1. PART 2
Basic Embryology

2. Changes in the Embryo Figure 3.7a, b
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3. Changes in the Embryo Figure 3.7c, d
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4. Week 4 – The Body Takes Shape
Folding of embryo laterally and at the head and tail
Embryonic disc bulges; growing faster than yolk sac
“Tadpole shape” by day 24 after conception
Primitive gut – encloses tubular part of the yolk sac
Site of future digestive tube and respiratory structures
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5. Week 4 – The Body Takes Shape
Figure 3.8
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6. Week 4 – The Body Takes Shape
Derivatives of the germ layers
Ectoderm forms
Brain, spinal cord, and epidermis
Endoderm forms
Inner epithelial lining of the gut tube
Respiratory tubes, digestive organs, and urinary bladder
Notochord (where vertebrae are) – gives rise to nucleus pulposus within intervertebral discs
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7. Week 4 – The Body Takes Shape
Mesoderm – forms
Muscle
Bone
Dermis
Connective tissues (all)
Mesoderm differentiates further and is more complex than the other two layers
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8. Derivatives of Germ Layers
Splancnic Mesoderm gives rise to: Heart and blood vessels
Figure 3.10
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9. Week 4 – The Body Takes Shape
Mesoderm (continued)
Somites divides into
Sclerotome
Dermatome
Myotome
Intermediate mesoderm forms
Kidneys and gonads
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10. Week 4 – The Body Takes Shape
Mesoderm (continued)
Splanchnic mesoderm
Forms musculature, connective tissues, and serosa of the digestive and respiratory structures
Forms heart and most blood vessels
Somatic mesoderm – forms
Dermis of skin
Bones
Ligaments
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11. 3. dorsal hollow nerve cord 4. notocord and vertebrae 5.segmentation
What do I need to know?
Which structures originate from ectoderm, mesoderm and endoderm – Slide 8
List 6 unique features found in all vertebrates at some stage of their life:
1. tube within a tube
2.bilateral symmetry
3. dorsal hollow nerve cord
4. notocord and vertebrae
5.segmentation
6. pharyngeal pounches
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12. Distinguish between the types of tissues that make up th eendoderm, ectoderm and mesoderm and explain how these tissues relate to their developmental processes.
Both endoderm and ectoderm are epithelial tissues. These cells are joined together in sheets that form external or internal linings of the body. The mesoderm consists of mesenchyme tissue whose cells don’t stick together. Instead, the cells and groups of cells are free to migrate within the embryo to eventually give rise to muscles, bones and viscera.(organs)
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