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Physiology > Ch 19: Blood Vessels > Flashcards

Ch 19: Blood Vessels Flashcards

1
Q

What does the cardiovascular system delivery system consist of?

A
  1. Arterties
  2. Capillaries
  3. Veins
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2
Q

What are arteries?

A

Carry blood away from the heart

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3
Q

When does the artery carry deoxygenated?

A

Pulmonary circulation and umbilical vessels of fetus

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4
Q

What are capillaries?

A

Contacts tissue cells

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5
Q

What are veins?

A

Carry blood toward heart

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6
Q

What is lumen?

A

Central blood containing space

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7
Q

What are the 3 wall layers of vessels?

A
  1. Tunica intima
  2. Tunica media
  3. Tunic externa (adventitia)
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8
Q

Where is the tunica intima comprised of?

A

Endothelium that lines lumen of all vessels

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9
Q

What is the purpose of the tunica intima?

A
  1. Continuous with endocardium
  2. Slick surface reduces friction
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10
Q

Where is the tunica media comprised of?

A

Smooth muscle and elastin

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11
Q

What is the purpose of the tunica media?

A

Sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels that influence blood flow and pressure

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12
Q

Where is the tunica externa comprised of?

A

Nerve fibers and lymphatic vessels

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13
Q

What is the purpose of tunica externa?

A
  1. Collagen fibers protect and reinforce
  2. Anchors to surrounding structures
  3. Vasa vasorum of larger vessels nourishes external layer
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14
Q

Why are capillaries considered fragile?

A

Only has an endothelium

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15
Q

How do vessels vary?

A
  1. Length
  2. Diameter
  3. Wall thickness
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16
Q

What are the components of the arterial system?

A
  1. Elastic arteries
  2. Muscular arteries
  3. Arterioles
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17
Q

What are the elastic arteries?

A

Large thick walled arteries with elastin in all three tunics

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18
Q

When are elastic arteries inactive?

A

Vasoconstriction

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19
Q

What is the purpose for elastic arteries?

A

Act as pressure reservoirs the expand and recoil as blood ejected from heart

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20
Q

What are muscular arteries?

A

Distal to elastic arteries that deliver blood to body organs

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21
Q

When are muscular arteries active?

A

Vasoconstriction

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22
Q

What are muscular arteries comprised of?

A

Thick tunica media with more smooth muscle

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23
Q

What are arterioles?

A

Smallest arteries that lead to capillary beds

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24
Q

What is the purpose for arterioles?

A

Control flow into capillary beds via vasodilation and vasoconstriction

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25
Q

Describe the structure of capillaries

A

Microscopic blood vessels that has walls of thin tunica intima

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26
Q

What is the function of pericytes?

A

Help stabilize their walls and control permeability

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27
Q

Describe the diameter of the capillaries?

A

Allows only single RBC to pass at a time

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28
Q

What are functions of capillaries?

A
  1. Direct access to almost every cell
  2. Exchange of gases, nutrients, wastes, hormones between blood and interstitial fluid
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29
Q

What are the types of capillaries?

A
  1. Continuous
  2. Fenestrated
  3. Sinusoid
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30
Q

What are continuous capillaries comprised of?

A
  1. Tight junctions connecting endothelial cells
  2. Intercellular clefts allowing passage of fluids and small solutes
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31
Q

What is the function of continuous capillaries?

A

Complete tight junctions that form the blood brain barrier

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32
Q

What are fenestrated capillaries comprised of?

A
  1. Some endothelial cells contain pores (fenestrations)
  2. More permeable than continuous capillaries
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33
Q

What are the functions of fenestrated capillaries?

A

Absorption or filtrate formation

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34
Q

What are sinusoids comprised of?

A
  1. Fewer tight junctions; usually fenestrated; larger intercellular clefts; large lumens
  2. Blood flow sluggish – allows modification
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35
Q

Where are sinusoid capillaries found?

A

Liver, bone marrow, spleen, adrenal medulla

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36
Q

What lines the sinusoid capillaries to destroy bacteria?

A

Macrophages

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37
Q

What does a vascular shunt do?

A

Directly connects terminal arteriole and postcapillary venule

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38
Q

What are the qualities of true capillaries?

A
  1. 10 to 100 exchange vessels per capillary bed
  2. Branch off metarteriole or terminal arteriole
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39
Q

What is the purpose for precapillary sphincters?

A

Regulate blood flow into true capillaries

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40
Q

What regulates blood flow through the capillary beds?

A

Local chemical conditions and vasomotor nerves

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41
Q

How are venules formed?

A

When capillary beds unite

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42
Q

Describe the structure of venules?

A

Smallest postcapillary venules that are very porous allowing fluids and WBCs into tissues

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43
Q

What are veins?

A

Have thinner walls, larger lumens compared with corresponding arteries

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44
Q

What are capacitance vessels?

A

Blood reservoirs that contain 65% of blood supply

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45
Q

What are the structures of veins that cause them to have lower pressure than arteries?

A

Large diameter lumens offer little resistance

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46
Q

What are venous valves’ function?

A

Prevent backflow of blood

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47
Q

What are venous sinuses?

A

Flattened veins with extremely thin walls

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48
Q

What are vascular anastomoses?

A

Interconnections of blood vessels

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49
Q

What is the purpose for arterial anastomoses?

A

Provide alternate pathways (collateral channels) to given body regions

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50
Q

What is an example of arteriovenous anastomoses?

A

Vascular shunts

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51
Q

What is blood flow?

A

Volume of blood flowing through vessel, organ, or entire circulation in given period

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52
Q

How is blood flow measured?

A
  1. Measured as ml/min
  2. Equivalent to cardiac output (CO) for entire vascular system
  3. Relatively constant when at rest
  4. Varies widely through individual organs, based on needs
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53
Q

What is blood pressure?

A

Force per unit area exerted on wall of blood vessel by blood expressed in mm Hg

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54
Q

What is the purpose for pressure gradient?

A

Provides driving force that keeps blood moving from higher to lower pressure areas

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55
Q

What is resistance?

A

Measure of amount of friction blood encounters with vessel walls, generally in peripheral circulation

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56
Q

What are the sources of resistance?

A
  1. Blood viscosity
  2. Total blood vessel length
  3. Blood vessel diameter
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57
Q

What factors of resistance remain constant?

A
  1. Blood viscosity
  2. Blood vessel length
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58
Q

What factors of resistance frequently change?

A

Blood vessel diameter

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59
Q

How does blood viscosity effect resistance?

A
  1. The stickiness of blood due to formed elements and plasma proteins
  2. Increased vessel = increased resistance
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60
Q

How does blood vessel length effect resistance?

A

Longer vessel = greater resistance encountered

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61
Q

How does blood vessel diameter effect resistance?

A
  1. Greatest influence on resistance
  2. Varies inversely with fourth power of vessel radius
  3. Vasoconstriction increases resistance
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62
Q

Why is resistance crucial?

A

Disrupt laminar flow and cause turbulent flow causing irregular fluid motion

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63
Q

Describe the relationship between blood flow and the pressure gradient

A

If delta P increases, blood flow speeds up

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64
Q

Describe the relationship between blood flow and peripheral resistance

A

If R increases, blood flow decreases

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65
Q

What is the importance of R?

A

Influences local blood flow

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66
Q

What occurs during systemic pressure?

A

Pumping action of heart generating blood flow

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67
Q

What are 2 factors of arteries close to the heart?

A
  1. Elasticity
  2. Volume of blood
68
Q

What is the blood pressure near the heart called?

69
Q

What is the difference between systolic and diastolic pressure?

A
  1. S: pressure exerted in aorta during ventricular contraction
  2. D: lowest level of aortic pressure
70
Q

What is pulse pressure?

A

Difference between systolic and diastolic pressure (pulse)

71
Q

What is mean arterial pressure?

A

Pressure that propels blood to tissues

72
Q

What is the formula to calculate MAP?

A

MAP=diastolic pressure + 1/3 pulse pressure

73
Q

What declines as distance from heart increases?

A
  1. Pulse pressure
  2. MAP
74
Q

What is range of capillary blood pressure?

A

17-35 mmHg

75
Q

Why is it important for capillaries to have low pressure?

A
  1. High BP would rupture fragile, thin-walled capillaries
  2. Most very permeable, so low pressure forces filtrate into interstitial spaces
76
Q

What occurs during venous blood pressure?

A
  1. Slight changes in the cardiac cycle
  2. Small pressure gradient
77
Q

What causes low venous pressure?

A

Energy of blood pressure lost as heat during each circuit

78
Q

What are the factors that aid venous return?

A
  1. Muscular pump
  2. Respiratory pump
  3. Venoconstriction
79
Q

How does muscular pumps aid venous return?

A

Contraction of skeletal muscles “milks” blood toward heart; valves prevent backflow

80
Q

How does respiratory pumps aid venous return?

A

Pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand

81
Q

How does venoconstriction aid venous return?

A

Pushes blood toward heart

82
Q

What is required to maintain BP?

A
  1. Cooperation of heart, blood vessels, and kidneys
  2. Supervision by brain
83
Q

What are the factors that influence BP?

A
  1. Cardiac output
  2. Peripheral resistance
  3. Blood volume
84
Q

What factors are proportional to BP?

A

CO, PR, blood volume

85
Q

Describe cardiac output during rest

A

Resting heart rate maintained by cardioinhibitory center via parasympathetic vagus nerves

86
Q

Describe cardiac output during stress

A

During stress, cardioacceleratory center increases heart rate and stroke volume via sympathetic stimulation

87
Q

What is short-term neural and hormonal control?

A

Counteract fluctuations in blood pressure by altering peripheral resistance and CO

88
Q

What is the purpose for short term neural control?

A
  1. Maintain MAP by altering blood vessel diameter
  2. Alter blood distribution to organs in response to specific demands
89
Q

What are factors are involved during reflex arcs?

A
  1. Baroreceptors
  2. Cardiovascular center of medulla
  3. Vasomotor fibers to heart and vascular smooth muscle
  4. Sometimes input from chemoreceptors and higher brain centers
90
Q

What is the cardiovascular center?

A

Clusters of sympathetic neurons in medulla oversee changes in CO and blood vessel diameter

91
Q

What does the cardiovascular center consists of?

A

Cardiac and vasometer center

92
Q

What does the vasomotor center achieve?

A

Sends steady impulses via sympathetic efferents to blood vessels → moderate constriction called vasomotor tone

93
Q

What are the receiving inputs of the cardiovascular center?

A
  1. Baroreceptors
  2. Chemoreceptors
  3. Higher brain centers
94
Q

Where are baroreceptors located?

A
  1. Carotid sinuses
  2. Aortic arch
  3. Walls of large arteries of neck and thorax
95
Q

What is the purpose for baroreceptors?

A
  1. Inhibits vasomotor and cardioacceleratory centers, causing arteriolar dilation and venodilation
  2. Stimulates cardioinhibitory center
  3. Decreases blood pressure
96
Q

How does baroreceptors decrease BP?

A
  1. Arteriolar vasodilation
  2. Venodilation
  3. Decreased cardiac output
97
Q

What occurs when MAP gets low?

A

Reflex vasoconstriction → increased CO → increased blood pressure

98
Q

What is an example of baroreceptors when MAP is low?

A

Baroreceptors of carotid sinus reflex protect blood to brain; in systemic circuit as whole aortic reflex maintains blood pressure

99
Q

What are chemoreceptor reflexes?

A

Detect increase in CO2, or drop in pH or O2

100
Q

How does chemoreceptor reflexes cause increased BP?

A
  1. Signaling cardioacceleratory center → increase CO
  2. Signaling vasomotor center → increase vasoconstriction
101
Q

What is the purpose of the hypothalamus and cerebral cortex?

A

Modify arterial pressure via relays to medulla

102
Q

What does the hypothalamus achieve in regards to blood?

A
  1. Increases blood pressure during stress
  2. Mediates redistribution of blood flow during exercise and changes in body temperature
103
Q

What does short term regulation of hormonal controls change?

A

Changes in peripheral resistance

104
Q

What does longterm regulation of hormonal controls change?

A

Changes in blood volume

105
Q

How hormone regulations increase BP?

A
  1. Epinephrine and norepinephrine from adrenal gland → increased CO and vasoconstriction
  2. Angiotensin II stimulates vasoconstriction
  3. High ADH levels cause vasoconstriction
106
Q

How does hormone regulation lower BP?

A

Atrial natriuretic peptide causes decreased blood volume by antagonizing aldosterone

107
Q

What is long term renal regulation?

A

Counteracts fluctuations in blood pressure by altering blood volume

108
Q

What is an example of long-term mechanisms?

A

Renal regulation: baroreceptors quickly adapt to chronic high or low BP so are ineffective

109
Q

How can kidneys regulate arterial BP?

A
  1. Direct renal mechanism
  2. Indirect renal (RAAS mechanism)
110
Q

What is direct mechanisms?

A

Alter blood volume independently of hormones

111
Q

How does direct mechanism alter blood volume?

A
  1. Increased BP or blood volume causes elimination of more urine, thus reducing BP
  2. Decreased BP or blood volume causes kidneys to conserve water, and BP rises
112
Q

What does indirect mechanism achieve?

A
  1. Decrease inArterial blood pressure →release of renin
  2. Renin catalyzes conversion of angiotensinogen from liver to angiotensin I
  3. Angiotensin converting enzyme, especially from lungs, converts angiotensin I to angiotensin II
113
Q

What are the functions of angiotensin II?

A

Increases blood volume by causing vasoconstriction

114
Q

How does angiotensin II increase blood volume?

A
  1. Stimulates aldosterone
  2. Cause ADH release
  3. Triggers hypothalamic thirst center
115
Q

What factors would we monitor of circulatory effect?

A
  1. Vital signs
  2. Pulse
  3. Radial pulse
  4. Pressure points
116
Q

What do vital signs monitor?

A
  1. Pulse
  2. Blood pressure
  3. Respiratory rate
  4. Body temperature
117
Q

What does pulse monitor?

A

Pressure wave caused by expansion and recoil of arteries

118
Q

Where is the radial pulse?

119
Q

What are pressure points?

A

Where arteries close to body surface that can be compressed to stop blood flow

120
Q

How is systemic arterial BP measured?

A

Sphygomanometer

121
Q

How is systolic pressure measured?

A

Pressure when sounds first occur as blood starts to spurt through artery

122
Q

How is diastolic pressure measured?

A

Pressure when sounds disappear because artery no longer constricted; blood flowing freely

123
Q

What are the variables that can change BP?

A
  1. Transient elevations
  2. Age
  3. Sex
  4. Weight
  5. Race
  6. Mood
  7. Posture
124
Q

What is hypertension?

A

High BP: 130/80 or higher

125
Q

What is prehypertension?

A

Values elevated but not yet in hypertension range

126
Q

How does prolonged hypertension cause disease?

A

Heart must work harder → myocardium enlarges, weakens, becomes flabby

127
Q

What is primary hypertension?

A
  1. No underlying cause identified
  2. No cure but can be controlled
128
Q

What is secondary hypertension?

A
  1. Due to identifiable disorders such diseases
  2. Treatment focuses on correcting underlying cause
129
Q

What is hypotension?

A

Low BP: less than 90/60

130
Q

What is orthostatic hypotension?

A

Temporary low BP and dizziness when suddenly rising from sitting and reclining

131
Q

What is chronic hypotension?

A

Hint of poor nutrition and warning sign for Addison’s disease or hypothyroidism

132
Q

What is acute hypotension?

A

Important sign of circulatory shock; threat for surgical patients and those in ICU

133
Q

What is the importance of tissue perfusion?

A
  1. Delivery of O2 and nutrients to, and removal of wastes from, tissue cells
  2. Gas exchange (lungs)
  3. Absorption of nutrients (digestive tract)
  4. Urine formation (kidneys)
134
Q

What vessel has the fastest velocity?

135
Q

What vessel has the slowest velocity?

A

Capillaries

136
Q

What happens to the velocity when blood enters the veins?

137
Q

What is autoregulation?

A

Automatic adjustment of blood flow to each tissue relative to its varying requirements

138
Q

How is autoregulation controlled?

A

Controlled intrinsically by modifying diameter of local arterioles feeding capillaries

139
Q

What are the types of autoregulation?

A
  1. Metabolic
  2. Myogenic
140
Q

What is metabolic autoregulation?

A

Vasodilation of arterioles and relaxation of precapillary sphincters

141
Q

What trigger metabolic control?

A
  1. Declining tissue O2
  2. Substances from metabolically active tissues
142
Q

What are the effects of metabolic controls?

A
  1. Relaxation of vascular smooth muscle
  2. Release of nitric oxide by endothelial cells
143
Q

What is the difference between endothelins and inflammatory chemicals?

A
  1. Endothelins are potent vasoconstrictors
  2. In: cause vasodialtion
144
Q

What is myogenic autoregulation?

A

Myogenic responses keep tissue perfusion constant despite most fluctuations in systemic pressure

145
Q

How do vascular smooth muscle respond to stretch?

A
  1. Passive
  2. Reduced
146
Q

What is the difference between passive and reduced stretch?

A
  1. Passive: promotes increased tone and vasoconstriction
  2. Reduced: Promotes vasodilation and increases blood flow to the tissues
147
Q

What is long term autoregulation?

A

Occurs when short-term autoregulation cannot meet tissue nutrient requirements

148
Q

What is angiogenesis?

A
  1. Number of vessels to region increases and existing vessels enlarge
  2. Common in heart when coronary vessel occluded, or throughout body in people in high-altitude areas
149
Q

What is vasomotion?

A

Slow intermittent flow that reflects on/off opening and closing of precapillary sphincters

150
Q

What can diffuse across the concentration gradient?

A

O2 and nutrients from blood to tissues

CO2 and metabolic wastes from tissues to blood

151
Q

How do lipid soluble molecules diffuse through capillaries?

A

Endothelial membranes

152
Q

How do water-soluble solutes pass through the capillaries?

A

Clefts and fenestrations

153
Q

How do proteins pass through capillaries?

A

Actively transported in pinocytotic vesicles or caveolae

154
Q

What is bulk flow?

A

Fluid leaving capillaries at arterial end and returns to blood at venous end

155
Q

What are the opposing forces that drive fluid flow?

A
  1. Hydrostatic pressure
  2. Colloid osmotic pressures
156
Q

What are the 2 hydrostatic pressures?

A
    1. Capillary blood pressure
    2. Interstitial fluid hydrostatic pressure
157
Q

What is capillary blood pressure?

A

Forces fluids through capillary walls

Greater pressure at arterial end

158
Q

What is Interstitial fluid hydrostatic pressure?

A

Pressure that would push fluid into vessels

159
Q

What are the 2 colloid osmotic pressures?

A
  1. Capillary colloid osmotic pressure (oncotic)
  2. Interstitial fluid osmotic pressure
160
Q

What is capillary colloid osmotic pressure (oncotic)?

A

Created by nondiffusible plasma proteins, which draw water toward themselves

161
Q

What is interstitial fluid osmotic pressure?

A

Low (~1mmHg) due to low protein content

162
Q

What is net filtration pressure?

A

The interactions of flow out the arterial end and in the venous end

163
Q

What causes circulatory shock?

A
  1. Blood vessels inadequately filled
  2. Blood cannot circulate normally
  3. Inadequate blood flow to meet tissue needs
164
Q

What is hypovolemic shock?

A

Shock from large-scale blood loss

165
Q

What is vascular shock?

A

Extreme vasodilation and decreased peripheral resistance

166
Q

What is cardiogenic shock?

A

An inefficient heart cannot sustain adequate circulation

Physiology (22 decks)

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