotic fluid.
 Facilitate dilation of the cervix during
labour.
 Rich source of glycerophospholipids
containing arachidonic acid precursor of
prostaglandin.

14. CHORION
 It is thicker than amnion friable and shaggy
on both side.
 Internally it is attached to the amnion by
loose areolar tissue and remnant of
primitive mesenchyme.
 Externally it is covered by vestiges of
trophoblastic layer and the decidual cells of
the fused decidua capsularis and parietalis
which can be distinguished microscopically.
 The term chorion contains no vessels and
nerves.

15. The umbilical cord or funis forms the
connecting link between the fetus and
the placenta.
Characteristics
 Its about 50 cm in length an usual
variation of 30-100cm.
 Its diameter average 1.5cm with
variation of 1 – 2.5cm.
cont

16.  Its thickness is not uniform but presents
nodes or swelling at places, these
swelling are false knots may be due to
dilatation of the umbilical veins or local
collection of Wharton's jelly.
 It shows a spiral twist from the left to
right from as early as 12th wk due to
spiral turn taken by the vessels vein
around the arteries.

17.  Maternal circulation or utero placental
circulation:- The blood is deliverd to the
placental bed in the decidua by spiral arteries
and flow into the blood spaces surrounding the
villi. Its direction of flow is similar to fountain.
 fetal circulation:-fetal blood low in oxygen is
pumped by the fetal heart toward the placenta
along the umbilical arteries and transported
along their branches to the capillaries of the
chorionic villi. yielded up Co2 & absorbed
oxygen, the blood is returned to fetus via
umbilical vein.

18.  Dutta D.C. ‘text book of Obstetrics’, sixth
edition,Pp:28 to34 and 218 to 220
 Ostrzenski adam; gynaecology; Lippincott ;
Second edition ; pg no - 209-216 ,193
 www.sciencedirect.com/science/journal
 www.en. Wikipedia.org/wik/placenta
 www.placentajournal.org/