Why is it important to eat healthy and exercise? If you don't, you might end up with a cardiovascular disease. These diseases are conditions that affect your heart and blood vessels. The job of your cardiovascular system is to transport blood through your heart, veins, and arteries, to provide oxygen and nutrients to your body. If this blood flow doesn't work properly anymore, it can have serious consequences. In this activity, you will find out what happens to the blood flow of people that have a condition called coronary heart disease.