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Similar to Basic embryology part i
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Basic embryology part i
- 2. EmbryologyEmbryology
Embryology – study of the origin and
development of single individual
Prenatal period
Embryonic period – first 8 weeks (56 days)
Fetal period – remaining 30 weeks (210 days)
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- 3. Development of embryologyDevelopment of embryology
Aristotle, B.C 384-322
Semen+menstration
Harvey, 1651:
All life from oocyte
Malpighi, 1675:
A micro-chicken in an egg
Leewenhoek, 1677 :
A micro-human in a sperm
Haeckel, 1868
Biogenetic law
Spemann, 1869-1941
Experimental embryology
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- 6. The Basic Body PlanThe Basic Body Plan
Skin – dermis and epidermis
Outer body wall – trunk muscles, ribs, vertebrae
Body cavity and digestive tube (inner tube)
Kidneys and gonads – deep to body wall
Limbs
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- 7. The Basic Body Plan
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Figure 3.2
- 8. The Embryonic PeriodThe Embryonic Period
Week 1 – from zygote to blastocyst
Conception – in lateral third of uterine tube
Zygote (fertilized oocyte) moves toward the uterus
Blastomeres – daughter cells formed from zygote
Morula – solid cluster of 12–16 blastomeres
“Mulberry”
Blastocyst – fluid-filled structure – ~ 60 cells
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- 9. The Embryonic PeriodThe Embryonic Period
Stages of first week
Zygote
4-cell
Morula
Early blastocyst
Late blastocyst (implants at this stage)
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- 10. Fertilization & Its processFertilization & Its process
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nucleus acrosome
Penetration and
release of acrosomal
enzyme
Cell membrane
of ovum
Sperm bind to sperm receptor ZP-3 induce
Acrosome reaction ： release of acrosomal enzyme
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ovum
sperm
fertilized ovum
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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.
- 13. Contac of sperm and ovumContac of sperm and ovum
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- 14. Sperm penetrate into the ovumSperm penetrate into the ovum
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- 15. Formation & Fusion of Male andFormation & Fusion of Male and
Female PronucleiFemale Pronuclei
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- 16. Fertilization and the Events of theFertilization and the Events of the
First 6 Days of DevelopmentFirst 6 Days of Development
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Figure 3.3
- 17. Process of fertilizationProcess of fertilization
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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
- 18. Week 2 – The Two-LayeredWeek 2 – The Two-Layered
EmbryoEmbryo
Bilaminar embryonic disc – inner cell mass
divided into two sheets
Epiblast and the hypoblast
Together they make up the bilaminar embryonic disc
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- 19. Week 2 – The Two-LayeredWeek 2 – The Two-Layered
EmbryoEmbryo
Amniotic sac – formed by an extension of epiblast
Outer membrane forms the amnion
Inner membrane forms the amniotic sac cavity
Filled with amniotic fluid
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- 20. Week 2 – The Two-LayeredWeek 2 – The Two-Layered
EmbryoEmbryo
Yolk sac – formed by an extension of hypoblast
Digestive tube forms from yolk sac
NOT a major source of nutrients for embryo
Tissues around yolk sac
Gives rise to earliest blood cells and blood vessels
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- 21. Implantation of the BlastocystImplantation of the Blastocyst
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Figure 3.4 (1 of 3)
- 22. Implantation of the Blastocyst…Implantation of the Blastocyst…
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Figure 3.4 (2 of 3)
- 23. Implantation of the Blastocyst…Implantation of the Blastocyst…
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Figure 3.4 (3 of 3)
- 24. Week 3 – The Three-LayeredWeek 3 – The Three-Layered
Embryo…Embryo…
Primitive streak – raised groove on the dorsal
surface of the epiblast
Gastrulation – a process of invagination of
epiblast cells
Begins at the primitive streak
Forms the three primary germ layers
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- 25. Week 3 – The Three-LayeredWeek 3 – The Three-Layered
Embryo…Embryo…
Three Germ Layers*
Endoderm – formed from migrating cells that
replace the hypoblast
Mesoderm – formed between epiblast and endoderm
Ectoderm – formed from epiblast cells that stay on
dorsal surface
*All layers derive from epiblast cells!
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- 26. The Primitive StreakThe Primitive Streak
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Figure 3.5e–h
- 27. The NotochordThe Notochord
Primitive node – a swelling at one end of
primitive streak
Notochord forms from primitive node and
endoderm
Notochord – defines body axis
Is the site of the future vertebral column
Appears on day 16
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- 28. Formation of the Mesoderm and NotochordFormation of the Mesoderm and Notochord
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Figure 3.6
- 29. NeurulationNeurulation
Neurulation – ectoderm starts forming brain and
spinal cord
Neural plate – ectoderm in the dorsal midline
thickens
Neural groove – ectoderm folds inward
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- 30. NeurulationNeurulation
Neurulation (continued)
Neural tube – a hollow tube pinches off into
the body
Cranial part of the neural tube becomes the
brain
Maternal folic acid deficiency causes neural
tube defects
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- 31. NeurulationNeurulation
Neural crest
Cells originate from ectodermal cells
Forms sensory nerve cells
Induction
Ability of one group of cells to influence
developmental direction of other cells
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- 32. The Mesoderm Begins toThe Mesoderm Begins to
DifferentiateDifferentiate
Somites – our first body segments
Paraxial mesoderm
Intermediate mesoderm – begins as a continuous
strip of tissue just lateral to the paraxial mesoderm
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- 33. Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Lateral plate – most lateral part of the mesoderm
Coelom – becomes serous body cavities
Somatic mesoderm – apposed to the ectoderm
Splanchnic mesoderm – apposed to the endoderm
The Mesoderm Begins toThe Mesoderm Begins to
DifferentiateDifferentiate
