1. GENERAL EMBRYOLOGY 1. Development of embryology
2. Germ cell and fertilization
3. Blastocyst and implantation
4. Formation of the germ layer
5. Differentiation of trilaminar germ and formation of embryo
6. Fetal membrane and placenta
7. Twins and multiple birth

2. Preembryonic period: 1st week to end of 2nd week
fertilization to formation of bilaminar germ disc
Embryonic period: 3rd week to end of 8th week
formation of embryo
Fetal period: 9th week to birth
growth
Perinatal stage: 26th week to 4 week after birth

3. Animal
Plant
Human ？

4. Development of embryology
Aristotle, B.C
Semen+menstration
Harvey, 1651:
All life from oocyte
Malpighi, 1675:
A micro-chicken in an egg
Leewenhoek, 1677 :
A micro-human in a sperm

5. Haeckel, 1868 Spemann, 1869-1941 Wilmut,1997 Biogenetic law
Experimental embryology
Wilmut,1997
Dolly

6. Germ cell and fertilization
spermatozoon and ovum
1. Spermatozoon
Capacitation：In female reproductive tract, the sperms were enabled to bind to the zona pellucida receptors.
removal of glycoproteins (decapacitation factor) which cover the sperms
2. Ovum
secondary oocyte arrested at metaphase in the second meiotic division

7. Fertilization: The process in which the spermatozoon penetrates into the ovum to form fertilized ovum In the ampulla of oviduct

8. Process of fertilization
Sperm bind to sperm receptor ZP-3 induce
Acrosome reaction：release of acrosomal enzyme
Cell membrane of ovum
Penetration and release of acrosomal enzyme
nucleus
acrosome

9. ovum
fertilized ovum
sperm

10. Zona reaction: Cortical granules→perivitelline space →degrade ZP-3, alteration of zona pellucida →barrier for sperm penetration
The second meiotic division of the secondary oocyte is rapidly lifted and the second polar body is released, leaving a haploid female nucleus.

11. Contac of sperm and ovum

12. Sperm penetrate into the ovum

13. Formation of female and male pronucleus

14. Fusion of pronuclei

15. Process of fertilization
① Fusion of the
membrane of
sperm and ovum
② The nucleus
of sperm
penetrate into
ovum
③ Formation of
pronuclei
④ Fusion of
pronuclei
Alteration of ovum
24 h

16. 2.Condition of fertilization
① Normal ovum
② Normal sperm
sufficient numbers
③ Certain time
12-24h
④ Free reproductive tract

17. 3.Significance of fertilization
① A new life
② Diploid
inheritance and aberrance
③ Sex determination

18. Formation of blastocyst and implantation
Cleavage and formation of blastocyst
1. Cleavage： early division of fertilized egg
2. Blastomere：daughter cells from cleavage
3. Morula：12 to 16- cell stage, enclosed in the zona pellucida,
like morus
4. Blastocyst：about 100 blastmeres
blastocoele、inner cell mass and trophoblast
polar trophoblast

19. Phase of cleavage Fertilized egg 2-cell stage 18~36h 4-cell stage

20. Morula
12 to 16-cell stage
The third day

21. Appearance and inner structure of blastocyst

22. Movement of fertilized egg in the oviduct

23. Implantation (imbed) into endometrium. 6th day to 11th day
The process by which the blastocyst settles
into endometrium th day to 11th day
Fundus and body of uterus
zona pellucida disappear at the 5th day
1.Trophoblast：proliferate and differentiate into two layers
①Syncytiotrophoblast：outer layer, fused each other, cell boundaries disappear
②Cytotrophoblast：inner layer， cell boundaries distinct, simple cuboidal cells

24. Movement and implantation of fertilized egg

25. Implantation at 7th day Cytotrophoblast Inner cell mass
Polar trophoblast
Endometrium

26. 2.Decidua： endometrium implantation decidua decidual response
Decidua basalis：under the implantation site
Decidua capsularis：between the implantation
site and the uterine lumen
Decidua parietalis：remaining endometrium

27. Decidua

28. Formation of germ layer
Bilaminar germ disc
1.Bilaminar germ disk：
Inner cell mass→2 layers of cell in disc (7th day)
Epiblast: columnar cells adjacent to trophoblast
Hypoblast: cuboidal cells adjacent to blastocoele

29. Epiblast
Columnar cells
Bilaminar germ disc
Hypoblast
Cuboidal cells
Epiblast
Hypoblast

30. 2. Amnion：8th day
epiblast → amnioblast → aminiotic membrane → amniotic cavity → amniotic fluid
3.Primary yolk sac： 9th day
hypoblast →extraembyronic endoderm →primary yolk sac

31. Bilaminar germ disc at 9th day
Primary yolk sac
Hypoblast
Epiblast
Amniotic cavity
Syncytio-trophoblast

32. Bilaminar germ disc Decidua Syncytiotrophoblast Cytotrophoblast
Amniotic cavity
Epiblast
Hypoblast
Primary
yolk sac

33. 4. Extraembryonic mesoderm: 10th-11th day
5. Extraembryonic cavity: 12th-13th day
Extraembryonic mesoderm: visceral layer
parietal layer
6. Secondary yolk sac: 13th day
7. Body stalk: 14th day

34. Extraembryonic mesoderm
Embryo at 10th day
Primary yolk sac
Extraembryonic mesoderm
Germ disc
Amnion

35. Bilaminar germ disc Decidua Amniotic cavity Epiblast Hypoblast
Primary
yolk sac
Hypoblast
Cytotrophoblast
Extraembryonic mesoderm
Syncytiotrophoblast

36. Embryo at 13th day Extraembryonic cavity Primary yolk sac
Secondary yolk sac
Body stalk

37. Bilaminar germ disc Primary stem villus Body stalk Secondary yolk sac
Extraembryonic mesoderm
Visceral layer
Secondary
yolk sac
Extraembryonic cavity
Extraembryonic mesoderm
Parietal layer

38. Formation of trilaminar germ
Trilaminar germ disc
primitive streak, primitive groove rd week
primitive node, primitive pit rd week
1. Endoderm: primitive groove →hypoblast → endoderm
2. Mesoderm： primitive groove →between epiblast and hypoblat →mesoderm
3. Ectoderm：epiblast →ectoderm

39. Primitive streak Primitive streak Epiblast Hypoblast Epiblast

40. Significance of primitive streak Determine the direction of the embryo
notochord
Significance of
primitive streak
Primitive node
Primitive pit
Primitive
groove
Primitive
streak

41. Formation of endoderm
Epiblast
Primitive
streak
Hypoblast
Endoderm

42. Formation of mesoderm
Epiblast
Mesoderm
Endoderm

43. Trilaminar germ disc
Ectoderm
Mesoderm
Endoderm

44. Significance of notochord ?
proliferation
Head
process
Notochordal tube
Neurenteric canal
Epiblast
Notochord
Primitive pit
Significance of notochord ?

45. Buccopharyngeal membrane
No mesoderm
Buccopharyngeal membrane
Cloacal membrane

46. Differentiation of trilaminar germ and formation of embryo
1.Differentiation of ectoderm
①Neural tube：blastema of CNS
neural plate (18th-19th day)
Neuro-epithelium (neural ectoderm): pseudostratified columnar
→neural groove , neural fold
→ neural tube (closed at 22nd day)

47. Neural groove
Paraxial mesoderm Intermediate mesoderm

48. Neural groove
Paraxial mesoderm intermediate mesoderm

49. Neural groove
Neural crest
Notocord

50. 1、Differentiation of ectoderm
Anterior neuropore closed at 25th
Neural fold
Neural tube
closed at 22nd day, from 4th somite
Posterior neuropore closed at 27th

51. Unclosed Anterior neuropore
Unclosed Posterior neuropore

52. ②Neural crest： blastema of PNS
chromaffin cell, parafollicular cell
some of bone, cartilage and
muscle of head
③Superficial ectoderm: after formation of neural tube
epidermis

53. 2.Differentiation of mesoderm 17th day
①Paraxial mesoderm：somite at 20th day, from the head
Dermotome→ dermis, hypodermis
Myotome → skeletal muscle,
Sclerotome → axial skeleton.
②Intermediate mesoderm：urinary and
reproductive system
③Lateral mesoderm：parietal mesoderm，
viseral mesoderm，
intraembryonic coelomic cavity

54. Somite

55. Differentiation of lateral mesoderm
Dermatome
Sclerotome
Parietal mesoderm
Intraembryonic
coelomic cavit
Visceral mesoderm

56. Differentiation of lateral mesoderm
Intraembryonic coelomic cavity
Extraembryonic coelomic cavity

57. 3. Differentiation of endoderm Epithelium of primitive gut →
epithelium of digestive tract, digestive gland,
respiratory tract and lung
Primitive pharynx →5 pairs of pharyngeal pouch

58. Formation of primitive gutB

59. Intraembryonic coelomic cavity
Parietal mesoderm
Intraembryonic coelomic cavity
Visceral mesoderm

60. Formation of embryonic body (4-8th week)
20-30th day
Disc
folds
Column
the number of somite increase
face development, formation of branchial pouch
breach of buccopharyngeal membrane
5th week: upper and lower limb buds
6th week: hand and foot plates
7th week: formation of face, disappear of somite
8th week: breach of cloacal membrane

61. At the end of 8th week—
a small human

62. Fetal membrane and placenta
Chorion
Amnion
Yolk sac
Allantois
Umbilical cord

63. Amnion
Yolk sac
Umbilical cord
Placenta

64. Secondary stem villus +chorinic plate
1.Chorion：
Secondary stem villus +chorinic plate
Primary stem villus：2nd week
Outer syncytiotrophoblast+
Inner cytotrophoblast
Chorinic plate : extraembryonic mesoderm +
trophoblast

65. Tertiary stem villus：end of 3rd week, Blood vessels
Secondary stem villus：3rd week
Outer syncytiotrophoblast+
Intermedial extraembryonic mesoderm+
Inner cytotrophoblast
Tertiary stem villus：end of 3rd week, Blood vessels
Anchoring villus, Free villus
cytotrophoblastic cell column →
cytotrophoblastic shell

66. Primary stem villus：at 2nd week，cytotrophoblast
Secondary stem villus：at 3rd week，extraembryonic mesoderm
Tertiary stem villus：at the end of 3rd week，blood vessels

67. Cytotrophoblastic column Cytotrophoblastic shell
Stem villus
Free villus
Anchoring villus
Cytotrophoblastic column
Cytotrophoblastic shell

68. Evolvement of chorion 6th weeks
Chorion laeve：adjacent to decidua capsularis
Chorion frondosum： adjacent to decidua basalis
6th weeks
Chorion laeve
Chorion frondosum

69. Abnormility of chorion：
Hydatidiform
Picture
Chorion carcinoma

70. Hydatidiform

71. Hydatidiform

72. Hydatidiform

73. Chorion carcinoma

74. Chorion carcinoma

75. Chorion carcinoma

76. 2. Yolk sac：5th-6th week, atresia
Abnormality:
① Meckel’s diverticulum
② Umbilical fistula　
① Primitive blood cells
② Primordial germ cells

77. amniotic membrane: 0.2-0.5mm
3. Amnion：
amniotic membrane: mm
amniotic epithelium + extraembryonic mesoderm
amniotic fluid: ml
abnormality: ＜500 ml, oligohydramnios
＞2000 ml, polyhydramnios
protection

78. 4. Allantois：degeneration
Abnormality:
Urachal fistula
2 pairs of blood vessel→
1 umbilical vein
1 pair of umbilical artery

79. (CT, umbilical vein， umbilical artery, covered with amniotic membrane
5. Umbilical cord：50 cm
(CT, umbilical vein， umbilical artery,
degenerated yolk sac and allantois)
covered with amniotic membrane
Abnormality: ＞80 cm,
＜35 cm
connect fetus with placenta

80. Fetal membrane

81. Placenta 1.Placenta: Chorion frondosum + Decidua basalis disk: 15-20cm
Sandwich: chorinic plate (fetus)
villi
basal plate (mother)
basal plate: decidua + cytotrophoblastic shell
placental septa → cotyledon (incomplete)

82. Umbilical artery
Umbilical vein
Decidua bsalis
Placenta septa
Uterus vein
Spiral artery

83. Structure between the blood of mother and fetus ①Syncytiotrophoblast；
2.Placental membrane：
Structure between the blood of mother and fetus
①Syncytiotrophoblast；
②Cytotrophoblast and its basal lamina；
③Connective tissue；
④Endothelium and its basal lamina
protection

84. Fetal membrane 胎儿血 Blood of mother Basal lamina Endothelium
Syncytiotrophoblast
Cytotrophoblast
胎儿血
Basal lamina
Nutriment
Blood of mother
Connective tissue
Metabolic product
Basal lamina
Endothelium

85. Human chorionic gonadotropin, HCG;
3.Function：
① Substance exchange
O2, nutriment, CO2, waste
② Hormone
Human chorionic gonadotropin, HCG;
Human placental lactogen, HPL;
Human placental progesterone, HPP,
Human placental estrogen, HPE

86. Placenta ① Substance exchange Function Capillary of fetus
Blood of mother Ｏ2
Nutriment
water、salt、others
ＣＯ2
Metabolic waste
Placenta membrane

87. Placenta ② Barrier Function Capillary of fetus Blood of mother No way！
Most of microorganism
No way！
Placenta barrier

88. Placenta ② Barrier Function Capillary of fetus Blood of mother
Most of drugs
Most of microorganism
Some of
microorganism
Placenta barrier

89. Placenta ③ Endocrine Function Function HCG Pregnancy 3rd week 8th week
Hormone
Function
Appearance
Fastigium
HCG
Corpus luteum
Pregnancy
3rd week
8th week
HCS
Mammary gland
2nd month
8th month
HPE
4th month
HPP

90. Twins and multiple birth
monozygotic twins
dizygotic twins

91. monozygotic multiple birth
polyzygotic multiple birth
mixed multiple birth

92. Dizygotic twins Blastocyst Blastocyst 2 Amnion 2 Amnion
2 Chorion Chorion
2 Placenta Placenta

93. separation of blastomere, of ICM, of primitive streak
Monozygotic twins
separation of blastomere, of ICM, of primitive streak
Blastocyst ICM primitive streak
2 Amnion Amnion Amnion
2 Chorion Chorion Chorion
2 Placenta Placenta Placenta