ZOO 3050 Lecture Notes - Lecture 6: Spindle Apparatus, Cell Adhesion Molecule, Blastocyst
13 Apr 2018
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Mammalian cleavage: compaction, only in mammals, at 8 cell stage blastomeres form compact ball. Increased expression of cell adhesion molecules (cadherins: morula, compacted ball of cells. Internal cells surrounded by a larger group of external cells. Mammalian blastocyst: external cells become trophoblast-extraembryonic membranes, necessary for embryo to adhere to uterus, secrete enzymes that digest extracellular matrix of uterine wall, allow blastocyst to implant into endometrium (inner membrane of the mammalian uterus, essential for nutrition. Inner cells become the inner cell mass (icm: no contact to exterior, embryo proper. Insects have very dense yolk, cells connected by cytoplasmic bridge: 13 mitotic divisions without cell division. 2^13-highly regulated process, actin not pinching off. Cell cycle: typical cycle of somatic cells, mitosis (m) stage, growth stage (g1, pause-allows for 2 divided cells to grow, dna synthesis (s) stage, second gap or growth (g2) stage. Lecture 6-cleavage: allows for replication of chromosomes and growth of cells.
