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02. Cardiovascular System > Pressure and Flow in Arteries and Veins > Flashcards

Pressure and Flow in Arteries and Veins Flashcards

1
Q

What is measurement of arteriolar pressure done by?

A

Auscultation of Karotkoff sounds using spygomanometer and stephoscope

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2
Q

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

A

Non-invasive

Cheap

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3
Q

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

A

Accuracy

Discontinuous

Needs care

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4
Q

What do elastic arteries act as?

A

Pressure reservoirs that damp down pressure variants

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5
Q

What is the pressure wave affected by?

A

Stroke volume

Velocity of ejection

Elasticity of arteries

Total peripheral resistance

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6
Q

What is normal arteriolar pressure?

A

120/80mmHg

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7
Q

How does normal arteriolar pressure change with age?

A

Increases

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8
Q

How does pressure and flow change from arteries to veins?

A

Pressure falls through the vascular tree:

Small drop through arteries (from about 95 to 90mmHg)
Large drop through arterioles (from about 90 to 40mmHg)
Pressure is already low when blood gets to capillaries
Leaves a small pressure difference pushing blood back through the veins (about 20 to 5mmHg)

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9
Q

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

A

Low resistance conduit

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10
Q

Why is there a large drop through arterioles?

A

Resistance vessels

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11
Q

Why is it important that the blood pressure is low once it reaches capillaries?

A

They are thin walled

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12
Q

What is the small pressure difference that pushes blood back through the veins called?

A

Systemic filling pressure

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13
Q

What is the systemic filling pressure?

A

Small pressure pushing blood back through the veins

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14
Q

How does pulmonary circulation pressure compare to systemic?

A

1/5 the size

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15
Q

What is the velocity of blood flow related to?

A

Total cross section (fastest in aorta and vena cava, slowest in capillaries)

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16
Q

Where is blood flow the fastest?

A

Aorta and vena cava

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17
Q

Where is blood flow the slowest?

A

Capillaries

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18
Q

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

A

Greater the total cross sectional area the smaller the velocity

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19
Q

What can central venous pressure be estimated by?

A

Jugular collapse

20
Q

How does the blood pressure drop as it goes through arteries?

A

Drops from 95 to 90mmHg

21
Q

How does blood pressure drop as it goes through arterioles?

A

From 90 to 40mmHg

22
Q

What is the value os systemic filling pressure?

A

20 to 5mmHg

23
Q

What is the pressure like in veins?

A

Low so difference in pressure driving blood back to heart is low

24
Q

What are the complications of veins being distensible and collapsible?

A

Flow is affected by external influences such as:

Gravity
Skeletal muscle pump
Respiratory pump
Venomotor tone
Systemic filling pressure

25
Q

Why do external factors affect flow in veins?

A

They are distensible and collapsible

26
Q

What are examples of external factors that affect flow in veins?

A

Gravity

Skeletal muscle pump

Respiratory pump

Venomotor tone

Systemic filling pressure

27
Q

What can gravity cause in terms of flow through veins?

A

Venous distension in legs

Venous collapse in neck

28
Q

What does venous distension in legs cause?

A

Decreases EDV

Decreases preload

Decreases stroke volume

Decreases cardiac output

Decreases mean arteriolar pressure

29
Q

What can the venous collapse in the neck be used to estimate?

A

Central venous pressure

30
Q

What are examples of skeletal muscle pump impacting venous flow?

A

Rhythmic vs static exercise

Hot guardsmen

Deep vein thrombosis

Varicose veins

31
Q

What is venomotor tone?

A

State of contraction of the smooth muscles surrounding the venules and veins

32
Q

What is the state of contraction of the smooth muscles surrounding the venules and veins valled?

A

Venomotor tone

33
Q

How does gravity impact the flow of blood through veins?

A

Greater pressure at the bottom of the body

34
Q

What does clotting involve?

A

Formation of a platelet plug

Formation of a fibrin clot

35
Q

What is converted into fibrin?

A

Fibrinogen

36
Q

What is fibrinogen converted into?

A

Fibrin

37
Q

What catalyses the reaction of fibrinogen to fibrin?

A

Thrombin

38
Q

What is blood in the capillaries in danger of due to travelling so slow?

A

Clotting

39
Q

What works hard to prevent blood clotting through capillaries?

A

Epithelium

40
Q

What are some anti-clotting mechanisms of the epithelium?

A

Stops blood contacting collagen

Produces prostacyclin and NO

Produces tissue factor pathway inhibitor (TFPI)

Expresses thrombomodulin

Expresses heparin

Secretes tissue plasminogen activator

41
Q

How does stopping blood contacting collagen prevent clots?

A

No platelet aggregation

42
Q

How does producing prostacyclin and NO prevent clots?

A

Both inhibit platelet aggregation

43
Q

How does producing tissue factor pathway inhibitor prevent clots?

A

Stops thombin production

44
Q

What does TFPI stand for?

A

Tissue factor pathway inhibitor

45
Q

How does expressing thrombomodulin prevent clots?

A

Binds to thrombin and inactivates it

46
Q

How does expressing heparin prevent clots?

A

Inactivates thrombin

47
Q

How does secreting plasminogen activator prevent clots?

A

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

02. Cardiovascular System (72 decks)

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