Blood pressure: Blood pressure is the product of the amount of blood pumped by the heart each minute (cardiac output) and the degree of dilation or constriction of the arterioles (systemic vascular resistance). It is a complex variable involving mechanisms that influence cardiac output, systemic vascular resistance, and blood volume. Hypertension is caused by one or several abnormalities in the function of these mechanisms or the failure of other factors to compensate for these malfunctioning mechanisms.
Systolic Pressure: Systolic pressure represents the pressure when the heart contracts and forces blood into the blood vessels. This is the higher of the two numbers and is usually expressed first.
Diastolic Pressure: Diastolic pressure represents the pressure when the heart is relaxed. This is the lower of the two numbers and is usually expressed second.
Hypertension: A medical condition in which blood pressure is consistently above the normal range.
To view Classifications of Hypertension (WHO/ISH) click here.
Another classification taxonomy described in the literature is presented by the National Institutes of Health (2003):