ZOO 2090 Lecture Notes - Lecture 4: Germ Layer, Neural Crest, Neural Tube
Document Summary
Early development of chordates: cleavage from zygote to multicellular hollow blastula, formation of germ layer. Aka archenteron : space enclosed by the gut: neurulation: formation of the neural tube. Nervous tissue: organogenesis: from tissue to organs. Differentiation of organs from tissues involve interactions and mixing between germ layers lots of cellular movement in the embryo! Fate of ectoderm nervous system, eye parts, epidermis. Fate of endoderm pharynx, digestive track, liver, pancreas, urinary bladder. Fate of mesoderm dermis, bones, muscles, blood vessels, heart, kidney, gonads: neural crest. Arise by delamination from the neural tube and peripheral migration. Present in urochordates, where it gives rise to pigment cells. Gives rise to a variety of structures in adult vertebrates: placodes. Arise from thickenings of the surface ectoderm and cavitation. Give rise sensory organs and receptors: maturation. Juvenile sexually mature adult (direct development) Larva metamorphosis sexually mature adult. Larva growth/reproduction as larva: heterochrony. Paedomorphosis maintenance of juvenile characters in the adults of descendants.