The blood pressure is generated by the contraction of ventricles and is highest in aorta. It gradually reduces in the arteries. The walls of our arteries are elastic and therefore the flow of blood stretches them. We can feel this stretch as pulse.
During the relaxation phase of the cardiac cycle (diastole), the heart is not exerting any pressure on blood in arteries and the pressure falls. The pressure reaches its maximum value during systole. The systolic pressure is 120 mm Hg in normal individuals and the diastolic pressure ranges between 75 – 85 mm Hg in normal individuals.
The blood pressure gradually declines. The decline of blood pressure is due to friction between flowing blood and the walls of blood vessels. Hence the blood flows in the body from a region of higher pressure towards a region of lower pressure.
There are also other changes which occur along the route of blood flow. The difference between systolic and diastolic pressure continues to reduce until it disappears in the capillaries and veins.
The rate of blood flow tends to reduce as blood moves through branches of arteries and arterioles; this rate is lowest in capillaries and increases again in veins. The muscular activity such as breathing movements helps to regulate the normal blood flow in the body.
Hypertension is a condition in which blood pressure becomes high. If this condition prolongs, it damages the linings of the blood vessels and also weakens the heart muscles. The muscles become thickened due to continuous stress on them, resulting in the declining efficiency of the pumping action of the heart. The blood starts to retain in the heart and lungs, and it often leads to fatal condition which is known as congestive heart failure.
Thrombus is a solid plug or mass of blood clots in blood vessels. This mass can block fully or partially or it may be dislodged and carried to some other location in the circulatory system. This condition is called an embolus. Thrombosis is called the formation of thrombus. Thromboembolism is the leading cause of deaths in western countries. The thrombus formation may be due to irritation or infection in lining of blood vessels, reduced rate of blood flow due to inactivity and pneumonia and tuberculosis.
Heart attack is due to blockage of blood vessels in the heart due to an embolus or locally formed thrombus. It causes necrosis or damage to portion of heart muscles. This condition is technically known as myocardial infarction or commonly heart attack. It is caused due to disruption of control system of the heart.
How to avoid these conditions?
We can avoid above conditions by avoiding too much fatty food especially rich in cholesterol and by maintaining normal body weight. We can control blood pressure by doing regular walk and exercise and quit smoking.