1. General Embryology
Lecture I
Sanjaya Adikari
Department of Anatomy

2. Our life begins as one cell formed by the union of the maternal and paternal germ cells
Haploid
(23)
Haploid
(23)
Diploid
(46/23 pairs)
Diploid
(46/23 pairs)
Diploid

3. Human chromosomes
Homologous pair

4. Mitosis

5. Meiosis

6. Non-disjunction (numerical chromosomal aberrations)

7. Gametogenesis Female Male Ovary Oogenesis (primodial germ cells)
Ovum/oocyte
Oogenesis
Male
Testis
(spermatogonia)
Spermatid
Spermatogenesis
Spermiogenesis
Sperm

8. Development of the fetus Development of the placenta
Ovarian cycle
Uterine cycle
Hormonal cycle
Development of the fetus
Development of the placenta

9. Ovarian cycle

13. Fertilization

14. Zygote

20. 14 28
FSH LH
hCG
Fetus
FSH & LH
Oestrogen
Progesteron
Uterus

21. Dating of pregnancy & the age of fetus
/POA

22. General Embryology
Lecture II
Sanjaya Adikari
Department of Anatomy

23. Early development of embryo

24. Cleavage

25. Blastocyst
Day 05
After 1 wk

26. Inner cell mass
(embryoblast)
Amniotic cavity
Blastocyst cavity
embryonic plate
Outer cell mass
(trophoblast)

27. Bilaminar disc (2 weeks)
Amniotic cavity
Epiblast
Hypoblast
Syncytiotrophoblast
Blastocyst cavity
Cytotrophoblast

28. embryonic pole abembryonic pole exocoelomic cavity
(primitive yolk sac)
abembryonic pole
exocoelomic membrane

29. Bilaminar disc….cont.
/Epiblast
/Hypoblast

31. Extra-embryonic mesoderm

33. Amniotic cavity
Secondary yolk sac
Extra-embryonic coelom
(chorionic cavity)
Connecting stalk

34. Gastrulation

35. Trilaminar disc (3 weeks)
Ectoderm
Intra-embryonic
mesoderm
Endoderm

37. Notochord

38. Neural tube & neural crest cells
Starts in the 3rd week
This is the earliest system to start developing
Neural crest
Neural fold
Notochord

40. Folding of the embryo

41. Paraxial mesoderm
Intermediate mesoderm
Ventral mesentary

42. Derivatives of germ layers
Ectoderm
CNS including neural crest cells
Peripheral nervous system
Sensory epithelium of ear, eye and nose
Skin (epidermis) and its appendages (hair, nails, sebaceous glands and sweat glands)
Secretory component and ducts of mammary gland
Pituitary gland
Secretory acini and ducts of parotid salivary gland
Enamal of teeth
Lens of the eye

43. Endoderm Lining epithelium of the gastrointestinal tract
Secretory acini and ducts of submandibular and sublingual salivary glands
Alveolar parenchyma and the lining epithelium of the respiratory tract
Liver parenchyma
Epithelium of the gall bladder
Exocrine pancreas
Epithelium of the urinary bladder and urethra
Parenchyma of the thyroid and parathyroid glands
Epithelial lining of the tympanic cavity and auditory tube
Epithelium of the palatine tonsil
Hassel’s corpuscles of thymus

44. Mesoderm Sclerotome Myotome Dermatome Somatic mesoderm
Paraxial mesoderm
Sclerotome
Myotome
Dermatome 
Intermediate mesoderm
Lateral plate mesoderm
Somatic mesoderm
Splanchnic mesoderm
Branchial mesoderm

46. Somites

48. Limb bud

49. Twins
identical

51. Totipotent
Pluripotent
Unipotent

56. 100 70 15 fail to get fertilized 15 fail to get implanted
42 survive by the time of first missed menstruation
Number of cases get aborted in coming weeks
Ovuma/oocytes

57. General Embryology
Lecture III
Sanjaya Adikari
Department of Anatomy

58. Placenta and the umbilical cord

59. Syncytiotrophoblast
Blastocyst cavity
Cytotrophoblast

60. Primary villus
Secondary villus
Tertiary villus

62. Placental barrier 2 1

63. Cotyledon (15-20)
Chorionic villi
Lacunar/intervillous spaces

64. Decidual plate
Chorionic plate

65. Macroscopic appearance of placenta

66. Placenta – fetal surface

67. Placenta – maternal surface

68. Umbilical cord
umbilical arteries
umbilical vein
Wharton’s jelly

70. References Medical embryology by Jan Langman
Human embryology and developmental biology by Bruce M. Carlson
Human embryology by Malkanthi S. Chandrasekera