The Heart

The Heart  Blood Pressure  Atherosclerosis  Physics  Treatment
 

The heart is an internal pump for the body pushing blood throughout the body through a pathway of blood vessels. These blood vessels act as roadways for blood to travel through and get to other organs and parts of the body. The heart creates pressure which pushes the blood through the body allowing oxygen to travel to the furthest extremities. This pressure is referred to as blood pressure.

Blood Pressure

Blood pressure is simply a measure of the force the blood puts against the walls of the blood vessels as it is push through the body. Pressure is measured by the formula P=FA. Blood pressure is most commonly measured with an electronic blood pressure cuff or a cuff with a stethoscope. In the process the doctor is cutting off the blood and measuring when the pressure when blood begins to flow again, this indicates the systolic. This measures the optimum pressure the heart can push the blood through the body. The next number indicates the diastolic  pressure which shows when the heart is at rest. A normal blood pressure has a systolic pressure 90-140 and a diastolic pressure of 60-90. Atherosclerosis is a problem that occurs in blood vessels which leads to a higher blood pressure.

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Atherosclerosis

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Atherosclerosis is a build-up of plaque, fat, or calcium on the walls of the arteries which blocks and hardens the arteries. This lessens the elasticity of the arteries and prevents the optimum amount of blood from flowing through them. This could end up blocking the blood flow if it is allowed to build up enough leading to a series of much more serious problems including heart attacks, strokes, and other cardiovascular diseases. Blood vessels consist of veins which send blood to the heart and arteries which send blood away from the heart. Atherosclerosis effects the arteries not allowing blood to travel to the parts of the body further from the heart. There is physics involved with this disease which will appear later in this blog.

How Flow Rate, Bernoulli's Equation,and Poiseuilles Law Relates to Atherosclerosis

The flow rate of blood shows the P1v1A1= P2v2A2 and flow rate=A1v1=A2v2 because blood is a non compressible fluid. To maintain a constant flow rate in a clogged artery, the blood must travel faster than normal through the constriction.  If the blood speed is high enough in the constricted region, the artery may collapse under external pressure, causing an interruption in this flow.  From this principle it is seen that a sign of atherosclerosis is high blood pressure. This is due to the narrowing of the arteries which causing the blood to travel more quickly through them. Since blood is thick and the arteries are not as elastic as they once were, the pressure traveling through the plaque filled arteries is more than the artery wants to handle with the limited space for the blood to travel through and eventually a clot forms. Bernoulli's equation relates speed, height and pressure by P + ½pv² + pgy = constant. This equations acts as another way of stating the work energy theorem. Poiseuilles Law states dP*pi*r^4/8*theta*L=V/t. From this one can see how the radius relates to the volume of the artery. Since it is to the 4th power in causes the volume to increase or decrease by a factor of 16 so a blocked artery with a smaller radius for blood to travel through decreases the volume of blood that it can hold by a factor of 16. This shows how atherosclerosis causes a large problem, however their are ways to treat atherosclerosis and solve these problems. 

Treatment and Physic Involved

Their are quite a few ways to treat atherosclerosis including an atherectomy, balloon angioplasty, a stint,or even blood thinners. The first three treatment options have their own special way of moving or removing the plaque that is built of in the arteries and opening up the artery solving the problems mentioned in the previous post by increasing the radius allowing for a constant velocity and area for the artery and allowing the less work to be done and more energy to be conserved by keeping a constant speed. Blood thinners such as aspirin use a different method to solve the problem by lowering the density of the blood allowing it to travel through the arteries more easily without as much surface tension and viscosity.

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