Cardiovascular System

Question 1

How much blood is pumped from the heart each minute?

Answer 1

5 Litres

Question 2

What are the differences in pressure between both sides of the heart?

Answer 2

The Left Hand Side generates 4x more pressure than the Right Hand Side

130mmHg vs 30mmHg

Question 3

What is the order that the blood flows through the heart?

Answer 3

Superior/Inferior Vena Cava
Right Atrium
AV tricuspid valves
Right Ventricle
Pulmonary Valve
Pulmonary Artery 
Lungs
Pulmonary Vein
Left atrium
AV bicuspid valves
Left Ventricle
Aortic Valve
Aorta
Rest of body

Question 4

What are percentage distribution of cardiac output at rest?

Answer 4

3% Heart Muscle
21% Digestive System
6% Liver
20% Kidneys
13% Brain
15% Skeletal Muscle
9% Skin
5% Bone

Total = 5L/min

Question 5

What are percentage distribution of cardiac output at moderate exercise?

Answer 5

As a percentage increase and decrease from before:

350% Heart muscle
-55% Digestive system 
No change in Liver
-45% Kidneys
No change in Brain
\+1050% Skeletal muscle
\+350% Skin
-30% Bone

Total = 12.5L/min

Question 6

What is the structure and function of the Aorta & Large Arteries?

Answer 6

Structure: thick walled, highly elastic
Function: distribution (conduit)
pressure reservoir - forward propulsion

Question 7

What is the structure and function of the Arterioles?

Answer 7

Structure: thick walled, muscular, highly innervated
Function: tissue distribution of flow, variable resistance

Question 8

What is the structure and function of the Capillaries?

Answer 8

Structure: thin walled (single cell)
Function: exchange

Question 9

What is the structure and function of the Venules and Veins?

Answer 9

Structure: -thin walled, some muscle, some innervation, valved (unidirectional)

Function: -reservoir (capacitance), at rest approximately 60% of blood volume
-return blood to heart (venous return)

Question 10

What are the average internal diameters of each blood vessel type?

Answer 10

Aorta: 25mm
Arteries: 4mm
Arterioles: 30micrometres
Capillaries: 8micrometres
Venules: 20micrometres
Veins: 5mm
Vena Cava: 30mm

Question 11

What are the average wall thicknesses of each blood vessel type?

Answer 11

Aorta: 2mm
Arteries: 1mm
Arterioles: 500micrometres
Capillaries: 0.5 micrometres
Venules: 1micrometre
Veins: 0.5mm
Vena Cava: 1.5mm

Question 12

What happens to velocity of blood if flow rate is constant?

Answer 12

Velocity becomes inversely proportional to the cross sectional area
ie. bloodflow is slowest in capillaries

Question 13

What is flow rate?

Answer 13

volume/unit time

Question 14

What are the factors that affect flow rate through a vessel?

Answer 14

1) Pressure
2) Length
3) Radius
4) Viscosity

Question 15

What is Poiseuille’s Law?

Answer 15

Q is inversely proportional to pi(PI-PO)r^4 all divided by 8nL

(Pi-Po) = difference between inflow and outflow Pressure
L = length
r^4 = radius of tube ^4
n = viscosity of fluid

Question 16

What are the most important variable in Poiseuille’s Law?

Answer 16

Vessel Radius

-arterioles have the greatest capacity to change their raduis and therefore influence resistance

Question 17

What is the equation for flow through the circulation (cardiac output)?

Answer 17

pressure drop (Pa - Pv) / total peripheral resistance

Question 18

What is Pa? How does it come about and what does it depend on?

Answer 18

Arterial Blood Pressure:

• pulsatile pressure generated by the heart
• force exerted by blood against vessel wall
• depends on the volume of blood and compliance of vessel wall (how easily it can be stretched)

Question 19

What is the difference between systole and diastole?

Answer 19

Systole - heart contracting (highest pressure) approx 120mmHg

Diastole - heart relaxing (pressure falls to lowesr) approx 80mmHg

Question 20

What is Mean BP?

Answer 20

Mean Blood Pressure = Diastolic BP + 1/3 pulse pressure