BIO380H5 Study Guide - Midterm Guide: Zona Pellucida, Fallopian Tube, Blastomere
Document Summary
Immediately after fertilization, the zygote undergoes a pronounced shift in metabolism and begins several days of cleavage. During this time, the embryo, still encased in its zona pellucida, is transported down the uterine tube and into the uterus. Roughly 6 days later, the embryo sheds its zona pellucida and attaches to the uterine lining. After the 2-cell stage, mammalian cleavage is asynchronous, with 1 or 2 cells (blastomeres) dividing from a 3 cell embryo. When the embryo consists of approximately 16 cells, it is called a morula. Compaction: a stage where individual outer blastomeres tightly adhere through gap and. As sodium and water move across the epitheliumlike outer blastomeres, and accumulate in spaces tight junctions and lose their individual identity when viewed from the surface. among the inner blastomeres. This process (occurring 4 days after fertilization) is called cavitation, and the fluid-filled space is known as the blastocyte.
