Pressure and Flow in Arteries and Veins Flashcards
Illustrate the changes in aortic pressure as it passes through the vascular tree
- Arteries: low resistance conduit, 95-90mmHg
- Arterioles: resistance vessels, 90-40mmHg
- Capillaries: low upon arrival - good because they are thin-walled
- Veins: low pressure to push back to heart, 20-5mmHg (= systemic filling pressure)
Explain the changes in blood velocity and total cross-sectional area of the vessels through the vasculature
Velocity is related to total cross-sectional area. Blood moves fastest in the vena cava and slowest in the capillaries
How does gravity affect pressure and flow in veins?
- Causes venous distension in legs
Decrease in EDV, decrease in preload, decrease in CO, decrease in SV, decrease in MAP - Causes venous collapse in neck (estimate CVP with JVP)
- Causes orthostatic (postural) hypotension
How does gravity affect pressure and flow in veins?
- Causes venous distension in legs
Decrease in EDV, decrease in preload, decrease in CO, decrease in SV, decrease in MAP - Causes venous collapse in neck (estimate CVP with JVP)
- Causes orthostatic (postural) hypotension
Define skeletal muscle pump
Venous valves prevent back flow of blood, which enhances venous return.
Define respiratory pump
The pressure changes that occur during respiration can encourage venous return. The negative pressure during inspiration pulls blood back towards the heart.
How does venomotor tone affect pressure and flow in veins?
Venomotor tone = state of contraction of the smooth muscles that surround the veins and venules
An increase in venomotor tone increases CVP, which in turn promotes venous return.
How does systemic filling pressure affect pressure and flow in veins?
Systemic filling pressure = pressure created by ventricles and transmitted through the vascular tree i.e. pressure when there is no blood motion
An increase in systemic filling pressure occurs if there is an increase in blood volume or decrease in venous compliance.
