The document describes the anatomy and structures of the heart. It discusses: - The heart is surrounded by the pericardium, a double-walled sac that has an outer fibrous layer and inner serous layers separated by fluid. - The heart has four chambers - two upper atria that receive blood and two lower ventricles that pump blood out. Blood flows through valves between the chambers. - The heart wall has three layers - the outer epicardium, middle muscular myocardium, and inner endothelial endocardium. - The heart is supplied by the right and left coronary arteries and drains into the coronary sinus vein. - Nerves from the autonomic nervous system