Chapter 19: Blood Vessels Flashcards
0
Q
Capillaries :
A
Contact tissue cells; directly serve cellular needs
1
Q
Arteries do what?
A
Carry blood away from the heart; oxygenated except for pulmonary circulation and umbilical vessels of fetus
2
Q
Veins:
A
Carry blood toward heart
3
Q
Lumen :
A
Central blood containing space
4
Q
Capillaries have which type of tissue?
A
Endothelium with sparse basal lamina
5
Q
Where is the subendothelial layer found?
A
In vessels larger than 1 mm ; connective tissue basement membrane
6
Q
Tunica media:
A
Smooth muscle and sheets of elastin
- sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels
- influence blood flow and blood pressure
7
Q
Tunica externa (tunica adventitia):
A
Collagen fibers protect and reinforce ; anchor to surrounding structures
- contains nerve fibers, lymphatic vessels
- vaso vasorum of larger vessels nourishes external layer
8
Q
Elastic arteries:
A
▪️large thick walled arteries with elastin in all three tunics
▪️aorta and it’s major branches
▪️large lumen offers low resistance
▪️inactive in vasoconstriction
▪️act as pressure reservoirs– expand and recoil as blood ejected from heart
-smooth pressure downstream
9
Q
Muscular arteries:
A
▪️distal to elastic arteries. Deliver blood to body organs
▪️thick tunica media with more smooth muscle
▪️active in vasoconstriction
10
Q
Arterioles:
A
▪️smallest arteries
▪️lead to capillary beds
▪️control flow into capillary beds via vasodilation and vasoconstriction.
11
Q
Capillaries:
A
▪️microscopic blood vessels
▪️walls of thin tunica intima. One cell thick
▪️pericytes : helps stabilize their walls and control permeability
▪️diameter allows only single RBC to pass at a time
12
Q
Capillaries are in all tissues EXCEPT?
A
Cartilage
Epithelia
Cornea and lens of eye
13
Q
What is the function of capillaries?
A
Exchange of gases, nutrients, wastes, hormones between blood and interstitial fluid
14
Q
What are the 3 structural types of capillaries ?
A
Continuous capillaries
Fenstrated capillaries
Sinusoid capillaries
15
Q
Continuous capillaries:
A
▪️abundant in skin and muscles :
-tight junctions connect endothelial cells
- intercellular clefts allow passage of fluids and small solutes
▪️continuous capillaries of brain are unique :
- tight junctions complete, forming blood brain barrier
16
Q
Fenstrated capillaries:
A
▪️some endothelial cells contain pores (fenstrations )
▪️more permeable than continuous capillaries
▪️function in absorption or filtrate formation (small intestines, endocrine glands, kidneys)
17
Q
Sinusoid capillaries:
A
▪️fewer tight junctions; usually Fenstrated ; larger intercellular clefts; large lumens
▪️blood flow sluggish– allows modification.
- large molecules and blood cells pass between blood and surrounding tissues
▪️FOUND ONLY IN LIVER, BONE MARROW, SPLEEN, ADRENAL MEDULLA
▪️macrophages in lining to destroy bacteria
18
Q
What is microcirculation in capillary beds?
A
▪️interwoven network of capillaries between Arterioles and venules
▪️terminal Arteriole ➡️ metarteriole
▪️metarteriole continuous with thoroughfare channel
▪️thoroughfare channel ➡️post capillary venule that drains bed
19
Q
Vascular shunt:
A
Metarteriole–thoroughfare channel
-directly connects terminal Arteriole and post capillary venule
20
Q
True capillary:
A
- 10 to 100 exchange vessels per capillary bed
- branch off metarteriole or terminal Arteriole
21
Q
How is the blood flow through capillaries?
A
▪️true capillaries normally branch from metarteriole and return to thoroughfare channel
▪️pew capillary sphincters regulate blood flow into true capillaries.
Blood may go into true capillaries or to shunt
▪️regulated by local chemical conditions and vasomotor nerves
22
Q
Venous system- venules:
A
▪️formed when capillary beds unite.
-smallest post capillary venules
-very porous ; allow fluids and WBC into tissues
-consists of endothelium and a few pericytes
▪️larger venules have one or two layers of smooth muscle cells
23
Q
Veins:
A
▪️formed when venules converge
▪️have thinner walls, larger lumens compared with corresponding arteries
▪️blood pressure lower than in arteries
▪️thin tunica media; thick tunica externa of collagen fibers and elastic networks
▪️called capacitance vessels (blood reservoirs ) ; contain up to 65% of blood supply
24
Vein adaptions ensure return of blood to heart despite low pressure:
▪️large - diameter lumens offer little resistance
▪️venous valves prevent backflow of blood. Most abundant in veins of limbs
▪️venous sinuses : flattened veins with extremely thin walls (coronary sinus of heart)
25
Vascular anastomoses :
▪️interconnections of blood vessels
▪️arterial anastomoses provide alternate pathways (collateral channels) to given body region.
- common at joints, in abdominal organs , brain, and heart NONE IN retina, kidneys , spleen
▪️Vascular shunts f capillaries are examples of arteriovenous anastomoses
▪️venous anastomoses are common
26
Blood flow:
▪️volume of blood flowing through vessel, organ, or entire circulation in given period.
- measured as ml/min
- equivalent to cardiac output for entire vascular system
- relatively constant when at rest
- varies widely through individual organs based on needs
27
Resistance(peripheral):
▪️opposition to flow
| ▪️measure of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation
28
What are the three important sources of resistance?
Blood viscosity
Total blood vessel length
Blood vessel diameter
29
Factors that remain constant in resistance?
▪️blood viscosity : the stickiness of blood due to formed elements and plasma proteins.
-increased viscosity = increased resistance
▪️blood vessel length : longer vessel = greater resistance encountered
30
Does blood vessel diameter have a great influence on resistance?
Yes
31
What are major determinants of peripheral resistance?
Small diameter Arterioles
32
Do abrupt changes in diameter or fatty plaques from atherosclerosis dramatically increase resistance ?
Yes.
- disrupt laminar flow and cause turbulent flow.
- irregular fluid motion ➡️ increased resistance
33
Relationship better bold flow, blood pressure, and resistance ?
- if pressure increases = blood flow increase
| - if R increase = blood flow decrease
34
Where is systemic blood pressure the highest?
In aorta
35
Systemic pressure declines throughout pathway. True or false.
True
36
In systemic pressure what is the pressure in the right atrium?
0mm Hg
37
Where is the steepest drop of systemic pressure occur?
Arterioles
38
Arterial blood pressure reflects what two factors?
Elasticity
And
Volume of blood forced into them at any time
39
What is the blood pressure near the heart called ?
Pulsatile
40
Systolic pressure:
Pressure exerted in aorta during ventricular contraction. Ex 120mm Hg
41
Diastolic pressure:
Lowest level of aortic pressure. Ex: 80mm Hg
42
Pulse pressure:
Is the difference between systolic and diastolic pressure (throbbing of arteries)
43
Mean arterial pressure:
Pressure that propels blood into tissues
| - MAP = diastolic pressure + 1/3 pulse pressure
44
Pulse pressure and MAP both decline with increasing distance from heart. True or false ?
True
45
Where does the capillaries blood pressure range?
17 to 35 mm Hg
46
Venous blood pressure:
Small pressure gradient : 15 mm Hg
| -low reassure due to cumulative effects of peripheral resistance
47
What are the 3 factors that aid in venous return?
Muscular pump
Respiratory pump
Venoconstriction
48
Muscular pump:
Contraction of skeletal muscles "milks" blood toward heart; valves prevent backflow
49
Respiratory pump:
Pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
50
Venoconstriction:
Under sympathetic control pushes blood toward heart
51
Maintaining blood pressure requires:
Cooperation of heart, blood vessels, and kidneys
52
Main factors influencing blood pressure:
- cardiac output
- peripheral resistance
- blood volume
53
Cardiac output is determined by what?
Venous return , neural and hormonal controls
54
Resting heart rate maintained by what?
Cardioinhibitory center via parasympathetic vagus nerves
55
Stroke volume is controlled by what?
Venous return
56
During stress, cardioacceleratory center increases heart rate and stroke volume via sympathetic stimulation. True or false
True.
| -ESV decreases and MAP increases
57
He does short term neural and hormonal control blood pressure?
Counteract fluctuations in blood pressure by altering peripheral resistance and CO
58
Long term renal regulation intros of blood pressure:
Counteracts fluctuations in blood pressure by altering blood volume
59
Neural controls of peripheral resistance:
Maintain MAP by altering blood vessel diameter
| -if low blood volume all vessels constricted except those in heart and brain
60
How do short term neural mechanisms control blood pressure?
Operate via reflex arcs that involve :
▪️baroreceptors
▪️cardiovascular center of medulla
▪️vasomotor fibers to heart and vascular smooth muscle
▪️sometimes input from chemoreceptors and higher brain centers
61
Cardiovascular center:
▪️clusters of sympathetic neurons on medulla oversee changes in CO and blood vessel diameter
▪️consists of cardiac centers and vasomotor center
▪️vasomotor center sends steady impulses via sympathetic efferent story blood vessels ➡️ moderate constriction called vasomotor tone
▪️receives inputs from baroreceptors, chemoreceptors, and higher brain centers
62
Where are baroreceptors located?
Carotid sinuses
Arortic arch
Walls of large arteries in neck and thorax
63
Increased blood pressure stimulates baroreceptors to do what?
To increase input to vasomotor center.
- inhibits vasomotor and cardioacceleratory center causing arteriolar dilation and venodilation
- stimulates cardioinhibitory center
- decreased blood pressure
64
Short term mechanism: baroreceptors decrease in blood pressure due to ?
- Ateriolar vasodilation
- venodilation
- decreased cardiac output
65
Short term: chemoreceptors :
▪️chemoreceptors in aortic arch and large arteries of neck detect increase in CO2 or drop in pH or O2
▪️caused by increased blood pressure by:
-signaling cardioacceleratory center ➡️ increase CO
-signaling vasomotor center ➡️ increase vasoconstriction
66
Short term mechanism: influence of higher brain centers :
▪️reflexes in medulla
▪️hypothalamus and cerebral cortex can modify arterial pressure via relays to medulla
▪️hypothalamus increases blood pressure during stress
▪️hypothalamus mediates redistribution of blood flow during exercise and changes in body temperature
67
Short term mechanisms : hormonal controls:
- Short term regulation via changes in peripheral resistance
- long term regulation via changes in blood volume
68
Short term mechanisms : hormonal control increased blood pressure ?
- Epinephrine and norepinephrine from adrenal gland ➡️ increased CO and vasoconstriction
- angiotensin II stimulates vasoconstriction
- high ADH levels cause vasoconstriction
69
Short term mechanism : hormonal controls LOW blood pressure?
Atrial natriuretic peptide caused decreased blood volume by antagonizing aldosterone
70
Long term mechanism: renal regulation?
▪️baroreceptors quickly adapt to chronic high or low BP so are ineffective
▪️long term mechanisms control BP by altering blood volume via kidneys
▪️kidneys regulate arterial blood pressure:
1.direct renal mechanism
2.indirect real mechanism
71
What two mechanisms do kidneys use to regulate arterial blood pressure ?
Direct renal
| And indirect renal (renin-angiotensin-aldosterone)
72
Direct renal mechanism:
Alters bold volume independently of hormones.
- increase BP or blood volume causes elimination of more urine this reducing BP
- Decreased BP Or blood volume causes kidneys to conserve water, BP rises
73
Renin-angiotensin-aldosterone mechanism:
- Decrease ⬇️ arterial pressure = release of renin
- renin catalyzes conversion of angiotensin from liver to angiotensin I
- angiotensin converting enzyme especially from lungs converts to angiotensin I to angiotensin II
74
Functions of Angiotensin II?
```
▪️increase blood volume:
-stimulates aldosterone secretion
- causes ADH release
- triggers hypothalamic thirst center
▪️causes vasoconstriction directly increasing blood pressure
```
75
Systolic pressure is heard first when using a korotkoff and stethoscope?
Pressure when sounds first occur as blood starts to spurt through artery
76
Diastolic pressure heard when while using karotkoff and stethoscope?
Is pressure when sounds disappear because artery is no loner constricted , blood is flowing freely
77
Hypertension is classified by BP of what?
140/90 or higher
78
Prolonged hypertension may cause what?
Heart failure
Vascular disease
Renal failure
Stroke
79
Primary/essential hypertension:
▪️90% of hypertensive conditions
▪️no underlying caused identified
▪️no cure but can be controlled
80
Secondary hypertension:
-Due to identifiable disorders including obstructed renal arteries , kidney disease , and endocrine disorders such as hyperthyroidism and cushions syndrome
81
Hypotension:
Low blood pressure usually 90/60 mm Hg
82
Orthostatic hypotension :
Temporary low BP an dizziness when suddenly rising from sitting or reclining position
83
Chronic hypotension:
Hint of poor nutrition and warning sign for Addison's disease or hypothyroidism
84
Acute hypotension:
Important sign of circulatory shock ; threat for surgical patients and those in ICU
85
Tissue perfusion involved in:
▪️delivery of O2 and nutrients to and removal of wastes from tissue cells
▪️gas exchange (lungs)
▪️absorption of nutrients (digestive tract)
▪️urine formation
▪️rate of flow is precisely right amount to provide proper function
86
Velocity in blood flow is fastest where?
In aorta
87
Velocity of blood flow is slowest where?
In capillaries
88
What is auto regulation?
▪️automatic adjustment of blood flow to each tissue
▪️controlled intrinsically by modifying diameter of local Arterioles feeding capillaries
- independent of MAP which is controlled as needed to maintain constant pressure
▪️organs regulate own blood flow by caring resistance of own Arterioles
89
Two types of auto regulation?
Metabolic control
And
Myogenic control
90
Metabolic autoregulation control:
Vasodilation of Arterioles and relaxation of precapillary sphincters occur in response to
-declining tissue O2
-substances from metabolically active tissues (H+ , K + , adenosine , prostaglandins )
And inflammatory chemicals
91
Effects of metabolic autoregulation?
▪️effects : relaxation of vascular smooth muscle and release of NO (powerful vasodilator ) by endothelial cells
▪️endothelins: released from endothelium are potent vasoconstrictors
▪️NO and endothelins balanced unless blood flow inadequate , then NO wins
▪️inflammatory chemicals also cause vasodilation
92
Myogenic autoregulation controls:
▪️myogenic responses keep tissue perfusion constant despite most fluctuations in systemic pressure
▪️vascular smooth muscle responds to stretch :
-passive stretch (increase intravascular pressure) promotes tone and vasoconstriction
-reduced stretch promotes vasodilation and increases blood flow to the tissue
93
Angiogenesis :
Number of vessels to region increases and existing vessel enlarge
-common in heart when coronary easel occluded, or throughout body in people in high altitude areas
94
Blood flow: skeletal muscles :
- at ret myogenic and general neural mechanisms predominate - maintain ~ 1 L /min
- during muscle activity : local controls override sympathetic vasoconstriction
95
What is the constant blood flow to the brain?
Averages 750 ml/min
96
Brain blood flow: metabolic control:
Decreased pH of increased carbon dioxide caused marked vasodilation
97
Blood flow to brain: myogenic control:
- decreased MAP causes cerebral vessels to dilate
| - increased MAP. Causes cerebral vessels to constrict
98
Brain MAP below 60 mm Hg causes?
Syncope (fainting )
99
Brian MAP above 160 causes?
Cerebral edema
100
Blood flow through the skin:
- Supplies nutrients to cells (autoregulation in response to O2 needs)
- helps regulate body temperature (neurally controlled ) - primary function
- provides a blood reservoir (neurally controlled )
101
Blood flow to venous plexus we below skin surfaces regulate body temperature :
- Varies from 50 ml/min to 2500 ml/min , depending on body temp.
- controlled by sympathetic nervous system reflexes initiated by temperature receptors and central nervous system
102
Temperature regulation:
- Hypothalamic signals reduce vasomotor stimulation of skin vessels➡️
- warm blood flushes into capillary beds ➡️
- heat radiates from skin
103
Sweat causes vasodilation via_?
Bradykinin in perspiration
| - bradykinin stimulates NO release
104
As temperature decreases, blood is shunted into deeper more vital organs. True or false
True
105
Pulmonary circuit unusual:
- Pathway short
- arteries/Arterioles more like veins /venules (thin walled large lumen)
- arterial resistance and pressure are low (24/10 mm Hg)
106
The auto regutory mechanism is opposite in most tissues (lungs) :
Low O2 levels cause vasoconstriction ; high levels promote vasodilation
- allows blood flow to O2 rich areas of lungs
107
Blood flow: heart: during ventricular systole ??
Coronary vessels are compressed
- myocardial blood flow ceases
- stored myoglobin supplies sufficient oxygen
108
Blood flow : heart: during diastolic high aortic pressure forces blood through coronary circulation. True or false?
True
109
Blood flow: heart: at rest blood flow equals?
~ 250 ml/min ; control probably myogenic
110
During strenuous exercise, heart blood flow does what?
- Coronary vessels dilate in response to local acclimation of vasodilators
- blood flow may increase 3 or 4 times
- important --- cardiac cells use 65% of O 2 delivered so increased blood flow provides more O 2
111
Vaso motion (in capillaries):
Slow, intermittent flow
| -reflects on/off opening and closing of precapillary sphincters
112
Capillary exchange of respiratory gases and nutrients :
▪️diffusion down concentration gradients.
O2 and nutrients from blood to tissues.
CO2 and metabolic waste from tissues to blood
▪️lipid soluble molecules diffuse directly through endothelial membranes
▪️water soluble solutes pass through clefts and fenstrations
▪️larger molecules such as proteins are actively transported in pinocytotic vesicles or caveolae
113
Fluid leaves capillaries at arterial end; most returns to blood at venous end . True or false?
True.
| Extremely important in determining relative fluid volumes in blood and interstitial space
114
Capillary hydrostatic pressure:
Tend a to force fluids trough capillary walls
| - greater at arterial end (35 mm Hg) of bed than at venule end (17mm Hg)
115
Interstitial fluid hydrostatic pressure:
- Pressure that would push fluid into vessel
| - usually assumed to be zero because of lymphatic vessels
116
Capillary colloid pressure (oncotic) :
-Created by mom diffusable plasma proteins, which draw water tears themselves
~ 26 mm Hg
-interstitial fluid osmotic pressure
(Low ~ 1mm Hg due to low protein content )
117
Hypovolemic shock:
Results from large scale blood loss
118
Vascular shock:
Results from extreme vasodilation and decreased peripheral resistance
119
Cardiogenic shock:
Results when an inefficient heart cannot sustain adequate circulation.
120
Twhat are the two main circulations?
Pulmonary
| Systemic
121
Pulmonary circulation :
Short loop that runs from heart to lungs and back to heart
122
Systemic circulation :
Long loop to all parts of body and back to heart
123
The heart pumps blood by what week of development ?
4 th week
124
What determines whether the vessel becomes an artery or vein?
Vascular endothelial growth factor
125
What forms rudimentary vascular tubes ?
Blood islands guided by cues
126
Where does endothelial lining rise from?
Mesodermal cells in blood vessels
