Flashcards in Circulation 2: The Systemic Circulation Deck (47):
What is pulse pressure? How does it change further from the heart? Describe pulse pressure in capillaries and veins.
pulse pressure = systolic - diastolic
pulse pressure widens in vessels further from the heart
no pulse pressure in capillaries and veins
Describe mean arterial pressure.
continuously declines throughout the circulatory system
is determined more by diastolic than systolic pressure bc in diasttole 2/3 of cycle
Where is the greatest decrease in arterial pressure?
across the arterioles
What happens to pulse pressure as you go into the larger arteries from the root of the aorta? Why?
systolic pressure goes up and diastolic pressure goes down so pulse pressure gets wider.
happens bc compliance (change in volume over change in pressure) declines as you go further from the heart.
What happens to systolic and diastolic pressures as compliance decreases?
What's happening to MAP and E throughout the system?
systolic goes up, diastolic goes down bc compliance decreases
higher pulse pressure result of decreasing compliance,
mean arterial pressure going down, E continuously dropping throughout system.
What drives blood forward then if systolic pressure higher downstream than it is upstream?
mean arterial pressure dropping and mean arterial pressure that drives the blood forward. so pressure gradient is really the mean arterial pressure and that always declines.
How is bp taken in R arm different than L? Why?
bp in L and R arm is different… mechanism due to fact that compliance characteristics of brachial a in R arm is lower than in L arm. further from heart the lower the compliance of arterial system and R brachial artery is further from heart than the L… expect if you took bp in right arm systolic higher than L arm and diastolic a little lower than L arm. so if you're doing bp for life insurance… they’re looking for diastolic hypertension… most older people get systolic hypertension. most younger people have diastolic hypertension..so you would rather have R arm taken for insurance bc will have about 5mm lower.
Does the pulmonary arterial system or the systemic circulation have a higher compliance?
pulmonary arterial system
Describe how systolic and diastolic pressure change as you go further from heart. Describe alterations in pressure profile depending on other locations (arch..lower abdomen..iliac..knee..ankle.. )
What happens to frequency? systolic peak? waveform?
What are some possible causes?
dep. on compliance, further from heart, lower compliance, stiffer the tissue… higher systolic, lower the diastolic
further from heart... high freq. components damped, systolic peak increased and waveform narrowed, late diastolic hump in waveform
( in cardiac sharp notch at root of aorta, then further away see that the notch kind of damps out by characteristics of arterial system and is more of a slow wave. waveform narrows-duration of wave pressure close to heart, then late diastolic hump..gets further out and has to do with impedance characteristics of heart. just know this wave form looks diff in diff places as get further from the heart.)
reflection at branch points
decrease in arterial compliance
(if you have a branch point in arterial system, pressure coming down hits branch point and reflects back and they summate. 2 waves summating, peak higher, vascular tapering- as vessels get narrower increase systolic pressure to some extent, but main issue is decrease in arterial compliance- main reason the wave forms change.)
What is arterial sclerosis?
hardening of arteries, compliance of arterial system is decreasing
(important implicates for how heart can pump blood into circulation)
arterial sclerosis is hardening of arteries (decrease in compliance of arterial system) why is this bad for you? bc changes pulse pressure (arterial bp, diastole to systole) that is afterload… changing pulse pressure then changing after load on heart. indep. risk factor is decrease in arterial compliance for congestive heart failure. rel. directly to hardening of arteries and hypertension
What is a dissecting aneurysm? What causes them?
if you damage endothelial lining, blood infiltrates between these layers (tunica intima, tunica media, tunica adventita)
and dissects them apart, weakens the wall to point it becomes an aneurysm then ruptures.
dissecting aneurysms not due to trauma, 95 percent of people who have them smoke
Describe internal elastic lamina.
What has the greatest amount of elastic tissue/lamina?
is around the intima.
its the component that allows vessels to distend when pressure increases and recoil
aorta has the greatest amount of elastic tissue/lamina
(not found in veins, they do not distend v much and recoil.
What is distinctive about arteries?
one of main features in arteries is a v strong vascular smooth muscle coat ... small artery can shunt off blood flow to an organ
What is something to look for after someone experiences hypovolumic shock?
baroreceptors can reduce blood flow to kidney to zero.. (arteries shunting off blood flow to organ- strong smooth vascular constriction of small vessels) ... so look - are kidneys producing fluid? have these arteries relaxed and is there any damage to kidney as a result of ischemia?
Describe the vascular smooth muscle of a vein. Describe veno-constriction.
vascular smooth muscle of vein is weak. veno-constriction not cutting off blood flow at all just making it a little stiffer so it cant flop open, reduces compliance of the venous system..allows blood to be shunted back through valves to heart-thats venous return
Compare connective tissue between veins/arteries.
veins have strong connective tissue as compared to arteries (dont need as much bc have other structures holding together)
Describe the endothelial lining of veins, arteries, capillaries.
arteries and veins have one layer of endothelial cells. protective lining, endothelial cells release a lot of substances.. most important one we know of is nitric-oxide. why important? if this arterial endothelial cells get damaged allows inflammation of rest of arterial wall.
(capillaries are just 1 layer of endothelial cells)
(all blood vessels and lymphatic vessels are lined by endothelial cells)
What are the 3 layers that the artery vessel wall is divided into?
tunica intima- subendothelial connective tissue; Internal Elastic Lamina (IEL)
tunica media- smooth muscle cells and external elastic lamina (EEL)
tunica adventita- mostly connective tissue with some smooth muscle cells; vasa vasorum ("vessel of a vessel") innervation. Nerves (nerves that come in, come in through adven. tissue.)
Describe the 3 layers of the vein wall.
Tunica Intima: subendothelial connective tissue; no Internal Elastic Lamina (IEL)
Tunica Media: less smooth muscle cells; no External Elastic Lamina (EEL)
Tunica Adventitia: well developed connective tissue with some smooth muscle cells; and vasa vasorum (“vessels of a vessel”).
What is vasa vasorum?
these are the small vessels in vessel wall that bring nourishment to cells in vessel wall. vessel wall needs blood flow and its not by diffusion from inside the vessel and endothelial cells etc- doesn't work that wall. its actually small vessels that are infiltrated through wall of artery and vein that carry blood to nourish the vascular smooth muscle cells and other cells involved.
Can veins withstand high pressures? How? When might they need to?
adventitia is well developed…v veins can if they have to, withstand v high pressures.
(when people have bypass… bypass bypasses blocked artery, connect to aorta then bypass blockage put the connection below the lesion to get perfusion of heart. to bypass lesion they use saphenous vein in leg, take this vein and put it in heart, works bc have strong connective tissue, and when inflated to 90mmHg (of arterial pressure) can withstand it bc of large connective tissue.
Compare arteries to veins.
- artery has elastic lamina, veins do not
- artery has more smooth muscle than veins
- artery has less connective tissue (adventitia) than veins
Describe the compliance properties of arterial wall components. (elastic lamina, smooth muscle, and collagen)
elastic lamina - highest compliance
smooth muscle - less compliant than elastin more compliant than collagen
collagen (connective tissue) - lowest compliance
compliance properties of arterial wall det. by these three structures. if look at elastic lamina under microscope, its scrunched up, so when pressure increases it straightens out. it stretches. so thats v compliant system- that something scrunched then can stretch it. small change in pressure for given volume-high compliant system. when you do increase pressure in artery the first portion of arterial wall to bear the load will be elastic lamina
How does compliance change as pressure increases? (What makes pressure increase?)
under low volume circumstances arteries have rel. high compliance bc thats only portion of arterial wall feeling the pressure. if increase pressure a little more by increasing volume more then get into vascular smooth muscle which has less compliance that elastin but is more compliant than collagen, so reducing the compliance of system more when increase volume..now stretching vascular smooth muscle which is stiffer, if then keep increasing volume now you try to stretch the collagen, most stiff… v low compliance
How do the compliance characteristics of these tissues affect arterial pressure?
if low volume, more compliant system, lower pressure. if have large volume, when u start to try to stretch collagen have low compliant system and high pressure.
Describe continuous capillary. Where are they found?
continuous endothelial cells; no fenestrations (holes) in capillary wall; tight junction between cells.
continuous basal lamina
found in muscle, connective tissues
What are fenestrated capillaries? Where are fenestrated capillaries found?
continuous endothelial cells with fenestrations (holes) with or without diaphragms.
continuous basal lamina
found in kidney, intestine.
Describe discontinuous (sinusoidal) capillaries.
Where are they found?
Discontinuous (sinusoidal) capillary:
discontinuous endothelial cells separated by wide spaces
discontinuous basal lamina
found in liver (proteins), bone marrow (WBCs), spleen (RBCs).
How does wall thickness and lumen diameter ratio affect blood flow and control of vessel diameter?
Describe precapillary sphincters, veins, aorta
The higher the WALL THICKNESS/LUMEN DIAMETER ratio, the greater is the control of vessel diameter and blood flow. This is a direct application of the Laplace relationship: (T=P x r/μ).
a) pre-capillary sphincters have the highest ratio and greatest control. (pre-capillary sphincters located right outside capillary networks and they allow blood to go into these capillaries.. lots of pre capillary resistance but little post capillary resistance)
b) veins have relatively small wall thickness/lumen diameter ratios (thin walls/large diameters) and therefore regulate volume more than flow or pressure.
aorta -large diameter, largest amount of elastic tissue. most compliant vessel in body. distends when volume ejected in and then recoils to give secondary pump to maintain arterial pressure … arterioles and pre capillary sphincters have v large or high wall thickness (vascular smooth muscle) to lumen diameter (small) which allows it to have greater control over vessel diameter and blood flow. bc of thickness of vascular smooth muscle and small diameter of lumen, they have v low wall tension
change in pressure for a given change in volume. dV/dP
Draw 2 graphs showing the relationship between changes in volume and pressure in aortas having high and low compliance.
How is diastolic/systolic pressure affected?
(for a given stroke volume, aortic pulse pressure is increased when compliance is reduced)
Slide 10. (compliance is change- not absolute. same volume and looking at effect on arterial pressure which is on abscissa bc slope is high compliance and this is low compliance and slope is low… associate slope of line with high and low compliance- thats why they changed axes.)
Compared to normal high compliance (left), a decrease in aortic compliance (right) results in an increase in systolic and decreasediastolic pressures, i.e. a widening or increase in pulse pressure.
Describe what is happening in a high compliant system (blood ejected into arterial system) in terms of energy.
related to B. Principle. total E in system divided between pressure (potential E) and kinetic movement, those two together have to remain constant. blood ejected into arterial system, and it creates a pressure, and in high compliant system it moves the wall (component of kinetic E) by moving wall you reduce pressure (bc pressure and kinetic E inversely related) so if you use some of that pressure to move arterial wall then you reduce peak pressure… thats what happens, by moving that wall and distending wall during systole you've kept systolic pressure low. when aortic valve closes, arterial wall-takes E stored, bc you’ve stretched it and it recoils and that kinetic component put back into the pressure and holds diastolic pressure up. that's why systolic pressure not quite as high and diastolic pressure not quite as low compared to stiff artery.
Describe what is happening in a low compliant system (blood ejected into arterial system) in terms of energy.
in tissue w low compliance…eject same volume of blood into low compliant artery, say lead pipe that didnt move at all, none of the pressure converted into kinetic component so all pressure goes toward pressure (potential E) thats why systolic is so much higher bc no loss of potential E or pressure by moving wall bc wall is stiff. then during diastole after valve closes theres no recoil so not adding any E to pressure so pressure drops out quickly as blood runs off, diastolic lower. its B principle-conversion of pressure into kinetic E or kinetic movement… restoration of pressure by recoil of kinetic component putting E back into pressure. conversation of potential E to kinetic E and kinetic E back into pressure.
so what happens in low compliant system have larger pulse pressure which is larger after load on heart. may be easier to open valve bc lower diastole but then after load is higher… and heart has to bring to a much higher systolic pressure so starting at a lower value to higher value. so total after load much larger. after load will increase oxygen consumption and a low compliant aorta is indep. risk factor for congestive heart failure. strain on heart bc of increase in afterload, continuous increase in O consumption.
How do the physical arrangement of the vascular components determine the compliance properties of the vessel wall? Draw graph.
Provide a clinical example.
How does compliance of blood vessel change at higher volumes? Why? What will this lead to?
Slide 11. this is showing that as you change the volume (indep. variable)… showing so graph bends over w compliance
Relation of radius (volume) and trans-mural pressure; note that compliance of the blood vessel wall decreases at higher volumes. That is because the load on the vascular wall is first borne by the elastin and smooth muscle (higher compliance) and lastly by the collagen (lowest compliance). Therefore, the lower compliance of the vessel wall at higher volumes can lead to disproportionately higher pressures.
Clinical Application: Blood volume expansion causes hypertension
this means if you have a higher than normal blood volume you’ll have hypertension and thats why give pt. with diaretics to try to lower blood volume so arterial system at higher compliant state… goes back to histology, at low volume its elastin and smooth muscle and at high tissue its adven tissue which is trying to be stretched by this volume of blood.
if can lower someones blood volume can usually lower bp.
What role does the aortic wall play during systole/diastole of L ventricle.
The volume ejected from the LV during systole is temporally stored by the distension of the elastic vascular component of the aorta. After systole ends, the distended aortic wall recoils and thereby acts as a secondary pump to maintain constant flow during diastole (as secondary pump to pump blood down system). This process is dependent on the compliance characteristics of the aortic wall.
when the arteries are normally compliant, a substantial fraction of the SV is stored in the arteries during ventricular systole. The arterial walls are stretched.
During ventricular diastole the previously stretched arteries recoil. The volume of blood that is displaced by the recoil furnishes continuous capillary flow throughout diastole. secondary pump maintains diastolic arterial pressure
What would happen if there was no recoil/no dichrotic notch?
dichotic notch- if didn’t have recoil (which causes notch) then there’d be no recoil, no increase in diastolic pressure, so ultimate diastolic pressure dropped down and now have to go from lower diastolic pressure to (higher) systolic pressure and thats an increase in pulse pressure. w loss of dichroic notch-reduces diastolic pressure (recoil causes notch)
How do rigid arteries change systole/diastolic pressure in regards to the recoil of the aorta.
a volume of blood equal to the entire SV must flow through the capillaries during systole. when the arteries are rigid, virtually none of the SV can be stored in the arteries.
Flow through capillaries ceases during diastole. Rigid arteries cannot recoil appreciably during diastole.
Low compliance system- results in larger afterload, increased O2 consumption
a low compliant aorta is an independent risk factor for congestive heart failure
Describe what happens to the arterial system as you age. Graph.
Slide 14. (slope corresponds with compliance, for any given volume you have pressure change, high slope, high compliant arterial system, as you age it drops..not good. for any given volume you have v large increase in pressure - lower compliant aorta results in wider pulse pressure bc of B principle. more cardiac work, O consumption. )
aortic compliance decreases with age; less elastin & more collagen.
as compliance decreases, a given increase in volume elicits a larger increase in pressure.
less compliant aorta results in a wider pulse pressure & more cardiac work (oxygen consumption)!!
an increased pulse pressure is an independent risk factor for the development of congestive heart failure, and contributes to systolic hypertension, cardiac hypertrophy, aortic dilation, and low exercise tolerance.
younger ppl have diastolic and older ppl usually get systolic hypertension- due to changes in compliance.
How does exercise affect central arterial compliance?
regular exercise increases central arterial compliance.
Describe the difference in compliance between an artery and vein at high and low volumes. Draw/graph for large artery and large vein.
What changes geometry of veins, compliance or distension?
Arteries exhibit a relatively constant low compliance throughout the physiological pressure range. Therefore arteries are considered resistance vessels.
Veins exhibit a relatively high compliance in the physiological pressure range (
Why is it veins can be used as coronary bypass grafts?
At higher (arterial) pressures, compliance of veins is very low. This allows saphenous veins to be used as coronary bypass grafts.
at high volumes, compliance goes down… this is decrease in slope, lower compliant system bc now all adven. tissue. compliance characteristics of saphenous vein being used as artery.
Graph arterial pressure pulse. Pressure vs time. (aortic arch, femoral artery, iliac artery, thoracic artery).
What does propagation of pressure pulse depend on?
How is velocity or propagation of pulse affected?
Propagation of the pressure pulse wave depends on the physical characteristics of the vessel wall, especially the arterial compliance. As compliance decreases down the arterial tree, the velocity of propagation of the pressure pulse increases.
The arterial pressure pulse is directly related to the changes in the arterial pressure profile (pulse pressure) (see figure).
What speed does the arterial pressure pulse travel down the aorta and small arteries?
The arterial Pressure Pulse (wave) travels down the aorta at 5 meters/sec and increases to about 10-15 meters/sec in the small arteries. In contrast, blood flow travels at about 1 meter/sec (Radial pulse, not flow but energy).
Describe pressure pulse.
(diff than pulse pressure)… this is pulse you feel at wrist. the radial pulse- is not blood flow, not feeling blood flowing through a, feeling E wave created by blood ejected from heart distending artery and that E or movement of arterial wall transmitted down arterial wall, E wave..related though to pulse pressure. larger pulse pressure more wall distends, more E put into wall, more E transmitted down the wall. if larger pulse pressure can feel someones pulse.
What will happen to pressure pulse if you have stiffer arterial walls? Why?
travels much faster than blood flow… if you have stiffer arterial walls that pulse will travel faster bc less movement and travels faster, less E lost as wave moves down arterial wall. movement loses E. at root of aorta 5m/sec but further from heart arterial compliance decreases therefore the wave speeds up
Compare pressure profile close to aorta then femoral artery. Why the difference?
Where would you feel a larger pulse?
pressure profile close to aorta small, then femoral artery the systolic much larger as result of decrease in compliance, so if you took someones pulse down here.. can feel much larger pulse pressure than at wrist. diff pulse in diff locations bc of compliance characteristics.