Chapter 20 Flashcards
1
Q
Name the layers of veins and arteries
A
tunica Interna
Tunica media
Tunica externa
2
Q
Which is the innermost layer of the tunicas?
A
Tunica interna
3
Q
Which is the middle layer of the tunicas?
A
tunica media
4
Q
Which is the outermost layer of the tunics?
A
tunica externa
5
Q
Explain the anatomy and physiology of the tunica interna
A
Lines the blood vessel and is exposed to blood.
Simple squamous endothelial overlying basement membrane and sparse layer of loose connective tissue allows rapid exchange.
Acts as a selectively permeable barrier
secretes chemicals that Stimulate vasodilation and constriction
6
Q
Explain the anatomy and physiology of the tunica media
A
middle layer
Consists of smooth muscle collagen and elastic tissue.
Strengthens blood vessels and prevents blood pressure from rupturing them
Regulates diameter of the blood vessel
Pump of the blood vessel
7
Q
Explain the anatomy and physiology of the tunica externa
A
outermost layer
Loose connective tissue that often merges with neighboring blood vessels, nerves and organs
Anchors vessel and provides passage for nerves and lymphatic vessels
Vasa vasorum, small vessels that supply blood to larger vessels
8
Q
What are vasa vasorum
A
small blood vessels found in the tunica externa that supply the larger blood vessels with blood
9
Q
What is the difference between the anatomy of veins and arteries?
A
The tunica media of the arteries are much thicker than the tunica media of the veins
10
Q
Place the following in the correct order
Large vein Conducting artery Venule Capillary Distributing,medium artery Medium vein Arteriole
A
conducting,large artery Distributing, medium artery Arteriole Capillary Venule Medium vein Large vein
11
Q
Why are arteries sometimes called resistance vessels
A
because of their strong resilient tissue structure
12
Q
What are the size classifications of arteries?
A
Conducting arteries, large
Distributing arteries, medium
Arteriole small
Metarterioles
13
Q
Name some of the conducting elastic large arteries
A
aorta Common carotid Subclavian Pulmonary trunk Common iliac
14
Q
Explain physiology of conducting elastic artery
A
expand during systole, recoil during diastole.
Expansion takes pressure of smaller downstream vessels
Recoil maintains pressure during relaxation and keeps pressure flowing
15
Q
Explain anatomy of conducting arteries
A
have a layer of elastic tissues internal elastic laminate at the border between lamina internal and media
16
Q
Name some of the distributing arteries
A
brachial
Femoral
Renal
Splenic
17
Q
Explain anatomy of distributing arteries
A
smooth muscle layers constitute three fourths of wall thickness
18
Q
Explains the physiology of distributing arteries
A
Distributes blood to specific organs
19
Q
Name the resistance arteries
A
arterioles
20
Q
Explain the physiology of resistance arteries
A
control amount of blood to various organs
21
Q
Explain the anatomy of resistance arteries
A
thicker tunica media in proportion to their lumen than large arteries and very little tunica externa
22
Q
What are metarterioles
A
short vessels that link Arteriole to capillaries
Muscle cells form pre capillary sphincter around the entrance to the artery
23
Q
What is the function of the pre capillary sphincter?
A
to direct blood towards the tissue by opening or to constrict, directing blood away and along the thoroughfare channel
24
Q
What is an aneurysm?
A
weak point in artery or heart wall
Forms a thin wall bulging sac that pulsates with each
heartbeat and may rupture at any time
25
What is a dissecting aneurysm?
When blood accumulates between the tunica of an artery and separates them. Usually because of degeneration of tunica media
26
What are the most common sites of aneurysms.
abdominal aorta
Renal arteries
Arterial circle at base of brain
27
what are the causes if an aneurysm?
Atherosclerosis and hypertension.
Congenital weakness of blood vessels
Trauma
Bacterial infections
28
What is the function if chemoreceptors?
detect fluctuations in PH usually due to CO2 fluctuations
29
What are arterial sense organs
sensory structures in walls of major vessels that monitor blood pressure and chemistry. They transmit I formation to the brainstem to regulate heart rate, blood pressure, vessel diameter and respiration
30
What is the function of baroreceptors?
Detect fluctuations in blood pressure
31
What are the carotid sinuses?
```
baroreceptors
In walls of internal carotid artery
Monitor blood pressure
Transmit signals through glossopharyngeal nerve
Allow baroreflex
```
32
What are carotid bodies
chemoreceptors
Oval bodies near branch of common carotids
Monitor blood chemistry
Transmit signals through glossopharyngeal nerve to brainstem respiratory centers
Adjust respiratory rate to stabilize PH CO2 and O2
33
What are aortic bodies
chemoreceptors
One to three bodies in aortic arch
Innervated by vagus nerve
34
Explain how the composition of capillary walls differs from that of other blood vessels.
Capillary walls consist only of endothelial and basal laminar. This makes exchange more rapid as they are the business end of the cardiovascular system.
35
What are the three types of capillaries?
Continuous capillaries
Fenestrated capillaries
Sinusoid/noncontinuous
36
Explain the anatomy and physiology of a continuous Capillary
occur in most tissues
Endothelial cells have tight junctions forming a continuous tube with intercellular clefts.
Because the clefts are so small, they allow only passage of the smallest solutes such as water and glucose.
Pericytes, peripheral to the endothelial cells wrap around the capillaries and contain the same contractile protein as muscle so they can contract and regulate blood flow.
37
Explain the anatomy and physiology of a fenestrated Capillary
found in organs where rapid absorption or filtration is needed. The endothelial cells are rich with filtration pores called fenestrations. Spanned by a very thin glycoprotein layer and allow passage of only small molecules.
38
Explain the anatomy and physiology of a sinusoid
Have large fenestrations that can allow entire cells, proteins such as albumins and clotting factors to pass through them.
39
Most common site of a fenestrated capillary
kidneys and small intestine
40
Most common site of a sinusoid
liver, bone marrow and spleen
41
How many capillaries make up a capillary bed
a network of 10-100
42
What are capillary beds supplied by?
A single arteriole or metarteriole
43
At the distal end of the capillary bed...
capillaries transition to venules or drain into the thoroughfare channel
44
How is bloodflow through the capillary bed controlled?
The control of bloodflow through the capillary bed involves constriction of arterioles that are upstream from the capillaries. Bloodflow is usually dependent upon the need of tissues or organs. Once the blood reaches the capillary bed, precapillary sphincters control flow. When sphincters are relaxed, capillaries are well perfused with blood. When sphincters contract, they constrict entry to the capillary and blood continues along the thoroughfare channel.
45
Where is the majority of blood found and what is the percentage?
Veins
| 54%
46
what are postcapillary venules?
the smallest veins
47
explain the anatomy and physiology of postcapillary venules
More porous than capillaries so also exchange fluid with surrounding tissues
Tunica interna with a few fibroblasts and no muscle fibers
most leukocytes emigrate from the bloodstream through venule walls
48
What are muscular venules?
veins that are up to 1mm in diameter
have one or two layers of smooth muscle in tunica media
thin tunica externa
49
What are medium veins?
veins up to 10mm in diameter
Thin tunica media and thick tunica externa
Tunica interna forms venous valves
50
What are varicose veins?
Blood pools in the lower legs of people who stand for long periods stretching the veins
cusps of the valves pull apart in enlarged superficial veins further weakening
blood backflows and further extends the vessels
51
What are venous sinuses?
Veins with especially thin walls. large lumens and no smooth muscle.
Not capable of vasomotor responses
52
Name the types of venous sinuses
Dural venous sinus and coronary sinus of the heart
53
What are large veins?
veins with a diameter of 10mm and above
contain some smooth muscle in all three tunics
Thin tunica media with moderate amount if smooth muscle
Tunica externa is the thickest layer containing longitudinal bundles of smooth muscle
54
Name some large veins
Venae Cavae, Pulmonary veins, internal jugular veins and renal veins
55
What are hemorrhoids?
Varicose veins of the anal canal
56
Common causes of varicose veins
Hereditary weakness, obesity and pregnancy
57
What are the circulatory routes?
Simple
Portal system
Anastomoses
58
Describe the simple circulatory route
Heart-arteries-arterioles-capillaries-venules-veins
| Passes through only one set of capillaries from when it leaves the heart and returns
59
Describe the Portal system
Passes through two consecutive capillary beds between leaving the heart and returning
60
Anastomosis
Convergence point between 2 vessels other than capillaries.
61
Types of anastomosis
Arteriovenous (shunt)
Venous anastomosis
Arterial anastomosis
62
Arteriovenous anastomosis
Artery flows directly into vein, bypassing capillaries
63
venous anastomosis
most common
one vein empties directly into another
reason vein blockage is less serios than arterial blockage
64
Arterial anastomosis
```
2 arteries merge
provides collateral (alternative) routes of blood supply to a tissue
coronary circulation and common around the joints
```
65
Blood flow
The amount of blood flowing through an organ, tissue or blood vessel in a given time (mL/min)
66
Perfusion
the flow per given volume or mass of tissue in a given time (mL/min/g)
67
What is resting blood flow
5.25 L/min and is equal to cardiac output
68
Importance of blood flow
important for delivery of nutrients and O2 and removal of metabolic wastes
69
Hemodynamics
study of bloodflow
70
Formula for physical principles of blood flow
F(flow)= AP(difference in pressure)/R(resistance)
71
Principle of blood flow
The greater the pressure difference between two point the greater the flow.
The greater the resistance, the less flow
72
What is blood pressure?
The force that blood exerts against a vessel wall
73
How is blood pressure measured?
At the brachial artery of the arm using a sphygmomanometer
74
Which two pressures are recorded when determining blood pressure?
Systolic pressure
| Diastolic pressure
75
What is systolic pressure?
Peak arterial BP taken during ventricular contraction (Ventricular systole)
76
What is diastolic pressure?
minimum arterial pressure taken during ventricular relaxation (diastole) between heartbeats
77
Normal blood pressure for a young adult
120/75 mm Hg
78
What is pulse pressure?
Difference between systolic and diastolic pressure
79
why is pulse pressure important?
It is an important measure of driving force on circulation and of stress exerted on small arteries by pressure surges generated by the heart
80
What is mean arterial pressure
the mean pressure obtained by taking measurements at several intervals throughout the cardiac cycle
81
Blood flow in arteries is
pulsatile
82
Blood flow in capillaries and veins
flows at steady speed
83
BP rises with age - true or false
true
84
Why does blood pressure rise with age?
Arteriosclerosis- stiffening of arteries
| atherosclerosis- build up of lipid deposits
85
What is hypertension?
chronic resting blood pressure of over 140/90
| resulting in weakening of arteries, aneurysms and atherosclerosis
86
What is hypotension
Chronic resting BP of less than 120/75 usually caused by blood loss, dehydration and anemia
87
What is arteriosclerosis
stiffening of arteries causing blood pressure to rise
88
What is atherosclerosis
build up of lipid deposits resulting in clogging of artery
89
What are the determining factors of Blood pressure?
Cardiac output, blood volume and resistance to flow
90
How is blood volume regulated
kidneys
91
what happens to blood pressure as we get further from the heart?
it gets lower
92
Where is blood pressure highest?
Aorta/ Arterial system
93
Where is blood pressure lowest?
Venae Cavae/Venous system
94
What is peripheral resistance?
The opposition of flow that blood encounters in vessels away from the heart
95
What are the three variables in peripheral resistance?
Blood viscosity
Vessel length
Vessel radius
96
How does blood viscosity affect peripheral resistance?
RBC count and albumin concentration elevate viscosity slowing flow
Decreased viscosity with anemia and hypoproteinemia speeding up flow
97
How does vessel length affect peripheral resistance?
The farther liquid passes through a tube, the more cumulative friction it encounters. Pressure and flow therefore decline with distance
98
How does Vessel radius affect peripheral resistance?
Vasoconstriction and vasodilation expand and contract vessel radius markedly affecting blood velocity.
99
Which factor is the most powerful influence over flow?
Vessel radius
100
What are vasoreflexes?
changes in vessel radius controlled by the tunica media
101
Explain laminar flow
Blood in the centre experiences less friction than blood in the periphery against vessel walls. So the wider the vessel the less friction and the greater the flow
102
Why does blood velocity decrease between the aorta and the capillaries?
Greater distance, more friction to reduce speed
Smaller radii of arterioles and capillaries offers more resistance
Farther from the heart, the number of vessels and their total cross sectional area become greater and greater
103
Why does blood velocity increase again between capillaries and vena cava?
Veins are larger so create less resistance than capillaries
104
Which vessels are the most significant point of contract over peripheral resistance and flow?
Arterioles because they are positioned on proximal end of capillary beds and best positioned to regulate flow into the capillaries
more muscular in proportion to their diameter
outnumber any other type of artery
105
How much of peripheral resistance do arterioles produce
Half
106
what are the three ways of controlling vasomotor activity?
Local control
Neural control
Hormonal control
107
List the local methods of vasomotor control
Autoregulation
Vasoactive chemicals
reactive hyperemia
angiogenesis
108
what is autoregulation?
The ability of tissues to regulate their own blood supply.
metabolic theory of autoregulation:
inadequately perfused tissues results in wastes accumulating stimulating vasodilation. bloodstream delivers o2 and removes metabolites
vessels constrict
109
What are vasoactive chemicals in local control?
substances secreted by platelets, endothelial cells and perivascular tissue to stimulate vasomotor responses
110
Examples of vasoactive chemicals
Histamine
Bradykinin
prostaglandins
111
What is reactive hyperemia
Local vasomotor control. If blood supply is cut off then restored, flow increases above normal
112
What is angiogenesis
growth of new blood vessels controlled by growth factors and inhibitors
113
Where does angiogenesis occur
regrowth of uterine lining
around coronary artery obstructions
exercised muscle
malignant tumors
114
Which Nervous systems does vasomotor control concern?
Central and autonomic nervous system (ANS)
115
Where in the brain is the vasomotor centre located?
Medulla oblongata
116
does the medulla oblongata exert sympathetic or parasympathetic control over blood vessels?
sympathetic
117
Does the vasomotor centre stimulate all vessels to constrict?
Most, but it dilates vessels in cardiac muscle to meet demands of exercise
118
The vasomotor centre is the integrating centre for which autonomic reflexes?
Baroreflexes
Chemoreflexes
Medullary ischemic reflex
119
what is a baroreflex?
An automatic negative feedback response to change in blood pressure detected in carotid artery
glossopharyngeal nerve sends the signal to the brain
Govern short term regulation of BP
120
What is a chemoreflex?
an automatic response to changes in blood chemistry
| PH, Co2 and O2 especially
121
What are chemoreceptors?
aortic bodies and carotid bodies located in the aortic arch, subclavian arteries and external carotid arteries
122
What is the primary role of chemoreceptors?
adjust respiration in response to changes in blood chemistry
123
What is the secondary role of chemoreceptors?
vasoreflexes
124
What is the medullary Ischemic reflex?
automatic response to drop in blood perfusion of the brain.
125
How is medullary Ischemic reflex triggered?
Medulla oblongata monitors its own blood supply and activates corrective reflexes when ischemia is detected
126
What other factors can trigger the vasomotor centre?
stress
anger
arousal
127
what is hormonal control of vasomotor activity?
influence on blood pressure with either vasoactive effects or regulation water balance
128
What is Angiotensin II?
A potent vasoconstrictor
raises blood pressure and volume
promotes NA+ and water retention by kidneys
129
What is Atrial netriuretic peptide (ANP)
Increases urinary sodium excretion
reduces blood volume and pressure
promotes vasodilation
130
What is ADH?
promotes water retention and raises BP
| pathologically high concentrations are aslo a vasoconstrictor
131
What is the effect of epinephrine and norepinephrine on blood vessels?
They promote Vasoconstriction of most blood vessels and vasodilation of the cardiac muscle vessels at the same time
132
what are the two main purposes of vasoreflexes?
General control of BP
| Routing blood from one region to another
133
How is blood flow rerouted in response to needs?
Arteries shift blood flow with changing needs
134
what is capillary exchange?
2 way movement of fluid across capillary walls
135
Name some of the things being exchanged in capillary exchange
water oxygen glucose immunoacids carbon dioxide wastes
136
Name the routes chemicals pass through capillary walls
endothelial cytoplasm
intercellular clefts between endothelial cells
filtration pores of the fenestrated capillaries
137
name the mechanisms involved in capillary exchange
Diffusion
Transcytosis
filtration
Reabsorption
138
Which is the most important form of capillary exchange?
Diffusion
139
What happens in capillary diffusion?
Glucose and O2 being more concentrated in the blood diffuse out of the blood and in to the tissue fluid.
Co2 and other waste being more concentrated in tissue fluid diffuse in to the blood
140
Which substances can pass through the plasma membrane during capillary diffusion?
Lipid soluble substances
141
Which substances must pass through filtration pores or intercellular clefts during capillary diffusion?
Glucose and electrolytes
142
Which substances cannot enter the blood via capillary diffusion?
large particles such as proteins
143
Which substances must be exchanged via transcytosis during capillary exchange?
fatty acids, albumin and some hormones such as albumin
144
What is the process of filtration in capillary exchange
Fluid filters out of the arterial end of the capillary
145
What is the process of reabsorption in capillary exchange?
fluid osmotically re-enters the capillary at the venous end
146
What is Blood hydrostatic pressure?
It drives fluid out of the capillary. It is high on the arterial end and low on the venous end
147
What is Colloid osmotic pressure (COP)
draws fluid in to the capillary . Results from plasma proteins being more in the blood
148
What is oncotic pressure ?
blood cop-tissue cop
149
What percentage of fluid to capillaries reabsorb?
85%
150
What happens to the 15% of fluid not reabsorbed by capillaries?
it is absorbed by the lymphatic system and returned to the blood
151
What is net filtration pressure (NFP)?
hydrostatic pressure - COP
152
At which end of the capillary bed does filtration occur?
Arterial end
153
At which end of the capillary bed does reabsorption occur?
Venous end
154
What is Edema?
accumulation of excess fluid in a tissue as a result of fluid entering a tissue faster than it is absorbed
155
What are the primary causes of edema?
Increased capillary filtration
Reduced capillary absorption
obstructed lymphatic drainage
156
What is tissue necrosis?
O2 delivery and waste removal impaired
157
What is Pulmonary edema
suffocation threat
158
what is Cerebral edema
Headaches, seizures, nausea and coma
159
What is Severe edema/circulatory shock?
Excess fluid in tissue spaces causing low blood volume and low blood pressure
160
What is venous return?
The flow of blood back to the heart
161
What does venous return rely on?
```
Pressure gradient
Gravity
skeletal muscle pump
thoracic pump
cardiac suction
```
162
What is the significance of pressure gradient in venous return?
Blood pressure is the most important force in venous return
163
What is the role of gravity in venous return?
drains blood from head and neck
164
What is the role of the skeletal muscle pump in venous return?
located in the limbs
| contracting muscle squeezes blood out of the compressed part of the vein
165
What is the role of the thoracic (respiratory) pump in venous return?
during inhalation, the thoracic cavity expands and thoracic pressure decreases, abdominal pressure increases, forcing blood upwards
166
What is the role of cardiac suction in venous return?
expanding of the arterial space creates suction and assists in venous return
167
Name some of the ways exercise increases venous return
Heart beats faster and harder increasing Cardiac output and BP
Vessels of muscles lungs and heart dilate
Increased respiratory rate means increased action of thoracic pump
increased activity of skeletal muscle pump
168
What is venous pooling?
pooling of blood that is not returned via venous return due to inactivity
169
What is circulatory shock?
any state in which cardiac output is insufficient to meet the body's needs
170
what are the types of circulatory shock?
Cardiogenic shock
| Low venous return
171
What is cardiogenic shock?
Inadequate pumping of the heart (MI)
172
What is Low venous return? (LVR)
Cardiac output is too low because too little blood is returning to the heart
173
what are the three principal forms of LVR shock?
```
Hypovolemic shock
Obstructed venous return shock
Venous pooling (Vascular shock)
```
174
What are the causes of Hypovolemic shock?
Loss of blood volume, trauma, burns, dehydration
175
what is the cause of obstructed venous return shock?
Tumor or aneurysm obstructing a vein
176
What are the causes of venous pooling (vascular) shock?
Long periods of standing, sitting or widespread vasodilation
177
What is Neurogenic shock?
Loss of vasomotor tone leading to vasodilation
178
What is septic shock?
Bacterial toxins trigger vasodilation and increased capillary permeability
179
What is anaphylactic shock?
Severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability
180
What are the responses to circulatory shock?
Compensated shock
| Decompensated shock
181
What is compensated shock?
several homeostatic mechanisms bring about spontaneous recovery
182
What is decompensated shock?
When compensation fails
Life threatening positive feedback loops occur
can be fatal
183
Blood flow to the brain fluctuates ----------------than that of any other organ
Less
184
What happens to the brain after seconds of blood deprivation?
loss of consciousness
185
What happens to the brain after 4-5 minutes of blood deprivation?
irreversible brain damage
186
Which organ regulates blood flow to the brain?
The brain
187
How does the brain regulate blood flow?
Cerebral arteries dilate as systemic BP drops and constrict as BP rises
188
What is the main chemical stimulus for brain regulation of blood flow?
PH
189
What is hypercapnia?
Co2 levels increase in brain, PH decreases triggering vasodilation
190
What is hypocapnia?
raised PH stimulates vasoconstriction (occurs for example with hyperventilation)
191
What is a stroke (CVA)?
Sudden death of brain tissue caused by ischemia
192
What are the two main circulatory pathways?
Pulmonary circulation
| Systemic circulation
193
What is the Pulmonary circulation?
A short loop that runs from heart to lungs and back to heart
194
What is the systemic circulation?
A long loop to all parts of the body and back to the heart
195
Which ventricle belongs to the systemic circuit
Left
196
which atrium receives blood from the systemic circuit?
Right
197
which ventricle has the thickest myocardium?
Left
