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Revision on General Embryology 2
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- 2. Fetal membranes: 1- Chorion 2-Placenta. 2- Amnion. 3- Umbilical cord. 4- Yolk sac. Dr.Sherif Fahmy
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- 4. It is thewall of chorionic vesicle. Time: Chorionic vesicle is formed at the 12th day by the formation of extra-embryonic mesoderm. Structure of chorion: 1- Syncytiotrophoblast. 2- Cytotrophoblast. 3- Somatic extra-embryonic mesoderm. Chorionic velli: 1- Primary. 2- Secondary. 3- Tertiary. Dr.Sherif Fahmy
- 5. Connecting stalk Somatic mesoderm Syncytio- trophoblast Cyto- trophoblast Chorion ChorionicVesicle Dr. Sherif Fahmy Dr. Sherif Fahmy Dr.Sherif Fahmy
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- 8. Dr. Sherif Fahmy Syncytio- trophoblast Cyto- trophoblast Mesoderm Fetalblood vessels Tertiary chorioniv villus Dr.Sherif Fahmy
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- 12. Morphology of Placenta •It is the organ of exchange of materials between fetal and maternal blood. • Shape: Disc like. • Surfaces: • -Fetal surface: It is covered with amnion and fetal blood vessels. Umbilical cord is attached near the center of this surface. • -Maternal surface: Shows 15 – 20 rounded elevations (cotyledons) with septa inbetween). • Diameter: 15 -25 cm. • Thickness: About 3 cm. • Weight: About 500 – 600 gm • Site: At original implantation site which is upper part of posterior wall of uterus. Dr.Sherif Fahmy
- 13. Cotyledon Groove between cotyledons Umbilical cord Maternalsurface Dr. Sherif Fahmy Dr.Sherif Fahmy
- 14. Fetal surface covered withamnion Umbilical cord Dr. Sherif Fahmy Dr.Sherif Fahmy
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- 21. Decidua basalis Arteriol Venule Decidual septum Cytotrophoblasticshell Decidual plate Stem villous Floating velli Intervillous space Chorionic plate Umbilical veinUmbilical artery Amnion Mesoderm Syncytiotrophoblast Cytotrophoblast Dr. Sherif Fahmy Dr.Sherif Fahmy
- 22. Placental barrier: It isthe separation between fetal and maternal blood. Structure: 1- Syncytiotrophoblast. 2- Cytotrophoblast. 3- Extraembryonic mesoderm. 4- Endothelium of fetal blood vessels. Functions of the barrier: 1- Separates between fetal and maternal blood. 2- Permites gaseous and nutritive exchange. 3- Prevents passage of bacteria, most viruses and damaging factors. Disappear in 2nd ½ of pregnancy Dr. Sherif Fahmy
- 23. Placental circulation: 1- Maternalpart: Maternal blood flow from endometrial arterioles to the intervillous spaces where floating velli are bathed in maternal blood. Exchange of gases and nutritive materials occurs. Then blood flows back from chorionic plate to endometrial veins. 2- Fetal part: umbilical arteries carry venous blood of the fetus to placenta while umbilical veins carry blood loaded with nutritive material and oxygen. Dr. Sherif Fahmy
- 24. Functions of placenta 1-Exchange of gases and metabolites. 2- Transmission of maternal antibodies starting from 14th week. 3- Production of hormones as progesterone, estrogen, HCG and somatomammotropin 3- Barrier against bacteria and most of viruses. 4- Excretory function as it excretes urea and creatinine. Dr. Sherif Fahmy
- 25. Anomalies of Placenta 1-Abnormalities in position: A- Placenta previa parietalis. B- Placenta brevia marginalis. C- Placenta brevia centralis. 2- Abnormality in shape: A- biloped placenta. B- Triloped placenta. 3- Abnormality in number: A- Twin placenta. B- Accessory placenta. 4- Abnormality in attachement of umbilical cord: A- Velamentous. B- Battle door. Dr. Sherif Fahmy Dr. Sherif Fahmy
- 26. Placenta previa Marginalis & parietalis Dr. SherifFahmy Dr. Sherif Fahmy
- 27. Placenta previa centralis Dr. Sherif Fahmy Dr.Sherif Fahmy
- 28. Velamentous placenta Dr. Sherif Fahmy Dr.Sherif Fahmy
- 29. Battle door placenta Dr.Sherif Fahmy Dr. Sherif Fahmy
- 30. Accessory placenta Dr. SherifFahmy Dr. Sherif Fahmy
- 31. Placenta acreta Placenta percreta Dr.Sherif Fahmy Dr. Sherif Fahmy
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- 33. AMNION -It is amembrane that enclose amniotic cavity. -Formation: -It is formed at the 8th day as a small cavity in epiblast cells with formation of amnioblasts. -So, floor of the cavity is epiblast while the roof is formed from amnioblasts. -By the 12th day it becomes separated from cytotrophoblasts by primary mesoderm (Extraembryonic). -Amnio-ectodermal junction is at the margin of oval embryonic disc at the 3rd week.
- 34. 8th day of pregnancy Dr.Sherif Fahmy Amnioblast Amniotic cavity Epiblast Hypoblast Dr. Sherif Fahmy
- 35. 9th & 10th days Dr. SherifFahmy Cyto- trophoblast Amnioblast Amniotic cavity Epiblast Dr. Sherif Fahmy
- 36. Dr. Sherif Fahmy Dr.Sherif Fahmy
- 37. -At 3rd month amnioncomes in contact with chorion to form amnio-chorionic membrane with obliteration of chorionic cavity. -By the end of 3rd month, uterine cavity is obliterated due to expansion of amniotic cavity. -Finally, the amniotic cavity surrounds the fetus and forms a tubular sheath around the umbilical cord. -Expansion of amniotic cavity leads to folding of the embryonic disc and amnio-ectodermal junction will be present at primitive umbilical ring. Dr. Sherif Fahmy
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- 39. Dr. Sherif Fahmy Dr.Sherif Fahmy
- 40. Dr. Sherif Fahmy Dr.Sherif Fahmy
- 41. Dr. Sherif Fahmy Extraembryoniccoelom (Chorionic Cavity) Dr. Sherif Fahmy
- 42. Dr. Sherif Fahmy Dr.Sherif Fahmy
- 43. Dr. Sherif Fahmy Deciduabasalis Decidua parietalis Decidua capsularis Chorion frondosum Uterine cavity Amniotic cavity Chorion frondosum Fused decidua parietalis and capsularis Amniotic cavity Decidua basalis Chorionic cavity Dr. Sherif Fahmy
- 44. Amniotic fluid - Normalvolume is 1000 – 1500 cc clear watery fluid. - Source: 1st from amnioblast then from kidney. - If the volume is less than 500 cc it is called oligohydramnios. -If the volume is more than 2000 cc is called polyhydramnios. Dr. Sherif Fahmy
- 45. Functions of amnioticfluid: 1- At early pregnancy: 1- Acts as water cushion that absorbs external shocks. 2- Acts as heat insulator. 3- Prevents adhesion of embryo to wall of uterus. 4- Prevents adhesion of fetal parts. 2- At late pregnancy: 1- A space for accumulated urine. 2- Allows fetal movements to help body muscles to develop. 3- Help suckling training and development of gut muscles. Dr. Sherif Fahmy
- 46. 3- During labor: 1-Protects against uterine contractions. 2- Formation of bag of water that gradually dilate the cervix. 3- Sterile amniotic washes vagina before passage of baby. 4- Rupture of amniotic sac is a sign of start of delivery. Dr. Sherif Fahmy
- 47. Abnormalities of amnioticfluid: 1- Polyhydramnios. Causes: 1- No cause (35 %). 2- Maternal diabetes. 3- Congenital malformation e.g. anencephaly and esophageal atresia. 2- Oligohydramnios. Cause: -Renal agenesis. 3- Premature rupture of amnion. Dr. Sherif Fahmy
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- 49. Fate & developmentof yolk sac • Primary yolk sac: It replaces cavity of blastocyst after the formation of Heuser’s membrane which is formed of flat cells that originate from hypoblast cells at 9th & 10th day. • Secondary yolk sac: additional endodermal cells from hypoblast cells will line the Heuser’s membrane, reduction of size of yolk sac and formation of allantois. This occurs in the 13th day. • Defenitive yolk sac: During 3rd week, hypoblast become replaced by endoderm. After folding, it shares in formation of gut and the part remains outside the embryo is called defenitive yolk sac. It is connected to yolk sac by vitello-intestinal duct.
- 50. 7th day: Dr. Sherif Fahmy Dr.Sherif Fahmy
- 51. 8TH Day of Pregnancy Endometrium CytotrophoblastsHypoblasts Amniotic cavity Epiblast Dr.Sherif Fahmy Dr. Sherif Fahmy
- 52. 9th & 10th days Primary yolksac Heuser’s membrane Hypoblast Amniotic cavity Epiblast Dr. Sherif Fahmy
- 53. 13th day Endodermal cells Secondary yolk sac Exocoelomic cyst Extra- embryonic coelom Chorionic cavity) Dr.SherifFahmy Chorionic Vesicle Dr. Sherif Fahmy
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- 56. Functions of yolksac: • Formation of gut: foregut, midgut and hindgut. • Allantois: forms part of urinary bladder. • Primordial germ cells: Which are spermatogonia and oogonia which are formed in its caudal part (hind gut). • Vitelline vessels: develop from mesoderm around vitelline duct. Intra-embryonic part form portal vein and arteries of intestine. • Blood cells: develop in the mesoderm around the yolk sac. Dr.Sherif Fahmy
- 57. Abnormalities of Yolk Sac •1- Vitelline cyst and fistula due to persistence of vitelline duct. • 2- Urachal cyst and fistula due to persistence of urachus from allantois. Dr.Sherif Fahmy
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- 61. Morphology of UmbilicalCord It is the connection between placenta and fetus. • Length: 50 – 60 cm • Diameter: 2 cm. • Shape: Tortous, showing false notes. • Contents: 2 umbilical arteries, one umbilical vein embedded in wharton’s jelly and surrounded by amniotic membrane. • Attachments: It is attached to fetal surface of placenta near its center, the other attachment is to ventral aspect of fetal abdominal wall. • Functions: – It contains umbilical vessels that connect the fetus to the placenta. Dr.Sherif Fahmy
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- 64. Development of theCord • Primitive umbilical ring: - Expansion of amniotic cavity, leads to folding with ventral shifting of amnio-ectodermal junction and formation of primitive umbilical ring - Contents: -Connecting stalk containing allantois and umbilical vessels. -Vitelline duct and vitelline vessels. -Connection between intraembryonic and extra- embryonic coelom. Dr.Sherif Fahmy
- 65. Primitive umbilical cord: -Expansion of amniotic cavity, leads to elongation of umbilical cord. Contents: 1- Yolk sac and vitelline duct. 2- Connecting stalk with remnant of allantois. 3- Intestinal loop in its proximal part. 4- Umbilical and vitelline vessels. Dr.Sherif Fahmy
- 66. Definitive umbilical cord: -Return of intestinal loop to abdominal cavity at 3rd month. -Obliteration of vitelline duct, allantois, extra- embryonic part of vitelline vessels. -Degeneration of one umbilical vein with persistence of other vein and 2 umbilical arteries. -Transformation of mesoderm of connecting stalk into wharton’s jelly. Dr.Sherif Fahmy
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- 68. Embryonic disc withremoved ectoderm Intra- embryonic ceolom Dr.Sherif Fahmy
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- 76. • Abnormalities ofUmbilical Cord • 1- Short cord: leads to premature separation of placenta. • 2- Long cord: It may encircle neck of fetus and may form true knots. • 3- Congenital umbilical hernia (omphalocele): the cord contains coils of intestine. • 4- Presence of one umbilical artery. • 5- Abnormal attachment of the cord: –Marginal attachment (battledore) –Through membranes (velamentous). Dr.Sherif Fahmy
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- 81. Types of TWINS Dizygotic(Fraternal) twins: - It is the commonest type as it represent 2/3 of twins and 7 – 11 / 1000 births. - Fertilization of 2 separate ova. - Each embryo has its own placenta, chorion and amniotic cavity. - Twins are non-identical and may of same sex or different. Dr.Sherif Fahmy
- 82. Monozygotic (Identical) twins: Developedfrom division of a fertilized ovum. Twins of this type are identical and of same sex. Its incidence is 0.3 – 0.4 % Division may occure at 3 different stages: 1- At morula stage: Twins has separate amnion, chorion and placentae (as in dizygotic). 2- At blastocyst stage: due to division of inner cell mass. Twins has separate amniotic cavity but single chorion and placenta. 3- At embryonic disc: Midline division of the embryonic disc. Twins has common amniotic cavity, common chorion and common placenta . Dr.Sherif Fahmy
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- 84. SIAMESE (CONJOINED) TWINS •Fused monozygotic twins that occurs due to incomplete separation of emberyonic disc. They could be either: Craniopagus: Fusion between 2 heads. Thoracopagus: Fusion at thoracic region. Pygopagus: Fusion at the pelvic region. Dr.Sherif Fahmy
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- 90. Cri du ChatSyndrome Dr.Sherif Fahmy
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- 93. A Child ofA Mother Treated by Antiepileptic drug
- 94. A Child ofA Mother Treated with Antithyroid drug
- 95. A Child ofA mother Exposed to Rubella Infection
- 96. External Appearance ofthe Embryo (4th – 8th week) At the embryonic period (4th – 8th week), human shape becomes easily identified. -Head, body and limb buds are easily identified. -Eyes, nose and ears are seen. Dr.Sherif Fahmy
- 97. C-R length inmms Age of embryo in weeks 5 – 8 5 10 – 14 6 17 – 22 7 28 – 30 8 Dr.Sherif Fahmy
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- 99. C-R length incm Age of embryo in months 5 – 8 cm 3rd month 18 cm 5th month 36 cm Full term fetus at birth Dr.Sherif Fahmy
- 100. Relative size ofhead to body: -At the beginning of the 3rd month, the head is ½ the CR length. -At the beginning of the 5th month, the head is 1/3 the CH length. -At birth, the head is ¼ of CH length. Weight growth: -At the end of 5th month, the weight is ½ kg. -At the 7th month, the weight is 1.75 kg. -At full term, the weight is 3.5 kg. Dr.Sherif Fahmy
- 101. Changes in externalfeatures: -Face becomes human looking. -Limbs become longer. -External genitalia are differentiated at 12th week. -Lanugo hair covers the fetus since the 4th month. -The skin is wrinkled till the end of 6th month. -Testes descend to scrotum just before birth. -Skin is covered by fatty substance called vernix caesosa. Fetal movement: It is clearly recognized since the 5th month. Dr.Sherif Fahmy
- 102. The End & Beginning Withmy best wishes Dr. Sherif Fahmy