Blood Flow

[Parietal Lobe]

Can someone help me understand this? Pressure is inversley related to area, right? If someone has plaque build-up in their arteries, they'll have higher blood pressure because there's reduced area? Or not? My friend says no, but if it's not then how come people who have plaque or cholesterol have higher blood pressure?

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[TooMuchResearch]

Can someone help me understand this? Pressure is inversley related to area, right? If someone has plaque build-up in their arteries, they'll have higher blood pressure because there's reduced area? Or not? My friend says no, but if it's not then how come people who have plaque or cholesterol have higher blood pressure?

The higher blood pressure refers to the pressure within the heart, not the arteries. The pressure within the arteries decreases, as shown by the continuity equation: k=Av (or A1v1=A2v2...the numbers should be subscripts).

Also, study questions belong in the Study Question Q&A.

 

[cm4433]

I think this is best observed looking at Bernoulli's principle which states that as the speed of a fluid increases (in an arterial stenosis), the pressure decreases.

 

[TooMuchResearch]

I think this is best observed looking at Bernoulli's principle which states that as the speed of a fluid increases (in an arterial stenosis), the pressure decreases.

Yeah...definitely need Bernoulli along with the continuity equation. My mistake.

 

[Vihsadas]

Moving to Study Question Q&A

Try searching for blood flow and bernoulli's principle in the Study Question Q&A. There are some old threads that covered this topic in depth.

 

[Parietal Lobe]

My book says that Bernoulli's equation does NOT apply to blood because blood is not an ideal fluid.

 

[PharMed2016]

Can someone help me understand this? Pressure is inversley related to area, right? If someone has plaque build-up in their arteries, they'll have higher blood pressure because there's reduced area? Or not? My friend says no, but if it's not then how come people who have plaque or cholesterol have higher blood pressure?

Let's see if I can get this question answered. First, Pressure = F/A... so they are inversely related. Second, you asked whether or not someone with plaque buildup in their arteries will have HTN because of reduced area (your refering to diameter of the artery), and the answer to that is variable but I would say yes generally. Why do people with high cholesterol have high blood pressures? Well, that excess cholesterol gets deposited somewhere... surprise... in your vessels making them less elastic and narrower in some cases which has a direct impact on your blood pressure.

We can go deeper into this and explore what is blood pressure (diastole/systole)... along with viscousity to get a more in-depth look... ahh just waiting for my damn chinese new years meal to begin...

 

[TooMuchResearch]

My book says that Bernoulli's equation does NOT apply to blood because blood is not an ideal fluid.

An ideal fluid is one that is totally incompressible and has no viscosity. Much like an ideal gas, an ideal fluid does not exist. It's just a theoretical model which we use to approximate real fluids.

 

[Vihsadas]

An ideal fluid is one that is totally incompressible and has no viscosity. Much like an ideal gas, an ideal fluid does not exist. It's just a theoretical model which we use to approximate real fluids.

True, and your book is right. Bernoulli's principle does not apply in full to the circulatory system. The continuity velocity equation does (cross-sec area up = velocity down), but the pressure side of it does not (as we get toward the capillaries blood pressure goes down, but bernoulli's equations says it should go up because the cross-sec area is greater in sum total of the capillaries as compared to the aorta).
I made an extermely detailed post on this a while back if someone want to search for it.

 

[TooMuchResearch]

True, and your book is right. Bernoulli's principle does not apply in full to the circulatory system. The continuity velocity equation does (cross-sec area up = velocity down), but the pressure side of it does not (as we get toward the capillaries blood pressure goes down, but bernoulli's equations says it should go up because the cross-sec area is greater in sum total of the capillaries as compared to the aorta).
I made an extermely detailed post on this a while back if someone want to search for it.

The Post. I'm reading it now.