Lecture 11 - Arterial haemodynamics and blood flow modelling Flashcards
How do the mechanical properties of the vascular wall vary along the arterial tree?
Large vessels are elastic and compliant, whereas peripheral arteries are narrow and stiff.
What role does the heart play in the cardiovascular system?
The heart pumps blood through the cardiovascular system by cyclic contraction, generating pulsatile waves that travel down the aorta and major arteries.
What types of waves can be generated by the cyclic contraction of the heart?
Pressure waves, flow or velocity waves, and diameter waves.
Why must capillary flow be continuous and slow?
To allow sufficient time for the exchange of nutrients, gases, and waste
What is the Windkessel effect, and who first described it?
The Windkessel effect describes how arterial elasticity converts the pulsatile flow from the heart into a constant and slow stream within the capillaries.
Otto Frank
Describe the structural components of the arterial wall.
The arterial wall comprises:
Adventitia: Collagen and elastin
Media: Thick layer of muscle cells and elastin
Intima: Thin elastin layer
Endothelium: Single layer of cells surrounded by elastin and collagen fibres
How does aging affect the arterial tree?
Aging causes a uniform increase in vessel radius, media and intima thickness, and overall Young’s modulus across the arterial tree.
How does the heart’s piston action affect blood flow in the aorta?
The fluid displaced by the heart’s piston flows into the elastic aorta, distending it and generating a forward wavefront that propagates along the tube.
What is the pulse wave speed, and how is it related to arterial properties?
Pulse wave speed is the speed at which pressure waves propagate through the arteries. It is related to the elastic modulus of the arterial wall via the Moens-Korteweg equation.
What factors influence wave reflection in the vasculature?
Wave reflection occurs at discontinuities such as bifurcations, stenosis, and areas with stiffened arterial walls.
How does wave reflection affect pressure waves in the cardiovascular system?
Reflected waves can increase pressure when they return to the heart, depending on the distance of the reflection site, wave speed, and the reflection characteristics.
What is characteristic impedance in the context of arterial haemodynamics?
Characteristic impedance is the frequency-dependent resistance of an artery, defined as the ratio of forward propagating pressure to forward propagating flow waves.
How can the reflection and transmission coefficients be expressed in terms of characteristic impedances?
If the density is the same across the junction, the reflection and transmission coefficients can be expressed as:
Reflection coefficient = z1-z0 / z0 + z1
what is the moens-korteweg equation
c = sqrt [ hE / 2 R0 *rho ]
What is the principle of superposition as it relates to wave pulses?
When wave pulses overlap, they do not bounce off each other but combine to form a resultant wave that is the algebraic sum of the individual pulses.
