Blood Vessels Flashcards
1
Q
Where are the arteries and arterioles located?
A
deep in the body for protection
2
Q
Which way do arteries flow?
A
carry blood away from the heart
3
Q
What are the types of arteries?
A
elastic and muscular arteries
4
Q
Elastic arteries characteristics
A
- Located close to heart
- Large diameter, lots of elastic fibers
5
Q
What is the function of elastic arteries?
A
maintain pressure during ventricular diastole
- pressure reservoir = storage
- pressure gradient)
6
Q
Elastic recoil
A
the ability of the arteries to expand and slowly return back to their original shape.
7
Q
What are examples of elastic arteries?
A
aorta, common carotid, subclavian, pulmonary
8
Q
Muscular arteries characteristics
A
- Smaller diameter than elastic
- Located further out from heart
- Contain more smooth muscle, therefore not as stretchy
- Thicker walls
- Change diameter using muscle
9
Q
Arterioles characteristics
A
Smaller than arteries
- Microscopic (CAN NOT SEE with naked eye)
Control blood flow to tissue
- Vasodilation
- Vasoconstriction
- Resistance vessels
10
Q
In what order do blood vessels go in regard to size?
A
large to small and back again
11
Q
What order do the blood vessels go in?
A
Arteries, arterioles, capillaries, venules, veins
12
Q
What are the three layers of a blood vessels?
A
- Tunica externa
- Tunica media
- Tunica intima
13
Q
What type of tissue is the tunica media composed of?
A
smooth muscle (helps with vaso- processes)
14
Q
What type of tissue is the tunica intima composed of?
A
endothelium tissue (simple squamous) and a basement membrane
15
Q
Arteries characteristics
A
Arteries have thicker walls so that:
* Lumen of arteries is smaller
* Under higher pressure
16
Q
Veins characteristics
A
- Veins have valves
- Under low pressure thus
- Prevents backflow
17
Q
Capillaries characteristics
A
Capillaries are composed of tunica intima
* Very thin walled
* For exchanges
* Smallest blood vessels
18
Q
What are the three types of capillaries?
A
- continuous capillaries
- fenestrated capillaries
- sinusoidal capillaries
19
Q
Continuous capillaries
A
- Most common
- Small gaps between
cells allow passage of
fluid & small solutes
20
Q
Fenestrated capillaries
A
Walls have pores
* Greater permeability
* Found in areas of
* High absorption (e.g.
intestines)
* Filtration (e.g.
kidney
21
Q
Sinusoidal capillaries
A
Very leaky
- Large gaps between
cells - Found in bone
marrow, liver, lymph
and some endocrine
tissue - Allow cells to cross
Blood flow is very
slow
22
Q
What do capillaries from?
A
capillary beds
23
Q
What controls blood flow in the capillaries/capillary beds?
A
pre-capillary sphincter
24
Q
What is vasomotion?
A
the change in diameter of the blood vessels
25
What is the metarteriole?
A metarteriole is a short micro vessel in the microcirculation that links arterioles and capillaries.
26
Veins characteristics
- Formed by joining of venules
* Return blood to heart
* Walls are very stretchy
* Under very low pressure
* Has valves that prevent backflow of blood
27
Veins act as what?
acts as a fluid reservoir: contains 60% of blood at rest
28
Define blood flow
volume of blood flowing through a
vessel, organ, or body per unit time (ml/min)
29
Define blood pressure
the force exerted on the walls of
vessels by the blood (mmHg)
30
How is blood pressure generated?
by the contraction of ventricles
31
Blood pressure is dependent on what?
blood volume
32
Pressure gradient
The tendency of blood to flow from an area of high to low pressure.
33
Where is pressure gradient the greatest and least?
Greatest near left ventricle, least in vena cavae
34
Define resistance
opposition to flow
35
What is friction in regards to blood vessels/blood flow?
Friction between blood and vessel wall
36
What are the three sources of resistance?
- blood viscosity
- total length of blood vessels
- blood vessel diameter
37
Source of resistance: blood viscosity
- As viscosity increases so does resistance
- Is a function of the number of cells per unit volume
- remains relatively constant
38
Source of resistance: total length of blood vessels
As length increases, so does resistance
- Stays relatively constant
- Weight gain can increase length
- 200 miles/lb of fat
39
Source of resistance: blood vessel diameter
- Not constant
- Most important factor in determining resistance
- smaller the diameter, the greater the resistance
- More fluid in contact with the walls of the vessel
- Capillaries have greatest resistance and large
vessels have low resistance
40
How does vessel diameter change from artery to capillaries?
decreases
41
How does vessel diameter change from capillary to vein?
increases
42
Capillaries have the ______________ cross sectional area.
greatest
43
Larger vessels have the ______________ cross sectional area.
smallest
44
How does pressure change from arteries to veins?
decreases
45
Which type of vessel experiences the greatest drops in pressure?
arterioles
46
Why do arterioles experience the greatest drops in pressure?
because there needs to
be a drop in pressure before the blood reaches the capillaries so that they do not burst
47
Which vessels have the greatest luminal diameter?
the Vs (venules, veins, vena cava)
48
Which vessels have the greatest velocity of flow?
the As (Elastic arteries, muscular arteries, arterioles)
49
What is the relationship between the velocity of flow and the cross sectional area?
* Decreases with increase in x sectional area
50
Where is the velocity of flow the slowest?
in the capillaries
51
Why is the velocity of flow the slowest in the capillaries? What does it aid in?
- because exchanges take place in the capillaries so the slow flow of blood aids in the exchange process
52
Where is the velocity of flow the greatest?
in the large vessels
53
Why is the velocity of flow the greatest in the large vessels?
* Speeds blood to capillaries
* Assists in returning blood to heart in large veins
54
Where is average blood pressure the greatest?
the elastic arteries
55
Where is average blood pressure the smallest?
the vena cava
56
What determines where the blood pressure is greatest and lowest?
- blood pressure is greatest at the arteries because they are closest to the left ventricle pushing blood to the rest of the body
- blood pressure is the lowest at the vena cava/veins because they are furthest from the pressure from the left ventricle in addition to the gravity acting on the body when blood tries to push blood back to the heart
57
Arterial pressure is dependent on what?
* How much the elastic arteries can be stretched
* Blood volume
58
Why is arterial pressure not constant?
As ventricle contract and eject blood, the arteries stretch causing an increase in pressure aka systolic pressure
59
Why does blood flow away from the heart?
because of differences in
pressure
* High in ventricle, low in veins
60
How does ventricular diastole effect arterial pressure?
Semilunar valves shut to prevent backflow into
heart
Elastic recoil in aorta propels blood forward
61
What is another name for arterioles?
pressure vessels
62
The blood pressure in the arterioles drops to what before entering the capillaries?
35-40 mmHg
63
What is the blood pressure at the ends of capillaries?
drops to 20 mmHg
64
Why is low pressure required in the capillaries?
* Capillaries are thin-walled
* Capillaries are permeable to fluid even at low pressure
65
What is venous pressure?
the blood pressure in the vena cava
66
Why is venous pressure steady or not pulsatile?
* Pressure gradient is low
- Resistance is low
- Increasing vessel diameter increases velocity
67
What factors aid in venous return?
respiratory pump and muscular compressions
68
Respiratory pump
Breathing causes low thoracic pressure
helps to pump blood back to the heart during inspiration. Inspiration increases the size of the thoracic cavity and decreases the pressure inside causing the pressure in the atria of the heart to drop to around 2.1 kPa, aspirating blood towards the right atrium from the thoracic vein.
69
Muscular compressions
* Skeletal muscles relax and contract forcing blood
along (milking)
* Blood cannot flow backwards due to valves in the veins
* Most important of 2 mechanisms
70
What three processes are involved in capillary exchange?
Diffusion
- Gases & small molecules
Transcytosis
* Large molecules
Bulk flow
* Filtration
* Reabsorption
70
Bulk flow =
a process used by small lipid-insoluble proteins to cross the capillary wall
70
Filtration =
pushed out
71
Reabsorption =
pulled in
72
Capillary exchange: define filtration
Movement of fluid and materials out of capillary due to pressure gradient
- Blood pressure is higher in the capillaries than tissue pressure
73
Where does filtration occur?
on arteriole end of capillary
74
Capillary exchange: define reabsorption
Movement of fluid back into capillaries due to osmotic pressure, caused by plasma proteins
75
Blood colloid osmotic pressure
the osmotic pressure exerted by large molecules
76
Reabsorption process:
* As fluid leaves the capillaries due to filtration, capillary pressure decreases.
* CAPILLARIES now have low pressure, and tissue have high pressure
* Due to pressure gradient the blood flows from the tissues to the capillaries
* Fluid from tissue enters capillaries by osmosis
77
What three factors effect blood/control blood pressure?
* Cardiac output
* Peripheral resistance
* Blood volume
78
What factors can change cardiac output (CO)?
* Change in heart rate
* Change in stroke volume
* Change in both
79
What organ controls blood volume?
kidneys
80
What are the kidneys capabilities on changing blood volume?
* Can remove excess fluid if volume is too great
* Cannot add fluid back if there has been loss
* Can only prevent further loss
81
What is the most influential/important factor when controlling blood pressure?
Peripheral resistance
82
How is Peripheral resistance altered?
* Altered by changing
- diameter of blood vessels
- distribution of blood between organs
83
What two pathways are used to control Peripheral resistance?
* Neural
* Chemical
84
What parts of the body are distributed the most blood at rest?
internal organs
- kidney
- digestive organs
85
What parts of the body are distributed the most blood when active?
- heart
- skin
- skeletal muscles
86
What three factors are responsible for Neural Control of Peripheral Resistance?
- Vasomotor center
- Baroreceptor (pressure receptors) initiated reflex
- Chemoreceptor initiated reflex
87
Where is the vasomotor center located?
in cardiovascular center of medulla oblongata
88
Vasomotor center function
Transmits signals along motor nerves to smooth muscle in blood vessels (tunica media)
89
The vasomotor center is always doing what?
Always sending out signals. Thus, when a muscle is at rest it is slightly constricted.
90
Vasomotor tone =
Muscles at “rest” are slightly constricted
91
Increased and decreased activity levels in the vasomotor center?
Increase in activity level causes muscle to contract (vasoconstriction)
Decrease in activity causes muscles to relax (vasodilation)
92
Baroreceptors are what kinds of receptors?
pressure receptors
93
Where are baroreceptors located?
Pressure receptors located in elastic arteries
94
What effect does an increase in pressure have on baroreceptors?
- causes receptors to signal vasomotor center to decrease activity resulting in vasodilation (blood pressure decreases)
- sends message to cardiac center to cause reduction in heart rate
95
What effect does a decrease in pressure have on baroreceptors?
- Causes opposite reaction
- Receptors send signal to vasomotor, increasing activity, causing vasoconstriction
- This causes an increase in blood pressure
96
Baroreceptor initiated reflex protects against what?
helps protect body from rapid changes in blood pressure, such as occur during standing
97
Chemoreceptors respond to what?
Respond to changes in O2 , CO2 , pH
98
Where are chemoreceptors located?
located in carotids and aortic arch
99
What chemical levels trigger chemoreceptors to send a signal to the vasomotor center to cause vasoconstriction?
Low O2 , high CO2 , or low pH
100
When a blood vessel vasoconstricts what effect does it have on blood pressure?
Increases blood pressure speeding blood to heart and lungs
101
What chemicals control the Chemical control of peripheral resistance?
- Epinephrine and norepinephrine
- Renin-Angiotensin-Aldosterone
- Antidiuretic Hormone
- Natriuretic peptides
- NO (nitric oxide)
102
Epinephrine and norepinephrine is secreted from where?
adrenal medulla
103
Epinephrine and norepinephrine is part of what system?
sympathetic nervous system
104
Epinephrine and norepinephrine affects the heart by doing what?
increasing CO
105
How does Epinephrine and norepinephrine increase cardiac output (CO)?
Causes vasoconstriction of arterioles and blood vessels supplying digestive organs
Causes vasodilation in skeletal and cardiac muscle
Causes an overall increase in blood pressure
106
Renin-Angiotensin-Aldosterone: How does the liver and kidneys respond to a decrease blood pressure?
- liver secretes angiotensinogen in blood
- kidney secretes renin into blood
107
Angiotensinogen and renin in the blood cause the rise of what?
angiotensin II
108
What are the effects of angiotensin II?
- Vasoconstriction of arterioles
- Release of Aldosterone and ADH
- Increased water and Na+ reabsorption
- Stimulates thirst
- Functions to increase blood pressure
109
Both Aldosterone and ADH cause what?
- causes salt reabsorption = keeping more water = steady blood volume
- both keep fluid in body
110
What is the function of Antidiuretic Hormone (ADH)?
- Stimulates kidneys to retain water
- Causes vasoconstriction
- Results in increase in blood pressure
111
ADH responds to what chemical levels?
- an increase in blood osmolarity,
- decrease in volume,
- increase in angiotensin II
112
Natriuretic peptides is an antagonist to what chemicals?
Aldosterone and ADH
113
Atrial natriuretic peptide (ANP) are produced by what?
both atria
114
When is Atrial natriuretic peptide (ANP) released?
increases in blood volume
115
What is the function of Natriuretic peptides/Atrial natriuretic peptide?
Lowers blood pressure
Vasodilation
Increases salt and water loss by kidneys
Suppresses ADH and aldosterone
116
NO (nitric oxide) effects
- Vasodilation
- Effects are short lived
- May be major factor in affecting blood pressure
117
NO (nitric acid) is released by what?
- Released by endothelial cells
118
NO (nitric acid) is produced by what?
- Produced by the tunica intima
