Cardial Opening is a term used to describe the opening of the heart. It is composed of two parts: ENDO, which stands for endocardium, and MYO, which stands for myocardium. The endocardium is the innermost layer of the heart wall, while the myocardium is the middle layer of the heart wall. Together, these two layers form the cardial opening, which allows blood to flow in and out of the heart.