Comparative Anatomy Early Embryology
description
Transcript of Comparative Anatomy Early Embryology
Comparative AnatomyComparative AnatomyEarly EmbryologyEarly Embryology
KardongKardongChapter 5Chapter 5
Part 7Part 7
Vertebrate EggVertebrate Egg
Amniotic egg- amnion presentAmniotic egg- amnion present Reptilian egg- possesses shell(cleidoic)Reptilian egg- possesses shell(cleidoic)
Figure 7.1. Cledoic egg.
Egg TypeEgg Type
Microlecithal egg- small amount of yolkMicrolecithal egg- small amount of yolk MammalsMammals
Mesolecithal egg- moderate amount of yolkMesolecithal egg- moderate amount of yolk AmphibiansAmphibians
Macrolecithal egg- large amounts of yolkMacrolecithal egg- large amounts of yolk Reptiles, birds, sharksReptiles, birds, sharks
Types of CleavageTypes of Cleavage
Holoblastic- division into Holoblastic- division into two equal sized cells two equal sized cells (e.g., in mammals)(e.g., in mammals)
Meroblastic- restricted Meroblastic- restricted to periphery, usually in to periphery, usually in embryos with large embryos with large amounts of yolk. amounts of yolk. Meroblastic discoidal - Meroblastic discoidal -
Blastodiscs occur in Blastodiscs occur in some fishes, reptiles, birds, some fishes, reptiles, birds, and monotremes and monotremes Figure 7.2. Blastodisc.
Amphibian EmbryogenesisAmphibian Embryogenesis
Figure 7.3. Frog development; stages of embryogenesis (book fig. 5-12)
Cleavage StagesCleavage Stages
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)
64 cell stage; blastula with blastocoel cavity
32 cell stage; morula
Figure 7.4.
Cells push inward to form gastrula Cells push inward to form gastrula Eventually eliminates blastocoelEventually eliminates blastocoel
Cleavage Stages Cleavage Stages (cont’d.)(cont’d.)
Figure 7.5.
GastrulationGastrulation
Archenteron- primitive gutArchenteron- primitive gut BlastoporeBlastopore
Gives rise to anus in deuterostomesGives rise to anus in deuterostomes Gives rise to mouth in protostomesGives rise to mouth in protostomes
3 primary germ layers3 primary germ layers
Figure 7.6. Gastrulation.
Figure 7.7. Cross section of frog gastrula.
Dorsal lip - invagination of cellsDorsal lip - invagination of cells Move around yolk cellsMove around yolk cells Yolk plugYolk plug
Notochord forms from mesodermal cellsNotochord forms from mesodermal cells
Figure 7.8. Early frog gastrula.
NeurulationNeurulation
Neural plate thickens and Neural plate thickens and pushed inwardpushed inward
Neurectoderm- gives rise to Neurectoderm- gives rise to nerve tubenerve tube
Neural crest cells- between Neural crest cells- between nerve tube and ectodermnerve tube and ectoderm Dorsal root ganglion, branchial Dorsal root ganglion, branchial
cartilages cells, and pigment cellscartilages cells, and pigment cells Anterior cells- dermis of face, Anterior cells- dermis of face,
cephalic armor, sensory capsulescephalic armor, sensory capsules
Figure 7.9. Embryonic neurulation.
Figure 7.10. Neural crest cell differentiation. (Table 5.2; page 189).
Dorsal MesodermDorsal Mesoderm
Dermatome- associated with ectodermDermatome- associated with ectoderm Dermis in most of bodyDermis in most of body
MyotomeMyotome Skeletal muscleSkeletal muscle
Sclerotone- associated with nerve tubeSclerotone- associated with nerve tube Skeletal and vertebral columnSkeletal and vertebral column
Figure 7.11.
Dorsal mesoderm (somite) Dorsal mesoderm (somite) splits to form coelom cavitysplits to form coelom cavity Somatic mesoderm - Somatic mesoderm -
bound to ectodermbound to ectoderm Splanchnic mesoderm- Splanchnic mesoderm-
bound to endodermbound to endoderm Somatopleure - somatic Somatopleure - somatic
mesoderm meets ectodermmesoderm meets ectoderm Splanchnopleure - Splanchnopleure -
splanchnic mesoderm splanchnic mesoderm meets ectodermmeets ectoderm
Figure 7.12. Mesoderm specialization (book Fig. 5.6).
Dorsal Mesoderm DifferentiationDorsal Mesoderm Differentiation
Dorsal mesoderm (somite)- Epimeric mesodermDorsal mesoderm (somite)- Epimeric mesoderm Intermediate mesoderm- Mesomeric mesodermIntermediate mesoderm- Mesomeric mesoderm Lateral plate mesoderm- Hypomeric mesodermLateral plate mesoderm- Hypomeric mesoderm
Figure 7.13.
Primary Germ LayersPrimary Germ Layers
Figure 7.14. Formation of the three primary germ layers.
Germ Layers Germ Layers (cont’d.)(cont’d.)
Figure 7.15. Organs derived from the germ layers.
Structures formed from Structures formed from the three germ layers.the three germ layers.
Figure 7.16.
Ectodermal placodes in a representative vertebrate.
Figure 7.17.
Extraembryonic Membranes
Figure 7.18. Extraembryonic membranes of cledoic egg.
Extraembryonic Membrane Formation in a Bird
Figure 7.19. Extraembryonic membranes.
Principles of Embryology
Figure 7.20. Embryological development.