Topic 5.2

Question 1

What does the Law of Laplace relate to in the context of fluids?

Answer 1

• Transmural pressure with wall stress
• It describes how pressure differences across a wall relate to the stress experienced by the wall

Question 2

What is the main formula of the Law of Laplace as used in hemodynamics?

Answer 2

ΔP = T/R

Where ΔP is the pressure within the vessel lumen, T is the wall tension, and R is the vessel radius.

Question 3

In what geometries does the Law of Laplace hold true?

Answer 3

Cylindrical or spherical geometries

It applies irrespective of material properties or wall thickness.

Question 4

What is a limitation of the Law of Laplace?

Answer 4

It gives average wall stress only = cannot provide information on stress distribution across the wall

Question 5

How does the Law of Laplace help in understanding cardiac function?

Answer 5

It relates wall stress to the geometry of the heart = the ratio of radius to wall thickness is crucial

Question 6

What happens to cardiac muscle cells in hypertension according to the Law of Laplace?

Answer 6

They increase in thickness = concentric hypertrophy + normalizes systolic wall stress despite higher pressure

Question 7

What does the equation of continuity represent?

Answer 7

The conservation of mass during flow = It states that the mass flow rate is constant throughout a closed system

Question 8

What is the equation of continuity formula for a fluid in a pipe?

Answer 8

ρAv = constant

Question 9

What happens in steady state regarding mass flow in a volume?

Answer 9

• The same mass flows in and out + flow through A1 must equal the flow through A2
• Q = A1v1 = A2v2

.

Question 10

When using Bernoulli’s equation, what three types of energy are considered?

Answer 10

Pressure energy, kinetic energy, potential energy = conservation of energy in flowing fluids

Question 11

What does Bernoulli’s equation predict about pressure and velocity?

Answer 11

When velocity is high, pressure is low

Question 12

What is Poiseuille’s Law used to describe?

Answer 12

The relation between pressure drop and fluid flow = under steady flow conditions in cylindrical tubes

Question 13

What is the velocity profile of fluid flow in a tube according to Poiseuille’s Law?

Answer 13

Parabolic = velocity is highest at the center and zero at the walls

Question 14

In Poiseuille’s Law, which factors significantly affect flow?

Answer 14

Radius, pressure drop, and viscosity

Question 15

What are the main assumptions for Poiseuille’s law to hold?

Answer 15

• The tube is stiff, straight, and uniform
• The fluid is Newtonian
• The flow is laminar and steady

Question 16

How does resistance in a fluid system relate to pressure and flow?

Answer 16

Resistance = ΔP/Q

Question 17

True or False: Bernoulli’s equation can be used to estimate the severity of arterial stenosis.

Answer 17

True

Question 18

What is the effect of narrowing an artery on blood flow according to Bernoulli’s principle?

Answer 18

Increased velocity and decreased pressure

Question 19

What is a common clinical application of Bernoulli’s equation?

Answer 19

Estimating severity of valve stenosis