Ch 19: Blood Vessels Flashcards
(166 cards)
1
Q
What does the cardiovascular system delivery system consist of?
A
- Arterties
- Capillaries
- Veins
2
Q
What are arteries?
A
Carry blood away from the heart
3
Q
When does the artery carry deoxygenated?
A
Pulmonary circulation and umbilical vessels of fetus
4
Q
What are capillaries?
A
Contacts tissue cells
5
Q
What are veins?
A
Carry blood toward heart
6
Q
What is lumen?
A
Central blood containing space
7
Q
What are the 3 wall layers of vessels?
A
- Tunica intima
- Tunica media
- Tunic externa (adventitia)
8
Q
Where is the tunica intima comprised of?
A
Endothelium that lines lumen of all vessels
9
Q
What is the purpose of the tunica intima?
A
- Continuous with endocardium
- Slick surface reduces friction
10
Q
Where is the tunica media comprised of?
A
Smooth muscle and elastin
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
12
Q
Where is the tunica externa comprised of?
A
Nerve fibers and lymphatic vessels
13
Q
What is the purpose of tunica externa?
A
- Collagen fibers protect and reinforce
- Anchors to surrounding structures
- Vasa vasorum of larger vessels nourishes external layer
14
Q
Why are capillaries considered fragile?
A
Only has an endothelium
15
Q
How do vessels vary?
A
- Length
- Diameter
- Wall thickness
16
Q
What are the components of the arterial system?
A
- Elastic arteries
- Muscular arteries
- Arterioles
17
Q
What are the elastic arteries?
A
Large thick walled arteries with elastin in all three tunics
18
Q
When are elastic arteries inactive?
A
Vasoconstriction
19
Q
What is the purpose for elastic arteries?
A
Act as pressure reservoirs the expand and recoil as blood ejected from heart
20
Q
What are muscular arteries?
A
Distal to elastic arteries that deliver blood to body organs
21
Q
When are muscular arteries active?
A
Vasoconstriction
22
Q
What are muscular arteries comprised of?
A
Thick tunica media with more smooth muscle
23
Q
What are arterioles?
A
Smallest arteries that lead to capillary beds
24
Q
What is the purpose for arterioles?
A
Control flow into capillary beds via vasodilation and vasoconstriction
25
Describe the structure of capillaries
Microscopic blood vessels that has walls of thin tunica intima
26
What is the function of pericytes?
Help stabilize their walls and control permeability
27
Describe the diameter of the capillaries?
Allows only single RBC to pass at a time
28
What are functions of capillaries?
1. Direct access to almost every cell
2. Exchange of gases, nutrients, wastes, hormones between blood and interstitial fluid
29
What are the types of capillaries?
1. Continuous
2. Fenestrated
3. Sinusoid
30
What are continuous capillaries comprised of?
1. Tight junctions connecting endothelial cells
2. Intercellular clefts allowing passage of fluids and small solutes
31
What is the function of continuous capillaries?
Complete tight junctions that form the blood brain barrier
32
What are fenestrated capillaries comprised of?
1. Some endothelial cells contain pores (fenestrations)
2. More permeable than continuous capillaries
33
What are the functions of fenestrated capillaries?
Absorption or filtrate formation
34
What are sinusoids comprised of?
1. Fewer tight junctions; usually fenestrated; larger intercellular clefts; large lumens
2. Blood flow sluggish – allows modification
35
Where are sinusoid capillaries found?
Liver, bone marrow, spleen, adrenal medulla
36
What lines the sinusoid capillaries to destroy bacteria?
Macrophages
37
What does a vascular shunt do?
Directly connects terminal arteriole and postcapillary venule
38
What are the qualities of true capillaries?
1. 10 to 100 exchange vessels per capillary bed
2. Branch off metarteriole or terminal arteriole
39
What is the purpose for precapillary sphincters?
Regulate blood flow into true capillaries
40
What regulates blood flow through the capillary beds?
Local chemical conditions and vasomotor nerves
41
How are venules formed?
When capillary beds unite
42
Describe the structure of venules?
Smallest postcapillary venules that are very porous allowing fluids and WBCs into tissues
43
What are veins?
Have thinner walls, larger lumens compared with corresponding arteries
44
What are capacitance vessels?
Blood reservoirs that contain 65% of blood supply
45
What are the structures of veins that cause them to have lower pressure than arteries?
Large diameter lumens offer little resistance
46
What are venous valves’ function?
Prevent backflow of blood
47
What are venous sinuses?
Flattened veins with extremely thin walls
48
What are vascular anastomoses?
Interconnections of blood vessels
49
What is the purpose for arterial anastomoses?
Provide alternate pathways (collateral channels) to given body regions
50
What is an example of arteriovenous anastomoses?
Vascular shunts
51
What is blood flow?
Volume of blood flowing through vessel, organ, or entire circulation in given period
52
How is blood flow measured?
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
53
What is blood pressure?
Force per unit area exerted on wall of blood vessel by blood expressed in mm Hg
54
What is the purpose for pressure gradient?
Provides driving force that keeps blood moving from higher to lower pressure areas
55
What is resistance?
Measure of amount of friction blood encounters with vessel walls, generally in peripheral circulation
56
What are the sources of resistance?
1. Blood viscosity
2. Total blood vessel length
3. Blood vessel diameter
57
What factors of resistance remain constant?
1. Blood viscosity
2. Blood vessel length
58
What factors of resistance frequently change?
Blood vessel diameter
59
How does blood viscosity effect resistance?
1. The stickiness of blood due to formed elements and plasma proteins
2. Increased vessel = increased resistance
60
How does blood vessel length effect resistance?
Longer vessel = greater resistance encountered
61
How does blood vessel diameter effect resistance?
1. Greatest influence on resistance
2. Varies inversely with fourth power of vessel radius
3. Vasoconstriction increases resistance
62
Why is resistance crucial?
Disrupt laminar flow and cause turbulent flow causing irregular fluid motion
63
Describe the relationship between blood flow and the pressure gradient
If delta P increases, blood flow speeds up
64
Describe the relationship between blood flow and peripheral resistance
If R increases, blood flow decreases
65
What is the importance of R?
Influences local blood flow
66
What occurs during systemic pressure?
Pumping action of heart generating blood flow
67
What are 2 factors of arteries close to the heart?
1. Elasticity
2. Volume of blood
68
What is the blood pressure near the heart called?
Pulsatile
69
What is the difference between systolic and diastolic pressure?
1. S: pressure exerted in aorta during ventricular contraction
2. D: lowest level of aortic pressure
70
What is pulse pressure?
Difference between systolic and diastolic pressure (pulse)
71
What is mean arterial pressure?
Pressure that propels blood to tissues
72
What is the formula to calculate MAP?
MAP=diastolic pressure + 1/3 pulse pressure
73
What declines as distance from heart increases?
1. Pulse pressure
2. MAP
74
What is range of capillary blood pressure?
17-35 mmHg
75
Why is it important for capillaries to have low pressure?
1. High BP would rupture fragile, thin-walled capillaries
2. Most very permeable, so low pressure forces filtrate into interstitial spaces
76
What occurs during venous blood pressure?
1. Slight changes in the cardiac cycle
2. Small pressure gradient
77
What causes low venous pressure?
Energy of blood pressure lost as heat during each circuit
78
What are the factors that aid venous return?
1. Muscular pump
2. Respiratory pump
3. Venoconstriction
79
How does muscular pumps aid venous return?
Contraction of skeletal muscles “milks” blood toward heart; valves prevent backflow
80
How does respiratory pumps aid venous return?
Pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
81
How does venoconstriction aid venous return?
Pushes blood toward heart
82
What is required to maintain BP?
1. Cooperation of heart, blood vessels, and kidneys
2. Supervision by brain
83
What are the factors that influence BP?
1. Cardiac output
2. Peripheral resistance
3. Blood volume
84
What factors are proportional to BP?
CO, PR, blood volume
85
Describe cardiac output during rest
Resting heart rate maintained by cardioinhibitory center via parasympathetic vagus nerves
86
Describe cardiac output during stress
During stress, cardioacceleratory center increases heart rate and stroke volume via sympathetic stimulation
87
What is short-term neural and hormonal control?
Counteract fluctuations in blood pressure by altering peripheral resistance and CO
88
What is the purpose for short term neural control?
1. Maintain MAP by altering blood vessel diameter
2. Alter blood distribution to organs in response to specific demands
89
What are factors are involved during reflex arcs?
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
What is the cardiovascular center?
Clusters of sympathetic neurons in medulla oversee changes in CO and blood vessel diameter
91
What does the cardiovascular center consists of?
Cardiac and vasometer center
92
What does the vasomotor center achieve?
Sends steady impulses via sympathetic efferents to blood vessels → moderate constriction called vasomotor tone
93
What are the receiving inputs of the cardiovascular center?
1. Baroreceptors
2. Chemoreceptors
3. Higher brain centers
94
Where are baroreceptors located?
1. Carotid sinuses
2. Aortic arch
3. Walls of large arteries of neck and thorax
95
What is the purpose for baroreceptors?
1. Inhibits vasomotor and cardioacceleratory centers, causing arteriolar dilation and venodilation
2. Stimulates cardioinhibitory center
3. Decreases blood pressure
96
How does baroreceptors decrease BP?
1. Arteriolar vasodilation
2. Venodilation
3. Decreased cardiac output
97
What occurs when MAP gets low?
Reflex vasoconstriction → increased CO → increased blood pressure
98
What is an example of baroreceptors when MAP is low?
Baroreceptors of carotid sinus reflex protect blood to brain; in systemic circuit as whole aortic reflex maintains blood pressure
99
What are chemoreceptor reflexes?
Detect increase in CO2, or drop in pH or O2
100
How does chemoreceptor reflexes cause increased BP?
1. Signaling cardioacceleratory center → increase CO
2. Signaling vasomotor center → increase vasoconstriction
101
What is the purpose of the hypothalamus and cerebral cortex?
Modify arterial pressure via relays to medulla
102
What does the hypothalamus achieve in regards to blood?
1. Increases blood pressure during stress
2. Mediates redistribution of blood flow during exercise and changes in body temperature
103
What does short term regulation of hormonal controls change?
Changes in peripheral resistance
104
What does longterm regulation of hormonal controls change?
Changes in blood volume
105
How hormone regulations increase BP?
1. Epinephrine and norepinephrine from adrenal gland → increased CO and vasoconstriction
2. Angiotensin II stimulates vasoconstriction
3. High ADH levels cause vasoconstriction
106
How does hormone regulation lower BP?
Atrial natriuretic peptide causes decreased blood volume by antagonizing aldosterone
107
What is long term renal regulation?
Counteracts fluctuations in blood pressure by altering blood volume
108
What is an example of long-term mechanisms?
Renal regulation: baroreceptors quickly adapt to chronic high or low BP so are ineffective
109
How can kidneys regulate arterial BP?
1. Direct renal mechanism
2. Indirect renal (RAAS mechanism)
110
What is direct mechanisms?
Alter blood volume independently of hormones
111
How does direct mechanism alter blood volume?
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
What does indirect mechanism achieve?
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
What are the functions of angiotensin II?
Increases blood volume by causing vasoconstriction
114
How does angiotensin II increase blood volume?
1. Stimulates aldosterone
2. Cause ADH release
3. Triggers hypothalamic thirst center
115
What factors would we monitor of circulatory effect?
1. Vital signs
2. Pulse
3. Radial pulse
4. Pressure points
116
What do vital signs monitor?
1. Pulse
2. Blood pressure
3. Respiratory rate
4. Body temperature
117
What does pulse monitor?
Pressure wave caused by expansion and recoil of arteries
118
Where is the radial pulse?
Wrist
119
What are pressure points?
Where arteries close to body surface that can be compressed to stop blood flow
120
How is systemic arterial BP measured?
Sphygomanometer
121
How is systolic pressure measured?
Pressure when sounds first occur as blood starts to spurt through artery
122
How is diastolic pressure measured?
Pressure when sounds disappear because artery no longer constricted; blood flowing freely
123
What are the variables that can change BP?
1. Transient elevations
2. Age
3. Sex
4. Weight
5. Race
6. Mood
7. Posture
124
What is hypertension?
High BP: 130/80 or higher
125
What is prehypertension?
Values elevated but not yet in hypertension range
126
How does prolonged hypertension cause disease?
Heart must work harder → myocardium enlarges, weakens, becomes flabby
127
What is primary hypertension?
1. No underlying cause identified
2. No cure but can be controlled
128
What is secondary hypertension?
1. Due to identifiable disorders such diseases
2. Treatment focuses on correcting underlying cause
129
What is hypotension?
Low BP: less than 90/60
130
What is orthostatic hypotension?
Temporary low BP and dizziness when suddenly rising from sitting and reclining
131
What is chronic hypotension?
Hint of poor nutrition and warning sign for Addison’s disease or hypothyroidism
132
What is acute hypotension?
Important sign of circulatory shock; threat for surgical patients and those in ICU
133
What is the importance of tissue perfusion?
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
What vessel has the fastest velocity?
Aorta
135
What vessel has the slowest velocity?
Capillaries
136
What happens to the velocity when blood enters the veins?
Increases
137
What is autoregulation?
Automatic adjustment of blood flow to each tissue relative to its varying requirements
138
How is autoregulation controlled?
Controlled intrinsically by modifying diameter of local arterioles feeding capillaries
139
What are the types of autoregulation?
1. Metabolic
2. Myogenic
140
What is metabolic autoregulation?
Vasodilation of arterioles and relaxation of precapillary sphincters
141
What trigger metabolic control?
1. Declining tissue O2
2. Substances from metabolically active tissues
142
What are the effects of metabolic controls?
1. Relaxation of vascular smooth muscle
2. Release of nitric oxide by endothelial cells
143
What is the difference between endothelins and inflammatory chemicals?
1. Endothelins are potent vasoconstrictors
2. In: cause vasodialtion
144
What is myogenic autoregulation?
Myogenic responses keep tissue perfusion constant despite most fluctuations in systemic pressure
145
How do vascular smooth muscle respond to stretch?
1. Passive
2. Reduced
146
What is the difference between passive and reduced stretch?
1. Passive: promotes increased tone and vasoconstriction
2. Reduced: Promotes vasodilation and increases blood flow to the tissues
147
What is long term autoregulation?
Occurs when short-term autoregulation cannot meet tissue nutrient requirements
148
What is angiogenesis?
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
What is vasomotion?
Slow intermittent flow that reflects on/off opening and closing of precapillary sphincters
150
What can diffuse across the concentration gradient?
O2 and nutrients from blood to tissues
CO2 and metabolic wastes from tissues to blood
151
How do lipid soluble molecules diffuse through capillaries?
Endothelial membranes
152
How do water-soluble solutes pass through the capillaries?
Clefts and fenestrations
153
How do proteins pass through capillaries?
Actively transported in pinocytotic vesicles or caveolae
154
What is bulk flow?
Fluid leaving capillaries at arterial end and returns to blood at venous end
155
What are the opposing forces that drive fluid flow?
1. Hydrostatic pressure
2. Colloid osmotic pressures
156
What are the 2 hydrostatic pressures?
-
1. Capillary blood pressure
2. Interstitial fluid hydrostatic pressure
157
What is capillary blood pressure?
Forces fluids through capillary walls
Greater pressure at arterial end
158
What is Interstitial fluid hydrostatic pressure?
Pressure that would push fluid into vessels
159
What are the 2 colloid osmotic pressures?
1. Capillary colloid osmotic pressure (oncotic)
2. Interstitial fluid osmotic pressure
160
What is capillary colloid osmotic pressure (oncotic)?
Created by nondiffusible plasma proteins, which draw water toward themselves
161
What is interstitial fluid osmotic pressure?
Low (~1 mm Hg) due to low protein content
162
What is net filtration pressure?
The interactions of flow out the arterial end and in the venous end
163
What causes circulatory shock?
1. Blood vessels inadequately filled
2. Blood cannot circulate normally
3. Inadequate blood flow to meet tissue needs
164
What is hypovolemic shock?
Shock from large-scale blood loss
165
What is vascular shock?
Extreme vasodilation and decreased peripheral resistance
166
What is cardiogenic shock?
An inefficient heart cannot sustain adequate circulation
