A it helps them classify stars because it groups based on temperature and brightness.
Since pressure is force per unit area, blood pressure could be thought as the force exerted by the blood to the surface area of your blood vessels. When your blood vessels dilate, it means that they expanded. The result would be faster flow of blood. When this happens, the force of the blood is not any more concentrated on your blood vessels because there is more room available.
Think of a faucet where tap water flows. When you stopper the faucet with your finger, you feel the force of the water. The pressure builds up as manifested by the sound your faucet makes. But when you release your finger, the water rushes through and flows faster. The pressure is released. Therefore, when your blood vessels are dilated, your blood pressure decreases.
The process is called the WaterCycle
