Foetal period & fetal membranes.pptxgfte

Embryology (anatomy), fetal period and fetal membranes

1. Fetal period 3 rd month IUL to end of birth

2. 9 th week 38 th week

3. Characterized by 1. Maturation of tissues & organs 2. Rapid growth of body

4. Fetal Development 10 th week 12 th week 16 th week 20 th week/5M 28 th week/7M 32 th week/8M 36 th week/9M u Upper limbs & f Formed

5. Age 5-12weeks CRL -5-8cms; Weight - 10-45g Age 15-20weeks, CRL- 15-20cms; Weight- 250-450g. Age 30-32weeks, CRL- 28-30cms; Weight - 1400-2100g Age 36-38weeks, CRL -36cms; Weight- 3000-3400g

6. Length of Pregnancy 280days or 40 weeks after the onset of last normal menstrual period (LNMP) . Accurately 266days or 38weeks after Fertilization.

7. Growth in length is particularly striking during 3 rd 4 th & 5 th month of gestation. Increase in weight is most striking during last 2 months( 8 th & 9 th month) of gestation.

8. Malformation are predominant during 3 rd to 8 th week of development ( organogenesis) It is crucial period for the embryo.

9. Few malformations also arise during Fetal period mainly due to mechanical forces leading to intrauterine compression.

10. 1. Slow growth of Head compared to rest body. 2. Face is more human looking. 3. Eyes come to lie ventrally & Ears attain definitive position. 4.Limbs reach relative length due to development of Primary centers of ossification : 8-12 th week. 3 rd month : (9 th -12 th week)

11. 12 5.External G enitalia develops Sex of fetus c an be determined in 3 rd month(12 th week) External genitalia

12. Female fetus Male fetus Genital tubercle /Penis

13. 4 th & 5 th months (16-20 weeks) 1.Fetus is covered with fine hair known Lanugo 2. Hair visible in eyebrows & head. 3. Fetus lengths rapidly. 4. Suckling of thumb Lanugo

14. 6.Movements of fetus can be felt during 5 th month (20weeks) by Mother  Quickening Quickening

15. 1. Several organs system are able to function. 2. Respiratory system & CNS have not differentiated sufficiently . 3.Coordination b/w the two systems not yet established. 4. Fetus born during 6 th month is difficult to survive.

16. 4. 6 th month (24weeks) : Weight increases. 5. Skin of Fetus: is reddish & wrinkled because of lack of underlying connective tissue. Weight increases 24 WEEKS

17. 7 th to 8 th month:(28-32 weeks) 1. Skin covered with whitish fatty substance known as Vernix caseosa composed of secretory products of sebaceous glands. Vernix caseosa protects fetal skin from the amniotic fluid. Traces of the substance may appear on skin after birth Vernix caseosa

18. 7 th to 8 th month (28-32Weeks) 2. Fetus obtains well rounded contours as a result of deposition of subcutaneous fat. 3. Foetus born at 7 th month (28weeks). Has 90% chance of surviving . Subcutaneous fat

19. 1.Weight : 3000- 3400gms. 2. CHL: 45-50cms

20. Skull has largest circumference of all parts of body an important fact helps in passage thro’ birth canal 9 th month (36-40 weeks) Birth canal

21. 9 th month/ 36-40 weeks Sexual characteristic are more pronounced : Testes in scrotum

22. Date of birth is most accurately indicated as 266 days or 38 weeks after fertilization Obstetrician calculates date of birth as 280 days or 40 weeks from first day LMP Most of fetuses are born within 10-14 days of calculated delivered date.

23. If they are born earlier  premature (32weeks) If born later post mature (42weeks) Valuable tool for assisting the age determination is by Ultra sound

24. Clinical correlation Low birth weight(  2.500g) 1 .Length & weight are genetically determined, but environmental factors also play important role. Intrauterine growth restriction( IUGR) . These infants are pathologically small. 2.Have neurological deficiencies & congenital malformations 3.Common in maternal nutritional status and others like multiple birth (twins, triplets)

25. Prenatal screening techniques Prenatal diagnosis Under Ultra sonography 1.Amnionocenetesis 2.Chorionic villous sampling. These Tests determine 1. Placental Growth 2. Fetal growth. 3. Congenital malformation 4. Chromosomal abnormalities.

26. 14-16 WEEKS 8-10 WEEKS

27. PLACENTA

28. I. UMBILICAL CORD Long ,twisted beaded 1-2cms in diameter, 30-90cms in length Umbilical cord

29. Umbilical cord is the life line that connects the fetus to its mother. Umbilical cord

30. Umbilical cord has smooth surface because it is covered by amnion Umbilical cord

31. UMBILICAL CORD Placenta At full term 1. One end of the cord is attached to center of anterior abdominal wall of the fetus. 2. Other end is fixed to the fetal surface of placenta Tubular cord enveloped by Amniotic membrane

32. 5 th week structures pass thro’ the primitive umbilical ring(5). 1.Umbilical cord  Umbilical vessels : 2 umbilical arteries & 1 umbilical vein). 2.Yolk stalk ( vitelline intestinal duct) & vitelline vessels. 3. Distal part of Allantois . 2UA &1UV Yolk Stalk Primitive Umbilical ring

33. 4. Intestinal loops(physiology hernia 5- 10 Weeks) Enters back to abdominal cavity by 10week Intestinal loops

34. Contents of Umbilical cord at full term Two umbilical arteries . Convey deoxygenated blood from fetus  mother. One umbilical vein early in pregnancy veins are two later rt. Umbilical vein disappears & left U V persists & carries oxygenated blood from placenta  fetus 2-UA 1-LUV

35. After birth umbilical cord is ligated

36. The circulation of blood in umbilical arteries is first stopped by reflex spasm of muscular wall, followed by cessation of blood flow in the vein

37. Short cord Short cord may cause difficulty during delivery by pulling the placenta from its attachment in the uterus (premature separation) Clinical correlation of umbilical cord Normal umbilical cord

38. Extremely long cord may encircle the neck of fetus : strangulation & hypoxia of fetus Normal umbilical cord Long cord

39. Cord prolapse long cord compressed b/w head of fetus & Pelvic wall of mother leading to hypoxia of Fetus Cord prolapse

40. One umbilical artery & one umbilical vein is associated with Cardio vascular defects & other anomalies. Abnormal

41. Applied Colour flow Doppler Ultrasonography may be used for prenatal diagnosis of abnormalities of umbilical cord & its vessels.

42. 2. Amnion Extraembryonic membrane that surrounds the fetus, protects it from external shocks or jolts

43. Development : Amniotic sac appears during 2 nd week of development

44. Amniotic fluid is Clear & watery & produced by amniotic cells Amniotic cavity

45. Amount of Amniotic fluid increases from 30ml at 10 weeks 450ml at 20weeks 800-1000ml at 38 weeks(at term)

46. Fetus is suspended by its umbilical cord in the amniotic fluid which acts as protective cushion Umbilical cord Amniotic fluid Fetus

47. Factors regulating the volume of Liquor amnoii Beginning of 5 th month fetus swallows its own amniotic fluid about 400ml a day It is absorbed by gut , then into blood stream. It then passes to maternal blood via placenta. Fetal urine is added daily to the amniotic fluid from 5 th month by fetal kidney , but this urine is mostly water, because the placenta functions as an exchange for metabolic wastes.

48. Absorbs jolts of fetus & prevents injuries. Prevents adherence of embryo to the amnion. Allows free movements of fetus aiding muscular development Maintains symmetrical external growth and differentiation of delicate tissues of embryo & mainly lung growth Assists in maintaining homeostasis of fluid & electrolytes. Functions Normal :1000ml-1200 ml

49. Abnormalities of liquor amnoii Polyhydramnios (Hydramnios) – high volume of amniotic fluid exceeds more than 2 litres. A) It occurs when fetus is unable to swallow in esophageal atresia or B) Anencephaly (swallowing reflex is absent) C) Maternal diabetes. Polyhydramnios

50. Oligohydramnios: decreased amount of fluid less than 400ml . It may be due renal agenesis. Oligohydramnios causes 1. Club foot 2. Lung hypoplasia 3. Facial defects Oligohydramnios

51. Premature rupture of amnion , is common cause of preterm labour. Causes of rupture sometimes may be due to trauma. Premature rupture

52. Amniotic bands is due infections & toxins. They form rings around the limbs & fingers causing physiological amputation of the part Amniotic band syndrome

53. Clinical importance Amniocentesis : aspiration of amniotic fluid through cervix or anterior abdominal wall. Nuclear sexing of fetus in sex linked diseases. Estimation of enzymes in case of gross fetal malformations.

54. 3.Yolk sac formed during 2 nd week 1. Primary:10 th day 2. Secondary :14 th day 3. Definitive Yolk sac : 3 rd week Primary Yolk sac Secondary Yolk sac

55. As the result of Cephalo caudal folds & lateral folds large portions of endodermal germ layer & yolk sac is incorporated into body of embryo to form gut tube Flattened trilaminar germ disc Primitive gut tube

56. The portion of Yolk sac not taken up by embryo is termed as Definitive yolk sac Definitive Yolk sac

57. Function /Role of yolk sac Nutritive organ during early stages prior to development of blood vessels. Hemopoiesis &Contributes for first blood cells. F orms Primitive gut(4 th week) & Respiratory system P rovide Primordial germ cells

58. 4.Allantoic diverticulum Allantoic diverticulum(3 rd week) arises from ventral wall of hindgut & forms Endodermal cloaca. Allantois Hindgut

59. 5. Chorion: 2 nd week Derived from EEM Chorion is one of the membranes that surround the  fetus : Nutrition Coelomic cavity

60. Chorion 2 main Functions: 1. Chorionic fluid in chorionic cavity protects the embryo 2 . Chorion villi which are extensions of the chorion that pass through the uterine decidua and connect with the maternal blood vessels. 

61. Chorion tertiary villi differentiates : Chorionic Frondosum (Placenta)overlapped by Decidua Basalis Chorionic Laeve (degenerates) overlapped by Decidua capusularis

62. Clinical correlation Chorionic villous biopsy is done to detect Genetic disorders in the fetus 8-10 WEEKS

63. 11 11. Umbilical cord

64. Eutherian Mammals Possess Placenta Human Placenta Is Discoid, Haemochorial & Deciduate

65. Placenta-Highly Vascular Attached to Uterine wall & establishes connection b/w Mother & Fetus via Umbilical cord Human Placenta Umbilical cord Uterine wall Fetus

66. Placenta in Latin means “a flat cake” In mammals develop during pregnancy. Fetomaternal Organ Human Placenta

67. Human placenta is Discoid, Haemochorial and Deciduate which connects the Fetus with uterine wall of the Mother. Discoid

68. Placental Structure has Maternal & Fetal tissues that come direct contact without rejection suggesting immunological acceptance. Maternal surface Fetal surface

69. Shortly after birth of fetus, placenta & fetal membranes are expelled from the uterus Placenta

70. EMBRYOBLAST TROPHOBLAST Embryoblast forms the Embryo proper Blastocyst: 5 th -6 th day

71. Development of Human Placenta Two sources Foetal part Trophoblast & extra embryonic mesoderm  Chorionic frondosum . Maternal part Uterine endometrium  Decidua basalis Chorionic frondosum Decidua basalis

72. Placental development starts as soon as the Blastocyst gets Implanted into endometrium : 1. 7 th day (1 week) & is completed by 12 th week/3month 2.Two layers of Trophoblast Multilayer Syncytiotrophoblast & Mononuclear Cytotrophoblast 3.Syncytiotrophoblast: Utero- Placental circulation

73. Changes in the Trophoblast- 3 rd week Primary, secondary & tertiary Villi

74. Plate Villi projection from chorion is chorionic villi.

75. Villi extend from chorionic plate to Decidual plate (D. basalis) are stem villi or Anchoring villi. Those that branch from the sides of stem villi are Floating villi

76. Extra embryonic vascular system is first formed which later communicates with intra embryonic vascular system & Heart by end of 3 rd week (22 nd day). Extra embryonic vascular system Intra embryonic vascular system Primordial Heart

77. Capillaries in tertiary villi make contact with capillaries developing in mesoderm of chorionic plate & with blood vessels the connecting stalk. Vessels of connecting stalk establish connection with intra embryonic circulating system which is also simultaneously developing. . End of 3 rd week: The villous system ready to supply the embryo proper with essentials & nutrients Chorionic Plate

78. Villous system of Trophoblast is ready to supply nutrients & O2 to embryo by 21 st -22 nd day Heart beats on 22 nd day. Chorionic villous biopsy is done to detect genetic disorders in the fetus Villous system

79. Early weeks of development (3 rd week) villi covers entire surface of Chorion & as pregnancy advances villi are more pounced at embryonic pole Embryonic pole

80. As pregnancy advances villi are more pounced at embryonic pole & continue to grow & expand give it a bushy appearance  Chorionic Frondosum Chorionic Frondosum

81. Villi at embryonic pole Chorionic Frondosum Villi at abembryonic pole degenerate. Chorionic Laeve 3 rd month/12 weeks Chorionic Frondosum bushy Chorionic Laeve

82. End of 3 rd week of development End of 4 th week of development

83. Chorionic frondosum overlapped by Decidua Basalis ( abundant lipid & glycogen). Chorionic laeve (less) Decidua Capsularis

84. CHORIONIC PLATE DECIDUAL PLATE

85. With increase in size of chorionic cavity , D.Capsularis is stretched & degenerated & subsequently Chorionic Laeve comes in contact with D. Parietalis. On the opposite side of uterus the two fuse thereby obliterating the uterine lumen . D. Parietalis lumen Chorionic laeve D. Capsularis Chorionic cavity

86. Only portion of chorion participating in exchange process is Chorionic Frondosum& Decidua Basalis which make up the placenta. Chorionic Frondosum Decidua Basalis Uterine cavity Placenta

87. Amniotic cavity also enlarges obliterating chorionic cavity leading to Fusion of amnion & chorion together & form amnion-chorionic membrane. It is this membrane that ruptures during labor. (breaking of water) amnion- chorionic membrane.

88. Structure of Placenta 4month(16weeks) 2 components Foetal part: Chorionic frondosum Maternal part: Decidua basalis On foetal side  placenta is bordered by chorionic plate , on the maternal side is decidua basalis , ( Decidua plate) Foetal part: Chorionic Frondosum Maternal part: Decidua Basalis Chorionic plate Decidua plate

89. b/w Chorionic plate & Decidual plate are Intervillous spaces filled with maternal blood in which are floating villi. Intervillous spaces

90. 4 th MONTH  decidua septa projects into Intervillous spaces but do not reach chorionic plate. As result of septum placenta is divided by number of compartment the cotyledons. Chorionic plate Cotyledons Decidua septa

91. Placental surface area is parallel to expanding uterus, through out pregnancy. Covers 15-30% of internal surface of uterus.

92. From stem villi(tertiary villi) branch floating villi which project in to Intervillous spaces. Terminal villi form functional units of placenta . Tertiary villous/ Stem Villi Floating villi/ Terminal villi

93. Each terminal villi is covered by 2 layers of trophoblast i.e. inner cytotrophoblast & outer Syncytiotrophoblast. Central core of villous 1. 1-6 Fetal capillaries 2. Stromal cells / Primitive Mesenchymal cells 3.Reniform Hofbauer cells (phagocytic)

94. Early part (3 Month) of pregnancy about 800-1000 stem villi radiate from entire chorionic wall. Later with regression of chorionic laeve (4 Month) only 60 stem villi persist in Human placenta. Early part Later part Chorionic villi

95. Maternal cotyledons are 15-30 in number Each cotyledon contains 2-4 stem villi with 2-4 fetal capillaries . Cotyledons 2-4 stem villi

96. Adult placenta

97. MACROSCOPIC APPEARANCE OF PLACENTA Foetal surface Maternal surface Foetal surface Maternal surface

98. Full term placenta : Discoid diameter 15-25 cms, 3cm thick weighs 500 to 600g . At birth torn from uterine wall, approximately 30minutes after birth of the child & is expelled from the uterine cavity Two surfaces 1.Foetal surface covered by chorionic plate . 2.Maternal surface irregular with 15-30 cotyledons 3. Peripheral margin. F M

99. Foetal surface: Large number arteries & veins converge toward the umbilical cord. Attachment of umbilical cord is usually eccentric or marginal.

100. Maternal surface: rough, irregular with 15-30 cotyledons covered by decidua basalis. F M M

101. placental Placental Circulation placental Utero- Placental Circulation placental Feto - Placental Circulation

102. Umbilical vein Umbilical arteries Fetal circulation Maternal circulation Endometrial veins & arteries Placenta at Term

103. P lacental circulation Umbilical Arteries(2)  C horionic arteries  intervillous spaces  E ndometrial veins  Mother. Mother  Endometrial arteries IVS C horionic veins U mbilical vein UA(2) CA EV EA CV UV IVS IVS

104. About 600ml of Maternal blood circulates through the Intervillous spaces / min. IVS

105. Volume of Intervillous spaces is 150 ml. Blood within the space therefore exchanged 4 times per min. Intervillous spaces

106. Placental Membrane(barrier ) which separates maternal blood from fetal blood • Early: 0.025mm: 4 layers(up to 4 month) • Later: 0.002mm: 2 layers (5 month onwards) In early(4M) pregnancy In later pregnancy

107. 1. Placenta succenturiate Accessory placenta connected to main placenta by Foetal membrane 2. Battle Dore Placenta Umbilical cord attached close to margin of placenta. 3 .Velamentous Placenta Cord fails to reach the placenta & attached to Foetal membranes Types of Placenta 1. 2. 3.

108. Battle Dore placenta Velamentous Placenta Placenta succenturiate

109. Abnormal Site of implantation Placenta previa lower part of uterus serious bleeding during parturition Placenta previa

110. Abruption placenta Premature separation of placenta

111. Degree of adhesion Placenta Accreta  adhered to D. Basalis. Placenta Increta  penetrates into myometrium. Placenta percreta  penetrates into uterine wall

112. Clinical Correlation

113. Erythroblastosis fetalis & Fetal Hydrops Fetal red blood cells antigens cross the placental barrier & stimulate maternal antibody These antibodies will attack & hemolyze fetal cells resulting in hemolytic disease in the new born Erythroblastosis fetalis Anaemia  leads to edema  Fetal Hydrops leading to fetal death Clinical correlation