About blood pressure

If you were to take out all the blood vessels inside your body and stretch them out,They would be 95000 km long and everyday they carry the equivalent of 7500 litres of blood (4-5 litres of blood recycled) . The blood carries oxygen glucose and amino acids and other nutrients to the tissues in the body. When blood is pumped through the heart and into the vessels, it exerts force on the wales of the vessels. This is called blood pressure. Blood pressure rises and falls on the phases of the heartbeat. It is highest during systole when the heart contracts. Normal systolic pressure is 90 to 120 mm Hg. Blood pressure is lowest during diastole when the heart is at rest. Normal diastolic pressure ranges from 60 to 80 mm Hg. So the normal blood pressure is a little less than 120/80 mm Hg.

Several things can increase the force that is acting up on the walls of the blood vessels: Properties of the blood, extra blood volume and narrower vessels. When blood thickens, higher pressure is needed to push it through the vessels. For example, when you have a high salt diet blood pressure rises. This is because salt promotes water retention. This extra fluid leads to a higher blood volume which leads to a higher blood pressure.

Stress releases hormones like epinephrine and norepinephrine which constricts the blood vessels thus increasing the resistance of the flow of blood. This raises the blood pressure.

Blood vessels can handle these changes in pressure easily because of the elastic fibres inside their walls. However, if blood pressure regularly rises above 140/90 mm Hg otherwise known as hypertension, it can cause some serious health problems. The extra strain can cause tears in the blood vessels. The injured tissue then swells up and gets inflamed. White blood cells, fat and cholesterol can collect at these inflammations and build up to form a plaque. This is called atherosclerosis.

If the plaque ruptures, blood clots form at the place of rupture, clogging the vessel. If the clog is big enough, it can completely block the flow of oxygen and nutrients to the tissues downstream. If this happens in the vessels feeding the heart, it can cause a heart attack. Blocked blood vessels in the brain will cause a stroke to happen.

Fortunately, dangerously clogged blood vessels can be widened by a procedure known as angioplasty. A deflated balloon catheter is passed over a wire into the narrowed vessel and then inflated to a fixed size. The balloon forces expansion of the blood vessel and the surrounding muscular wall, allowing an improved blood flow. A stent may be inserted at the time of ballooning to ensure the vessel remains open, and the balloon is then deflated and withdrawn.