Vertebrate Development

1
Vertebrate Development

• Chapter 51

2
Fertilization

• Penetration
• hydrolytic enzymes in acrosome of sperm head
• Activation
• events initiated by sperm penetration
• egg nucleus complete second meiotic division
• metabolic activity
• Nuclei fusion Syngamy - fusion of sperm nucleus
  with egg nucleus to form the diploid nucleus.

3
Cell Cleavage Patterns

• Cleavage - size of cells
• holoblastic cleavage Sea Urchins
• meroblastic cleavage Reptiles and birds

4
Cell Cleavage Patterns

• Mammals
• little yolk -holoblastic cleavage
• morula - Each cell is a blastomere.
• blastula is formed
• inner cell mass - embryo
• trophoblast - implantation

5
Blastula Gastrulation

• Certain groups of cells invaginate and involute
  from the surface of the blastula during
  gastrulation.
• By the end of gastrulation - 3 germ layers
• ectoderm
• mesoderm
• endoderm

6
Gastrulation in primitive chordates
7
Gastrulation

• Gastrulation in most aquatic vertebrates
• Yolk-laden cells of the vegetal pole are fewer
  and much larger than the yolk-free cells of the
  animal pole.

8
Gastrulation

• Gastrulation in reptiles, birds, mammals
• primitive streak

9
Extraembryonic Membranes

• Fluid-filled amniotic membrane an adaptation to
  terrestrial life amnion, chorion, yolk sac, and
  allantois.

10
Vertebrate Embryonic Development Ontogeny
recapitulates phylogenyEmbryological development
(ontogeny) involves the same progression of
changes that have occurred during evolution
(phylogeny