What is BP

• Blood Pressure and Blood Pressure Regulation:

  • Although blood has a number of different functions, undoubtedly its main role is to perfuse tissues in order to maintain organ and organism viability
  • In order to adequately perfuse organs, we need the heart and arterioles to create a driving pressure - blood pressure, to push blood through the circulation generally
  • We also need a means of regulating blood flow to each organ dependent on the needs of the organ
  • Arterioles regulate the blood flow to specific organs and tissues
• What is blood pressure?

  • Blood pressure can be defined as the force exerted by the blood against any unit area of vessel wall or the resistance that blood encounters as it flows through the system of blood vessels
  • BP is always expressed in mmHg
  • A mean adult BP is typically given as 120 / 80 mmHg
  • Unless otherwise stated BP refers to pressure within the arterial system i.e. systemic BP
  • Traditionally BP is always measured from the largest available artery closest to the heart
  • Although it is neither the largest nor closest, the left brachial artery is the best accessible option
• What is blood pressure?

  • 120 mmHg reflects the peak pressure obtained in systole – the pressure that the left ventricle must produce in order to eject blood into the aorta
  • 80 mmHg represents the lowest pressure obtained in diastole, therefore the normal resting pressure in the aorta
  • These pressures are a reflection of the elasticity of the aorta as it distends to accommodate the volume of blood ejected by the heart on systole, and slowly recoils during diastole whilst the heart chambers are re-filling
  • Hence the elastic aorta functions as an auxiliary pump, secondary to the heart itself