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Second Year - Biomedical Sciences BS22001 > Lecture 15 - Pressure Gradients And Blood Flow > Flashcards

Lecture 15 - Pressure Gradients And Blood Flow Flashcards

1
Q

What is the resistance like within arteries

A

Low

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2
Q

What do arteries act as in relation to pressure

A

Pressure reservoirs

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3
Q

What allows for the arteries to hold extra blood after contraction

A

Elasticity

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4
Q

What explains why arterial blood pressure doesn’t return to zero during diastole

A

Elastic recoil

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5
Q

What are the major sites of resistance

A

Arterioles

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6
Q

What are arterioles responsible for

A

The patten of blood flow distribution and the regulation of the arterial blood pressure

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7
Q

What are capillaries the site of

A

Gas exchange

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8
Q

What do capillaries determine

A

The distribution of extracellular fluid between the plasma and interstitial fluid

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9
Q

What is the resistance like in veins

A

Low

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10
Q

Why is a veins capacity adjusted

A

To facilitate the flow of blood

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11
Q

What is the outer layer of blood vessels composed of

A

Collagen and elastin

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12
Q

What do collagen and elastin give blood vessels

A

Strength and elasticity

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13
Q

Composition of the endothelium blood vessel wall

A

5% elastic artery, 10% arteriole, 95% capillary and 20% venule

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14
Q

Composition of smooth muscle blood vessel wall

A

25% elastic artery, 60% arteriole and 20% venule

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15
Q

Composition of elastic tissue blood vessel walls

A

40% elastic artery and 10% arteriole

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16
Q

Composition of connective tissue blood wall

A

30% elastic tissue, 20% arteriole, 5% capillary and 60% venule

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17
Q

What is the interaction between pressure, flow and resistance of blood known as

A

Haemodynamics

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18
Q

In the vascular system how does blood flow in relation to pressure

A

Blood always flows from a region of high pressure to one of a lower pressure

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19
Q

What is the pressure exerted by a fluid known as

A

Hydrostatic pressure

20
Q

What are the units of flow

A

Volume per unit time

21
Q

What are the units of pressure difference

A

mmHg

22
Q

What is needed to calculate the flow

A

The pressure between two points and the resistance

23
Q

What is resistance

A

A measure of how difficult it is for blood to flow between two points at any given pressure difference

24
Q

What is known as the measurement of the friction impeding flow

A

Resistance

25
Q

What is the driving force of blood

A

The pressure generated by contractions of the heart

26
Q

What are the factors that affect the resistance of blood

A

The viscosity of blood, the vessel length and the vessel radius

27
Q

What does an increase in viscosity of blood cause

A

A decrease in flow

28
Q

What is the main factor that influences resistance of blood

A

The vessel diameter

29
Q

What equation states that a two-fold change in radius will produce a 16-fold change in flow

A

The poiseuille equation

30
Q

What is Laplace’s law for blood vessels

A

The pressure within a vessel is equal to the tension in its walls divided by the radius of the vasculature

31
Q

What does thickness increase in proportion to

A

Diameter

32
Q

What is the average internal pressure of capillaries

A

4kPa

33
Q

What is the average internal pressure of the aorta

A

13kPa

34
Q

What is the radius and wall thickness of the capillaries

A

4 um and 1um

35
Q

What is the radius and wall thickness of the aorta

A

13mm and 20 mm

36
Q

What does the higher arteriolar resistance cause

A

A marked drop in mean pressure as blood flows through the arterioles

37
Q

Why is the drop in pressure in arterioles physiologically important

A

The pressure gradient helps to drive the blood from the heart to the tissue capillary beds

38
Q

What do arterioles convert pulsatilla arterial pressure into

A

Non-fluctuating capillary pressure

39
Q

What do the walls of arterioles include

A

A thick layer of smooth muscle

40
Q

What innervates the thick layer of smooth muscle in arterioles

A

The sympathetic nervous system

41
Q

What is the smooth muscular layer sensitive to

A

Local chemical changes and certain circulating hormones

42
Q

What is vasoconstriction

A

Contraction causes a decrease in radius which increases the resistance which causes a decrease in local blood flow

43
Q

What is vasodilation

A

During relaxation the radius is increased which decreases resistance which causes an increase in local blood flow

44
Q

What is the rate of partial contraction in arteriolar smooth muscle known as

A

Vascular tone

45
Q

What are the two factors responsible for vascular tone

A

Myogenic activity and sympathetic activity

46
Q

Why is vascular tone important

A

As it makes it possible to either decrease or increase contractile activity

47
Q

What does a change in contractility of arteriolar smooth muscle cause

A

A substantial change in resistance to flow in these vessels

Second Year - Biomedical Sciences BS22001 (28 decks)

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