8/ pressure and flow in arteries and veins Flashcards
what is the point of having elastic arteries?
act as a pressure reservoir to dampen down pressure variations
what does the pressure wave in the arteries depend on?
- stroke volume
- velocity of ejection
- elasticity of arteries
- total periphery resistance
what is the “normal” arterial pressure?
120/80 mmHg (values need to be remembered)
how does arterial pressure and pulse pressure vary with age?
they increase (especially pulse pressure)
how does pressure vary through vascular tree?
pressure falls
what pressure drop occurs through arteries? what type of conduit is it?
95 to 90 mmHg (low resistant conduit) (values need to be remembered)
what pressure drop occurs through arterioles? what type of conduit is it?
90 to 40 mmHg (resistance vessels) (values need to be remembered)
why is it important that pressure is low when blood gets to capillaries?
they are thin-walled
how does the blood get back through the veins?
using the small pressure difference remaining, the systemic filling pressure (20-5 mmHg) (values need to be remembered)
what is blood velocity related to? where is it fastest/ slowest?
cross-sectional area (pi x R^2), fastest in aorta and vena cava, slowest in capillaries
what is the characteristics of veins (histologically)?
they are distensible and collapsible
what is the outcome of this?
external influences are likely to affect flow
does gravity affect driving pressure from arteries to veins?
no
what is the effect of gravity on the veins in the leg?
causes venous distension (leading to decreased EDV, decreased preload, decreased SV, decreased CO, decreased MAP, can therefore cause orthostatic (postural) hypotension
what is the effect of gravity on the veins in the neck?
causes venous collapse in neck (pressure is lower than the weight of organs around it), can be used to estimate central venous pressure
what can the height of jugular collapse be used to estimate?
central venous pressure (CVP)
apart from gravity, what are the other mechanisms which affect pressure and flow in veins?
- skeletal muscle pump (significance because rhythmic vs static exercise, deep vein thrombosis, varicose veins)
- respiratory pump
- venomotor tone (= state of contraction of the smooth muscle surrounding the venules and veins; mobilises capacitance)
- systemic filling pressure (pressure created by ventricles and transmitted through vascular tree to the veins)
what are the three Korotkoff sounds?
silence - tapping - thumping - muffled - silence
what percentage of the systemic circulation pressure is the pulmonary circulation?
20%, 1/5th of systemic
is venous pressure directly related to venous return
duh
