8/ pressure and flow in arteries and veins

Question 1

what is the point of having elastic arteries?

Answer 1

act as a pressure reservoir to dampen down pressure variations

Question 2

what does the pressure wave in the arteries depend on?

Answer 2

• stroke volume
• velocity of ejection
• elasticity of arteries
• total periphery resistance

Question 3

what is the “normal” arterial pressure?

Answer 3

120/80 mmHg (values need to be remembered)

Question 4

how does arterial pressure and pulse pressure vary with age?

Answer 4

they increase (especially pulse pressure)

Question 5

how does pressure vary through vascular tree?

Answer 5

pressure falls

Question 6

what pressure drop occurs through arteries? what type of conduit is it?

Answer 6

95 to 90 mmHg (low resistant conduit) (values need to be remembered)

Question 7

what pressure drop occurs through arterioles? what type of conduit is it?

Answer 7

90 to 40 mmHg (resistance vessels) (values need to be remembered)

Question 8

why is it important that pressure is low when blood gets to capillaries?

Answer 8

they are thin-walled

Question 9

how does the blood get back through the veins?

Answer 9

using the small pressure difference remaining, the systemic filling pressure (20-5 mmHg) (values need to be remembered)

Question 10

what is blood velocity related to? where is it fastest/ slowest?

Answer 10

cross-sectional area (pi x R^2), fastest in aorta and vena cava, slowest in capillaries

Question 11

what is the characteristics of veins (histologically)?

Answer 11

they are distensible and collapsible

Question 12

what is the outcome of this?

Answer 12

external influences are likely to affect flow

Question 13

does gravity affect driving pressure from arteries to veins?

Answer 13

no

Question 14

what is the effect of gravity on the veins in the leg?

Answer 14

causes venous distension (leading to decreased EDV, decreased preload, decreased SV, decreased CO, decreased MAP, can therefore cause orthostatic (postural) hypotension

Question 15

what is the effect of gravity on the veins in the neck?

Answer 15

causes venous collapse in neck (pressure is lower than the weight of organs around it), can be used to estimate central venous pressure

Question 16

what can the height of jugular collapse be used to estimate?

Answer 16

central venous pressure (CVP)

Question 17

apart from gravity, what are the other mechanisms which affect pressure and flow in veins?

Answer 17

• 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)

Question 18

what are the three Korotkoff sounds?

Answer 18

silence - tapping - thumping - muffled - silence

Question 19

what percentage of the systemic circulation pressure is the pulmonary circulation?

Answer 19

20%, 1/5th of systemic

Question 20

is venous pressure directly related to venous return

Answer 20

duh