Pressure and Flow in Arteries and Veins

Question 1

What is the main method used for measurement of arterial pressure?

Answer 1

Auscultation of Karotkoff sounds using spygomanometer and stethoscope.

Question 2

What sound is heart when cuff pressure is just less than systolic pressue?

Answer 2

tapping

Question 3

What sound is heard when cuff pressure is between diastolic and systolic pressure?

Answer 3

a thumping sound

Question 4

What sound is heard when cuff pressure is the same as diastolic pressure?

Answer 4

a muffled sound, often inaudible though

Question 5

What are the advantages of auscultation of Korotkoff sounds using sphygomomanometer and stephoscope? (2)

Answer 5

Non-invasive

Cheap

Question 6

What are disadvantages of auscultation of Korotkoff sounds using sphymomanometer and stephoscope? (3)

Answer 6

Accuracy

Discontinuous

Needs care

Question 7

What do elastic arteries act as?

Answer 7

Pressure reservoirs that damp down pressure variants.

prevents pressure getting too high in systole and too low in diastole

Question 8

What factors affect the pressure wave for blood in arteries? (4)

Answer 8

Stroke volume

Velocity of ejection

Elasticity of arteries

Total peripheral resistance

Question 9

What is normal arteriolar pressure?

Answer 9

120/80mmHg

Question 10

How does normal arteriolar pressure change with age?

Answer 10

It increases, as blood vessels lose elasticity.

Question 11

The aorta _______ energy during systole and ________ energy during diastole.

Answer 11

absorbs

releases

Question 12

Which factors affect the rising phase of the pressure wave?

Answer 12

• velocity of projection
• SV
• HR
• strength of contraction

Question 13

Which factors affect the falling phase of the pressure wave?

Answer 13

• elasticity of arteries

- TPR

Question 14

What happens at the dicrotic notch in the pressure wave?

Answer 14

• isovolumetric relaxation

- small and brief increase in arterial pressure due to closing of aortic valve.

Question 15

In one word, what happens to pressure in blood vessels moving from the arteries all the way through to the veins?

Answer 15

it decreases

Question 16

Between which two types of vessels is the decrease in pressure the greatest?

Explain this.

Answer 16

Arteries to arterioles.

Arterioles, the resistance vessels, have smaller diameters and overall larger surface area which reduces the pressure force.

Question 17

Pulse pressure = ______ - ________

Answer 17

systolic pressure - diastolic pressure

Question 18

There is a _______ _______ in pressure through arteries (from about __ to __ mmHg).

Answer 18

small decrease

95 to 90

Question 19

There is a _____ drop through arterioles (from about __ to __ mmHg)

• the _________ vessels

Answer 19

large
90 to 40

resistance

Question 20

How would you describe pressure in the capillaries?

Why is this good?

Answer 20

low, 20-40 mmHg

Because capillaries are extremely thin walled and fine.

Question 21

Leaving the capillaries, a ______ pressure difference remains pushing blood back through the ______ (from around __ to __ mmHg).

This is known as the _______ ________ pressure, which returns blood to the ______ ______ of the heart.

Answer 21

small
veins
20 to 5

systemic filling
right side

Question 22

Why is there only a small drop in pressure through arteries?

Answer 22

Low resistance conduit, elasticity releases energy

Question 23

How does pulmonary circulation pressure compare to systemic circulation?

Answer 23

1/5th the size, same curve

Question 24

What is the velocity of blood flow related to?

Which vessels is it fastest/slowest in?

Answer 24

Total cross sectional area

Fastest in aorta/arteries, slowest in capillaries.

Question 25

How does velocity of blood flow relate to total cross sectional area?

Answer 25

Greater the total cross sectional area, the smaller the velocity.

Question 26

What is the systemic filling pressure?

Answer 26

The pressure of blood exiting the circulatory system.

Question 27

Which of the two ventricles has the lower pressure? Why?

Answer 27

RV Less pressure required to push blood through the pulmonary circulation.

Question 28

Why do external influences affect flow in veins?

Answer 28

Due to their thin walls, they are distensible and collapse.

Question 29

What effect does gravity not have on pressure and flow between arteries and veins?

Answer 29

It does not affect the pressure gradient, as it is acting on both arteries and veins.

Question 30

Where is venous distension caused by gravity most likely to happen? What is the clinical term for this? What effect does this have on the heart?

Answer 30

Legs Orthostatic hypotension - decreased EDV - decreased preload - decreased SV - decreased CO - decreased MAP/afterload

Question 31

The height of jugular collapse can be used to estimate ______.

Answer 31

Central venous pressure

Question 32

If there is a high CVP, the jugular vein collapse will happen ______.

Answer 32

higher

Question 33

Explain the concept of jugular venous collapse.

Answer 33

- jugular vein height increase = decrease in pressure - pressure becomes sub-atmospheric - venous distension - High CVP, collapse occurs higher in neck

Question 34

What are examples of external factors that affect flow in veins? (5) Which of these is the main driving force for venous return to the heart?

Answer 34

- Gravity - Skeletal muscle pump - Respiratory pump - Venomotor tone - Systemic filling pressure Systemic filling pressure

Question 35

What can gravity cause in terms of flow through veins?

Answer 35

Venous distension in legs Venous collapse in neck

Question 36

How does the skeletal muscle pump work?

Answer 36

Skeletal muscle contracting in a rhythmic fashion helps pump blood back from the peripheries, as valves prevent blood moving away from the heart.

Question 37

What are examples of skeletal muscle pump impacting venous flow?

Answer 37

Rhythmic vs static exercise Hot guardsmen Deep vein thrombosis Varicose veins

Question 38

How does venomotor tone affect pressure and flow in veins?

Answer 38

Contraction of smooth muscle round the veins helps to mobilise capacitance and increase EDV.

Question 39

Describe how the respiratory pump changes the flow in veins?

Answer 39

- Inspiration = negative pressure in thorax/positive pressure in abdomen

Question 40

What does clotting involve?

Answer 40

Formation of a platelet plug. Formation of a fibrin clot.

Question 41

What are the anti-clotting mechanisms of the endothelium aiming to do?

Answer 41

- prevent platelet plug - prevent fibrin clot - break down developed clots

Question 42

Outline the anti-clotting mechanisms of the endothelium.

Answer 42

- physical barrier (no platelet aggregation) - prostacyclin and NO production - produces TF pathway inhibitor - expresses thrombomodulin - expresses heparin - secretes tissue plasminogen activator.

Question 43

What do prostacyclin and NO do?

Answer 43

inhibit platelet aggregation

Question 44

What does TFPI do?

Answer 44

stops thrombin production

Question 45

What does thrombomodulin do?

Answer 45

binds thrombin & inactivates it.

Question 46

What does heparin do?

Answer 46

also inactivates thrombin

Question 47

What does tissue plasminogen activator do?

Answer 47

Catalyses the reaction of plasminogen to plasmin, and plasmin digests the clot.

Question 48

What is converted into fibrin and what carries this out?

Answer 48

fibrinogen thrombin