Final answer:
The hormone secreted by the trophoblastic cells during implantation that helps preserve the corpus luteum is Human Chorionic Gonadotropin (hCG). It ensures the corpus luteum continues to produce important hormones like progesterone and estrogen, which are necessary for a favorable pregnancy environment.
Step-by-step explanation:
The hormone secreted by the trophoblastic cells during implantation that helps to preserve the corpus luteum is Human Chorionic Gonadotropin (hCG). When implantation is successful, the cells from the outer layer of the blastocyst, the trophoblast, differentiate into the syncytiotrophoblast. This structure then begins to secrete hCG. The role of hCG in early pregnancy is to maintain the corpus luteum, which is crucial for producing and maintaining levels of progesterone and estrogen necessary for suppressing menstruation and supporting the early stages of pregnancy.
Progesterone, which is secreted by the corpus luteum, is vital for maintaining pregnancy by preventing new ovarian follicles from developing and suppressing uterine contractility. The continued secretion of progesterone by the corpus luteum is directed by hCG, which ensures the proper environment is created for the developing embryo.