Topic 5.3 Flashcards
What are the three components of the cardiovascular system?
- Blood = vehicle
- Circulatory system = distribution system
- Heart = pump
What percentage of body mass does blood represent?
About 7%.
How much blood does each section of the heart pump on each contraction?
About 80 mL.
What type of fluid is blood classified as?
Non-Newtonian fluid.
What components make up the blood solution?
- Plasma
- Red blood cells
- White blood cells
- Platelets
How does blood viscosity change with hematocrit?
Blood viscosity increases with the hematocrit.
What is the mean blood pressure formula given systolic and diastolic pressures?
Mean BP = (Systolic + 2 * Diastolic) / 3
What is the arterial pulse pressure?
The difference in pressure of 40 mmHg between systole and diastole.
Where does much of the pressure drop occur in the arterial system?
In the arterioles and capillaries.
How does standing upright affect blood pressure?
An additional pressure ρgh is added, where h is the height relative to the heart.
What is the approximate pressure increase due to standing at a height of 1 m?
10,400 Pa = 79 mmHg.
What is the density of blood at standing height 1m?
ρ = 1,060 kg/m3
What happens to blood volume in leg veins when standing up?
The volume of blood in the leg veins increases + pressure in veins back to heart decreases
What are the two types of conditions under which the mechanical properties of blood vessels can be measured?
- Constant length while measuring diameter
- Constant diameter while measuring length
What are the two physical attributes of blood vessels in steady state?
- Resistance to flow
- Compliance in response to distending pressure
What is the Law of Laplace for hollow cylinders?
Tension T = ΔP * R.
What is a stenosis in the context of arterial health?
A localized narrowing in the arterial lumen, typically a result of atherosclerosis.
How is stenosis quantified?
By the ratio As/Ao, called the area ratio, often expressed as % area occlusion.
What does the first term in the pressure drop-flow equation account for?
Viscous losses within the stenosis.
What does the second term in the pressure drop-flow equation account for?
Losses due to turbulence.
How much % occulsion is severe stenoses
85% = turbulent loss dominates
At what stenosis percentage do complaints from ischemia typically arise suddenly?
Typically for a stenosis of 60-70%.
What happens to pressure in a narrow section when velocity is high, according to Bernoulli’s equation?
Pressure decreases.
What is the effect of gravity on blood pressure in the aorta?
Blood pressure has to be high enough to pump blood to the top of the brain.
What is a compliance vessel?
An elastic vessel that has no noticeable resistance.
What is a resistance vessel?
A rigid vessel with constant volume.
Which blood vessels are primarily compliance vessels?
- Aorta
- Large arteries
- Large veins
Which blood vessels act like resistance vessels?
- Arterioles
- Capillaries
- Venules
