Lecture 5 Arteries

Question 1

What is blood flow?

Answer 1

Blood flow is the quantity of blood that passes a given point in the circulation in a given period of time

Question 2

What is overall blood flow in the circulation of an adult?

Answer 2

5 liters per minute

Question 3

How is velocity of blood flow determined, and what proportional relationship exists for blood velocity?

Answer 3

Velocity = blood flow / cross sectional area.

As cross section size increases, velocity increases.

Question 4

What are the determinants of blood flow?

Answer 4

Pressure difference between two ends of the blood vessel and resistance of the vessel - give by Ohm’s Law, F = delta P / R.

Question 5

How to calculate resistance for parallel circuit?

Answer 5

1/resistance = 1/R1 + 1/R2…

Question 6

What is laminar flow?

Answer 6

How the blood in vessels flows in streamlines, with a parabolic profile - velocity in the center is greatest due to reduced resistance

Question 7

What are 4 causes of turbulent flow?

Answer 7

• High velocities
• Sharp turns
• Rough surfaces
• Obstruction eg rapid narrowing of a vessel

Question 8

How to tell laminar and turbulent flow apart? What can turbulent flow diagnose?

Answer 8

Laminar is silent, turbulent flow causes murmurs.

Murmurs (bruits) diagnose vessel stenosis, vessel shunts, and cardiac valvular lesions.

Question 9

How can we measure turbulent flow?

Answer 9

By using Reynold’s number, which is the tendency of turbulence to occur.

(Re 200-400 branches, 2000 in straight vessel)

Question 10

What blood vessels always have turbulent flow and why?

Answer 10

Proximal portion of aorta and pulmonary artery because high velocity, pulsatile flow, elastic walls, valve movement.

Question 11

How does atherosclerosis cause turbulence?

Answer 11

Rough surface from plaques

Question 12

How does aneurysm cause turbulence?

Answer 12

No longer straight vessel, large open space causes change in diameter and direction

Question 13

How could we calculate the resistance of a vessel?

Answer 13

Diameter to the power of four (d^4).

Question 14

What is blood pressure?

Answer 14

The force exerted by the blood against any unit area of the vessel wall.

Question 15

What are the systolic and diastolic pressures referring to?

Answer 15

Systolic - height of the pressure pulse, 120mmHg

Diastolic - lowest point of the pressure, 80mmHg

Question 16

What is pulse pressure?

Answer 16

Difference between systolic and diastolic pressure

Question 17

What does a pressure pulse contour look like for arteriosclerosis?

Answer 17

Increase in pulse pressure since the pressure is not being absorbed by the elasticity of the aorta. Very high spikes.

Question 18

What does a pressure pulse contour look like for aortic stenosis?

Answer 18

Reduced aortic valve opening reduces blood flow so low systolic pressure flattens out pressure contour.

Question 19

What does a pressure pulse contour for aortic insufficiency look like?

Answer 19

Larger pulse pressure with no dips due to incomplete closing of aortic valve, excessive turbulence, regurgitation.

Question 20

What do you listen for during the Auscultatory method for measuring blood pressure?

Answer 20

Korotkoff sounds

Question 21

Why does blood pressure raise with age?

Answer 21

Arteries are less compliant and elastic so less pressure is absorbed by the elastic arteries.

Question 22

Why is mean blood pressure closer to diastolic pressure?

Answer 22

Systole is very fast, not much time spent there - spend more time in diastole.