Blood Vessels and Circulation Flashcards

1
Q

Arteries

A

Carry blood away from the heart

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2
Q

Arterioles

A

Smallest artery branches leading to capillaries

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3
Q

Capillaries

A

Where diffusion between blood and interstitial fluid takes place

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4
Q

Venules

A

Unite to form larger veins that return blood to heart

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5
Q

Path of blood

A

Heart > arteries > arterioles > capillaries > venules > veins > heart

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6
Q

Where does blood leave the heart through?

A

Pulmonary trunk (right ventricle) > pulmonary arteries > lungs

Aorta (left ventricle) > systemic arteries > all other organs

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7
Q

Vessel wall structure in arteries and veins

A
  1. Tunica intima
  2. Tunica media
  3. Tunica externa
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8
Q

Tunica intima

A
  • Inner layer
  • Endothelial lining and a surrounding layer of connective tissue with a variable number of elastic fibres
  • Thick layer of elastic fibres (internal elastic membrane) in arteries
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9
Q

Tunica media

A
  • Middle layer
  • Concentric sheets of smooth muscle tissue in a framework of loose connective tissue
  • Typically thickest layer
  • Smooth muscle cells encircle endothelium that lines the lumen
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10
Q

What separates tunica media and tunica externa?

A

External elastic membrane

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11
Q

Tunica externa

A
  • Outer layer

- Connective tissue sheath

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12
Q

Vasa vasorum

A

Blood vessels in the walls of large vessels

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13
Q

Why do large vessels contain vasa vasorum?

A

Because the vessel walls are too thick for diffusion

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14
Q

Differences between arteries and veins

A
  1. Artery walls thicker
  2. Arteries keep shape in sectional view
  3. Arteries have folds in sectional view
  4. Veins have valves
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15
Q

3 main types of arteries

A
  1. Elastic
  2. Muscular
  3. Arterioles
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16
Q

What gives arteries their elasticity and contractility?

A

Thick, muscular walls

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17
Q

Vasoconstriction

A

When stimulated, arterial smooth muscles contract, constricting the arteries

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18
Q

Vasodilation

A

When arterial smooth muscles relax, the diameter of the lumen increases

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19
Q

What do vasoconstriction and vasodilation affect?

A
  1. Afterload on heart
  2. Peripheral blood flow
  3. Capillary blood flow
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20
Q

Elastic arteries

A

Pulmonary trunk and aorta and their major branches

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21
Q

Muscular arteries

A

Distribute blood to the body’s skeletal muscles and internal organs

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22
Q

Arterioles

A

Smaller than muscular arteries

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23
Q

Resistance vessels

A

Arterioles

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24
Q

Aneurysm

A

Bulge in the weakened wall of an artery

When local blood pressure exceeds the capacity of the elastic component of the arterial walls

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25
Q

Types of capillaries

A
  1. Continuous capillaries
  2. Fenestrated capillaries
  3. Sinusoids
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26
Q

Continuous capillaries

A
  • The endothelium is a complete lining of the lumen

- Tight junctions and desmosomes connect endothelial cells

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27
Q

Fenestrated capillaries

A

Contain pores in the wall due to an incomplete or perforated endothelial lining

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28
Q

Sinusoids

A

Discontinuous endothelium

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29
Q

Capillary bed

A

Interconnected collective network

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30
Q

Precapillary sphincter

A

Surrounds the entrance of a capillary and controls arterial blood flow to the tissues

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31
Q

Thoroughfare channel

A

Central passageway in the arteriole system

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32
Q

What happens when a precapillary sphincter constricts?

A

Blood is diverted into other branches of the network

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33
Q

Collaterals

A

Multiple arteries that supply blood to a capillary bed

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34
Q

Arterial anastomosis

A

The fusion of two collateral arteries that supply an arterial bed

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35
Q

Arteriovenous anastomoses

A

Direct connections between arterioles and venules

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36
Q

What happens when an arteriovenous anastomosis is dilated?

A

Blood bypasses the capillary bed and flows directly into venous circulation

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37
Q

Angiogenesis

A

Formulation of new blood vessels from preexisting vessels

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38
Q

Vascular endothelial growth factor (VEGF)

A

Directs angiogenesis

39
Q

Types of veins

A
  1. Venules
  2. Medium sized veins
  3. Lagre veins
40
Q

Venules

A
  • Smallest veins

- Collect blood from capillary beds

41
Q

Medium sized veins

A

Similar in size to muscular arteries

42
Q

Large veins

A

Includes superior and inferior venae cavae and their branches within the abdominopelvic and thoracic cavities

43
Q

Venous valves

A

In limbs, in venules and medium sized veins

44
Q

What makes up valves?

A

Folds of the tunica intima

45
Q

Varicose veins

A

Occurs when valves weaken or become stretched, blood pools in the veins

46
Q

Which vessels are capacitance?

A

Veins

47
Q

Why do veins act as blood resevoirs?

A

Because they have high capacitance

48
Q

Venoconstriction

A

If serious hemorrhaging occurs, sympathetic nerves stimulate smooth muscle cells in the walls of medium sized veins in the systemic system to constrict

This decreases the amount of blood within the venous system, increasing the volume within the arterial system and capillaries

49
Q

Capillary hydrostatic pressure (CHP)

A

Pressure of blood within capillary walls

50
Q

Venous pressure

A

Pressure of the blood within the venous system

51
Q

Total peripheral resistance

A

The resistance of the entire cardiovascular system

52
Q

Vascular resistance

A

The forces that oppose blood flow in the blood vessels

53
Q

What is the most important factor in vascular resistance?

A

Friction between blood and vessel walls

54
Q

Two factors affecting amount of friction

A
  1. Increasing vessel length increases friction

2. Narrower vessel more resistance to blood flow

55
Q

Viscosity

A

Resistance to flow caused by interactions among molecules and suspended materials in a liquid

More viscous = more resistance

56
Q

Turbulence

A

Eddies and swirls

57
Q

Systolic pressure

A

Peak blood pressure measured during ventricular systole

58
Q

Diastolic pressure

A

Minimum blood pressure at the end of the ventricular diastole

59
Q

Pulse pressure

A

Difference between systolic and diastolic pressures

60
Q

Mean arterial pressure (MAP)

A

Diastolic pressure + (pulse pressure/3)

61
Q

Hypertension

A

Abnormally high blood pressure

62
Q

Hypotension

A

Abnormally low blood pressure

63
Q

Is hypertension or hypotension more common?

A

Hypertension

64
Q

Stage 1 hypertension

A

Systolic: 140-159
Diastolic: 90-99

65
Q

Pre-hypertension

A

Systolic: 120-139
Diastolic: 80-89

66
Q

Why is there a risk of fainting when knees are locked?

A

Leg muscles are immobilised and unable to assist pushing blood against gravity back up to heart

67
Q

Respiratory pump

A

Inhale: thoracic cavity expands, reducing pressure, air enters lungs, blood pushed into inferior vena cava and right atrium
Exhale: thoracic cavity decreases, increasing pressure, air forced out of lungs, blood pushed into right atrium

68
Q

Capillary exchange

A

Chemical and gaseous exchange between blood and interstitial fluids across capillary walls

69
Q

Filtration

A

Removal of solutes as a solution flows across a porous membrane

70
Q

Reabsorption

A

Occurs as the result of osmosis

71
Q

Osmotic pressure (OP)

A

Pressure that must be applied to prevent osmotic movement across a membrane

72
Q

Bulk flow

A

The continuous net movement of water out of the capillaries, through peripheral tissues and back to the bloodstream by way of the lymphatic system

73
Q

Forces acting across capillary walls

A

At the arterial end of the capillary, CHP is greater than BCOP do fluid moves out of the capillary (filtration)

Near the venule, CHP is lower than BCOP, so fluid moves into capillary (reabsorption)

74
Q

Net filtration pressure (NFP)

A

Difference between net hydrostatic pressure and net osmotic pressure

75
Q

Tissue perfusion

A

Blood flow through tissues

76
Q

Factors affecting tissue perfusion

A
  1. Cardiac output
  2. Peripheral resistance
  3. Blood pressure
77
Q

Vasomotion

A

Changes in vessel diameter

78
Q

Autoregulation

A

Causes immediate, localised homeostatic adjustments

79
Q

Neural mechanisms

A

Respond to changes in arterial pressure or blood gas levels senses at specific sites

Short term adjustments to cardiac output and peripheral resistance to maintaining BP

80
Q

Endocrine mechanisms

A

Hormones that enhance short term adjustments and that direct long term changes in cardiovascular performance

81
Q

Vasodilators

A

Factors that promote dilation of precapillary sphincters

82
Q

Local vasodilators

A

Cause the capillary sphincters to relax so blood flow increases to the area when dissolved oxygen concentration decreases within a tissue

83
Q

Cardiovascular (CV) centre

A

Centre in the medulla oblongata that is responsible for adjusting cardiac output and peripheral resistance to maintain blood flow

84
Q

Vasomotor centre

A
  • In CV centre
  • Group of neurons responsible for controlling vasoconstriction
  • Group of neurons responsible for controlling vasodilation
85
Q

Cardioacceleratory centre

A

Increases cardiac output through sympathetic innervation

86
Q

Cardioinhibitory centre

A

Decreases cardiac output through parasympathetic innervation

87
Q

Baroreceptor reflexes

A

Monitor the degree of stretch within expandable organs

88
Q

Where are baroreceptors located?

A

Carotid sinuses, aortic sinuses and right atrium

89
Q

Chemoreceptor reflexes

A

Respond to changes in oxygen or CO2 levels in blood

90
Q

What triggers chemoreceptor reflexes?

A

Sensory neurons located in the carotid bodies and the aortic bodies

91
Q

Endocrine mechanisms

A
  1. Antidiuretic hormone - peripheral vasoconstriction and water conservation
  2. Angiotensin II - decreases renal BP
  3. Erythropoietin - causes vasoconstriction
  4. Natriuretic peptides - reduce blood volume and BP
92
Q

Light exercise

A
  1. Extensive vasodilation
  2. Venous return increases
  3. Cardiac output rises
93
Q

How does exercise lower cholestrol?

A

By stimulating enzymes that help move LDLs from the blood to the liver where it’s converted to bile and excreted