The document discusses the formation and features of the umbilical cord, amniotic fluid, and the embryological basis of twins, detailing structures like the connecting stalk and characteristics of the umbilical cord. It outlines the significance of amniotic fluid, including its average volume, functions, and associated conditions like oligohydramnios and polyhydramnios. The document further explains the types of twinning, including dizygotic and monozygotic twins, along with their anatomical configurations and potential complications during pregnancy.

1. Formation & features of
umbilical cord, amniotic fluid,
chorion, uterine cavity,
embryological basis of twins

4. • Primitive Umbilical Ring- Amnio- Ectodermal Junction ( 5th week)
• Primitive Umbilical cord

5. Allantoenteric
diverticulum
Wharton’s jelly
Covering of
amnion
Umbilical arteries
Umbilical vein
Vitellointestinal duct
The umbilical cord contains the following structures:
1. Connecting Stalk - Allantois, umbilical vessels (two
arteries and one vein).
2. Vitello-intestinal duct ( Yolk Stalk) - Vitelline Vessels,
3. Remains of the extra-embryonic coelom
4. A tubular covering of amniotic sheath.
5. Wharton’s jelly - from the primary mesoderm of the
connecting stalk. It forms a protective layer

6. Umbilical cord
• A tubular cord like
structure enveloped by
amniotic membrane.
• Extent –
1. To the anterior
abdominal wall of the
feotus
2. To the center of foetal
surface of placenta.

7. Measurement
• Length – 50cm
• Breadth – 2cm
• Unusually long cord – strangulation
• Too short cord – difficulty during parturation
• It is twisted presenting false knots.
Characteristics

10. Velamentous attachment of the cord
Battledore placenta
False knot True knot
ANOMAILIES OF THE CORD
1. Velamentous attachement: cord is attached to the amnion
2. Battledore placenta: cord is attached to the edge the placenta.
4. Abnormally long or short cord (normally it is 50 cm long).
5. True knot.
6. Long Cord - Encircle head of foetus
7.Short cord – Difficulty in delivery

11. AMNIOTIC CAVITY
* In the blastocyst stage the amniotic
cavity appears on the 7th days as small
cavity between the primary ectoderm (
Epiblast) and the trophoblast.
* The floor of the amniotic cavity is
formed by the ectoderm ( Epiblast),
while the rest of its walls are formed
by flat amniotic cells and are
surrounded externally by a layer of
Parietal layer of Extraembryionic
mesoderm.

12. gz

15. AMNIOTIC FLUID
• Clear, Watery fluid – Amniotic Cells & Maternal Blood
• Average amount 1000 ml at 37 wks.( 500ml – 2oth wk)
• Fetus - swallows the fluid - 400ml/day & fetal Urine is
added which is mainly water
• Having < 300ml – Oligohydramnios, associated,
associated with fetal renal Agenesis , GI and other
malformations.
• with Having > 2 L – Poly Hydramnios – Idiopathic,
Maternal Diabetics, atresia of oesophagus – prevents
swalloning of fluid; Anencephaly

16. • Protects Fetus from external shocks.
• Prevents Adherence to amnion
• Aseptic medium surrounding the embryo &
allows Fetal Movement
• Controls Temperature
• Provides equal pressure on all aspects of the
embryo, thus Supports Symmetrical Growth
• Provides a hydrostatic medium allowing the
embryo to move and its muscles to develop.
• It is a good dilator of the cervix of the uterus
at labour

18. Amniotic Bands
• Tears in Amnion
• Encircle Parts of
Fetus
• Constrictions,
Amputations etc
• Infections ,
Toxic agents etc
involving fetal
membranes

19. Twining and multiple
births.

20. Dizygotic twins – (Dichorionic, Diamniotic)
• Two ova discharged
at the same time
and are fertilized by
two separate
sperms. ( 70%)
• Results in fraternal
or unlike twins
• Separate Genetic
Constitution
• Have 2 separate
Placenta, Amnion &
Chorion
Chorion

21. Monozygotic twins ( Identical)
• Two embryos derived from a single fertilized
ovum
• Splitting of zygote at various levels of
development
• Identical offsprings with similar genetic
constitution, appearance, structure and
belong to same sex

22. Monozygotic (dichorionic)
• Separation occurs early
at two cell stage
• Two separate zygotes
later
• Embryo – Has its own
placenta, chorion
• Similar to Fraternal
Twins – but SEX, Blood
group, colour etc -
Same

23. Monochorionic diamniotic
• Separation at – Early
blastocyst stage
• Inner cell mass - Splits into
two separate groups within
same blastocyst cavity
• Two embryo – Common
Placenta & Chorion, but
2 separate Amniotic Cavity
• Usual type

24. Monochorionic monoamniotic
• Separation - formation
of bilaminar germ disc,
Just before apperance
of primitive streak
• two embyos – Single
Placenta, single chorion
& Amnion

25. Conjoined (Siamese) twins
Partial Separation at the later stages of development
leading to splitting of Primitive Node & Primitive
Streak – Conjoined Twins
Misexpression of - Goosecoid Genes

26. Different types of conjoined twins
Parasitic twin

27. Photographs of Siamese twins

28. Dicepahlus
Craniopagus

29. • Twin Pregnancy – risk
• Premature birth ;low birth wt.
• Vanishing Twin -
Fetus Papyraceus – Compressed
& mummified Foetus

30. Fetal transfusion syndrome
• Monochorionic,
twins showing a
wide discrepancy
in size due to
placental Vascular
Anastomosis
• I twin receives
most of blood
supply