Cardiovaslcular Physiology Part 2: The Vascular System Flashcards
(92 cards)
1
Q
Endothelium
A
layer of endothelial cells in contact with the flowing blood in all blood vessels and heart chambers
2
Q
Capillaries and endothelium
A
endothelium and associated extracellular basement membrane
3
Q
All other vessels and endothelium
A
one layer of connective tissue and smooth muscle in addition to endothelial cell lining
4
Q
relationship between systemic and pulmonary arterial pressure
A
higher in systemic because it has greater vascular resistance
5
Q
pressure decrease as blood flows from
A
ventricles to capillary beds to atria bc of resistance to flow (dissipation of pressure generated by ventricles)
6
Q
Compliance
A
- how easily a structure can be stretched
- Compliance= change in volume / change in pressure
7
Q
Arteries function
A
- low-resistance conduits
- pressure reservoirs for maintaining blood flow
to the tissues during ventricular relaxation
8
Q
Pulse pressure
A
systolic or max arterial pressure minus diastolic or min arterial pressure
9
Q
Mean arterial pressure (MAP)
A
diastolic plus 1/3 pulse pressure
10
Q
Arterioles determine
A
- mean arterial pressure
- distributing flows to various organs and tissues
11
Q
Blood flow through any organ equation
A
f= (MAP- Venous Pressure)/ Resistance Venous pressure = 0
12
Q
intrinsic tone
A
aka basal tone
baseline level of contraction that can be increased or decreased based on external signals
- increase above intrinsic tone leads to vasoconstriction
13
Q
control of vasoconstriction and vasodilation is dependent on
A
1) Local controls
2) extrinsic (reflex) controls
14
Q
local controls are
A
independent of nerves and hormones
self regulated by organs and tissues
15
Q
active hyperemia
A
increased blood flow when metabolic activity (ex: activity of muscle in exercise) is increased
- LEADS TO ARTERIAL DILATION
16
Q
See factors that cause arteriolar smooth muscle relaxation
A
- increased metabolic activity
17
Q
flow autoregulation
A
changes arteriolar resistance to maintain a constant blood flow when arterial
blood pressure changes
18
Q
flow autoregulation is caused by
A
local metabolic factors and arteriolar myogenic responses to
stretch
19
Q
myogenic responses and what are they caused by
A
- responses of arteriolar smooth muscle to stretch are termed myogenic responses
- caused by ca2+ movement into smooth muscle cells
20
Q
reactive hyperemia
A
- extreme form of flow auto regulation
- increase in flow when local flow is reestablished after complete occlusion
21
Q
Paracrine agents
A
- chemical inputs stimulate endothelial cells to release vasodilators or vasoconstrictors released by endothelial cells to act on smooth muscle
22
Q
Extrinsic controls
A
neural and hormonal
23
Q
sympathetic innervation
A
vasoconstriction via a-adrenergic
receptors
24
Q
in some cases in neural extrinsic control, non-cholinergic, non-adrenergic neurons release
A
nitric oxide or
other vasodilators also innervate blood vessels (sildenafil aka viagra and tadalafil aka Cialis)
25
In hormonal control, plasma epinephrine
- binds to a adrenergic receptors causes vasoconstriction
- binds to b2 receptors causes vasodilation
26
angiotenson II
vasoconstrictor: hormone that constricts most arterioles
27
vasopressin
vasoconstrictor: released in blood due to posterior pituitary in response to decreased blood pressure
28
atrial natriuretic peptide
vasodilator, influences blood pressure by regulating Na+ balance and blood volume
29
Some chemical inputs act by stimulating endothelial cells to release
vasodilator or
vasoconstrictor paracrine agents, which then act on adjacent smooth muscle
30
paracrine agent vasodilators
nitric oxide (EDRF), Prostacylin (aka prostaglandin I2)
31
Why are capillaries highly efficient for diffusion and exchange?
Most cells are within 0.1 mm of a capillary, making diffusion distances very small. This proximity, along with the thin structure of capillaries, ensures highly efficient exchange.
32
what is the main purpose of capillaries in circulatory system
- exchange of nutrients, metabolic end products, and cell secretions
- Even though only about 5% of the total blood is flowing through capillaries at any given moment, this is the part of the circulatory system that performs its ultimate function
33
Which part of the body lacks capillaries, and why?
The cornea lacks capillaries to allow light to pass through it, maintaining its transparency.
34
What is angiogenesis and what role do VEGF and fibroblasts play in it?
Angiogenesis is the growth of new blood vessels. VEGF (vascular endothelial growth factor), secreted by fibroblasts and endothelial cells, stimulates endothelial cells to divide and migrate to form new capillaries
35
How do cancer cells utilize angiogenesis for tumor growth?
Cancer cells secrete angiogenic factors to stimulate the formation of blood vessels needed for supplying nutrients to the tumor.
36
What is angiostatin and how is it used in cancer therapy?
- Angiostatin is a natural peptide that inhibits blood vessel growth. - Administering it reduces tumor size by blocking angiogenesis.
- An antibody that binds VEGF is also used in colorectal cancer treatment.
37
what does a typical capillary wall consist of?
A capillary wall is a thin tube of endothelial cells (one cell layer thick) resting on a basement membrane. It has no surrounding smooth muscle or elastic tissue.
38
How do capillaries differ in certain organs like the brain?
Some capillaries have a second set of cells around the basement membrane that restrict substance diffusion—important for the blood-brain barrier.
39
What are the key components of a capillary cross-section?
Endothelial cells
Basement membrane
Intercellular clefts
Fused-vesicle channels
Erythrocytes
Exocytotic vesicles
Capillary lumen
Nucleus (visible in some cells)
40
How do plasma proteins move typically move across capillaries and interstitial fluid
by vesicle transport
41
What are intercellular clefts and fused-vesicle channels?
- Intercellular clefts are narrow, water-filled gaps between endothelial cells allowing molecule passage
- Fused-vesicle channels are formed by continuous endocytotic and exocytotic vesicles facilitating transport across endothelial cells.
42
How is capillary blood flow regulated?
It’s controlled by the state of nearby arterioles and metarterioles. Vasodilation increases capillary flow; vasoconstriction decreases it.
43
What is the structure of the microcirculation system (Figure 12.41)
Arterioles with smooth muscle and precapillary sphincters
Metarterioles connecting to capillaries
Capillaries (no smooth muscle)
Venules leading to veins
Intercellular clefts in capillaries
44
Why does blood flow slowly through capillaries?
Because capillaries have a huge total cross-sectional area, which slows the flow of blood more than any other part of the vascular system.
45
What determines capillary blood flow?
The resistance of arterioles supplying the capillaries and the number of open precapillary sphincters.
46
What is the main mechanism for exchange of substances in capillaries?
Diffusion
47
How do lipid-soluble substances and polar molecules move across capillary walls?
Lipid-soluble substances pass through endothelial cells; ions and polar molecules move through water-filled intercellular clefts or fused-vesicle channels.
48
Can plasma proteins easily move across capillary walls?
No, they generally cannot; however, specific proteins like certain hormones may be transported by vesicles.
49
How does metabolism affect diffusion in capillaries?
Increased metabolism raises the diffusion gradient, increasing the rate of diffusion.
50
Bulk Flow in Capillaries
- process in addition to diffusion across capillaries
51
what determines the distribution of extracellular fluid across capillaries?
Bulk flow of protein-free plasma or interstitial fluid
52
What favors filtration from plasma to interstitial fluid?
The hydrostatic pressure difference between capillary and interstitial fluid.
53
What favors absorption from interstitial fluid to plasma?
The protein concentration difference between plasma and interstitial fluid (oncotic pressure).
54
filtration
hydrostatic pressure across capillary wall behaves as a filter to allow protein free plasma to interstitial fluid through water filled channels
55
what is the comparison between the concentration of all plasma solutes except protein in filtered fluid and plasma
no difference, the concentration of non proteins are the same
56
Magnitude of bulk flow is determined
difference between capillary BP (Higher) and interstitial fluid pressure (Lower)
57
Considerable hydrostatic pressure difference between capillaries and interstitial fluid exits to
filter out protein free plasma out of capillaries in to interstitial fluid leaving the
58
Does filtration and absorption change solute concentration?
No, crystalloids move with water, so their concentrations remain unchanged.
59
What happens to the small excess of filtration over absorption in capillaries?
It is returned to the bloodstream via lymphatic vessels.
60
How can altered Starling forces lead to edema?
Conditions like heart failure, tissue injury, liver/kidney disease, and protein malnutrition can disrupt balance and cause fluid buildup.
61
Starling forces
net filtration pressure= (capillary hydrostatic pressure plus protein osmotic pressure *these push fluid out) minus (interstitial hydrostatic pressure plus plasma protein pressure *these push fluid in)
62
Capillary hydrostatic pressure and interstitial protein pressure
favor filtration
63
interstitial hydrostatic pressure and plasma protein concentration
favor absorption
64
what are crystalloids and their concentrations in interstitial fluids
- low molecular weight solutes
- concentrations are not changed; they move with water
65
excess fluids are returned to the bloodstream
via lymphatic vessels
66
permiability of macromolecules are greater in
venules than for capillaries, particularly in damages areas
67
Venules have a large capacity for (blank) and are also a site for
- large capacity for blood (aka capacitance vessels)
- site of migration for leukocytes into tissues during inflammation and infection
68
in systemic circulation the force driving venous return to the heart is
the pressure difference between the peripheral veins (10-15 mmHg) and the right atrium (0 mmHg)
- total pressure difference is 10-15 mmHg, which is adequate bc low resistance to flow offered by veins
69
major function of veins is to act as
low resistance conduits for blood flow from the tissues to the heart
70
peripheral veins of the arms and legs contain
valves that permit flow only towards the heart
71
Veins perform a second function apart from being a low- resistance conduit, their
diameters are reflexively altered in response to changes in blood volume, maintaining peripheral venous pressure and venous return to the heart
- determines end diastolic ventricular volume and thereby stroke volume
72
factors determining pressure in any elastic tube are
- fluid volume
- compliance of walls
73
major determinant of venous pressure is
total blood volume because the most blood is in the veins
74
the walls of the veins are
thinner and more compliant than arteries therefore can accomodate large volumes of blood with relatively small increase in hydrostatic pressure
75
percentage of blood volume present in systemic venules and veins
- 60% at venous pressure of 10 mmHg
- systemic arteries only contain less than15% blood volume at a pressure of 100 mmHg
76
walls of veins contain smooth muscle innervated by
sympathetic neurons which release norepinephrine which causes contraction of venous smooth muscle, decreasing diameter and compliance which increases the pressure within them which drives more blood out of the veins and into the heart
77
different effect of venous constriction compared to arterioles
arteries constrict --> reduces flow through systemic circuit
veins constrict --> increases forward flow
78
2 other mechanisms that increase venous pressure and facilitate venous return
- skeletal muscle pump
respiratory pump
79
during skeletal muscle contraction, skeletal muscle pump
the veins running through the muscle are partially compressed, which reduces their diameter and flow back to the heart
80
use of peripheral vein valves
when skeletal muscle pump increases local venous pressure, the valves permit blood flow only towards the heart and prevent backward flow into capillaries
81
respiratory pump works by
inspiration of air causes diaphragm
- increase intrabdominal pressure which transmits to intra-abdominal veins
- decrease in pressure in thorax, decreasing pressure in the interthoracic veins and right atrium
82
net effect of pressure changes in abdomen and thorax
increase in pressure difference between peripheral veins and heart (increases pressure gradient) --> increases venous return
83
any change in venous return
cause equivalent changes in cardiac output, through Frank sterling mechanism
84
The lymphatic system
is a network of small organs (lymph nodes) and tubes (lymphatic vessels) through which the lymph (fluid derived from interstitial fluid) flows
85
lymphatic capillaries
are tubes made of only a single layer of endothelial cells resting on a basement membrane, but they have large water filled channels permeable to all interstitial fluid constituents including protein
86
unlike blood vessel capillaries, lymphatic capillaries are the first of the lymphatic vessels that have
NO tubes flow into them
87
interstitial fluid enter lymphatic capillaries
through bulk flow, one way valves into lymphatic capillaries
88
describe pathway through lymphatic system
- capillaries to vessels, into larger vessels to lymph nodes (part of immune system) in armpits groin neck, into 2 large lymphatic ducts that drain into veins at junction of jugular and sub clavicle veins which have valves which permit one way flow into the veins from the ducts
- this process carries interstitial fluid to the circulatory system
89
Lymphatic system is important because
vessel capillaries filters out more fluid than is absorbed each day
this fluid is returned via lymphatic system
90
lymphedema
when lymphatic system is damaged or occluded, accumulation of excessive interstitial fluid
- nodes removed during treatment of cancer can cause this
91
in addition to draining excess fluid lymphatic system provides
- pathway where fat absorbed in the gastrointestinal tract enters the blood
- cancer cells spread from their area of origin to different parts of the body
92
factors that increase lymph flow include
- contraction of smooth muscle in the lymphatic vessels (no fluid no stretch, yes fluid yes stretch)
- skeletal muscle pump, respiratory pump (minor effects)
