BIOL 204 Study Guide - Desiccation, Metabolic Waste, Organogenesis
Document Summary
Fertilized egg (zygote) rapidly divides to form a morula (solid ball of cells). Blastula formation cells form a blastula, with the hollow space inside called the blastocoel. Zygote rapidly divides, but cleavage is limited to a disk due to the large yolk. Hypoblast forms on top of the yolk, with the epiblast on top. Space between hypoblast and epiblast is the blastocoel. Cells from the outer surface migrate through the primitive streak, forming the three embryonic layers. Hensen"s node then moves posteriorly to close the primitive streak. Cells from outer surface migrate through the blastopore, forming the three embryonic layers. Mesoderm further differentiates and the neural tube and notochord appear. Coelom formed from hypomere mesoderm; dorsal and ventral mesentery formed. All vertebrates: coelom divided by transverse septum into pericardial and pleuroperitoneal cavity. Mammals: coelomic fold further divides pleuroperitoneal cavity into pleural and peritoneal cavity. Interaction between the germ layers stimulates the formation of organs.