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Pathophysiology of atherosclerosis essay
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Atherosclerosis is a cardiovascular disease characterized by the deposition of materials such as lipids, cholesterol, and proteins such as fibrins in the arteries, as seen in Figure 1 below. This leads to increased resistance to blood flow and causes the stress on the heart to increase.
The main risk of atherosclerosis is that it greatly increases the probability of blood clots forming in arteries. Should such clots occur in the carotid or coronary arteries, they can result in strokes or myocardial infarctions, which can be fatal2. This paper seeks to analyze how physical principles can be used to elucidate the pathophysiology of atherosclerosis and its effects on the human body.
Physical Principles
Continuity Equation
This equation states that for an incompressible, non-viscous fluid with constant density flowing through a channel, the mass and volume of the fluid are conserved. As a result, the rate of fluid volume flow has to be constant at different points where the cross-sectional area differs.
∆V/∆T=A_1 V_1= A_2 V_2 (1)
With reference to Eq. (1), ∆V/∆T refers to the rate of fluid volume flow, while A refers to the cross-sectional area and V the fluid velocity at points 1 and 2 in a tube respectively. From Eq. (1), it can be seen that as the rate of fluid volume flow is assumed to be constant for an incompressible fluid, a decrease in the cross-sectional area of a tube would lead to an increase in the fluid velocity passing through it3.
Bernoulli’s Equation
Ideally, in the absence of fluid friction, the flow of incompressible fluids can be described by Bernoulli’s Equation:
P_1+ ρgy_1+1/2 ρv_1^(2 )= P_2+ ρgy_2+1/2 ρv_2^(2 ) (2)
With reference to Eq. (...
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...lp to reduce the levels of low-density lipoprotein levels and potentially slow the development of atherosclerotic plaques in blood vessels16. With these advancements in pharmaceuticals, it may be much easier to control the advancement of atherosclerosis in future.
Works Cited
1. Merck - MK-0524B - Treatment of Atherosclerosis. (June 6, 2014); from http://www.pharmaceutical-networking.com/merck-mk-0524b-treatment-of-atherosclerosis/.
2. J. Losos, K. Mason, S. Singer, based on the work of P. Raven, & G. Johnson, Biology, 8th ed., (McGraw-Hill Education (Asia), Singapore, 2008), pp. 994-995.
3. H. Young, & R. Geller, Sears & Zemansky's College Physics, 8th ed., (Pearson Education Inc., San Francisco, 2007), pp. 422-426, 428, 430-431.
4. P. Davidovits, Physics in Biology and Medicine, 3rd ed., (Elsevier Inc., United States of America, 2008), pp. 101-104, 110-112.
They just forgot to mention the other effects of fluids in nature. “The influence of the fluid on a body moving through it depends not only on the body’s velocity but also on the velocity of the fluid,” this is called relative velocity ( ). The relative velocity of a body in a fluid has an effect on the magnitude of the acting forces. For example, as a long distance runner is running into a head wind, the force of the fluid is very strong. If the runner is running with the help of a tail wind, the current’s force is reduced and may even be unnoticeable.
Have you wondered why airplanes were ever able to fly or how racecars are able to stay on the ground at high speeds? They all use a scientific concept called Bernoulli’s principle, or more commonly known as Bernoulli’s equation. His principle simply states that the faster a fluid flows, the less pressure it applies, the slower the fluid flows, the more pressure it applies.
Coronary artery disease (CAD) is the most common type of multifactorial chronic heart disease. It is a consequence of plaque buildup in coronary arteries. The arterial blood vessels, which begin out smooth and elastic become narrow and rigid, curtailing blood flow resulting in deprived of oxygen and nutrients to the heart [1].
Coronary heart disease is defined by the hardening of the epicardial coronary arteries. The buildup of plaque in the arteries slowly narrows the coronary artery lumen. In order to better understand the physiology of the disease, it is important to first know the basic anatomy of the human heart. The aorta, located in the superior region of the heart, branches off into two main coronary blood vessels, otherwise known as arteries. The arteries are located on the left and right side of the heart and span its surface. They subsequently branch off into smaller arteries which supply oxygen-rich blood to the entire heart (Texas Heart Institute, 2013). Therefore, the narrowing of these arteries due to plaque buildup significantly impairs blood flow throughout the heart.
Atherosclerosis is the culprit behind coronary heart disease (CHD) and stroke, which is the most common cause of death worldwide and in the United States10. Among the modifiable risk factors of CHD and stroke is the serum low density lipoprotein level (LDL)8, 11. Several randomized clinical trials have established that reducing the serum LDL level results in a reduction in the future risk of CHD and stroke in a linear relationship, in one study it was estimated that reducing the LDL by 1 % would reduce the risk by 1.7 %.1-4, 7, 9, 13
... middle of paper ... ... 14 Nov 2011.. http://web.ebscohost.com/lrc/detail?vid=4&hid=110&sid=fef50b1c-4aba-40fd-83b1- 583a32991f55@sessionmgr110&bdata=JnNpdGU9bHJjLWxpdmU=> Edrich, Matthias. The.
Bernoulli’s principle is the concept that as the speed of a moving fluid (liquid or gas) increases, the pressure within that fluid decreases. This principle was originally formulated in 1738 by the Swiss mathematician and physicist Daniel Bernoulli, it states that the total energy in a steadily flowing ...
The shear viscosity is a transport coefficient for momentum in inhomogeneous flows. This transport coefficient, which is widely used to describe both plasmas and fluids, relates two hydrodynamic quantities: shear stress and shear rate. The shear stress Pxy is the off-diagonal element of a pressure tensor, and the shear rate γ is the transverse gradient of the flow velocity u. For a flow in the y direction,
When one or several lipids combine with proteins this forms lipoproteins, these transport fat throughout the bloodstream. High-density lipoproteins, also known as HDL, carry fat away from body cells, therefore preventing its growth in the artery walls. Low-Density Lipoproteins, also known as LDL, contain a high amount of cholesterol and seem to help the build up of fatty materials in the artery walls. The situation that you should go for would be high HDL and low LDL levels. Your goal should be to keep your overall cholesterol at below 200, with LDL lower than 40, and your HDL should be at around 160. This will lower the risk of heart disease and other related problems with cholesterol.
Atherosclerosis begins when the inner wall of the artery becomes damaged and cholesterol and fatty plaques begin to lodge in the arteries. Damage to the endothelial wall inside the artery can be caused by hypertension, hyperlipidemia, and hyperglycemia (“Subclinical Atherosclerosis..” 443). When this happens, the immune system responds by sending monocytes to the damaged area. The monocytes turn into macrophages; their job is to eat up the excess cholesterol and unblock the artery. The macrophages are unable to digest all of the cholesterol, and as a result turn in to foam cells. When many macrophages are turned into foam cells, plaque results, and protrudes into the arterial wall, restricting blood flow and raising blood pressure (“Atherosclerosis Growth Process.” 8). If the plaque becomes too large it may break, releasing plaque into the blood. This can cause a great reduction in blood flow or a clot, resulting in stroke or myocardial infarction (“Stroke Risk.” 3).
Viscosity is the tendency of a fluid to resist flow and can be thought of as the internal friction of a fluid. Microscopically, viscosity is related to molecular diffusion and depends on the interactions between molecules or, in complex fluids, larger-scale flow units. The opposite of the viscosity is the fluidity which measures the mobility for fluid layers (Secco et al, 2013). Viscosity is affected by the temperature and composition of the fluid and, for compressible fluid, also by pressure (Serway et al, 2012).
The flow is unsteady and sufficiently fast so that the inertial nonlinearities can not be ignored, thus the term needs to be retain.
The Bernoulli’s equation was mainly derived for ideal fluids i.e zero viscous fluids hence they are frictionless. But all the fluids are real and has some viscosity and hence offer resistance to flow. When the fluid is flowing there will always be some losses across the sections and Bernoulli’s equation considers all the losses.
It can be presumed that the volumetric flow rate will be reduced similarly to the Hagen–Poiseuille equation, due to the laminar flow within the tube in Yeh, H. experiment in 2009, he takes into account convection as well as mass, and momentum balance: