PATHOPHYSIOLOGY OF HYPERTENSION

     In the development of hypertension, there is increase in peripheral resistance which usually involve the constriction of arterioles due to constriction of smooth muscles upon stimulation by sympathetic nerves
(constriction of arterioles is also affected by oxygen concentration,metabolic production,hormones and drugs).
The increase peripheral resistance causes increase in heart beat in an attempt to overcome the resistance subsequent there is increased cardiac output.
The consistent resistance place a greater demand on the heart resulting in myocardial hypertrophy and
cardiomegally.The increased cardiac output (increase blood volume)flows through the vessels and against
the resistance.The result is increased pressure within the vessels.This is related to hydraulic principle which states that the flow through a tube is proportional to the pressure inside the tube and is inversely proportional
to the resistance in the tube.
     The arteries are subjected to arteriosclerotic changes which in addition to constricted arterioles results in reduced blood supply to many organs in the body such as the brain,the lungs,the heart,the kidney and
muscles.
The tiny vessels are prone to rupture due to the arteriosclerotic changes and increased pressure within them.Where this occurs,it accounts for the haemorrhage which usually accompanies HTN as epistaxis.
Bleeding to the retina may occur resulting in blurred vision and blindness.Apoplexy (stroke) is usually
due to this  facts.