Blood pressure is the force that keeps the liquid blood moving in our veins. A good analogy for this is water pressure. If you've ever taken a hose and put your thumb over the end, you've felt water pressure, forcing the water out of the hose. If you put your thumb over the top of the hose and felt nothing, no water would flow. Similarly, if you had no blood pressure, or too low of blood pressure for adequate flow, you could die. If you have high blood pressure, it is like having such high water pressure that the hose may tear (and you could have internal bleeding). Thankfully, humans are very stable systems and blood pressure has a wide acceptable range!

First, I want to start by giving you a brief background about the circulatory system.

Blood and blood vessels are two of the three parts of the circulatory system - the third being the heart, which pumps the blood of these blood vessels by rhythmic contractions. The main blood vessels are veins, arteries, and capillaries. Veins carry deoxygenated blood from the body to the heart to be oxygenated. Arteries carry oxygenated blood from the heart to the rest of the body; the aorta is the largest artery in the human body. Capillaries, the tiniest blood vessels in the body, function to exchange nutrients and oxygen for waste products; they connect the arteries and the veins. The system of blood vessels is very important to our bodies so that our cells can be replenished with oxygen and nutrients.

Blood pressure is the pressure created of the blood against the walls of the arteries. It is measured as diastolic and systolic. Diastolic blood pressure is the pressure between beats when the heart is at rest, and systolic blood pressure is the pressure during heart beats. On a blood pressure monitor, the systolic blood pressure is read before the diastolic. You might here the doctor saying that your blood pressure is "110 over 70"; your systolic is 110 mm Hg (millimeters mercury) and your diastolic is 70 mm Hg. Mercury is used to measure pressure, and you can find conversions to Pascals and atmospheres online. Blood pressure between 90/60 to 120/80 is usually the healthiest range.

Remember blood pressure (in mm Hg) is different that heart rate (in beats per minute). The first measures pressure of blood against walls of arteries, and the other measures the rate at which your heart is beating. Priyanka

Your blood is being squeezed by layers of muscle lining your blood vessels. This squeezing exerts a pressure on it, and this pressure is necessary for biochemistry to happen (for example, cells getting oxygen from your blood). The pressure is also necessary for your blood to actually flow when your heart pumps it. Of course, having too much pressure is bad because blood vessels can break.