ANATOMY OF PLACENTA PLACENTAL BARRIER

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1 ANATOMY OF PLACENTA PLACENTAL BARRIER
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2 INTRODUCTION Placenta is a remarkable organ
Has a relative short life span, it undergoes rapid growth ,differentiation and maturation. A unique fetal –maternal communication system which creates a hormonal environment that helps initially to maintain pregnancy and eventually initiates the events leading to parturition

3 The human placenta is: Discoid Hemochorial Deciduate Larynthine

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5 Implantation is complete on 10 or 11th postovulatory day
On the 7th day ovum Cytotrphoblast Syncytiotrophoblast

6 Development of Placenta
Ovum Morula Blastocyst

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9 Nitabuch’s layer Placenta on 21 day of gestation – vascularised villous organ The region of fibrinoid degeneration where the trophoblasts meet the decidua is calld nitabuchs layer. This layer is absent in placenta accreta

10 Primary villi Secondary villi Tertiary villi

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14 During this period there is some regression of the cytotrophoblastic elements in the chorionic plate and in the trophoblastic shell where cytotrophoblastic columns degenerate and largely replaced by fibrinoid material –Rohr’s layer

15 PLACENTA AT TERM: Placenta is a discoid organ 15 – 20cm in diameter 3cm Thick at center Weighs about 500gms

16 AT TERM MATERNAL SURFACE

17 FETAL SURFACE

18 Aging of placenta

19 Placental membrane Total area-4 to 14 sq m
Similar to absorbtive area in adult git In later part of pregnancy the membrane thickness reduces from mm to0.002mm Is classified as haemochorial

20 FETAL MEMBRANES 2 LAYERS: Outer chorion Inner amnion

21 Chorion Internally attached to amnion by loose areolar tissue
Externally covered by trophoblastic layer and decidual cells of fused decidua capsularis and parietalis

22 Amnion Internal surface is smooth and shiny and in contact with liquor amnii Outer surface consists of a layer of connective tissue Amnion can be peeled off from the fetal surface of the placenta except at the insertion of the umbilical cord.

23 Hypertension

24 Development of membranes and formation of amniotic fluid
On the 8th and 9th postovulatory day Endoderm Ectoderm Amniotic cavity Primary yolk sac Parietal extra embryonic mesenchyme Visceral extra embryonic mesenchyme

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26 Amniotic fluid 12 weeks:50ml 16 weeks:150ml 38 weeks :900-1000ml
At term : ml Clinical applications Composition of amniotic fluid functions

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28 Placental circulation
Uteroplacental circulation Circulation in the intervillous space Feto-placental circulation

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33 PLACENTAL BARRIER Inspite of close proximity , there is no mixing of the maternal and fetal blood. They are separated by placental membranes or barrier.

34 In early pregnancy it consists of:
Syncytiotrophoblast cytotrophoblast Basement membrane Stromal tissue Endothelium with fetal capillary wall Its about mm thick

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36 Near term.. Attenuation of syncytial layer
Sparse cytotrophoblast and distended capillaries fill the villus. Vasculo- syncytial membrane: is the specialised zone of villi where the suncytiotrophoblast is thin and anuclear These alphazones are for gas exchange. Betazones of terminal villi are for hormone synthesis

37 BARRIER FUNCTION Fetal membrane is a protective barrier to the fetus against noxious agents circulating in the maternal blood. Antigen and antibody can traverse through the placental barrier The race of drug transfer is increased in late pregnancy

38 Maternal infections caused by :
Virus Bacteria Protozoa , is transmitted to the fetus by crossing the placental barrier.

39 Placental functions Simple diffusion Facilitated diffusion
Active transfer Endocytosis Exocytosis Respiratory functions Excretory functions

40 Nutritive function Enzymatic function Barrier function Immunological function Hormones

41 Hormones produced by placenta
HCG HUMAN PLACENTAL LACTOGEN CHORIONIC ADRENOCORTICOTROPIN RELAXIN PARATHYROID HORMONE RELATED PROTEIN GROWTH HORMONE RELATED VARIENT HYPOTHALAMIC LIKE RELEASING HORMONE GONADOTROPIN RELEASING HORMONE CORTICOTROPIN RELEASING HORMONE

42 Clinical aspects of placenta
Multiple pregnancy

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45 Placenta praevia Normal sites of implantation of ovum
Upper uterine segment Abnormal sites of implantation of ovum Types of placenta praevia First degree Second degree Third degree Fourth degree

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47 Placental abruption

48 Bleeding following premature separation of normally situated placenta
Incidence: 0.49 to 1.8% Types : concealed :20 to 35% revealed : 65 to 85%

49 Gestational trophoblastic disease
Proliferative abnormality of trophoblast associated with pregancy Persistance GTD = GESTATIONAL TROPHOBLASTIC NEOPLASIA

50 Classification Hyaditiform mole complete partial Invasive moles
Placental site trophoblastic tumors Choriocarcinoma Non metastatic disease confirmed to uterus

51 Chorionic villi sampling (CVS) &placental biopsy
Indications : Prenatal diagnosis of genetic disorder throughout gestation

52 Procedure

53 PLACENTAL TRANSFER Drugs that doesn’t cross placenta:
Heparin large molecule highly polar Curare

54 Teratogenic drugs Anticonvulsants Phenytoin: cleft lip /palate
Microcephaly Hypertelorisum Fingernail hyperplasia Sodium valproate: Neural tube defects

55 Lithium Ebstein’s anomaly Warfarin Chondrodysplasia punctate Microcephaly Aspleenaia Diaphragmatic hernia

56 Diethyl stil bestrol Adenocarcinoma of vagina Danazol Virulization of female

57 Retinoids Crainofacial Cardiac Thymic Cns

58 Thank you