Placenta is a hemochoreal. It is deciduate. It develops from trophoblasts.5/6 of placenta is fetal origin and 1/6 is maternal origin.It act as semipermiable memberane to exchange substances between fetus and mother. Amniotic fluid if less in volume is called oligohydramnios .If excee,called polyhydramnios. Oligohydramnios is associated with IUGR,renal agenesis and posterior urethral valve . Polyhydramnios is associated with anencephly, meningocele, sacral agenesis ,diabetes in mother etc

1. PLACENTA , MEMBERANES AND
AMNIOTIC FLUID

2. PLACENTA
• Hemochorial
• Deciduate
• It is attached to uterine wall, it has a
connection between mother and fetus
through umbilical cord.

5. Development
After implantation, endometrium is called
decidua
Decidua basalis
Decidua capsularis
Decidua parietalis

7. Chorionic villi
• Very small finger like processes.
• Off shooting from surface of trophoblast.
• Maternal blood.
• Villi have fetal capillaries and fetal blood
vessels through which fetal blood circulate.

8. • Villi toward decidua capsularis degenerate
called chorionic leavae.
• Villi toward decidua basalis called chorionic
frondosum.

9. Formation of chorionic villi
• Single layer of trophoblastic cell.
• Multiply
• Layers near decidua loss cell boundaries.
• Continuous sheet of cytoplasm with many
nuclei is formed.
• This layer is called syncytiotrophoblast layer.
• Deep to this is cytotrophoblastic layer called
Langhan’s layer.

12. • Syncytiotrophoblastic layer grow rapidly become
thick.
• Formation of lacunae.
• Arranged radially around blastocyst.
• Lacunae separated from each other by syncytium
called trabeculae.
• Lacunae gradually communicate each other to
form intervillous space.
• Syncytiotrophoblast erode endometrium and
blood vessels, lacunae are filled with blood.

13. Primary villi
• Trabeculae made up of syncytiotrophoblast.
• Cytotrophoblast multiply and grow in to
trabeculae and form a central core.
• Trabeculae now called primary villi.
• Lacunar space is now called intervillous space.
• Primary villi is formed on 12th -13th days.
•

14. Primary villus

15. Secondary villi
• The extra-embryonic mesoderm invade the
Centre of each primary villi.
• Villi have core of mesoderm surrounded by
layer of cytotrophoblast and syncytium.
• Secondary villi.
• 16 days.

16. Secondary villus

17. Tertiary villi
• Blood vessel can be seen in core of mesoderm
of secondary villi.
• Tertiary villi.
• 21 days.
• Villi with thick syncytiotrophoblast area called
beta zone. Synthesis area.
• Villi with thin syncytiotrophoblast area called
alpha zone.

18. Tertiary villus

19. Formation of cytotrophoblastic shell
• The cells of cytotrophoblast spread form layer
and cut the syncytium from decidua.
• This layer multiply rapidly and increases
placental size.

20. Anchoring villi
• The villi 1st formed are attached on fetal side
to embryonic mesoderm.
• On maternal side to cytotrophoblastic shell
called anchoring villi.
• Anchoring villi consist of stem villi – divided in
to number of branches which turn into fine
branches.

21. Anchoring villi

23. • Whole intervillous space become filled with
villi.
• More surface area available for exchange.
• One anchoring villus and its branches consist
of fetal cotyledon.

24. Placenta
• Placenta has 15 -20 lobes called maternal
cotyledons by septa that grow into intervillous
space.
• Maternal lobe contains numbers of anchoring villi
and its branches.
• One maternal cotyledon has 3-5 fetal cotyledons.
• Placental development begins at 6 wks
completed by 12 wks alone with fusion of
decidua parietalis with decidua capsularis.

25. • Up to 16 wks, placenta grows in thickness and
circumference due to growth of chorionic villi.
• Later ,it increases in circumference.

26. Placenta
• Fleshy
• Discoid
• Wts 500 gms
• 1/6 of the fetal weight
• Diameter 15 -20 cms
• Thickness 2.5 cms
• Spongy to feel
• Occupy 1/3 of uterine wall

27. Placenta
• 4/5 of placenta is fetal origin and 1/5 maternal
origin.
• Fetal surtace
Formed from chorion frondosum and
chorionic plate.
umbilical cord is attached here central or
ecentral.
It is covered by chorion on which thin amnion
lie.

28. Placenta
• Maternal surface
Develop from decidua basalis.
It is rough, shaggy fleshy dull red in
appearance.
15-20 elevated convex areas called
cotyledons.
Margin- formed by fused chorionic and basal
plate.

29. Placenta

30. Placenta
• Attachment
2/3 cases – upper part of uterine body
posterior wall.
1/3 cases attach to anterior wall.
Separation- through intermediate spongy layer
of the decidua basalis.

31. Placenta
• Chorionic plate
outside inward – syncytiotrophoblast
cytotrophoblast
extraembryonic mesoderm
branches of umbilical vessels
Stem villi actually start from this plate.

32. Placenta
• Basal plate
outside inward
compact and spongy layer of decidua
layer of Nitabuch
cytotrophoblast shell
syncytiotrophoblast
spiral arteries passes through the basal plate

33. Placental barrier
Placental memberane or barrier has : -
1. Endothelium of fetal blood vessel
2.Basement memberane
3.Mesodern (connective tissue)
4. Cytotrophoblast and its basement memberane
5. Syncytiotrophoblast
Thickness 0.002mm.
Human placenta is hemochoreal.

34. Placental barrier

35. Circulation of blood through placents
• Utroplacental circulation
• Fetoplacental circulation

36. UTROPLACENTAL CIRCULATION
• it is 700 – 900 ml per minute at term.
• it deals with maternal blood therough inter-
villous space.
• intervillous blood flow is replaced every 15-20
sec.
• there are 100-200 spiral arteries discharge
there blood into intervillous space.

37. • Trophoblastic invasion into spiral arteries
within the intra decidual portion by 12
weeks of pregnancy replacing the
endothelial lining as well as destroying the
muscular elastic media and replacing it by
febrionoid material thus making it low
pressure channel.
• second invasion of trophoblast occurs at
spiral arteries at 12-16 weeks of gestation
extending up to radial arteries thus spiral
arteries are converted into spacious low
pressure uteroplacental arteries.

38. • Arterial blood, which enters the
intervillous space under pressure get
dispersed laterally after it reaches
the chorionic plate. Villi mix the
blood and slows blood flow. Blood
migrate towards basal plate and
uterine vein by villi pulsation
augmented by uterine contraction.

39. • Venous blood of intervillous space is drained
by uterine vein which perforate the basal
plate.
• during uterine contraction veins are closed,
arterial blood enters the intervillous space.
• During uterine relaxation venous drainage
occurs so, large volume of blood is made
available for exchange.

42. Fetoplacental circulation
• deoxygenated venous like foetal blood flows to
the placenta through two ambilocal arteries by
pumping action of foetal heart. With each artery
feeding roughly half of placenta.
• these umbilical vessels branches into primary,
secondary and tertiary vessels beneath amnion.
• finally blood with significantly higher oxygen
content return from placenta to foetus through
single umbilical vein .

43. Function of placenta
• Respiratory function
• Nutritive function
• Excretory function
• Immunological function
• Endocrinal function
• Barrier function
• Other functions –placental transfer of heat

44. Factor affecting placental transfer
• Molecular weight- molecules having lower
molecular weight are transferred easily.
• Molecule >500 daltons have limited access.
• Lipid soluble substances diffuses easily.
• Ionised substances diffuses poorly.
• Integrity of plasma memberane.
• Concentration gradient of substance on either
side

45. Machanisms
• Simple diffusion- it allow passage of
substances <500 daltons
• O2 and co2
• Facilitated diffusion – occurs by carrier protein
• Exp – glucose and vitamins
• Active transfer against concentration gradient-
• Exp ions

46. • Endocytosis and exocytosis-
invagination/evagination of plasma
memberane occurs
• IgG

47. • Urea uric acid and creatinine by simple
diffusion.
• Immunological protection against graft
rejection.
• Placenta is rich source of human placental
lactogen, beta hcg,estrogen and progestron.
• Placenta has oxytocinase which inactivate
oxytocin.

48. • Diamine oxidase which inactivate pressor amines
• Phospholipase A2 – help in synthesis of
prostaglandins.
• Barrier function- rubella, CMV, herpes
simplex,HIV , hepatitis ,chicken pox ,measle
mumps, polio,treponema pallidum, tubercle
bacillus protozoa, malarial parasite can cross the
placental barrier to adversely affect the fetus’

49. Anomalies of placenta
• Bidiscoid – consists of two discs.
• Lobed – it divides into lobes.
• Diffuse- chorionic villi present all over
blastocyst. Placenta is thin,does not assume
shape of the disc
• Placenta succenturiate-small part of placenta
is separated from rest of it.

50. • Fenestrated placenta- there is a hole in the
disc.
• Circumvallate placenta- peripheral edge of
placenta is covered by circular fold of decidua.

52. Anomalies of cord
• Marginal- cord is attached to margin of
placenta.
• This type of placenta is called battledore
placenta
• Furate –blood vessels divide before reaching
the placenta.
• Vilamentous insertion- blood vessels are
attached to amnion,where they ramify before
reaching the placenta.

54. Fetal memberane
• Chorion
• Amnion
• Chorion has two layers –outer trophoblast.
inner mesenchyme
At term it does not contain any nerves and
vessels

55. Amnion
• Cuboidal epithelium single layer.
• Basement memberane
• Layer of reticular structure.
• Fibroblastic layer.
• Spongy layer
• It does not have any blood supply,nerve supply
and lymphatic suppty.
• It provide tensile strength to fetal memberane.

56. • It maintains amniotic fluid haemostasis.
• Produces growth hormones and cytokines.

57. Function of chorion and amnion
• Formation of amniotic fluid by transudation.
• Present ascending infection.
• Provide tensile strength.
• Enzymatic activity for steroidal hormone
synthesis.
• Source of arachidonic acid which is the
precursor for prostaglandin synthesis.
• Production of growth factors and cytokines.

58. • Dilatation of cervix.
• Amnion is used in burn ,eye ulcers and
amnion vaginoplasty.

59. Amniotic Fluid
• Origin
Trasudation from maternal circulation
through the placental surface and fetal
memberane.
Trasudation acrose surface of Umbilical
cord.
Active secretion from amniotic
memberane.
Contribution from fetal urine.
Tracheo- bronchial secretion.

60. Amniotic Fluid
Transfer across fetal skin prior to its
keratinization at 20 wks of gestation.
Quanitity—
20 ml at 10 wks
400 ml at 20 wks
750 ml at 28 wks
800-1000 ml at 36 wks
700 ml at term
200 ml at 43wks

61. Amniotic Fluid
Composition-
Water 98.4 %
Solid components 1.6%
Organic constituents—
Albumin 0.2-0.3mg/dl, Glucose-10-20 mg/dl
Non nitrogen protein-30-35mg/dl,uric acid-4-
7mg/dl,creatinine-0.7-0.9mg/dl
Lipids-50-100mg/dl
Hormones-
insulin,prolactin,cortisol,estrogen,progesterone,reni
n

62. Amniotic Fluid
Inorganic constituents- sodium, chloride and
potassium.
Solid particles- Lanugo,desequamated fetal skin
cell,vernix caseosa,shedded amniotic
cell,epithelial cell from respiratory tract
gastrointestinal cell and genitourinary tract of
fetus and dermal fibroblasts.

63. Amniotic Fluid
• Physical feature-
Slightly basic, pH-7
Specific gravity 1.007-1.010
Hypotonic at term
Osmolarity-275m osmol/lt at
term.
PO2-15 mm Hg
PCO2- 55mmHg

64. Amniotic Fluid
Color-
Early pregnancy ,it is colorless
Near term,pale straw in color due to
presence of exfoliated lanugo and epidermal
cells. It may be terbid due to presence of vernix
caseosa.
Abnormal appearance—
Greenish seen in
meconium

65. Amniotic Fluid
Golden yellow- in Rh incompatibility due to
presence of bilirubin from cell hemolysis.
Greenish yellow- post maturity.
Dark maroon-accidental hemorrhage.
Dark brown-retained dead fetus.
Blood stained- bright red in vasa previa or low
lying placenta.

66. Function of amniotic fluid
• Cushion and protect fetus from trauma.
• Maintain fetal temperature.
• Allow free movements and growth of fetus.
• Prevent adhesion formation.
• Ingestion of amniotic fluid in to
gastrointestinal tract and fetal respiratory
tract helps in growth and differentiation of
these tissues

67. Function of amniotic fluid
• It has some nutritive value because it contains
small amount of protein and salt.
• Help in cervical dilatation due to hydrostatic
pressure.
• During uterine contractions,amniotic fluid in
intact memberane prevents interference with
placental circulation.
• Provide pools for fetus to excrete urine.
• Protects fetus from ascending infection.

68. Function of amniotic fluid
• Clinical significance-
Analysis of amniotic fluid helps to
know the fetal well being and maturity.
Intra amniotic installation of
prostaglandins and hypertonic saline can be
used for induction of abortion.
Excess of amniotic fluid can be seen in duodenal
atresia ,diabetes,multiple pregnancy due to
large placenta, Rh incompatibility and congenital
malformation

69. Function of amniotic fluid
• Low volume of fluid is seen in fetal growth
restriction, leakage.
• Artificial rupture of membrane to drain liquor
amnii is a method of induction and
augmentation of labour.

70. Umbilical cord
• Epithelium contains single layer of amniotic
epithelium.
• Remnants of yolk sac and vitello-intestinal
duct.
• Extra-embryonic mesoderm of connecting
stalk. This mesoderm becomes converted into
gelatinous substance called Wharton’s jelly.
• Blood vessels
• A small part of the extra-embryonic coelom.

72. Umbilical cord

73. Cord
• Length -50 cms , average 30-100 cms
• Diameter 1.5cms
• There are false knots due to distension of
umbilical veins or local collection of Wharton’s
jelly.
• There are spiral turns taken by vein around
the artery usually in anticlockwise to prevent
crimping and maintain constant curvature.

74. Cord
• Umbilical vein lack an internal elastic lamina
but have developed muscular coat helping in
their effective closure due to reflex spasm
after parturition.
• There is absent vasa vasorum in the umbilical
vessels.