lecture 12 - haemodynamics

Question 1

What are the 2 factors that Flow depends on in haemodynamics?

Answer 1

Pressure gradient, resistance

Question 2

What is the definition of blood flow?

Answer 2

The quantity of blood passing a given point in the circulation in a given period

Question 3

What is the unit of blood flow?

Answer 3

mL/min

Question 4

What are the 3 key patterns of blood flow?

Answer 4

Laminar, Turbulent, Bolus

Question 5

Where is laminar flow typically found in the vasculature?

Answer 5

Arteries, arterioles, venules ,veins

Question 6

Where is turbulent flow typically found in the vasculature?

Answer 6

Ventricles, sometimes aorta

Question 7

Where is bolus flow typically found in the vasculature?

Answer 7

Capillaries

Question 8

What is the profile of lamina flow?

Answer 8

Parabolic profile

Question 9

What is the stress occuring in lamina flow?

Answer 9

Shear stress

Question 10

What is the possible effect of high shear stress on blood vessels?

Answer 10

can tear the endothelium

Question 11

What is the critical value for turbulent flow?

Answer 11

Reynold’s number - Re

Question 12

What is the equation for Reynold’s number (for turbulence of blood flow)?

Answer 12

Re = (velocity x vessel diameter x blood density)/blood viscosity

Question 13

What is the effect on the Re in athersclerotic blood vessels?

Answer 13

Increased - therefore there is increased turbulence

Question 14

What is Poiseuille’s Law used to determine?

Answer 14

resistance

Question 15

What are the 3 factors that govern resistance, according to Poiseuille’s Law?

Answer 15

Length of tube, liquid viscosity, tube radius

Question 16

How can be arterioles be changed to have the biggest effect on peripheral resistance, and why?

Answer 16

Change their radius - because resistance is related to radius^4

Question 17

What is the pressure difference across the circulation?

Answer 17

The difference between arterial and venous blood pressure

Question 18

Why are large arteries elastic?

Answer 18

The elasticity helps to reduce fluctuations in flow and pressure generated by the intermittent ejection of the stroke volume. Energy is stored in elastic vessels during systole and released in diastole to keep BP more constant.

Question 19

What is pulse pressure?

Answer 19

The difference between diastolic and systolic blood pressure

Question 20

What are the 2 factors that determine pulse pressure?

Answer 20

Stroke volume of left ventricle, arterial stiffness/compliance

Question 21

How does arteriosclerosis (hardened arteries) increase pulse pressure (difference between diastolic and systolic blood pressure)?

Answer 21

Reduced compliance due to reduced elasticity, which increases pulse pressure

Question 22

What are some examples of pathologies that would cause a reduced pulse pressure?

Answer 22

Congestive heart failure, haemorrhage, aortic stenosis - because of the decreased stroke volume

Question 23

What is the effect of a full bladder on blood pressure?

Answer 23

Increased BP with a full bladder

Question 24

how does smoking affect arterial blood pressure?

Answer 24

Increases due to vasoconstriction

Question 25

What features of veins allow them to act as capacitance vessels/reservoirs for blood?

Answer 25

They are highly distensible to their high compliance at normal operating pressures.

Question 26

What are some of the determinants of venous pressure?

Answer 26

Sympathetic innervation, blood volume, breathing, skeletal muscle pump