placental development - Its process .ppt

The placenta develops gradually during pregnancy, starting from a few cells and growing into a vital organ that supplies oxygen and nutrients to the fetus.

2. PLACENTAL
DEVELOPMENT

3. INTRODUCTION
The placenta is the organ with dual origin.
A part of it develops from fetus ( chorion ) and part
from mother ( endometrium).

4. IMPLANTATION
The cells of the trophopblast gets attached with the
epithelial layer of the endometrium.
The trophopblast cells in contact with endometrium
proliferate and form a layer, this layer is called as
syncytiotrophoblast ( outer layer )
The syncytiotrophoblast erode the epithelium and enter
the endometrium.
Cytotrophoblast (inner layer ) is the covering of the
blastocyst.

5. 5
DECIDUA
Decidua is the endometrium of the gravid (pregnant)
uterus.
It has four parts:
Decidua basalis: it forms the maternal part of
the placenta
Decidua capsularis: it covers the conceptus
Decidua parietalis: the rest of the endometrium

7. DEVELOPMENT
Initially the ovum appears to be covered with a
fine, downy hair, which consists of the
projections from the trophoblastic layer.
This part of the trophoblast is known as the
chorion frondosum.
These projections proliferate and forming its
branch from 3 weeks after fertilization, the
braches is known as chorionic villi.

8. Syncitiotrophoblast cells proliferate in to the
endometrium of the decidua.
The Syncitiotrophoblast continuos to erode the decidua
basalis, and goes to thickness.
Number of small spaces appear in the
Syncitiotrophoblast, is called as lacunae.
Lacunar spaces fuse each other, enlarge and are arranged
in radical order around the chorion.
The lacunae are separated from each other by colums of
syncitiotrophoblast. These colums are called as trabeculi.

9. As the Syncitiotrophoblast erode the endometrium, the
blood vessels of the endometrium enter in to the
lacunar spaces.
The cells of cytotrophobalst invade the trabeculi in its
centre.
The trabeculi now has two layers, an outer layer of
Syncitiotrophoblast and inner is cytotrophobalst. The
trabeculi now is called as PRIMARY VILLI.

10. The extraembryonic mesoderm deeply invade in to
the central part of each trabeculus.
The trabeculi are now is having three layers. Outer –
Syncitiotrophoblast, middile – cytotrophobalst, and
inner – mesoderm.
Now the trabeculi is called as SECONDARY VILLI.

11. Blood vessels are developed in to the mesoderm of the
secondaty villi.
These vessels are connected to the fetal vascular system
through CHORION AND UMBLICAL CARD.
This villi is called as TERTIORY VILLI.

12. The cells of cytotrophobalst in the villi proliferate andf
pass through the Syncitiotrophoblast at the tip of the
villi and form the continuous layer on the surface of the
decidua.
This layer is called as cytotrophobalstic shell and it fix
the villi to the decidua.
This villi is called ANCHORING OF VILLI.

14. The intercommunicating lacunar spaces now form a
continuous inetvillus spaces.
The new villi are aslo formed from chorion projecting in
to intervillus space between two anchoring of villus.
The intervillus space is filled with maternal blood and
the villi freely flaot on this blood.

16. PLACENTAL BARRIER
Blood comes in to intervillus space through
endometrial arteries and trained through
endometrial veins.
The chorianic villi contain the fetal blood vessels.
The maternal blood cross this membrane, and
filtered though this membrane, and exchange of
gases, nutrients and waste products takes this
membrane.

17. The placental mebrane is made up of following layers
starting from maternal side.
Syncitiotrophoblast
Cytotrophobalst
Basement of mebrane
of cytotrophobalst
Mesoderm
Basement of mebrane
of fetal blood vessels in the villi.

18. FUNCTIONS OF PLACENTA
Respiration
Nutrition
Storage
Excretion
Protection
Endocrine

19. FUNCTIONS OF PLACENTA
1.Respiration:
Pulmonary exchange does not takes place in the uterus.
The fetus must obtain oxygen & excrete Co2 through the placenta.
O2 from mother’s hemoglobin passes to fetal blood by simple
diffusion & fetus passes Co2 into maternal blood.

20. 2.Nutrition
Amino acids - body building,
Glucose - energy
Calcium & phosphorus- bones & teeth
Iron & other minerals – blood formation
Placenta is able to select those substances required by the fetus
Proteins are transferred across the placenta as amino acids,
carbohydrates as glucose & fats as fatty acids.

21. 3.Storage:
Placenta metabolises glucose, stores it in the form of glycogen &
reconverts it in to glucose as required.
It also store iron The fat-soluble vitamins.
4.Excretion:
Main substance excreted from the fetus is Co2.
Billirubin also be excreted as RBC’s.
Amounts of urea & uric acid excreted are very small.

22. 5.Protection:
Placenta provides a limited barrier to infection
Treponema of syphilis & tubercle bacillus, few bacteria can
penetrate.
Viruses can cross freely and may cause congenital
abnormalities.

23. 6. Endocrine:
HCG :
This is produced by the cytotrophoblastic layer of the
chorionic villi.
It excrete through urine.
Its function is to stimulate the growth & activity of the corpus
luteum.

24. B. Oestrogen:
When the activity of corpus luteum declines, the placenta takes over
the production of estrogen.
C. Progesterone:
This is made in syncitial layer of placenta. It may be measured in the
urine as pregnanediol.
D. HPL:
It has a role in glucose metabolism in pregnancy. As the HCG level
falls, the HPL level rises and continues to do so throughout
pregnancy.

25. •Discoid shape
•Average weight 500 gm (200 – 800 gm)
•1/6 of baby’s weight at term
•Average diameter 20 cm and thickness 2.5 cm
•Maternal Surface rough and granular. Each villus and its
branches form the cotyledon or lobes.15-30 lobes(average 20)
•Fetal surface smooth, shiny and transparent, and has two layers
chorion and umnion.
•Umbilical cord- attached to fetal surface
MATURE PLACENTA

27. AMNIOTIC FLUID
Origin:
The source of amniotic fluid is thought to be both fetal and maternal.
It is secreted by the amnion, especially that which covers the
placenta and umbilical cord.
Fetal urine also contributes to the volume from the 10
th
week of
gestation onwards.

28. Volume:
It measures about 50 ml at 12 weeks, 400ml at 20 weeks and reaches
peak of 1 liter at 36-38 weeks.
If the total amount exceeds 1500ml, the condition known as
polyhydramnios, and if less than 300ml, the term is oligohydramnios.
Such abnormalities are often associated with congenital
malformations of the fetus.

29. Physical features :
The fluid is faintly alkaline with low specific gravity of 1.010. It
becomes highly hypotonic to maternal serum at term pregnancy.
Colour:
In early pregnancy, it is colourless, but near term, it becomes
pale straw coloured due to presence of exfoliated lanugo and
epidermal cells from the fetal skin.

30. Abnormal colour:
Meconium stained (green) – is suggestive of fetal distress

Golden colour – In Rh incompatibility
Greenish yellow – seen in postmaturity.
Dark colour - In concealed accidental
hemorrhage
Dark brown – Amniotic fluid is found in IUD

31. Composition:
It includes water 98-99% and solid 1-2%. The following are the solid
constituents;
a. Organic:

--Protein - 0.3 gm% --Glucose- 20mg%
--Urea - 30mg
--Uric acid- 4mg% --Creatinine- 2mg %
--Total lipids- 50mg %
--Hormones ( prolactin, insulin & renin)

32. b. Inorganic :
The concentration of the sodium, chloried & pottassium is
almost the same as that found in maternal blood.
c. Suspended particles :
It incluides lanugo, exfoliated sqamous epithelial cells from
the fetal skin, vernix caseosa.sss

33. Function:
During pregnancy-
Act as a shock absorber, protecting the fetus from injury.
Maintains an even temperature.
Allows for growth & free movement of the fetus.
During labour-
The amnion & chorion are combained to from a hydrostatic wedge which
helps in dilatation of the cervix.
It flushes the birth canal.

34. UMBILICAL CORD

The umbilical cord or forms the connecting link between the
fetus & placenta.
Development:

The umbilical cord is developed from connective stalk which
is band of mesoblastic tissue stretching between the embryonic disc
and the chorion.

35. Initially, it is attached to the caudal end of the embryonic disc.
As a result of cephalocaudal folding of the embryo And simultaneous
enlargement of the amniotic cavity
As the amniotic cavity enlarges out of proportion to the embryo &
becomes distended with fluid.
The embryo is carried more & more into the amniotic cavity with
simultaneous elongation of the connective stalk.
It is a future umbilical cord.

36. Structures
Covering epithelium
Wharton’s jelly
Blood vessels- 2 arteries, 1 vein
Remnant of umbilical vesicle & its vitelline duct
Allantois
Obliterated extra embryonic coelom.

37. Characteristics
It is about 50cm in length
Diameter average 1.5cm.
Thickness is not uniform
Presents of nodes or swelling.
Swellings may be due to dilatation of the umbilical vein or local
collection of wharton’s jelly.

38. Attachment:
In the early period, the cord is attached to the ventral surface of the
embryo close to the caudal extremity.
But as the coelom closes & the yolk sac atrophies, the point of
attachment is moved permanently to the centre of the abdomen at 4
th

month.
The attachment may be central,marginal or even on the chorionic
laeve at varying distance away from the margin of the placenta, called
velamentous insertion.

39. ABNORMALITIES OF PLACENTA AND CORD

There is a marked variation in the morphology
including size, shape and weight of the placenta.
Placenta succenturiata
Placenta Extrachorialis
Two types are described;
- Circumvallate placenta
- Placenta marginata
Bipartite placenta
Tripartite placenta

40. ABNORMALITIES OF CORD
Battledore placenta
Vellamentous Placenta
 Short cord
Long cord
True knot
False knot

41. PLACENTA SUCCENTURIATA
One or more small lobes of placenta, size of a
cotyledon, may be placed at varying distance from the main
placental margin. A leash of vessels connecting the main to
the small lobe traverse through the membranes.

42. Placenta Extrachorialis
Circumvallate Placenta
The fetal surface is divided into a central
depressed zone surrounded by a thickened white ring which
is usually complete.
The ring is composed of a double fold of amnion and chorion
with degenerated deciduas and fibrin in between.
Vessels radiate from the cord insertion as for as
the ring and then disappear from view.
The peripheral zone outside the ring is thicker and edge is
elevated and rounded.

43. Circumvallate Placenta

44. Placenta marginata :
A thin fibrous ring is present at the margin of the chorionic plate
where the fetal vessels appear to terminate.

45. Bipartite placenta:
Two complete an d separate lobes are present, each with
a cord leaving it. There are also two umbilical cords, these do
not joint at any point.
Tripartite placenta:
There will be three distinct lobes.

46. CORD ABNORMALITIES
Battledore placenta :
The cord is attached to the margin of the placenta. If
associated with low implantation of the placenta, there is chance of cord
compression in vaginal delivery leading to fetal hypoxia and even death.

47. VELLAMENTOUS PLACENTA:
The cord is attached to the membranes. The branching vessels
traverse between the membranes for a varying distance before
they reach and supply the placenta.

48. ABNORMAL LENGTH OF THE CORD
The cord may be too long or short.
Short cord:
The cord may be true or commonly relative due to
entanglement of the cord round any fetal part.
Long cord:
The presence of a long cord is that there is increased chance
of cord prolapse , cord entanglement round the neck or the body. True
knot is rare. False knot are the result of accumulation of wharton’s
jelly or due to varices.

49. FALSE KNOT

50. TRUE KNOT

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E.Fetal Blood and Circulation
1.Substances diffuse through the
placental membrane and umbilical
vessels carry them to and from the
fetus; fetal blood has a greater oxygen-
carrying capacity than maternal blood.
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2.The umbilical vein, transporting blood
rich in oxygen and nutrients, enters
the body and travels to the liver where
half of the blood is carried into the liver
and half bypasses the liver through the
ductus venosus on its way to the
inferior vena cava.
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3.A foramen ovale conveys a large
portion of the blood entering the right
atrium from the inferior vena cava,
through the atrial septum, and into the
left atrium, thus bypassing the lungs.
4.A second lung bypass is the ductus
arteriosus, which conducts some
blood from the pulmonary trunk directly to
the aorta.
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5.Umbilical arteries carry blood from
the internal iliac arteries to the placenta,
where it can exchange wastes and
again pick up nutrients and oxygen.
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