The direction of waves of contraction in the heart are very important because they represent the cardiac contraction pathway. It decides where the blood reflux will take place.
The blood flows from the right atrium to the right ventricle via the tricuspid valves when the atrium contracts and ventricles expand. Once the ventricles receive its full amount of blood, the tricuspid valves close to prevent any backflow into the atrium. When the ventricles contract, blood enters the aorta through the aortic valve.
Iron is important because it produces the heme part of hemoglobin in the red blood cells of the blood. Lack of iron can lead to many conditions.
Polycythemia vera is a condition which leads to more production of red blood cells. This increases the blood volume and it thickens the blood and slows down the blood flow and causes blood clots. The slowness of blood can lead to heart failure and heart attacks.
(This is a simplified version of someone else's answer, please don't come at me lol)