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Human Systems and Anatomy > Arteries, Veins, PVR > Flashcards

Arteries, Veins, PVR Flashcards

1
Q

what is PVR

A

peripheral vascular resistance

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2
Q

what are arterioles

A

smaller arteries

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3
Q

what does the vascular role play an active role in

A

regulation of blood pressure and distribution of blood flow to tissues

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4
Q

what are the blood vessels of the body

A
  • arteries
  • arterioles
  • capillaries
  • venules
  • veins
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5
Q

how is the mean arterial pressure calculated

A

diastolic blood pressure plus one third of the pulse pressure

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6
Q

which factors can impact the mean arterial pressure

A

the cardiac output and the total peripheral resistance

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7
Q

what does the pulse pressure represent

A

the force the heart generates with each contraction to overcome the arterial resistance

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8
Q

what is the afterload

A

the force against which the heart must contract to eject blood into the arteries

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9
Q

what are the parameters that can influence pulse pressure

A

stroke volume
ejection velocity of stroke volume
arterial compliance

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10
Q

what can increase pulse pressure

A

increase in stroke volume
increase in ejection velocity
less complacency in the arteries

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11
Q

describe the walls of the arteries

A

thick and muscular with large quantities of elastic tissue

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12
Q

what do arteries act as a reservoir for

A

pressure, maintaining blood flow through tissues during diastole

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13
Q

what are the major branches of the aorta

A

subclavian
common carotid
iliac

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14
Q

describe the blood content of arteries

A

low volume, high pressure

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15
Q

what are the muscular arteries

A

coronary and renal arteries

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16
Q

diameters of small arteries

A

less than 2mm

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17
Q

diameter of arterioles

A

20-100 micrometers

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18
Q

where are arterioles found

A

within organs and tissues

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19
Q

why is there variable resistance in the arterioles

A

to distribute the blood and dissipate most of the aterial blood pressure

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20
Q

how large is the cross sectional area of the aorta

A

small

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21
Q

how large is the cross sectional area of the capillaries

A

large

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22
Q

why do capillaries get described as having a large surface area

A

they form large networks within tissues and have a large overall cross sectional area

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23
Q

what is the lumen diameter of the capillaries

A

5-10 micrometers

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24
Q

how does the size of the lumen of capillaries compare to the diameter of erythrocytes

A

the same size roughly

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25
Q

what does flow of capillaries depend on

A

the flow from arterioles

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26
Q

how do red blood cells flow in smaller capillaries

A

single file

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27
Q

how thick are the capillary cell walls

A

one cell thick

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28
Q

how thick are capillary walls

A

20 micro meters

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29
Q

function of capillary walls

A

allow optimal exchange between blood and tissues via fenestrations

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30
Q

what diffuses from the capillaries to the tissues

A

gases and glucose

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31
Q

what do the capillary walls lack

A

tunica media and tunica adventitia

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32
Q

how do veins compare to arteries

A

larger lumen and diameter, thinner vessel walls, work at low pressure

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33
Q

how much of total blood volume is within the veins

A

70%

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34
Q

what is the purpose of venous valves

A

they prevent the backward flow of blood

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35
Q

what can happen to the venous walls or valves if there is loss of elasticity

A

they can become weakened, causing turbulent blood flow within the vessel

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36
Q

what can cause varicose veins

A

distension of vessel walls caused by a weakening in the elasticity of the venous walls and valves

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37
Q

how many layers are there to the vessel wall structure (all apart from capillaries)

A

three

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38
Q

what are the three layers found in the blood vessels apart from the capillaries

A
  • tunica intima
  • tunica media
  • tunica adventita
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39
Q

what is the tunica intima

A
  • endothelial cells attached to a basement membrane
  • has an underlying layer of extracellular matrix
  • separated from the media by the internal elastic lamina
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40
Q

what is the tunica media

A
  • layers of elastin fibres and smooth muscle cells, in which the proportion is dependent on whether it is an elastic or a muscular artery
  • high elastin content, enabling vessel wall expansion during systole and recoil during diastole
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41
Q

what is the tunica adventitia

A
  • external layer of vessel wall
  • separated from the media by external elastic lamina
  • thick connective tissue, elastic and collagen fibres
  • contains a network of nerve fibres, lymphatics and smaller arterioles which perfuse from the outer media
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42
Q

what are vasa vesorum

A

the small arterioles that perfuse from the outer media - vessels of vessels

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43
Q

when is there vaso vasorum in the tunica adventita of vessels

A

only in the larger arteries is this found

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44
Q

what is meant by the compliance of blood vessels

A

the ability of the blood vessel wall to passively expand and recoil in response to changes in pressure

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45
Q

what is compliance in relation to volume and pressure

A

change in volume over change in pressure

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46
Q

what does compliance reflect about a vessel

A

its buffering function

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47
Q

describe arterial compliance

A

this is when the arterial wall expands to accommodate the ventricular stroke volume, allowing it to act as a pressure reservoir

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48
Q

what happens to the compliance of arteries during diastole

A

the wall will recoil to help drive the flow of blood within the artery

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49
Q

what does arterial compliance decline with

A

age

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50
Q

what can a decline in arterial compliance do to pulse pressure

A

increase

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51
Q

what is anteriosclerosis

A

arterial stiffness due to calcificaion of elastin, collagen and extracellular matrix in the vessel walls

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52
Q

what forms the inner lining of the entire blood vessel system and the heart

A

the endothelial cells

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53
Q

what is the inner lining of the blood vessel

A

the tunica intima

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54
Q

how are endothelial cells arranged in the blood vessels

A

along the axis of the blood vessel to minimise shear stress and provide a friction free surface for blood flow

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55
Q

how do endothelial cells regulate the permeability of blood vessels

A

they form a selective barrier between blood and tissues

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56
Q

what are endothelial cells

A

highly specialised cells that play a key role in cardiovascular function

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57
Q

list the functions of endothelial cells

A
  • form the tunica intima
  • inner lining of the heart
  • provide a friction free surface for blood flow
  • regulate the permeability of blood vessels
  • regulate platelet function and fibrinolysis
  • promote angiogenesis and vessel remodelling
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58
Q

what is angiogenesis

A

the process of new capillaries forming out of preexisting blood vessels in the body

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59
Q

where is the vascular smooth muscle found in the vessel walls

A

in the tunica media

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60
Q

function of vascular smooth muscle

A
  • control total peripheral resistance
  • contral arterial and venous tone
  • control distribution of blood flow
  • provide elasticity
  • determine the vessel radius by contraction and relaxation
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61
Q

describe the shape of smooth muscle cells

A

single nuclei, spindle shaped, non striated

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62
Q

what does vascular smooth muscle secrete to give vessels their elastic properties

A

extracellular matrix

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63
Q

how is vascular tone altered

A

through the contraction or relaxation of the vascular smooth muscle cells

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64
Q

what is vasoconstriction

A

contraction of the vascular smooth muscle to narrow the vessel lumen and reduce the radius

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65
Q

what is vasodilation

A

relaxation of vascular smooth muscle to widen the vessel lumen and increase the radius

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66
Q

what is local control of blood pressure

A

this refers to the mechanism of altering small artery and arteriole resistance in organs and tissues, and is done through self regulation of blood flow and also include regulation by autocrine and paracrine substances

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67
Q

which hormones are involved in the local control of blood pressure

A

adrenaline
atrial natriouretic peptide
angiotensin 2

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68
Q

how does adrenaline locally control blood pressure through vasodilation

A

circulates in the blood and binds to beta two adrenoreceptors, leading to vasodilation
this occurs via an increase in cAMP and reduced calcium sensitivity, meaning there is relaxation of the smooth muscle cells

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69
Q

how does adrenaline locally control blood pressure through vascoconstriction

A

when at high concentrations, the adrenaline binds to alpha one adrenoreceptors
this causes contraction

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70
Q

how does atrial natriuretic peptide function in local control of blood pressure

A

vasodilator by regulating sodium balance and blood volume. released when the atria of the heart are stretched or stimulated by other factors, and causes the kidneys to excrete more sodium and water, lowering the blood volume and blood pressure.

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71
Q

how does angiotensin 2 regulate blood pressure on a local level

A

constricts the arterioles, important part of RAAS

72
Q

what does RAAS stand for

A

renin angiotensin aldosterone system

73
Q

what is RAAS

A

a key regulatory pathway in hormonal control of blood pressure and intravascular volume

74
Q

describe the process of RAAS

A
  • reduced blood flow to the kidney is sensed by receptors in the juxta glomerular apparatus in the kidney
  • release of renin from the juxta glomerular cells
  • renine acts on circulating angiotensinogen to convert it to angiotensin 1
  • angiotensin 1 is converted by antiotensin converting enzyme in the lungs and kidney to angiotensin II
  • this is a vasoconstrictor
75
Q

what produces angiotensinogen

A

the liver

76
Q

what produces angiotensin converting enzyme

A

endothelial cells

77
Q

what does angiotensin do

A
  • stimulates sodium and water reabsorption
  • stimulates the release of aldosterone from the adrenal cortex
  • stimulate antidiuretic hormone release from the posterior pituitary gland
78
Q

what does aldosterone do

A

acts on distal convoluted tubule and collecting duct of the kidney to increase sodium and water retention to increase intravascular volume

79
Q

what does antidiuretic hormone do

A

released from the posterior pituitary gland, it functions to increase water via aquaporin-2 channels in the distal convoluted tubule and the collecting duct of the kidney
increases vasoconstriction of blood vessels via the V1 receptors on the vascular smooth muscle cells

80
Q

which drugs lower blood pressure on the RAAS pathway

A

ACE inhibitors and angiotensin II receptor blockers

81
Q

what are ACE inhibitor examples

A

captopril and enalapril

82
Q

what are angiotensin II receptor blockers

A

losartan

83
Q

what produces ACE

A

the surface of the lungs and renal epithelium

84
Q

how do endothelial cells regulate vascular tone

A

by producing vasoactive substances

85
Q

what are examples of vasodilators

A

nitric oxide and prostoglandin 12

86
Q

breakdown the production and function of nitric oxide

A

produced by nitric oxide synthase from the L arginine in vascular endothelial cells.
diffuses into the smooth muscle cells to indude relaxation via the cGMP activation of guanylate cyclase

87
Q

when is nitric oxide released

A

in response to factors like the binding of endothelium dependent vasodilators like acetylcholine, ATP and bradykinin to receptors on the surface membrane of endothelial cells, or in response to shear stress

88
Q

what is prostoglandin 12

A

an eicosanoid produced in endothelial cells

89
Q

what is the function of prostoglandin 12

A

activates adenylate cyclase to increase cAMP production, and activate protein kinase A, leading to vasodilation

90
Q

what are eicosanoids

A

fatty acid hormones found in cell membranes that act locally. their synthesis and action can be modulated by drugs

91
Q

what are examples of vasoconstrictors

A

endothelin-1 and thromboxane A2

92
Q

describe the mechanism of endothelin-1

A

secreted by endothelial cells in response to stimuli like pulsatile stress, shear stress, neurohormones and cytokines.
acts on the ETa receptor on vascular smooth muscle cells to initiate vasconstriction

93
Q

which family does endothelin-1 belong to

A

the endothelin family of peptide agents

94
Q

what activates thromboxane A2

A

tissue injury and inflammation

95
Q

what is thromboxane an example of

A

an eicosanoid

96
Q

what is the dominant effect on nitric oxide production

A

shear stress produced by the interaction of blood flow with endothelial cells

97
Q

what does the interaction between ET-1 with the ETa receptor on vascular smooth muscle lead to

A

vasoconstriction

98
Q

what does the interaction between ET-1 and the ETb receptors on vascular smooth muscle lead to

A

synthesis of nitric oxide, and hence vasodilation

99
Q

what destroys nitric oxide in cells

A

the superoxide anion

100
Q

when in the cardiac cycle is there a drop in blood pressure in systemic circulation

A

as blood circulates from the left ventricle to the right ventricle

101
Q

when in the cardiac cycle is there a decrease in blood pressure for pulmonary circulation

A

as blood circulates from the right ventricle to the left ventricle

102
Q

what does circulation of blood require in order to meet the metabolic demands of the body

A

a certain volume per minute

103
Q

what is the average pressure pushing blood around the circulatory system

A

the mean arterial pressure

104
Q

what ejects the blood into the arteries

A

the ventricles

105
Q

what happens to the elastic wall as the blood is ejected into the arteries

A

it is stretched out due to the raised pressure, ie there is compliance

106
Q

how does blood leave the aorta

A

continuously through branches > arterioles > capillaries

107
Q

what offers resistance to blood flow during systemic circulation

A

the total vascular system downstream

108
Q

when does pressure rise and fall in the arteries

A

during the cardiac cycle

109
Q

why are blood vessels under constant mechanical load

A

due to blood pressure and flow

110
Q

when does shear stress occur

A

due to blood travelling at different velocities within a blood vessel

111
Q

what is shear stress

A

the force of flowing blood on the endothelial layer of the blood vessel

112
Q

what can lead to the physiological adaptation or disease of the vessel wall

A

physiological and pathological factors

113
Q

what are the physiological factors that alter homeostatis conditions of blood flow

A

exercise
pregnancy
growth

114
Q

what are the pathological factors leading to alterations in homeostatic blood flow

A

hypertension
flow reduction
flow overload

115
Q

what is the capillary system the primary location for

A

exchange of fluid, electrolytes, and gases

116
Q

what separates the endothelial cells of the capillary wall

A

junctions known as intercellular clefts

117
Q

what are the different classifications of capillaries

A
  • continuous
  • fenestrated
  • discontinuous
118
Q

describe continous capillaries

A
  • continuous basement membrane with tight intercellular clefts
  • continuous capillaries with low permeability
119
Q

describe fenestrated capillaries

A
  • perforations or fenestrations in the endothelium
  • enables high permeability
120
Q

describe discontinous capillaries

A

extremely high permeability due to large intercellular clefts and gaps int he basement membrane

121
Q

where are continuous capillaries found

A

muscle
skin
pulmonary system
central nervous system

122
Q

where are fenestrated capillaries found

A

exocrine glands
renal glomeruli

123
Q

where are discontinuous capillaries found

A

in the liver

124
Q

how are the capillary microcirculations of each organ arranged

A

so that it meets the organ’s metabolic requirements

125
Q

how many times can arterioles branch when they supply blood to the capillaries

A

2-5 times

126
Q

what are metarterioles

A

terminal arterioles that do not contain a continuous layer of smooth muscle, but instead contain smooth muscle fibres encircling the vessel at intermittent points along its length

127
Q

is blood flow through capillaries continuous

A

no

128
Q

describe blood flow through capillaries

A

intermittent due to vasomotion

129
Q

what is vasomotion

A

spontaneous oscillation in tone of blood vessel walls, independent of heart beat, innervation or respiration

130
Q

what surrounds the branching of metarterioles

A

pre capillary sphincters

131
Q

what are pre capillary sphincters

A

rings of smooth muscle surrounding the branch site of capillaries from metarterioles that contract and relax in response to local metabolic factors. the contraction of these sphincters closes the entery to the capillary

132
Q

what does hydrostatic pressure do

A

force fluid and dissolved substances through the capillary intercellular spaces to the interstitial spaces

133
Q

what causes osmotic pressure

A

plasma proteins

134
Q

what does osmotic pressure do

A

force fluid movement from the interstitial space to the blood via capillary intercellular spaces

135
Q

what is net filtration pressure

A

the interaction of the hydrostatic and osmotic pressures that drive fluid out of the capillary

136
Q

what happens if the net filtration pressure is positive

A

there will be net fluid filtration across the capillaries

137
Q

what happens if the net filtration pressure is negative

A

there will be a net fluid absorption from the interstitial spaces into the capillaries

138
Q

what happens to hydrostatic pressure as blood pressure drops from the arteriol to the venous systems

A

it will also decrease

139
Q

what is hydrostatic pressure

A

pressure exerted by a fluid at equilibrium at any point of time due to the force of gravity

140
Q

what is osmotic pressure

A

pressure required to stop water from diffusing through a barrier by osmosis

141
Q

what happens to the osmotic pressure of the capillaries if there is a decrease in blood pressure

A

nothing as the proteins are too big to leave the capillary

142
Q

how does the amount of fluid filtering outward from the arterial end of capillaries equate to the fluid returned to circulation by absorption

A

they are almost exactly equal

143
Q

what does it mean if there is disequilibrium between the amount of fluid filtering outward from the arterial end compared to the fluid returned to circulation by absorption

A

there is excess fluid that is returned to the circulation via the lymphatic system

144
Q

why is the lymphatic system important

A

there would be a build up of fluid in the tissues leading to oedema

145
Q

what is the lymphatic system

A

a network of small lymph nodes and lymphatic vessels through which the lymph flows

146
Q

what is lymph

A

fluid derived from interstitial fluid

147
Q

how does lymph move through the lymphatic system

A

they contract to aid the movement of fluid, and is also responsible for moving absorbed fat into the circulation

148
Q

what is found in lymph nodes

A

masses of lymphocytes and macrophages

149
Q

what are the main groups of lymph nodes in the body

A

cervical
axillary
inguinal
mesenteric and retroperitoneal
mediastinal

150
Q

what is the function of the lymphatic system

A

act as an overflow mechanism to return excess fluid volume from tissue spaces to the circulation

151
Q

what does the lymphatic system control

A

concentration of proteins in interstitial fluids
volume of interstitial fluids
interstitial fluid pressure

152
Q

what does increasing colloid osmotic pressure in interstitial fluid lead to

A

shift of the balance of forces at the membrane of blood capillaries in favour of fluid filtration

153
Q

what does an increase in interstitial fluid pressure increase

A

the rate of lymph flow

154
Q

what does the lymph flow do

A

carry excess interstitial fluid volume and protein that accumulates in interstital spaces away

155
Q

is the hydrostatic pressure in the systemic system lower or higher than the pulmonary system

A

higher

156
Q

is the osmotic pressure in the systemic circulation higher or lower than in pulmonary circulation

A

they are the same

157
Q

what is pulmonary oedema

A

excess fluid in the lungs that collects in the alveoli

158
Q

what can cause pulmonary oedema

A
  • left side heart failure when there is an increase in hydrostatis pressure in the extremities
  • right side heart failure
  • high altitude exposure
  • lung damage due to severe infection
  • adult respiratory distress syndrome
  • following major injury
159
Q

pressure in the venous system

A

low

160
Q

pressure in the arterial system

A

high

161
Q

what are the muscular artery branches

A

renal and coronary

162
Q

what can cause turbulent blood flow in veins

A

loss of elasticity in the vessels

163
Q

what is the proportion of smooth muscle within the vessel wall dependent on

A

the function the vessel has

164
Q

what are vasal vesorum

A

smaller arterioles within the larger arterioles

165
Q

what does the contraction and relaxation of the tunica media allow

A

vascular flow

166
Q

what does it mean to say that vessels have buffering capacity

A

they are able to withstand the high pressure that blood goes through when it goes through the heart

167
Q

why does the aterial wall expand upon receipt of the blood

A

to allow for high volume and high pressure to be maintained

168
Q

why is arterial recoil important

A

allows for the pushing of blood along the arteries to aid in travel of the blood through the vascular system

169
Q

what is atherosclerosis

A

plaque build up in the vascular wall causing clots which leads to strokes and cardiac arrest

170
Q

what is arterial sclerosis

A

age related stiffness caused by calcification of elastic fibres in the artery wall leading to the cardiac tissued

171
Q

what is involved in the local control of blood pressure

A

endothelial cells and hormones

172
Q

what are the two pressures involved in fluid exchange through intercellular exchanges

A

hydrostatic and osmotic

173
Q

what derives lymph

A

interstitial fluid from the circulation

174
Q

what is oedema

A

fluid accumulation in the tissues

175
Q

why can oedema be observed in heart failure

A

the balance between the lymphatic system and blood volume is impacted. damage and difficulty to maintain respiratory function

Human Systems and Anatomy (57 decks)

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