Pressure and flow in arteries and veins pt.1,pt.2,pt.3. Flashcards
How do you measure arterial pressure?
catheter- insert in artery
-however invasive
OR
auscultation of korotkoff sound using sphygomanometer and stethoscope
OR
oscillatory blood pressure measurement- blood flow vibrations
-know MAP and estimate diastolic and systolic
Describe arterial pressure in ventricular contraction?
when left ventricle contracts during systole and blood is ejected into aorta, the walls of aorta will stretch and act as a pressure reservoir.
Then during ventricular relaxation or during diastole , we get elastic recoil from the walls of the aorta that pushes on that column of blood .
Closes aortic valve and it keeps blood flowing even during relaxation phase.
What causes the dicrotic notch?
caused by elastic recoil from the aorta as the aortic valve closes
What is the pressure wave affected by?
stroke volume- rising phase will rise much more rapidly
velocity of ejection -if blood pumped into aorta a lot quicker, then there’s less time for the walls of the aorta to stretch- systolic pressure higher.
Diastolic lower as less of elastic energy stored up and and so less pressure pushing back on that column of blood during diastole
elasticity of arteries-
as we age- lose this elasticity and cause systolic pressure to rise . The aorta will be less able to act as pressure reservoir and diastolic will fall because we’ve got less of that elastic recoil.
total peripheral resistance - mostly affects falling phase after the aortic valve has closed (where blood is being pushed from arteries into the arterioles. If arterioles are very constricted then TPR will be higher. Therefore harder to push blood from arteries into arterioles and falling phase more gradual and higher diastolic pressure.
When is blood pressure generally higher?
in morning
Describe pressure in LV?
higher pressure during systole and low pressure during diastole
Describe pressure changes through vascular tree ?
small drop through arteries (from 95 to 90mmHg)
- arteries are low resistance due to wide lumen
large drop through arterioles (from 90 to 40mmHg)
-are resistance vessels and have narrow lumen and thick muscular walls
pressure is already low blood gets to capillaries
-good because they are thin walled
when blood reaches veins and venules- about 20mmHg and dropping to about 5mmHg when it reaches right atrium (systemic filling pressure)
What percentage of systemic filling pressure is pulmonary circulation pressure?
20% of systemic
Describe velocity in vascular tree?
velocity high in aorta and decreases as it moves through arteries and arterioles
lowest in capillaries
when reaches veins and venules - velocity increases
high in vena cava
How does velocity react to total cross sectional area?
total cross-sectional area of aorta is very small-
capillaries have a very large total cross -sectional area
