Pressure and Flow in Arteries and Veins Flashcards
What Korotkoff sounds are heard when decreasing the pressure of a sphygmomanomater and auscultating with a stethoscope on the arteries?
- Dotted line represents pressure
- Tapping sound tells you systolic pressure
- Muffled sound tells you diastolic pressure

What are elastic arteries able to do during systole?
Store some of the energy in their elastic fibres
What 4 things effect the pressure wave?
- Stroke volume
- Velocity of injection
- Elasticity of arteries
- Total peripheral resistance
What is the systemic filling pressure?
Pressure left after a full systemic blood travel that allows the blood to get back to the ventricles
What happens to pressure throughout the vascular tree?
It falls
How much does pressure drop through the arterioles?
Tiny drop from about 95 to 90mmHg
What is the change in pressure in the arterioles like?
90 to 40 mmHg
Why is it good that pressure is low when the blood reaches the capillaries?
They are very thin walled and would rupture
What is the pressure difference through the veins?
From 20 to 5mmHg
This is the systemic filling pressure
What fraction of systemic blood pressure is pulmonary?
1/5th
What is velocity of blood related to?
- Total cross section
- Fastest in aorta and vena cava
- Slowest in capillaries
What would happen to blood flow if pressure didn’t fall throughout the vascular tree?
Blood would reverse
Study the vascular tree diagram

Why do external influences affect flow through veins?
- Pressure is low
- Vessels are distensible and collapsible
What effect does gravity have on pressure and flow in veins?
- Causes venous distention in legs
- Reduces EDV, preload, SV, CO and MAP
What conditions can be caused by gravity?
- Can cause orthostatic (postural) hypotension
- Can cause venous collapse in neck
What is the difference in venous pressure from the head to the thorax while standing?
Roughly - 40mmHg difference
What is the venous pressure change from the thorax to the foot while standing?
About +100mmHg
What can the height of jugular collapse allow to be estimated?
Central venous pressure (the higher the collapse the higher the pressure
What is the skeletal muscle pump?
Skeletal muscles in the leg that increase venous return
When do these skeletal muscle pumps fail?
During static exercise
How does the respiratory pump aid venous return?
Respiratory inspiration increases thoracic pressure and venous return increases due to a decrease in right atrial pressure
What is the venomotor tone?
State of contraction of smooth muscle surrounding venules and veins
What does the venomotor tone do?
Decides the capacitance of the vessels, can contract to increase venous return