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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
Q

Describe some of the general features of capillaries

A

They are the smallest blood vessel
Diameter range: 8-10micrometres
They are just large enough for red blood cells to pass through them

26
Q

Which of the two types of capillaries is the most common type?

A

The continuous capillaries

27
Q

Describe some features of continuous capillaries

A

Endothelial cells have tight junctions between them

Have intercellular clefts which limit passage of fluid and small solutes

28
Q

Where are fenestrated capillaries found?

A

Areas where active absorption of filtrate formation occurs

E.g. Small intestine, kidneys

29
Q

Describe some features of fenestrated capillaries

A

Some of the endothelial cells have oval pore (fenestrations)

This makes them more permeable to fluids and small solutes

30
Q

What are capillary beds?

A

Interweaving networks of capillaries

31
Q

What is microcirculation?

A

Blood flow through the capillary beds

32
Q

Interweaving networks of capillaries is called

A

Capillary beds

33
Q

Blood flowing through the capillary beds is termed…?

A

Microcirculation

34
Q

What are true capillaries and how many are their per capillary bed?

A

Actual exchange vessels

Around 10-100 per bed

35
Q

What is capillary flow regulated by?

A

A ring of smooth muscle fibres called the precapillary sphincter

36
Q

What, in most beds, by passes the true capillaries?

A

A vascular shunt called a metarteriole

37
Q

What is a metarteriole?

A

A vascular shunt that bypasses the true capillaries

38
Q

How do venules form and what is their diameter range?

A

They form when capillaries unite

Their diameter range: 8-100 micrometers

39
Q

Describe the differenced between small and large venules

A

Small venules consists of only endothelium

Larger venules posses a sparse tunica media and tunica adventitia

40
Q

Give some characteristics of veins

A 
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
Q

Where in the systemic circulatory system is pressure greatest?

A

In the left ventricles and then the aorta

Basically closer to the pump=greater pressure

42
Q

Where in the systemic circulatory system is pressure smallest?

A

Right atrium

43
Q

Where does the steepest drop in pressure occur?

A

In the arterioles as they offer the greatest resistance to flow

44
Q

When does pressure occur?

A

When flow is opposed by resistance

45
Q

What 2 things does arterial blood pressure reflect?

A
  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
Q

Why does arterial blood pressure vary during the cardiac cycle?

A

As the volume of blood being forced into the arteries at a particular point in time varies during the cardiac cycle

47
Q

When is arterial pressure at its highest?

A

During the systolic phase of the cardiac cycles

Typically 120mmHg

48
Q

When is arterial pressure at its lowest?

A

During the diastolic phase of the cardiac cycles

Typically 80mmHg

49
Q

How do you calculate pulse pressure (PP)?

A

Systolic pressure-Diastolic pressure
SP-DP= PP
E.g. 120-80=40mmHg

50
Q

How do you calculate mean arterial pressure (MAP)?

A

Diastolic pressure + (Pulse pressure/3)
DP+(PP/3)= MAP
E.g. 80+(40/3)=93.3

51
Q

What is the blood pressure at the arterial end of the capillary bed?

A

Around 40mmHg

52
Q

What is the blood pressure at the venous end of the capillary bed?

A

Around 20mmHg

53
Q

Why is capillary pressure important?

A

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
Q

What is the pressure gradient over the whole venous system?

A

About 20mmHg

55
Q

What is the pressure gradient over the whole arterial system?

A

About 60mmHg

56
Q

Since the venous pressure is quite low what problems does this create?

A

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
Q

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?

A

Respiratory pump

The skeletal muscle pump

58
Q

How does the respiratory pump influence venous return?

A

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
Q

How does the skeletal muscle pump influence venous return?

A

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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