Pressure and Flow in Arteries and Veins Flashcards
What is measurement of arteriolar pressure done by?
Auscultation of Karotkoff sounds using spygomanometer and stephoscope
What are the advantages of auscultation of Korotkoff sounds using sphygomomanometer and stephoscope?
Non-invasive
Cheap
What are disadvantages of auscultation of Korotkoff sounds using sphymomanometer and stephoscope?
Accuracy
Discontinuous
Needs care
What do elastic arteries act as?
Pressure reservoirs that damp down pressure variants
What is the pressure wave affected by?
Stroke volume
Velocity of ejection
Elasticity of arteries
Total peripheral resistance
What is normal arteriolar pressure?
120/80mmHg
How does normal arteriolar pressure change with age?
Increases
How does pressure and flow change from arteries to veins?
Pressure falls through the vascular tree:
Small drop through arteries (from about 95 to 90mmHg)
Large drop through arterioles (from about 90 to 40mmHg)
Pressure is already low when blood gets to capillaries
Leaves a small pressure difference pushing blood back through the veins (about 20 to 5mmHg)
Why is there only a small drop in pressure through arteries?
Low resistance conduit
Why is there a large drop through arterioles?
Resistance vessels
Why is it important that the blood pressure is low once it reaches capillaries?
They are thin walled
What is the small pressure difference that pushes blood back through the veins called?
Systemic filling pressure
What is the systemic filling pressure?
Small pressure pushing blood back through the veins
How does pulmonary circulation pressure compare to systemic?
1/5 the size
What is the velocity of blood flow related to?
Total cross section (fastest in aorta and vena cava, slowest in capillaries)
Where is blood flow the fastest?
Aorta and vena cava
Where is blood flow the slowest?
Capillaries
How does velocity of blood flow relate to total cross sectional area?
Greater the total cross sectional area the smaller the velocity
What can central venous pressure be estimated by?
Jugular collapse
How does the blood pressure drop as it goes through arteries?
Drops from 95 to 90mmHg
How does blood pressure drop as it goes through arterioles?
From 90 to 40mmHg
What is the value os systemic filling pressure?
20 to 5mmHg
What is the pressure like in veins?
Low so difference in pressure driving blood back to heart is low
What are the complications of veins being distensible and collapsible?
Flow is affected by external influences such as:
Gravity
Skeletal muscle pump
Respiratory pump
Venomotor tone
Systemic filling pressure
