[2] Lecture 11: Arterial And Venous Systems And Lymphatics Flashcards
Term used to describe the ease asso. W/ spread of the vessel
Vascular distensibility
TellsThe total quantity of blood (mL) that a be stored in a given portion of the circulation for each mm Hg rise in pressure
Vascular compliance
Describes how volume changes in response to Change in pressure
Capacitance
A measure of the ease w/ which a hollow viscus may be distended
I.e. The ∆V resulting from the application of a unit pressure differential btw inside and outside of viscus; reciprocal of elastance
Compliance
A measure of the tendency of a hollow viscus to recoil towards its original dimensions upon removal of a distending or collapsing force
Elastance
Formula for vascular distensibility
F= (increase in V / increase in P x Original volume)
Which is more distensible veins or arteries?
Veins are 8 times more distensible.
Pulmonary arteries vs systemic artery distensibilities:
Pulmonary arteries are 6 times MORE distensible than systemic arteries
Pulmonary veins and systemic veins-distensibility
Same
Vascular compliance formula:
Increase in V /
Increase in P
=
VD x V(orig) = compliance
This term describes distensibility of blood vessels:
Capacitance
_________ is inversely proportional to elastance
Capacitance [mL/ mm Hg]
Directly proportional to volume and inversely proportional to pressure
Capacitance
This is higher in veins than arteries:
And decreases in arteries with age
Capacitance
The more elastic tissue:
Higher the elastance and lower compliance
Total quantity of blood that can be stored in a given portion of the circulatory system.
Vascular compliance
A systemic vein is 8x as distensible as it corresponding artery and have volume 3 x as great. How would its compliance compare to that of the corresponding artery?
24 times more
Removing a little volume from arteries has drastic effect, however hundreds of ml can be removed from venous system w/ little change in pressure. Why?
Arteries are elastic and not very compliant, volume is removed= P will drop.
Because veins are VERY compliant, volume can be removed with little change in Pressure.
Pressure-volume curves show: [veins/arteries]
Veins: little change in pressure w/ big ∆ in volume
Arteries: big change in pressure w/ little ∆V
SV /
Arterial compliance =
Pulse pressure
2 factors affect pulse pressure
SV output of the heart
Compliance of arterial tree
Most important determinant of pulse pressure
Diastolic P remains unchanged during ventricular systole; pulse pressure increases to same extent as the systolic pressure
SV output of the heart
Decreases in compliance (capacitance) i.e. Aging, result in an increase in pulse pressure
Compliance of the arterial tree
What happens to pulse pressure when compliance goes down?
Increases
4 conditions that cause abnormal contours of the pressure pulse wave:
1-aortic valve stenosis
2-atherosclerosis
3-patent ductus arteriosus
4-aortic regurgitation
Diameter of the aortic valve opening is narrowed significantly, and the aortic pressure pulse is decreased greatly.
Blood flow through aortic valve is diminished.
Aortic valve stenosis
Half or more of the CO flows back into the pulmonary artery and lung blood vessels
Diastolic pressure falls very low before next heartbeat
patent ductus arteriosus
Aortic valve is absent or will not close completely
Aortic pressure may fall all the way to 0 btw heart beats.
Aortic regurgitation
A downward notch in the curve recording aortic blood pressure that occurs btw systole and diastole and is caused by backflow of blood for a short time before aortic valve closes
Incisura
Why does atherosclerosis cause pulse pressure to rise above 120 mmHg
?
Greater afterload to pump against
Why does aortic regurgitation lack a incisura on pressure curve?
The incisura is usually caused by aortic valve backflow of blood. There’s essentially no aortic valve in aortic regurgitation.
Like a one way pipe
Explain why the pulse pressure drops below 80 mm Hg in patent ductus arteriosus and aortic regurgitation:
Half or more of CO flow back into pulmonary artery and lung. Decreasing pressure greatly.
As pressure pulse waves progress from large vessels toward smaller vessels
Damping of the pressure pulses
Sounds of blood while taking BP:
Korotkoff sounds are the opposing forces of the blood flow.
Mean pressure lie closer to diastolic or systolic?
Diastolic: 60% of cardiac cycle is spent in diastole, 40% in systole.
Average arterial pressure w/ respect to time
Mean arterial pressure
MAP is simple average of diastolic and systolic?
No, more time is spent in diastole.
FOrmula for MAP:
Diastole Pressure + 1/3pulse pressure = MAP
Pressure in the R atrium
Central venous pressure [CVP]
Factors that regulate CVP or R atrial pressure:
Ability of heart to pump blood out of R atrium/ventricle
Tendency of blood to flow into R atrium
Estimating L atrial pressure. HOw?
Pulmonary wedge pressure: catheter w/ almost direct contact w/ pulmonary capillaries…almost equal to L atrial pressure
Increase venous pressure =
Increased R atrial pressure
Factors that increase R atrial pressure
Increased blood volume
Increased peripheral venous pressures d/t increased large vessel tone
Dilation of arterioles
When lying down, pressure in peripheral veins is:
is +4 to +6mm Hg > R atrial pressure
When intra-and pressure increases venous pressure must:
Increase above the bad pressure before blood can flow from the legs to the heart through the abd veins
Points that can collapse veins when entering thorax
Compression points
When standing, effect of pressure on venous pressures
The further distal and inferior = the greater pressure
BLood reservoir in circulatory system:
Spleen. Can introduce more blood into circulation if tissues req’
When volume is added:
Compensates by decreasing tone = increasing compliance
When volume is depleted :
Compensation by increasing tone = decreasing compliance
What helps to push blood back to the heart in the veins?
Muscle contraction
What is a cause of venous varicosities
Backflow of blood creates enough pressure to destroy valves.
Small vessels control blood flow to each tissue
Highly muscular
Arterioles
What controls diameter of arterioles?
Local conditions in tissues
Continuous musculature present in metarterioles?
No only arterioles
Smooth muscle fiber encircles capillary at point where it originates
Metarteriole - also called precapillary sphincter
Do capillaries have smooth muscle?
No
Unicellular layer of endothelial cells
Thin basement membrane
Total wall thickness= 0.5microns
Internal capillary diameter=4-9microns
Capillaries
Refers to the opening and closing of precapillary sphincter
Vasomotion
Occluding parts of the metarteriole to another capillary bed
Perferential channel
Spacing 6-7 nm
Allows for raid diffusion of water,water-soluble ions, and small solutes
Slit pores [in capillary]
Formed from caveolins
Plays a role in endocytosis and transcytosis
Plasmalemmal vesicles
Ex; of organs w/ capillaries w/ pores
Liver, GI tract, kidney
Intercellular cleft can form
Transport channels
Caveolin is important for
Endocytosis and transcytosis
What is the most important factor in regulation of vasomotion?
[oxygen] in the tissues
- determines how much blood flow to feed tissues
The most important means for the exchange of substances btw the blood and the interstitial fluid
Diffusion
What 2 lipid-soluble substances can rapidly diffuse through capillary cell membranes:
Oxygen
Carbon dioxide
Where do nonlipid-soluble substances diffuse through membrane?
Intercellular clefts/pores
Compare rate of diffusion btw capillary membrane and flow of plasma within capillary:
Rate of water diffusion thru capillary membrane is 80x faster than flow of plasma w/in capillary
Blood flow from arterial end, capillary, venous end and lymphatic can be described as:
Bidirectional
Directly proportional to [ ] differences of the diffusing substance
Rate of diffusion
Passage of substances through the interstitium is mostly via ____ rather than flow
Diffusion
Major component of interstitium and main reason diffusion is most common way of transport in interstitium
Proteoglycan filaments
Also, rivulets allow fluid flow through the interstitium do sometimes form
Free fluid in interstitium
rivulets
What determines direction of diffusion into or out of a capillary?
Starling forces
Name the 4 starling forces:
Capillary pressure-outward F
Interstitial fluid pressure- inward F
Capillary Plasma colloid osmotic pressure-inward F
Interstitial fluid colloid osmotic pressure- outward F
Sum of starling forces=
Net filtration pressure [NFP]
Name the coefficient that can be added to the NFP formula to make it more accurate:
Capillary filtration coefficient - takes into consideration the number and size of pores
Just multiply it by NFP
What happens When fluid enters the lymphatic?
The lymph vessel walls contract momentarily and pump fluid into blood circulation.
Fluid entering lymphatic so pushes some other fluid into the bloodstream. Why?
Movement into lymphatic creates a slightly negative pressure in the interstial spaces.
Forces of filtration at venous end of capillary
Net inward force= 7 mm Hg
Forces of filtration at arterial end of capillary
Net outward force = 13 mm Hg
Only starling force that changes during exchange from arterial to venous:
Capillary pressure=
30->10 from arterial end to venous end
Lymph vessels possess _______ valves
1 way
When does lymph flow reach a maximum?
When interstitial pressure rises slightly above atmospheric pressure
Factors that increase lymph flow:
Elevated capillary hydrostatic pressure
Decreased plasma colloid osmotic pressure
Increased interstitial fluid colloid osmotic pressure
Increased permeability of capillaries
Interstitial pressure x activity of lymphatic pump =
Rate of lymph flow
Proteins help open interstial space of lymph capillaries:
Anchoring filament
Goal for arteriolar end of capillary?
Move fluid from capillary to interstitium
Goal for venous end of capillary?
push fluid into vein from interstitium
