How does exercise prevent cardio-vascular disease????

Deep diaphragmic breathing (very similar to Yoga), stimulates the lymph system (body's sewage system & it is the only system that does not have it's own pump, ie. blood - the heart, air - the lungs). So this cleans the body, the body heals. In effect, you don't need to do any cadio excercise, just deep breathing will do same job. There are other benefits of cadio, muscle strengthening. Most important statement I am going to make (this is not public knowledge as "the real world is unseen world"), we live by reactions due to modern lifestyles effects of "fight & flight" due to emotional (mainly anger), environmental stressors (food, pollution, modern accelerated farming, electrical pollution). When excercise, burn the adrelain produced by this fight & flight stressors.

Exercise will increase breating and blood flow rate there by expanding muscles, this helps in preventing cardio-vascular disease.

It doesn't always. If you over exert yourself for pro-longed periods and not get extra sleep and nutrients. You can weaken your heart and die. Not smoking and eating a diet high in vegetables,whole grains and food with a lot of anti-oxidants like Black or Green Tea and even Chocolate and not eating foods in fried oils(trans-fats) is more important than exercises,since the quality of the building blocks is what matters. It's not just one factor when it comes to Cardio vascular disease. But, excersise if done right can buld or strengthen muscles (like the heart). Since,you develop in your mothers womb. The mothers nutrition and health is the most important. When it comes to your health. Our organs develop in the first months and years of our lives. So, the foundation is the most critical. Married people supposedly live longer too. So, excersise is just one of the factors.