Pressure and flow in arteries and veins Flashcards
How is Korotkoff sounds auscultated ?
Using a sphygmomanometer and stethoscope
What are the advantages and disadvantages of using a sphygmomanometer ?
Disadvantages:
- accuracy
- discontinuous
- needs care
Advantages:
- non-invasive
- cheapWhat is the effect of high diastolic pressure on the aorta ?
There is a higher total peripheral resistance so the aorta finds it harder to release blood
What is the effect of elastic vessels on pressure variations ?
Dampens them down
What is the pressure wave affected by ?
Stroke volume
Velocity of ejection
Elasticity of arteries
Total peripheral resistance
Define pulse pressure ?
Pulse pressure is the difference between the systolic and diastolic pressure readings
What is normal arterial pressure ?
120/80mmHg
What feature of arteries allows maintenance of high pressure during high systolic pressure ?
Elastic fibres
What is name given to the blood pressure left to bring the blood back to the heart ?
Systemic filling pressure
Why is flow constant throughout the systemic circulation ?
Because everything is in series
What is the pressure drop through the arteries ?
Arteries (from ~ 95 to 90 mmHg)
–low resistance conduit
What is the drop in blood pressure through the arterioles ?
Large drop through arterioles (from ~ 90 to 40 mmHg)
– the resistance vessels
Why is it good that blood pressure is low when blood reaches the capillaries ?
good, because they are thin-walled
What is the small pressure difference pushing blood back through the veins ?
(from ~ 20 to 5 mmHg)
–the systemic filling pressure
What is the pulmonary pressure in relation to the systemic pressure ?
Pulmonary circulation is 1/5th of the systemic
Where is velocity fastest ?
In the aorta and the vena cava - slowest in the capillaries
What is the pressure in veins ?
Pressure is low:
- therefore difference in pressure driving blood back to the heart is low
Vessels of veins are distensible and collapsible what does this mean ?
External influences affect flow
Does gravity affect driving pressure from arteries to veins ?
No
What is the effect of gravity in venous blood in the leg ?
Cause venous distension in legs:
- decreased EDV, decreased preload, decreased SV, decreased CO, decreased MAP (orthostatic hypotension)
What is the effect of gravity in the neck ?
Causes venous collapse in the neck:
- can be used to estimate central venous pressure
If pressure in the arteries always remains constant what does this mean for the driving force of the blood ?
Always remains the same
What is the purpose of skeletal muscle pump ?
Rhythmic contraction increases venous return and EDV
Significance re:
- rhythmic vs static exercise
- deep vein thrombosis
What is meant by the respiratory pump ?
Increased respiratory rate and depth increases venous return and EDV
What is meant by Venomotor tone ?
State of contraction of the smooth muscle surrounding the venues and veins
Mobilises the capacitance
What are all the factors that affect venous pressure and blood flow in veins ?
Gravity Skeletal muscle pump Respiratory pump Venomotor tone Systemic filling pressure
What does clotting involve ?
