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FETAL MEMBRANES AND PLACENTA BY PROF MASOOD AHMED MBBS, MPHIL PHD.

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Presentation on theme: "FETAL MEMBRANES AND PLACENTA BY PROF MASOOD AHMED MBBS, MPHIL PHD."— Presentation transcript:

1 FETAL MEMBRANES AND PLACENTA BY PROF MASOOD AHMED MBBS, MPHIL PHD

2 Relative Size of Human Conceptus

3 Implantation of the Blastocyst

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5 FETAL MEMBRANES REFRESH FEW TERMS DECIDUA BASALIS, CAPULARIS AND PARIETALIS VILLI FORMATION CYTOTRPHOBLASTIC SHELL FORMATION CHORIONIC MEMBRANE PARTS CHORION FURONDOSUM AND CHORION LAEVE AMNIOCHORIONIC MEMBRANE

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9 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

10 CYTOTROPHOBLASTIC SHELL FORMATION PLACENTAL BARRIER/ MEMBRANE

11 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

12 AMNION WITHIN CHORION

13 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

14 UTERO PLACENTAL CIRCULATION –12 TH DAY CIRCULATION 4 TH MONTH CHORION FRONDOSUM AND DECIDUA BASALIS 5 TH MONTH DECIDUAL SEPTA AND COTYLEDON FORMATION CONTIOUS FLOW IN INTERVILLOUS SPACE

15 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 COTYLEDONS Functional type hemochorial

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17 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 IN NUMBER SHAPE-DISCOID SURFACE AREA 15-20cm THICKNESS-3cm WEIGHT gms

18 Placentation

19 Placenta 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 4 TH 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

20 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

21 AMNIOTIC FLUID SYNTHESIZED BY CLEAR WATERY FLUID MAINLY BY MATERNAL CIRCULATION PARTLY BY AMNIOCYTES 30-ML—10 TH WEEK 350 ML—20 TH WEEK ML---37 TH WEEK REPLACED /3-4 HRS 5 TH 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

22 Membranes in twins DIZYGOTIC OR FRATERNAL twins Separate amniotic and chorionic membranes and placenta May be different sex, blood groups, features

23 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

24 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

25 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


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