So you have a blood pressure reading of 120/80, or maybe you don’t. What the heck does that mean? Let’s provide some context.
Think of your vascular system as a continuous tubular conveyor belt carrying oxygen and nutrients out to your body tissues, and collecting carbon dioxide and waste products to take back to the core organs for treatment and elimination. The fluid transported along the conveyer belt is blood, and you have about 5.6 liters, or 6 quarts of it. A blood circuit around your entire vascular system takes less than a minute at rest (I can’t pin it down, some resources say 45 seconds, some say 20), but it’s definitely faster if you are working out. The volume of blood pumped out by the heart per beat multiplied by the number of beats per minute is called “cardiac output”. The heart beats between 80-100 thousand times a day, and every beat gives the fluid in the tubes another shove, forcing it all to continue moving along. It shoves by means of contracting and squeezing the blood out of the ventricles and into big tubes - arteries, which split into numerous smaller tubes - arterioles, which split into even smaller and more numerous periferal tubes - capillaries, where it drops it’s load of O2 and nutrients to body cells. The dispersed blood then returns via the increasingly widening tubes of the venous system.
As you can imagine, pumping out blood into smaller and smaller vessels causes friction against tube walls, and there’s also resistance from the periferal blood volume that then has to be forced back to the pumping station, mostly uphill against gravity. This resistance to blood movement through the tubes is measured as ‘blood pressure’. The upper BP number, Systolic Pressure is the arterial pressure measured when the ventricles contract to push blood through the system. The lower number, Diastolic Pressure, is the remaining arterial pressure between pushes. The healthy range is between 90-120/ 60-80. Too high or too low is cause for concern and lifestyle/diet change. A great way to maintain a healthy BP is less red meat, fat, alcohol and stress, and more water, fiber, vegetables, fruits, and - you guessed it - exercise.