This type of exhange facilitates nourishment of the embryo prior to implantation, i.e. where no placenta exists. In horses, this type of exchnage is very important as there is a long period prior to implantation (up to 35 days). Nutrition is supplied by uterine secretions/debris, often referred to as 'uterine milk'. Uterine milk secretions are usually maintained by '''progesterone'''. Pinocytosis (cellular drinking) is the main exchange mechanism. | This type of exhange facilitates nourishment of the embryo prior to implantation, i.e. where no placenta exists. In horses, this type of exchnage is very important as there is a long period prior to implantation (up to 35 days). Nutrition is supplied by uterine secretions/debris, often referred to as 'uterine milk'. Uterine milk secretions are usually maintained by '''progesterone'''. Pinocytosis (cellular drinking) is the main exchange mechanism. |