BIO 121 Lecture Notes - Lecture 27: Vitelline Membrane, Polarity In Embryogenesis, Blastocoel
24 Jul 2020
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Transverse from one side to other, across body. Transverse section section cut at right angles to long axis of structure. Longitudinal section section cut parallel to long axis of structure. Animal hemisphere area rich /w black/brown pigment. Vegetal hemisphere area where yolk concentrated. Single-celled egg carved into large # of cells (blastomeres: yolk present in blastomeres as small platelets/granules. At end of cleavage, embryo known as blastula & is ball of cells several layers thick /w internal cavity (blastocoel: blastocoel closer to animal than vegetal pole. Beginnings marked by appearance of pigmented slit (blastopore on surface of blastula) Animal hemisphere cells move as sheet into embryo interior roll over blastospore lip. Cell layers shaped & remodelled to form various external/internal organs. Cns 1st to form known as neurulation: marked by thickening of neuroectoderm in dorsal midline forms neural plate. Folds form on lateral edges of neural plates folds move toward midline creates neural groove.
