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General Embryology Sanjaya Adikari Department of Anatomy Lecture I.

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Presentation on theme: "General Embryology Sanjaya Adikari Department of Anatomy Lecture I."— Presentation transcript:

1 General Embryology Sanjaya Adikari Department of Anatomy Lecture I

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

3 Homologous pair Human chromosomes

4 Mitosis

5 Meiosis

6 Non-disjunction (numerical chromosomal aberrations)

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

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

9 Ovarian cycle




13 Fertilization

14 Zygote






20 FSH &LH Oestrogen Progesteron 01428 FSH LH Uterus hCG Fetus

21 Dating of pregnancy & the age of fetus /POA

22 General Embryology Sanjaya Adikari Department of Anatomy Lecture II

23 Early development of embryo

24 Cleavage

25 Blastocyst Day 05After 1 wk

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

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

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

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


40 Folding of the embryo

41 Ventral mesentary Paraxial mesoderm Intermediate mesoderm

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 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 PluripotentUnipotent





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

57 General Embryology Sanjaya Adikari Department of Anatomy Lecture III

58 Placenta and the umbilical cord

59 Blastocyst cavity Syncytiotrophoblast Cytotrophoblast

60 Primary villus Secondary villus Tertiary villus


62 2 1 Placental barrier

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

64 Chorionic plate Decidual 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

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