BIO380H5 Lecture Notes - Lecture 7: Umbilical Cord, Homeobox Protein Nanog, Primitive Knot
Document Summary
Bio 380 lecture 7 germ layers. The trophoblast will give you the bulk of the extraembryonic membranes including the placenta. The inner mass cell forms the embryo but also adds some of the extraembryonic membranes. After cleavage, the trophoblast develops cytotrophoblasts (cells from trophoblasts), these cytotrophoblasts then form syncytiotrophoblasts which have the function of invasion through the uterine lining. Apposition is the first step of implantation: once the blastocyst is implanted within the uterine cavity, it come in contact with the endometrial epithelium. Adherence: the trophoblast begins to secrete l-selectin which helps the blastocyst to adhere to the uterine lining. There is then the formation of the syncytiotrophoblasts that multiple and invade through the uterine lining. In order to invade, they begin to lose their cell membrane, the bulk of cytoplasm and nuclei can then easily move through the uterine lining penetration. The syncytiotrophoblasts cytoplasm will then be attacked by the maternal immune system via a decidual reaction.
