Session 5 - Blood Flow Flashcards
Define Veloicty
The rate of movement of fluid particles along the tube
What is the relationship between flow, volume and time?
Flow = Volume / Time
What is laminate flow?
The most common type of blood flow. The velocity is. Highest in the centre and there is a gradient out to the edges
What is turbulent flow?
If mean velocity increases eventually blood will become turbulent. The velocity gradient breaks down and the fluid layers begin to tumble over one another with a great increase in flow resistance
Define viscosity
Extent to which fluid layers resist sliding over one another
What will happen to velocity if viscosity increases?
The velocity will decrease
How does diameter of the tube effect velocity?
If diameter of the tube increases the middle layers of the fluid will flow faster and hence the average velocity will increase
What is relationship between flow, resistance and pressure?
Pressure = Flow x Resistance
What is the relationship between resistance and radius?
The resistance decreases with thee fourth power of the radius
How do we work out total resistance of tubes in series?
We simply sum together the resistances of each tube
How do we work out the total resistance of tubes in parallel?
1/total resistance = 1/one tubes resistance + 1/other tubes resistance
(Add 1/tube resistance for all tubes in parallel)
Which vessels of the body have the highest resistance?
Arterioles
What makes the arteries have a high pressure?
Arterioles have a high resistance which means that when the heart pumps it is difficult for the blood to pass into the Arterioles so pressure in the arteries rises.
What will happen in a distensible blood vessel if pressure decreases too low?
The wall will eventually collapse and blood flow ceases.
This happens before pressure falls to zero
What feature of vessels allow them to have capacitance?
As vessels widen, more blood transiently flows in than out
