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General Embryology Lecture I Sanjaya Adikari Department of Anatomy.

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

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

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

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