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HHP- Cardiovascular Physiology > The Systemic Circulation > Flashcards

The Systemic Circulation Flashcards

1
Q

Vessels cane arranged in either S______ or in P________

A

Series

Parallel

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2
Q

which blood vessel has the greatest total cross sectional area? State this area given units

A

Capillaries

1357cm^2

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3
Q

In which blood vessel is the majority of blood found? State the percentage of blood found in that vessel

A

Veins

67% of all blood is found in the venous circulation

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4
Q

In which blood vessel is flow rate slowest?

A

The capillaries

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5
Q

In which blood vessel is flow rate fastest?

A

Aorta

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6
Q

What is the relationship between velocity of blood flow and the Toal cross sectional area?

A

They are mirror images of each other

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7
Q

Approximately how many arteries are there?

A

10^6

1,000,000

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8
Q

Approximately how many arterioles are there?

A

10^7

10,000,000

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9
Q

Approximately how many capillaries are there?

A

10^10

10,000,000,000

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10
Q

Approximately how many veins are there?

A

10^12

1,000,000,000,000

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11
Q

What are the 3 district layers (Walls) in blood cells?

A 
Tunica adventitia (outermost) 
Tunica media 
Tunica intima (innermost)
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12
Q

Describe the tunica adventitia

A

Outermost layer made up of connective tissue (collagen fibre)

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13
Q

Describe the tunica media

A

Middle layer made up of smooth muscle and elastin

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14
Q

Describe the tunica intima

A

Innermost layer made up of endothelium (specifically squamous epithelium)

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15
Q

Name the two variations in arteries

A

Elastic arteries

Muscular arteries

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16
Q

What are the main elastic arteries?

A

Aorta and major branches

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17
Q

State the characteristics of elastic arteries

A

Large diameter
Low resistance pathway
Large amounts of tunica media to be able to withstand and smooth out large pressure fluctuations

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18
Q

What do muscular arteries do?

A

Deliver blood to specific organs

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19
Q

What is the diameter range for muscular arteries?

A

0.3-10mm

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20
Q

State the characteristics of muscular arteries

A

Less elastin and more smooth muscle in the tunica media
Less distensible
more active in vasoconstriction

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21
Q

What do arterioles do?

A

Deliver blood to the capillary beds

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22
Q

What is the diameter range for arterioles?

A

10 micrometres - 0.3mm

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23
Q

State some characteristics of arterioles

A

Their tunica media is made of entirely smooth muscle
The arterioles diameter regulates blood flow to capillary beds in response to neural stimuli and local chemical influences

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24
Q

What are the two different types of capillaries?

A

Continuous

Fenestrated

25
Describe some of the general features of capillaries
They are the smallest blood vessel Diameter range: 8-10micrometres They are just large enough for red blood cells to pass through them
26
Which of the two types of capillaries is the most common type?
The continuous capillaries
27
Describe some features of continuous capillaries
Endothelial cells have tight junctions between them | Have intercellular clefts which limit passage of fluid and small solutes
28
Where are fenestrated capillaries found?
Areas where active absorption of filtrate formation occurs | E.g. Small intestine, kidneys
29
Describe some features of fenestrated capillaries
Some of the endothelial cells have oval pore (fenestrations) | This makes them more permeable to fluids and small solutes
30
What are capillary beds?
Interweaving networks of capillaries
31
What is microcirculation?
Blood flow through the capillary beds
32
Interweaving networks of capillaries is called
Capillary beds
33
Blood flowing through the capillary beds is termed...?
Microcirculation
34
What are true capillaries and how many are their per capillary bed?
Actual exchange vessels | Around 10-100 per bed
35
What is capillary flow regulated by?
A ring of smooth muscle fibres called the precapillary sphincter
36
What, in most beds, by passes the true capillaries?
A vascular shunt called a metarteriole
37
What is a metarteriole?
A vascular shunt that bypasses the true capillaries
38
How do venules form and what is their diameter range?
They form when capillaries unite | Their diameter range: 8-100 micrometers
39
Describe the differenced between small and large venules
Small venules consists of only endothelium | Larger venules posses a sparse tunica media and tunica adventitia
40
Give some characteristics of veins
``` They have 3 distinct tunicae Walls are thinning Lumen is larger Capacitance vessels They have valves to ensure blood flows to the heart even at lore pressures ```
41
Where in the systemic circulatory system is pressure greatest?
In the left ventricles and then the aorta | Basically closer to the pump=greater pressure
42
Where in the systemic circulatory system is pressure smallest?
Right atrium
43
Where does the steepest drop in pressure occur?
In the arterioles as they offer the greatest resistance to flow
44
When does pressure occur?
When flow is opposed by resistance
45
What 2 things does arterial blood pressure reflect?
1. The compliance (distensibility) of the elastic arteries near the heart 2. The volume of blood being forced into these arteries at a particular point in time
46
Why does arterial blood pressure vary during the cardiac cycle?
As the volume of blood being forced into the arteries at a particular point in time varies during the cardiac cycle
47
When is arterial pressure at its highest?
During the systolic phase of the cardiac cycles | Typically 120mmHg
48
When is arterial pressure at its lowest?
During the diastolic phase of the cardiac cycles | Typically 80mmHg
49
How do you calculate pulse pressure (PP)?
Systolic pressure-Diastolic pressure SP-DP= PP E.g. 120-80=40mmHg
50
How do you calculate mean arterial pressure (MAP)?
Diastolic pressure + (Pulse pressure/3) DP+(PP/3)= MAP E.g. 80+(40/3)=93.3
51
What is the blood pressure at the arterial end of the capillary bed?
Around 40mmHg
52
What is the blood pressure at the venous end of the capillary bed?
Around 20mmHg
53
Why is capillary pressure important?
It must be low or the capillary walls may rupture | It must be closely controlled so that the filtration of solutes in the interstitial space is regulated
54
What is the pressure gradient over the whole venous system?
About 20mmHg
55
What is the pressure gradient over the whole arterial system?
About 60mmHg
56
Since the venous pressure is quite low what problems does this create?
It means the blood is returning to the heart at a slower rate than which the heart is pumping the blood out into the systemic arterial system This imbalance is unsustainable
57
What special adaptations does the body have to counter act the imbalance in blood into and out of the heart caused by low venous blood pressure?
Respiratory pump | The skeletal muscle pump
58
How does the respiratory pump influence venous return?
Inspiration increases abdominal pressure and compresses the abdominal veins Venous valves prevent the back flow of blood forcing blood to the heart Inspiration also decreases thoracic pressure. So thoracic veins expand further aiding the movement of blood towards the right atrium
59
How does the skeletal muscle pump influence venous return?
When skeletal muscle contract they compress deep veins and propel blood towards the heart Valved prevent the backflow of blood

HHP- Cardiovascular Physiology (7 decks)

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