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FETAL MEMBRANES AND PLACENTA BY. PROF MASOOD AHMED MBBS, MPHIL PHD. Relative Size of Human Conceptus. Implantation of the Blastocyst. Implantation of the Blastocyst. FETAL MEMBRANES. REFRESH FEW TERMS DECIDUA BASALIS, CAPULARIS AND PARIETALIS VILLI FORMATION - PowerPoint PPT Presentation
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FETAL MEMBRANES AND PLACENTABY
PROF MASOOD AHMEDMBBS, MPHIL PHD
Relative Size of Human Conceptus
Implantation of the Blastocyst
Implantation of the Blastocyst
FETAL MEMBRANES
REFRESH FEW TERMSDECIDUA BASALIS, CAPULARIS
AND PARIETALISVILLI FORMATIONCYTOTRPHOBLASTIC SHELL
FORMATIONCHORIONIC MEMBRANE
PARTSCHORION FURONDOSUM AND
CHORION LAEVEAMNIOCHORIONIC
MEMBRANE
Embryonic Membranes
• Amnion – Epiblast cells form a transparent membrane filled with amniotic fluid– Provides a buoyant environment that protects the
embryo– Helps maintain a constant homeostatic
temperature– Amniotic fluid comes from maternal blood, and
later, fetal urine
CYTOTROPHOBLASTIC SHELL FORMATIONPLACENTAL BARRIER/ MEMBRANE
Embryonic Membranes
• Allantois – a small outpocketing at the caudal end of the yolk sac– Structural base for the umbilical cord– Becomes part of the urinary bladder
• Chorion – helps form the placenta– Encloses the embryonic body and all other
membranes
AMNION WITHIN CHORION
Placentation
• The chorion develops fingerlike villi, which: – Become vascularized – Extend to the embryo as umbilical arteries and
veins– Lie immersed in maternal blood
• Decidua basalis – part of the endometrium that lies between the chorionic villi and the stratum basalis
• UTERO PLACENTAL CIRCULATION –12TH DAY CIRCULATION
• 4TH MONTHCHORION FRONDOSUM AND DECIDUA BASALIS• 5TH MONTHDECIDUAL SEPTA AND COTYLEDON FORMATIONCONTIOUS FLOW IN INTERVILLOUS SPACE
PLACENTAL SURFACES
• FETAL SURFACE • CHORIONIC VESSELLS
CONVERGING TOWARDS UMBLICAL CORD
• 2-ARTERIES AND ONE VEIN• CHORION COVERED BY AMNION• ECCENTRIC ATTACHMENT OF
UMBILICAL CORD• MATERNAL SURFACE• 15-20 COTYLEDONS
• Functional type• hemochorial
FULL TERM PLACENTA• 15-20% INNER SURFACE COVERED WITH PLACENTA• ALL THE TIME SYNCITIAL SURFACE SEPARATES THE
MATERNAL BLOOD• COTYLEDONS- CORE OF ENDOMETRIAL TISSUE COVERED
BY SYNSITIUM• 15-20 IN NUMBER• SHAPE-DISCOID• SURFACE AREA 15-20cm• THICKNESS-3cm • WEIGHT-500-600gms
Placentation
Placenta
• 80-100 MATERNAL ENDOMETRIALSPIRAL ARTERIES SUPPLYING VILLI
• A TOTAL 150 ML BLOOD IN PLACENTAL CIRCULATION
• REPL;ENISHES 3-4 TIMES / MINUTE• PLACENTAL BARRIER • SEPARATES MATERNAL AND FETAL BLOOD• COMPRISED OF • ENDOTHELIAL LINING OF VILLI CAPPILARIES• C.T IN VILLI• TROPHOBLASTIC LAYER• CYTO TROPHOBLAST LAYER• 4TH MONTHS ONWARD• INCREASED EXCHANGE BY• C.T AND TROPHOBLAST LAYER DISAPPEAR
• CLOSE TO END OF PREGNANCY
• DECREASE EXCHANGE BY• INCREASE FIBROUS
TISSUE IN VILLI• FIBRINOID DEPOSIT ON
SURFACE OF VILLI• OBLITERATION OF SMALL
CAPPILARIES
Variations of placenta• Normally---hemochorial and eccenteric• Variations• velamentous –when umblical vessels divide before and branches come to
placenta• Marginal- when umblical vessels join placenta at margin• Succenturiate- when additional small plcental lobe is present or separate
small placenta is present• accreta- when placental reaches up to basal layer of endometrium• Increta- when placental infiltrates in the myometrium• Percreta- when placenta infiltrates up to connective tissue and crosses the
muscule layer
AMNIOTIC FLUID• SYNTHESIZED BY• CLEAR WATERY FLUID • MAINLY BY• MATERNAL CIRCULATION• PARTLY BY AMNIOCYTES• 30-ML—10TH WEEK• 350 ML—20TH WEEK• 800-1000 ML---37TH WEEK• REPLACED /3-4 HRS• 5TH MONTH ONWARD • SWALLOWING• AND ADDITION OF URIN• FUNCTIONS• ABSORBS JOLTS• ALLOW FETAL MOVEMENTS• HORMONE PRODUCTION• AVOIDS ADHERENCE
• Polyhydroamnios• Amount of amniotic fluid• more than 1500 ml eg• Esophageal atresi, anencephaly
• Oligohydroamnios• Amount of amniotic fluid• less than 400 ml eg• Renal agenesis
Membranes in twins
• DIZYGOTIC OR FRATERNAL twins
• Separate amniotic and chorionic membranes and placenta
• May be different sex, blood groups, features
Monozygotic twins
• If twins form by the division of zygot at two cell stage with the formation of two separate blastocyst
• Two Separate amniotic and chorionic membranes and placenta
• Features,Sex and blood groups same
• If twins form by the division of inner cell mass in blastocyst
• Two Separate amniotic cavities
• Common chorionic membranes and placenta
• Features, Sex and blood groups same
• If twins form by the late division of inner cell mass in blastocyst or by division of bilaminar germ disc
• Common amniotic, chorionic membranes and placenta
• Features, Sex and blood groups same