FETAL MEMBRANES UMBILICAL CORD Initially connecting stalk Blood

FETAL MEMBRANES

UMBILICAL CORD § Initially connecting stalk § Blood vessels develop § Normally 2 arteries, 1 vein § Doppler Velocimetry § With folding shifts ventrally § LENGTH: 30 -90 cm (average 55 cm) § Abnormally long- prolapse § Abnormally short- premature separation

§ Covered by Amnion § Knots § False- length of blood vessels more than umbilical cord § True- head passes through loop of cord, dangerous

Amnion § § § Initially located cranially Oval attachment Cavity expands, obliterates chorionic cavity, lining of umbilical cord

AMNIOTIC FLUID § Plays major role in fetal growth and development § SOURCES § Initially secreted by amniotic cells § Maternal tissue, diffusion across amniochorionic membrane § Diffusion through chorionic plate, from intervillous space

§ § § § § FETAL Before keratinization, fetal interstitial tissue After that; fetal respiratory tract (300 -400 ml/ day) GIT By 11 th week: fetal excretory system (500 ml/day) Volume normally increases slowly 30 ml- 10 weeks 350 ml- 20 weeks 700 -1000 ml– 37 weeks

COMPOSITION § Aqueous solution with suspended materials § Epithelial cells § Organic: proteins, enzymes, hormones, pigments, carbohydrates § Inorganic: salts

AMNIOCENTESIS § AMNIOTIC FLUID EXAMINATION § Fetal proteins, hormones, enzymes can be studied § Fetal cells; chromosomal abnormalities § Alpha fetoproteins: § High- NTD § Low- Trisomy etc

SIGNIFICANCE § § § § § Embryo floats, moves freely Cushioning effect Barrier to infections Symmetrical growth of fetus Muscular development Normal fetal lung development Prevents adherence of amnion to embryo Controls body temperature Maintains homeostasis

ABNORMALITIES § OLIGOHYDROAMNIOS § Causes § Renal agenesis § Obstructive uropathy § Complications § Pulmonary hypoplasia § Facial defects § Limb defects

§ POLYHYDROAMNIOS § Causes § § § Idiopathic Anencephaly Esophagial atresia § Complications § Premature onset of labour

YOLK SAC (UMBILICAL VESICLE)

SIGNIFICANCE § § § Transfer of neutrients Blood vessels development Endoderm- epithelium of gut, trachea, lungs § PGCs

Allontois

MULTIPLE GESTATION § § DIZYGOTIC: 2/3 rd 7 -11/10, 000 births Simultaneous shedding of two ova, fertilization by two sperms § Different genetic make up § Resemblance like other siblings

§ Implant individually § Each develop own placenta, amnion, chorionic sacs

§ If placents lie closely, may fuse § ERYTHEROCYTE MOSAICISM

MONOZYGOTIC TWINS § Single ovum is fertilized § 3 -4/10, 000 births § From splitting of ovum at different stages of development § Earliest at two cell stage § Implant separately, separate placentae etc § Resemble dizygotic but same genetic constitution

§ At early Blastocyst stage § Inner cell mass splits into two within same blastocyst cavity § Common placenta, chorionic cavity § Separate amniotic cavity § At bilaminar germ disc § Before the appearance of primittive streak § Common placentae, amnion, chorionic cavity § Usually blood supply is well balanced § May be unbalanced § Risks are more (one fetus may die)

§ TWIN TRANSFUSION SYNDROME § Shunting of arterial blood from one fetus to venous circulation of other. Donor is small, pale, anemic while recipient is large and polycythemic § FETUS PAPYRACEUS § VANISHING TWIN

INCOMPLETE SEPARATION § § § CONJOINED TWINS (Siamese) Craniopagus Thoracopagus pyopagus