Flashcards in Flow through Tubes Deck (84)
What are the two major subdivisions of the vascular system?
Systemic circulation and Pulmonary circulation
How are the systemic and pulmonary circulations arranged?
In series with one another
What is each subdivision of the circulation composed of?
How are most vessels of a given type arranged?
In parallel with each other
What must happen in order for blood to keep flowing?
Blood pressure must fall all the way from the aorta to the venae cavae
How is flow of blood driven through vessels?
By the gradient of pressure
What is flow proportional too?
The pressure difference between the ends of a vessel
What is the result of a higher pressure difference on flow?
What is the flow for a given pressure gradient determined by?
The resistance of a vessel
What is the resistance of a vessel determined by?
The nature of the fluid and the vessel
The volume of fluid passing a given point per unit time
The rate of movement of fluid particles along the tube
How does flow differ at different points along a vessel?
When can velocity vary along the length of a vessel?
If the radius of the tube changes
What is the relationship between velocity and cross sectional area at a given flow?
They are inversely proportional
What is the velocity of vessels with a small cross sectional area at a given flow?
What is the velocity of vessels with a large collective cross sectional at a given flow?
What vessels have a large cumulative cross sectional area?
What happens as arteries branch?
The total cross sectional area of the vascular bed increases, and thus so does flow
How can the flow be described in most blood vessels?
What happens in laminar flow?
There is a gradient of velocity from the middle (highest), to the edge, where fluid is stationary
What happens as mean velocity increases?
Flow eventually becomes turbulent
What happens in turbulent flow?
The velocity gradient breaks down as fluid tumbles over, and the flow resistance greatly increases
What is flow determined by in a vessel with constant pressure?
What does mean velocity depend on?
Viscosity of fluid
Radius of tube
How does fluid move in laminar flow?
In concentric layers, with middle edges moving faster than the outer layers, and therefore the layers must slide over one another
What is the extent to which fluid layers resist sliding over one another known as?
What does a higher viscosity result in?
Slower flow of central layers, and a lower average velocity
What does viscosity determine?
The slope of the gradient of velocity