1. Comparative Anatomy Early Embryology
Kardong
Chapter 5
Part 7

2. Vertebrate Egg Amniotic egg- amnion present
Figure Cledoic egg.
Amniotic egg- amnion present
Reptilian egg- possesses shell(cleidoic)

3. Egg Type Microlecithal egg- small amount of yolk
Mammals
Mesolecithal egg- moderate amount of yolk
Amphibians
Macrolecithal egg- large amounts of yolk
Reptiles, birds, sharks

4. Types of Cleavage
Holoblastic- division into two equal sized cells (e.g., in mammals)
Meroblastic- restricted to periphery, usually in embryos with large amounts of yolk. Meroblastic discoidal - Blastodiscs occur in some fishes, reptiles, birds, and monotremes
Figure Blastodisc.

5. Amphibian Embryogenesis
Figure Frog development; stages of embryogenesis (book fig. 5-12)

6. Initial: fertilized egg with fertilization membrane (arrows)
Cleavage Stages
Figure 7.4.
Initial: fertilized egg with fertilization membrane (arrows)
2 cell stage;
1st cleavage
4 cell stage;
4 blastomeres
8 cell stage;
micromeres and macromeres
16 cell stage (not shown)
32 cell stage;
morula
64 cell stage; blastula with blastocoel cavity

7. Cleavage Stages (cont’d.)
Figure 7.5.
Cells push inward to form gastrula
Eventually eliminates blastocoel

8. Gastrulation Archenteron- primitive gut Blastopore
Figure Gastrulation.
Archenteron- primitive gut
Blastopore
Gives rise to anus in deuterostomes
Gives rise to mouth in protostomes
3 primary germ layers
Figure Cross section of frog gastrula.

9. Dorsal lip - invagination of cells Move around yolk cells Yolk plug
Figure Early frog gastrula.
Dorsal lip - invagination of cells
Move around yolk cells
Yolk plug
Notochord forms from mesodermal cells

10. Neurulation Neural plate thickens and pushed inward
Neurectoderm- gives rise to nerve tube
Neural crest cells- between nerve tube and ectoderm
Dorsal root ganglion, branchial cartilages cells, and pigment cells
Anterior cells- dermis of face, cephalic armor, sensory capsules
Figure Embryonic neurulation.

11. Figure 7.10. Neural crest cell differentiation. (Table 5.2; page 189).

12. Dorsal Mesoderm Dermatome- associated with ectoderm Myotome
Figure 7.11.
Dermatome- associated with ectoderm
Dermis in most of body
Myotome
Skeletal muscle
Sclerotone- associated with nerve tube
Skeletal and vertebral column

13. Dorsal mesoderm (somite) splits to form coelom cavity
Somatic mesoderm - bound to ectoderm
Splanchnic mesoderm- bound to endoderm
Somatopleure - somatic mesoderm meets ectoderm
Splanchnopleure - splanchnic mesoderm meets ectoderm
Figure Mesoderm specialization (book Fig. 5.6).

14. Dorsal Mesoderm Differentiation
Figure 7.13.
Dorsal mesoderm (somite)- Epimeric mesoderm
Intermediate mesoderm- Mesomeric mesoderm
Lateral plate mesoderm- Hypomeric mesoderm

15. Primary Germ Layers
Figure Formation of the three primary germ layers.

16. Germ Layers (cont’d.)
Figure Organs derived from the germ layers.

17. Structures formed from
the three germ layers.
Figure 7.16.

18. Ectodermal placodes
in a representative
vertebrate.
Figure 7.17.

19. Extraembryonic Membranes
Figure Extraembryonic membranes of cledoic egg.

20. Extraembryonic Membrane Formation in a Bird
Figure Extraembryonic membranes.

21. Principles of Embryology
Figure Embryological development.