--Mary Nicolas 23:38, 28 July 2010 (UTC)
--Mary Nicolas 23:37, 4 August 2010 (UTC)
1. Syncytiotropoblast cells secrete:
• Progesterone which maintains the integrity of the uterine lining.
• Human chorionic gonadotropin (hCG) which prevents the degeneration of the corpus luteum.
• Human placental lactogen (HPL) which modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus
2. The corpus luteum secretes progesterone (signalled by hCG secreted by the trophoblast cells of the blastocyst) which consequently maintains the endometrium which provides an area rich in blood cells so that the zygote can develop.