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FM1020 Physiology > The Circulatory System > Flashcards

The Circulatory System Flashcards

1
Q

What percentage of blood volume is in systemic circulation?

A

84%

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2
Q

How much of the blood is in the veins at one time?

A

64%

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3
Q

How much blood is in arteries at one time?

A

13%

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4
Q

How much blood is in systemic arterioles/capillaries at one time?

A

7%

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5
Q

How much blood is in the heart at one time?

A

7%

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6
Q

How much blood is in pulmonary vessels at one time?

A

9%

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7
Q

What is the tunica externa comprised of?

A

Connective tissue

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8
Q

What is the tunica media comprised of?

A

Smooth muscle

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9
Q

What is the tunica intima comprised of?

A

Layer of elastin
Basement membrane
Innermost simple squamous endothelium

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10
Q

What is microcirculation?

A

Arterioles, capillaries, venules

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11
Q

What are elastic arteries?

A

Conduits
Aorta and large arteries
Numerous layers of elastin fibers which expand when the pressure of the blood rises during systole and recoil when ventricles relax

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12
Q

What are muscular arteries and what is their makeup?

A

Resistance vessels
Are much less elastic and have a thicker layer of smooth muscle which regulates the diameter of the lumen

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13
Q

What are capillaries?

A

Exchange vessels
Smallest blood vessels
single layer of endothelium
Permits exchange of nutrients and waste between blood and tissue fluid

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14
Q

What is the diameter of capillaires?

A

5-10 microns

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15
Q

What are some other ways to describe veins?

A

Blood reservoirs
Capacitance vessels

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16
Q

What helps venous return?

A

Skeletal muscle pump and contraction of diaphragm assist

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17
Q

Where are the most vessels found?

A

Microcirculation

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18
Q

How many capillaries are there?

A

3 x 10^9

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19
Q

What vessels have the highest cross-sectional area?

A

Capillaries

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20
Q

Which vessels are wider and by how much: veins or arteries?

A

Veins have larger cross-sectional areas
~4 times wider than the corresponding arteries

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21
Q

What word can be used to describe veins high cross-sectional areas?

A

Highly distensible

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22
Q

What is the defintion of blood pressure?

A

Pressure of blood in the heart/circulatory system exerted outwards onto a unit area of the vessel wall

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23
Q

What is blood pressure measured in?

A

mmHg
Other units: cmH2O, atm, kPa

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24
Q

How do we calculate the pressure gradient?

A

P1 - P2 = delta P

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25
What is the rate of blood flow directly proportionate to?
Delta P
26
What is the mean aortic pressure?
100mmHg
27
What is the mean venous pressure?
0mmHg
28
What kind of circulation is the pulmonary circulation?
Low resistance, Low pressure circulation
29
What is the blood pressure in the pulmonary artery?
20mmHg
30
What does resistance to blood flow cause?
Reduction in the rate of blood flow through vasculature
31
What is resistance to blood flow?
Vascular resistance Friction between blood and walls of blood vessels Friction from blood cells rubbing against each other (blood viscosity)
32
What is the rate of blood flow inversely proportional to?
Resistance
33
Define Ohm's Law
F = DELTA P / R F = blood flow R = resistance
34
What factors does blood flow depend on?
Length of the blood vessel Radius of the blood vessels Viscosity of blood
35
What is R directly proportional to?
Lη/r^4 Length of vessel*viscosity of blood/ radius of vessel^4
36
What are the major regulators of blood flow?
Mean arterial pressure Vascular blood vessel diameter - NB Blood viscosity
37
Where does more than half of all resistance to flow orginate?
Small arterioles
38
What effect does the fourth power law have on resistance to blood flow?
Small changes in diameter result in large changes in resistance (256-fold)
39
What is blood viscosity?
Cells suspended in blood plasma which exert friction; drag on each other and walls of blood vessels
40
What is haematocrit?
% of total blood volume composed of cells
41
What is the mean percentage of haematocrit in males?
42%
42
What is the mean haematocrit percentage in females?
38%
43
What is the viscosity of normal blood?
~ 3 times that of water (3)
44
What condition may cause a haematocrit of 60?
Polycythaemia
45
What can viscosity reach in the case of polycythaemia?
60
46
What happens if viscosity is high?
Resistance increases and flow through blood vessels can be compromised
47
What viscosity would you expect from a patient with severe anaemia?
1.5
48
What does decreased resistance result in?
Increased peripheral blood flow Increased venous return Increased cardiac output
49
What does hypoxia do?
Blood vessel dilation, increasing cardiac output
50
What is ΔP?
Pressure drop that results from a given flow and resistance
51
What is ΔP increased by?
Increase in flow or resistance
52
What is blood vessel compliance?
Volume of blood that can be stored in a blood vessel for each mmHg pressure rise
53
What is the equation for compliance?
Ca = ΔV/ΔP compliance = distensibility*volume
54
What is compliance closely related to?
Ability of a vessel to stretch or distend to accomadate larger volume of blood
55
What is distensibility determined by?
Quantity of elastin fibers in vessel wall Wall thickness
56
When is blood flow in the vasculature continuous?
While ventricular ejection is pulsatile
57
What is the property by which the vessels change a pulsatile ejection into a continuous blood flow called?
Hydraulic filter
58
What is elastin content replaced by in older individuals?
Collagen
59
Where does the increased pressure caused by stroke volume go?
Absorbed by arterial walls
60
How do rigid and compliant arteries affect the workload of the heart?
Compliant reduce the workload Rigid increase the workload
61
What is systolic blood pressure?
120mmHg
62
What is diastolic blood pressure?
80mmHg
63
What are blood pressure measurements quoted as?
Systolic/diastolic pressure
64
What is the best blood pressure?
120/80
65
What is mean arterial pressure?
Diastolic pressure + 1/3 (systolic - diastolic pressure)
66
What is hypertension?
Chronically elevated blood pressure
67
What is the minimum value of systolic and diastolic pressure to be diagnosed with mild hypertension?
140 sys or 90 dia
68
What are the two types of hypertension?
Essential Secondary
69
What is the most common form of hypertension?
Essential hypertension - accounts for 95% of cases
70
What is the cause of essential hypertension?
Unclear, multifactorial such as diet or genetics
71
What causes secondary hypertension?
Another condition such as renal disease
72
How does renal disease cause secondary hypertension?
Chronically elevated salt and water reabsorption in the nephron will increase blood volume and chronically raise blood pressure
73
What is the issue with hypertension?
Causes long-term damage to heart and kidneys and is a risk factor for heart attack and stroke
74
How is afterload increased due to hypertension?
Ventricles must contract more forcefully to maintain an adequate stroke volume resulting in damage to myocardium
75
What does damage to endothelial lining of arteries promote?
Formation of atherosclerotic plaques, increased risk of heart attack or stroke
76
What is pulse pressure?
The difference between systolic pressure and diastolic pressure
77
When is the dicrotic wace visible?
Diastole
78
What is the dicrotic wave caused by?
recoil of blood from the closed aortic valve Reflection of the systolic pressure wave back from small arteries in the lower body - NB Measure of elasticity of one's arteries

FM1020 Physiology (12 decks)

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