ABSTRACT
Hypertension means an elevation above normal of the pressure within the arterial system. This pressure is a product of the amount of blood ejected by the heart at each beat, multiplied by the resistance to flow of blood, resulting from the limited calibre of the vessels through which it must flow. Peripheral resistance, as it is termed, is a function of the calibre of the arterial system, which can be readily understood from the traditional analogy with a standard hosepipe. For a given flow of water in such a pipe, the pressure of water ejected increases as the calibre of the pipe is reduced.
