Chapter 47: The Three Stages of Early Embryonic Development

cleavage-gastrulation-organogenesis

1. Cleavage-

• rapid miotic division
• cuts cytoplasm of zygote into blastomeres (each has its own nucleus)
• forms a ball of cells called a morula
• a fluid filled cavity, a blastocoel, forms within the morula to make a blastula

2. Gastrulation-

• rearrangement of cells in blastula
• the 3 germ layers (ectoderm, mesoderm, and endoderm) are produced
• ectoderm- beginning of nervous system and outer layer of skin
• mesoderm- skeleton, most organs and tissues
• endoderm- digestive system

3. Organogenesis

• development of the three germ layers into rudiments of organs

http://www.youtube.com/watch?v=UgT5rUQ9EmQ&feature=related

embryonic development video!!