Pressure And Flow In Arteries And Veins Flashcards
Sphygmomanometer
Measures blood pressure
Series of sounds when taking blood pressure
Korotkoff sounds
Silence first when blood is cut off Tapping of blood getting through a bit Thumping of blood Muffled blood getting through Silence of blood just flowing
What acts as pressure reservoirs
Arteries, damp down variations by stretching
What affects the pressure wave
Stroke volume
Velocity of ejection
Elasticity of arteries
Total peripheral resistance
Pressure falls in the vascular tree
95 to 90 in arteries (low resistance)
90 to 40 in arterioles (high resistance)
Low in capillaries which is good as they have thin walls
20 to 5 in veins (systemic filling pressure)
External influences on venous flow
Gravity, skeletal muscle pump, respiratory pump, venomoter tone, systemic filling pressure
Effect of gravity on venous flow
When lying down pressure away from heart is positive and equal(20)
But standing up, higher veins will be under negative pressure(-20) and lower veins will be under higher pressure (100)
This can cause venous distension in neck
As well as venous collapse in jugular, which can be used to estimate CVP (low collapse is low pressure etc)
Effect of gravity on venous flow
When lying down pressure away from heart is positive and equal(20)
But standing up, higher veins will be under negative pressure(-20) and lower veins will be under higher pressure (100)
This can cause venous distension in neck
As well as venous collapse in jugular, which can be used to estimate CVP (low collapse is low pressure etc)
What is the skeletal muscle pump
When muscles move rhythmically it squeezes venous blood back to the heart
What is the respiratory pump
The diaphragm has a negative pressure above it and positive below so Vena Cava blood is squeezed upwards
What is venomoter tone
The state of contraction of the smooth muscle surrounding venules and veins.
What is venomoter tone
The state of contraction of the smooth muscle surrounding venules and veins.
What is systemic filling pressure
The pressure created by the ventricles and transmitted through the vascular tree to the veins
