1.3 Biophysics of Pressure, Flow and Resistance Flashcards
What are the two types of blood flow?
- Turbulent
- Laminar
What characterises laminar blood flow
- Streamlines
- Blood remains an even distance from the vessel wall
What are some real-world instances where we would observe turbulent blood flow, both in instances of pathology and normal blood flow?
- Atherosclerosis
- Regions of high velocity (e.g. beginning of aorta)
Where is the highest/lowest velocity blood flow seen during laminar flow? Why?
Highest: centre
Lowest: Edge
Minimal/Maximal influence of frictional forces of vessel wall
What are three conditions that can cause turbulent blood flow
- Rate of flow is too high
- Blood passes obstruction/tight turn
- Blood passes over a rough surface
Why is turbulent blood flow potentially harmful?
Increases Resistance
More energy required to maintain flow
Why can hypertension cause turbulent blood flow?
- Increased pressure
- Increased velocity
- Increased Reynolds number
- Increased probability of turbulence
According to the Reynolds Number calculation, what factors is turbulent blood flow proportional/inversely proportional to?
Proportional:
- Blood density
- Blood velocity
- Vessel diameter
Inversely Proportional:
- Viscosity
List five factors that influence vascular resistance
- Vessel diameter
- Vessel length
- Organisation of vascular network
- Characteristics of blood
- Extravascular mechanical forces (e.g. muscle contraction)
Relationship between conductance and resistance is…
Inversely proportional
Relationship between conductance and diameter to the power of four is…
Proportional
Using Poiseuille’s Equation, state the factors that increase and decrease blood flow
Inc
Increase:
- Pressure gradient
- Radius of blood vessel
Decerase:
- Viscosity
- Length of vessel
