Topic 5.3

Question 1

What are the three components of the cardiovascular system?

Answer 1

• Blood = vehicle
• Circulatory system = distribution system
• Heart = pump

Question 2

What percentage of body mass does blood represent?

Answer 2

About 7%.

Question 3

How much blood does each section of the heart pump on each contraction?

Answer 3

About 80 mL.

Question 4

What type of fluid is blood classified as?

Answer 4

Non-Newtonian fluid.

Question 5

What components make up the blood solution?

Answer 5

• Plasma
• Red blood cells
• White blood cells
• Platelets

Question 6

How does blood viscosity change with hematocrit?

Answer 6

Blood viscosity increases with the hematocrit.

Question 7

What is the mean blood pressure formula given systolic and diastolic pressures?

Answer 7

Mean BP = (Systolic + 2 * Diastolic) / 3

Question 8

What is the arterial pulse pressure?

Answer 8

The difference in pressure of 40 mmHg between systole and diastole.

Question 9

Where does much of the pressure drop occur in the arterial system?

Answer 9

In the arterioles and capillaries.

Question 10

How does standing upright affect blood pressure?

Answer 10

An additional pressure ρgh is added, where h is the height relative to the heart.

Question 11

What is the approximate pressure increase due to standing at a height of 1 m?

Answer 11

10,400 Pa = 79 mmHg.

Question 12

What is the density of blood at standing height 1m?

Answer 12

ρ = 1,060 kg/m3

Question 13

What happens to blood volume in leg veins when standing up?

Answer 13

The volume of blood in the leg veins increases + pressure in veins back to heart decreases

Question 14

What are the two types of conditions under which the mechanical properties of blood vessels can be measured?

Answer 14

• Constant length while measuring diameter
• Constant diameter while measuring length

Question 15

What are the two physical attributes of blood vessels in steady state?

Answer 15

• Resistance to flow
• Compliance in response to distending pressure

Question 16

What is the Law of Laplace for hollow cylinders?

Answer 16

Tension T = ΔP * R.

Question 17

What is a stenosis in the context of arterial health?

Answer 17

A localized narrowing in the arterial lumen, typically a result of atherosclerosis.

Question 18

How is stenosis quantified?

Answer 18

By the ratio As/Ao, called the area ratio, often expressed as % area occlusion.

Question 19

What does the first term in the pressure drop-flow equation account for?

Answer 19

Viscous losses within the stenosis.

Question 20

What does the second term in the pressure drop-flow equation account for?

Answer 20

Losses due to turbulence.

Question 21

How much % occulsion is severe stenoses

Answer 21

85% = turbulent loss dominates

Question 22

At what stenosis percentage do complaints from ischemia typically arise suddenly?

Answer 22

Typically for a stenosis of 60-70%.

Question 23

What happens to pressure in a narrow section when velocity is high, according to Bernoulli’s equation?

Answer 23

Pressure decreases.

Question 24

What is the effect of gravity on blood pressure in the aorta?

Answer 24

Blood pressure has to be high enough to pump blood to the top of the brain.

Question 25

What is a compliance vessel?

Answer 25

An elastic vessel that has no noticeable resistance.

Question 26

What is a resistance vessel?

Answer 26

A rigid vessel with constant volume.

Question 27

Which blood vessels are primarily compliance vessels?

Answer 27

• Aorta
• Large arteries
• Large veins

Question 28

Which blood vessels act like resistance vessels?

Answer 28

• Arterioles
• Capillaries
• Venules